Changelog

Python 3.9.0 final

Release date: 2020-10-04

Library

  • bpo-41815: Fix SQLite3 segfault when backing up closed database. Patch contributed by Peter David McCormick.

  • bpo-41662: No longer override exceptions raised in __len__() of a sequence of parameters in sqlite3 with ProgrammingError.

  • bpo-41662: Fixed crash when mutate list of parameters during iteration in sqlite3.

  • bpo-39728: fix default _missing_ so a duplicate ValueError is not set as the __context__ of the original ValueError

Tests

  • bpo-41602: Add tests for SIGINT handling in the runpy module.

Build

  • bpo-38249: Update Py_UNREACHABLE to use __builtin_unreachable() if only the compiler is able to use it. Patch by Dong-hee Na.

Python 3.9.0 release candidate 2

Release date: 2020-09-16

Core and Builtins

  • bpo-41780: Fix __dir__() of types.GenericAlias. Patch by Batuhan Taskaya.

  • bpo-41690: Fix a possible stack overflow in the parser when parsing functions and classes with a huge ammount of arguments. Patch by Pablo Galindo.

  • bpo-41681: Fixes the wrong error description in the error raised by using 2 , in format string in f-string and str.format().

  • bpo-41654: Fix a crash that occurred when destroying subclasses of MemoryError. Patch by Pablo Galindo.

  • bpo-41631: The _ast module uses again a global state. Using a module state per module instance is causing subtle practical problems. For example, the Mercurial project replaces the __import__() function to implement lazy import, whereas Python expected that import _ast always return a fully initialized _ast module.

  • bpo-41533: Free the stack allocated in va_build_stack if do_mkstack fails and the stack is not a small_stack.

  • bpo-41531: Fix a bug that was dropping keys when compiling dict literals with more than 0xFFFF elements. Patch by Pablo Galindo.

  • bpo-41525: The output of python --help contains now only ASCII characters.

  • bpo-29590: Make the stack trace correct after calling generator.throw() on a generator that has yielded from a yield from.

Library

  • bpo-41517: fix bug allowing Enums to be extended via multiple inheritance

  • bpo-39587: use the correct mix-in data type when constructing Enums

  • bpo-41789: Honor object overrides in Enum class creation (specifically, __str__, __repr__, __format__, and __reduce_ex__).

  • bpo-39651: Fix a race condition in the call_soon_threadsafe() method of asyncio.ProactorEventLoop: do nothing if the self-pipe socket has been closed.

  • bpo-41720: Fixed turtle.Vec2D.__rmul__() for arguments which are not int or float.

  • bpo-41696: Fix handling of debug mode in asyncio.run(). This allows setting PYTHONASYNCIODEBUG or -X dev to enable asyncio debug mode when using asyncio.run().

  • bpo-41687: Fix implementation of sendfile to be compatible with Solaris.

  • bpo-39010: Restarting a ProactorEventLoop on Windows no longer logs spurious ConnectionResetErrors.

  • bpo-41609: The pdb whatis command correctly reports instance methods as 'Method' rather than 'Function'.

  • bpo-32751: When cancelling the task due to a timeout, asyncio.wait_for() will now wait until the cancellation is complete also in the case when timeout is <= 0, like it does with positive timeouts.

  • bpo-37658: asyncio.wait_for() now properly handles races between cancellation of itself and the completion of the wrapped awaitable.

  • bpo-40782: Change the method asyncio.AbstractEventLoop.run_in_executor to not be a coroutine.

  • bpo-41520: Fix codeop regression that prevented turning compile warnings into errors.

  • bpo-41503: Fixed a race between setTarget and flush in logging.handlers.MemoryHandler.

  • bpo-41344: Prevent creating shared_memory.SharedMemory objects with size=0.

  • bpo-41025: Fixed an issue preventing the C implementation of zoneinfo.ZoneInfo from being subclassed.

  • bpo-31122: ssl.wrap_socket() now raises ssl.SSLEOFError rather than OSError when peer closes connection during TLS negotiation

  • bpo-33660: Fix pathlib.PosixPath to resolve a relative path located on the root directory properly.

Documentation

  • bpo-37149: Change Shipman tkinter doc link from archive.org to TkDocs. (The doc has been removed from the NMT server.) The new link responds much faster and includes a short explanatory note.

  • bpo-41624: Fix the signature of typing.Coroutine.

  • bpo-40204: Enable Sphinx 3.2 c_allow_pre_v3 option and disable c_warn_on_allowed_pre_v3 option to make the documentation compatible with Sphinx 2 and Sphinx 3.

  • bpo-40979: Refactored typing.rst, arranging more than 70 classes, functions, and decorators into new sub-sections.

  • bpo-39883: Make code, examples, and recipes in the Python documentation be licensed under the more permissive BSD0 license in addition to the existing Python 2.0 license.

Tests

  • bpo-41731: Make test_cmd_line_script pass with option '-vv'.

Build

  • bpo-41617: Fix pycore_byteswap.h header file to support old clang versions: __builtin_bswap16() is not available in LLVM clang 3.0.

Windows

  • bpo-41526: Fixed layout of final page of the installer by removing the special thanks to Mark Hammond (with his permission).

C API

  • bpo-41524: Fix bug in PyOS_mystrnicmp and PyOS_mystricmp that incremented pointers beyond the end of a string.

Python 3.9.0 release candidate 1

Release date: 2020-08-11

Core and Builtins

  • bpo-38156: Handle interrupts that come after EOF correctly in PyOS_StdioReadline.

Library

Documentation

  • bpo-41045: Add documentation for debug feature of f-strings.

  • bpo-41314: Changed the release when from __future__ import annotations becomes the default from 4.0 to 3.10 (following a change in PEP 563).

Windows

  • bpo-41492: Fixes the description that appears in UAC prompts.

  • bpo-40948: Improve post-install message to direct people to the "py" command.

  • bpo-41412: The installer will now fail to install on Windows 7 and Windows 8. Further, the UCRT dependency is now always downloaded on demand.

  • bpo-40741: Update Windows release to include SQLite 3.32.3.

IDLE

  • bpo-41468: Improve IDLE run crash error message (which users should never see).

  • bpo-41373: Save files loaded with no line ending, as when blank, or different line endings, by setting its line ending to the system default. Fix regression in 3.8.4 and 3.9.0b4.

Python 3.9.0 beta 5

Release date: 2020-07-20

Security

  • bpo-41304: Fixes python3x._pth being ignored on Windows, caused by the fix for bpo-29778 (CVE-2020-15801).

  • bpo-41162: Audit hooks are now cleared later during finalization to avoid missing events.

  • bpo-29778: Ensure python3.dll is loaded from correct locations when Python is embedded (CVE-2020-15523).

  • bpo-39603: Prevent http header injection by rejecting control characters in http.client.putrequest(...).

Core and Builtins

  • bpo-41295: Resolve a regression in CPython 3.8.4 where defining "__setattr__" in a multi-inheritance setup and calling up the hierarchy chain could fail if builtins/extension types were involved in the base types.

  • bpo-41247: Always cache the running loop holder when running asyncio.set_running_loop.

  • bpo-41252: Fix incorrect refcounting in _ssl.c's _servername_callback().

  • bpo-41215: Use non-NULL default values in the PEG parser keyword list to overcome a bug that was preventing Python from being properly compiled when using the XLC compiler. Patch by Pablo Galindo.

  • bpo-41218: Python 3.8.3 had a regression where compiling with ast.PyCF_ALLOW_TOP_LEVEL_AWAIT would aggressively mark list comprehension with CO_COROUTINE. Now only list comprehension making use of async/await will tagged as so.

  • bpo-41175: Guard against a NULL pointer dereference within bytearrayobject triggered by the bytearray() + bytearray() operation.

  • bpo-39960: The "hackcheck" that prevents sneaking around a type's __setattr__() by calling the superclass method was rewritten to allow C implemented heap types.

Library

  • bpo-41288: Unpickling invalid NEWOBJ_EX opcode with the C implementation raises now UnpicklingError instead of crashing.

  • bpo-39017: Avoid infinite loop when reading specially crafted TAR files using the tarfile module (CVE-2019-20907).

  • bpo-41235: Fix the error handling in ssl.SSLContext.load_dh_params().

  • bpo-41207: In distutils.spawn, restore expectation that DistutilsExecError is raised when the command is not found.

  • bpo-39168: Remove the __new__ method of typing.Generic.

  • bpo-41194: Fix a crash in the _ast module: it can no longer be loaded more than once. It now uses a global state rather than a module state.

  • bpo-39384: Fixed email.contentmanager to allow set_content() to set a null string.

Documentation

  • bpo-37703: Updated Documentation to comprehensively elaborate on the behaviour of gather.cancel()

macOS

  • bpo-40741: Update macOS installer to use SQLite 3.32.3.

IDLE

  • bpo-41300: Save files with non-ascii chars. Fix regression released in 3.9.0b4 and 3.8.4.

  • bpo-37765: Add keywords to module name completion list. Rewrite Completions section of IDLE doc.

C API

Python 3.9.0 beta 4

Release date: 2020-07-02

Security

  • bpo-41004: The __hash__() methods of ipaddress.IPv4Interface and ipaddress.IPv6Interface incorrectly generated constant hash values of 32 and 128 respectively. This resulted in always causing hash collisions. The fix uses hash() to generate hash values for the tuple of (address, mask length, network address).

Core and Builtins

  • bpo-41094: Fix decoding errors with audit when open files with non-ASCII names on non-UTF-8 locale.

  • bpo-41084: Prefix the error message with 'f-string: ', when parsing an f-string expression which throws a SyntaxError.

  • bpo-41076: Pre-feed the parser with the location of the f-string expression, not the f-string itself, which allows us to skip the shifting of the AST node locations after the parsing is completed.

  • bpo-40939: Deprecate PyNode_Compile().

  • bpo-41056: Fixes a reference to deallocated stack space during startup when constructing sys.path involving a relative symlink when code was supplied via -c. (discovered via Coverity)

  • bpo-41061: Fix incorrect expressions and asserts in hashtable code and tests.

  • bpo-41052: Opt out serialization/deserialization for _random.Random

  • bpo-40939: Deprecate PyParser_SimpleParseStringFlags(), PyParser_SimpleParseStringFlagsFilename() and PyParser_SimpleParseFileFlags().

  • bpo-35975: Stefan Behnel reported that cf_feature_version is used even when PyCF_ONLY_AST is not set. This is against the intention and against the documented behavior, so it's been fixed.

  • bpo-40985: Fix a bug that caused the SyntaxError text to be empty when a file ends with a line ending in a line continuation character (i.e. backslash). The error text should contain the text of the last line.

  • bpo-40958: Fix a possible buffer overflow in the PEG parser when gathering information for emitting syntax errors. Patch by Pablo Galindo.

  • bpo-40957: Fix refleak in _Py_fopen_obj() when PySys_Audit() fails

  • bpo-40947: The Python Path Configuration now takes PyConfig.platlibdir in account.

  • bpo-40847: Fix a bug where a line with only a line continuation character is not considered a blank line at tokenizer level. In such cases, more than a single NEWLINE token was emitted. The old parser was working around the issue, but the new parser threw a SyntaxError for valid input due to this. For example, an empty line following a line continuation character was interpreted as a SyntaxError.

  • bpo-40824: Unexpected errors in calling the __iter__ method are no longer masked by TypeError in the in operator and functions contains(), indexOf() and countOf() of the operator module.

  • bpo-19569: Add the private macros _Py_COMP_DIAG_PUSH, _Py_COMP_DIAG_IGNORE_DEPR_DECLS, and _Py_COMP_DIAG_POP.

Library

  • bpo-41193: The write_history() atexit function of the readline completer now ignores any OSError to ignore error if the filesystem is read-only, instead of only ignoring FileNotFoundError and PermissionError.

  • bpo-41161: The decimal module now requires libmpdec-2.5.0. Users of --with-system-libmpdec should update their system library.

  • bpo-40874: The decimal module now requires libmpdec-2.5.0.

  • bpo-41138: Fixed the trace module CLI for Python source files with non-UTF-8 encoding.

  • bpo-31938: Fix default-value signatures of several functions in the select module - by Anthony Sottile.

  • bpo-41068: Fixed reading files with non-ASCII names from ZIP archive directly after writing them.

  • bpo-41058: pdb.find_function() now correctly determines the source file encoding.

  • bpo-41056: Fix a NULL pointer dereference within the ssl module during a MemoryError in the keylog callback. (discovered by Coverity)

  • bpo-41056: Fixed an instance where a MemoryError within the zoneinfo module might not be reported or not reported at its source. (found by Coverity)

  • bpo-41048: mimetypes.read_mime_types() function reads the rule file using UTF-8 encoding, not the locale encoding. Patch by Srinivas Reddy Thatiparthy.

  • bpo-41043: Fixed the use of glob() in the stdlib: literal part of the path is now always correctly escaped.

  • bpo-40448: ensurepip now disables the use of pip cache when installing the bundled versions of pip and setuptools. Patch by Krzysztof Konopko.

  • bpo-40967: Removed asyncio.Task.current_task() and asyncio.Task.all_tasks(). Patch contributed by Rémi Lapeyre.

  • bpo-40955: Fix a minor memory leak in subprocess module when extra_groups was specified.

  • bpo-40855: The standard deviation and variance functions in the statistics module were ignoring their mu and xbar arguments.

  • bpo-40924: Removed support for loaders implementing .files and supplying TraversableResources.

  • bpo-40939: Use the new PEG parser when generating the stdlib keyword module.

  • bpo-40834: Fix truncate when sending str object with_xxsubinterpreters.channel_send.

  • bpo-26407: Unexpected errors in calling the __iter__ method are no longer masked by TypeError in csv.reader(), csv.writer.writerow() and csv.writer.writerows().

  • bpo-38488: Update ensurepip to install pip 20.1.1 and setuptools 47.1.0.

  • bpo-36543: Restored the deprecated xml.etree.cElementTree module.

  • bpo-34226: Fix cgi.parse_multipart without content_length. Patch by Roger Duran

Tests

  • bpo-41085: Fix integer overflow in the array.array.index() method on 64-bit Windows for index larger than 2**31.

  • bpo-41069: test.support.TESTFN and the current directory for tests when run via test.regrtest contain now non-ascii characters if possible.

  • bpo-38377: On Linux, skip tests using multiprocessing if the current user cannot create a file in /dev/shm/ directory. Add the skip_if_broken_multiprocessing_synchronize() function to the test.support module.

  • bpo-41009: Fix use of support.require_{linux|mac|freebsd}_version() decorators as class decorator.

  • bpo-41003: Fix test_copyreg when numpy is installed: test.pickletester now saves/restores warnings filters when importing numpy, to ignore filters installed by numpy.

  • bpo-40964: Disable remote imaplib tests, host cyrus.andrew.cmu.edu is blocking incoming connections.

  • bpo-40927: Fix test_binhex when run twice: it now uses import_fresh_module() to ensure that it raises DeprecationWarning each time.

  • bpo-34401: Make test_gdb properly run on HP-UX. Patch by Michael Osipov.

Build

  • bpo-40204: Pin Sphinx version to 2.3.1 in Doc/Makefile.

Windows

macOS

  • bpo-39580: Avoid opening Finder window if running installer from the command line. Patch contributed by Rick Heil.

  • bpo-41100: Fix configure error when building on macOS 11. Note that the current Python release was released shortly after the first developer preview of macOS 11 (Big Sur); there are other known issues with building and running on the developer preview. Big Sur is expected to be fully supported in a future bugfix release of Python 3.8.x and with 3.9.0.

  • bpo-41005: fixed an XDG settings issue not allowing macos to open browser in webbrowser.py

IDLE

  • bpo-41152: The encoding of stdin, stdout and stderr in IDLE is now always UTF-8.

  • bpo-41144: Make Open Module open a special module such as os.path.

C API

  • bpo-36346: Mark Py_UNICODE_COPY, Py_UNICODE_FILL, PyUnicode_WSTR_LENGTH, PyUnicode_FromUnicode, PyUnicode_AsUnicode, _PyUnicode_AsUnicode, and PyUnicode_AsUnicodeAndSize as deprecated in C. Remove Py_UNICODE_MATCH which was deprecated and broken since Python 3.3.

  • bpo-36020: On Windows, #include "pyerrors.h" no longer defines snprintf and vsnprintf macros.

  • bpo-40703: The PyType_FromSpec*() functions no longer overwrite the type's "__module__" attribute if it is set via "Py_tp_members" or "Py_tp_getset".

Python 3.9.0 beta 3

Release date: 2020-06-09

Library

  • bpo-40924: importlib.resources: Reverted TraversableResources implementations from the built-in loaders (SourceFileLoader and ZipImporter) as it was an incompatible change introduced in 3.9.0 beta 2 causing through a chain of events for root TLS certificates to be missing.

Build

  • bpo-40684: make install now uses the PLATLIBDIR variable for the destination lib-dynload/ directory when ./configure --with-platlibdir is used.

Python 3.9.0 beta 2

Release date: 2020-06-08

Core and Builtins

  • bpo-40904: Fix possible segfault in the new PEG parser when parsing f-string containing yield statements with no value (f"{yield}"). Patch by Pablo Galindo

  • bpo-40903: Fixed a possible segfault in the new PEG parser when producing error messages for invalid assignments of the form p=p=. Patch by Pablo Galindo

  • bpo-40880: Fix invalid memory read in the new parser when checking newlines in string literals. Patch by Pablo Galindo.

  • bpo-40883: Fix memory leak in when parsing f-strings in the new parser. Patch by Pablo Galindo

  • bpo-40870: Raise ValueError when validating custom AST's where the constants True, False and None are used within a ast.Name node.

  • bpo-40854: Allow overriding sys.platlibdir via a new PYTHONPLATLIBDIR environment variable.

  • bpo-40826: Fix GIL usage in PyOS_Readline(): lock the GIL to set an exception and pass the Python thread state when checking if there is a pending signal.

  • bpo-40780: Fix a corner case where g-style string formatting of a float failed to remove trailing zeros.

  • bpo-38964: When there's a SyntaxError in the expression part of an fstring, the filename attribute of the SyntaxError gets correctly set to the name of the file the fstring resides in.

  • bpo-40750: Support the "-d" debug flag in the new PEG parser. Patch by Pablo Galindo

  • bpo-40217: Instances of types created with PyType_FromSpecWithBases() will no longer automatically visit their class object when traversing references in the garbage collector. The user is expected to manually visit the object's class. Patch by Pablo Galindo.

  • bpo-40696: Fix a hang that can arise after generator.throw() due to a cycle in the exception context chain.

Library

  • bpo-39791: Refresh importlib.metadata from importlib_metadata 1.6.1.

  • bpo-40807: Stop codeop._maybe_compile, used by code.InteractiveInterpreter (and IDLE). from from emitting each warning three times.

  • bpo-39791: Built-in loaders (SourceFileLoader and ZipImporter) now supply TraversableResources implementations for ResourceReader, and the fallback function has been removed.

  • bpo-17005: The topological sort functionality that was introduced initially in the functools module has been moved to a new graphlib module to better accommodate the new tools and keep the original scope of the functools module. Patch by Pablo Galindo

  • bpo-40777: Initialize PyDateTime_IsoCalendarDateType.tp_base at run-time to avoid errors on some compilers.

  • bpo-40767: webbrowser now properly finds the default browser in pure Wayland systems by checking the WAYLAND_DISPLAY environment variable. Patch contributed by Jérémy Attali.

  • bpo-40791: hashlib.compare_digest() uses OpenSSL's CRYPTO_memcmp() function when OpenSSL is available.

  • bpo-40795: ctypes module: If ctypes fails to convert the result of a callback or if a ctypes callback function raises an exception, sys.unraisablehook is now called with an exception set. Previously, the error was logged into stderr by PyErr_Print().

  • bpo-30008: Fix ssl code to be compatible with OpenSSL 1.1.x builds that use no-deprecated and --api=1.1.0.

  • bpo-30064: Fix asyncio loop.sock_* race condition issue

  • bpo-40759: Deprecate the symbol module.

  • bpo-40737: Fix possible reference leak for sqlite3 initialization.

  • bpo-40698: distutils upload creates SHA2-256 and Blake2b-256 digests. MD5 digests is skipped if platform blocks MD5.

  • bpo-40695: hashlib no longer falls back to builtin hash implementations when OpenSSL provides a hash digest and the algorithm is blocked by security policy.

  • bpo-9216: func:hashlib.new passed usedforsecurity to OpenSSL EVP constructor _hashlib.new(). test_hashlib and test_smtplib handle strict security policy better.

  • bpo-40614: ast.parse() will not parse self documenting expressions in f-strings when passed feature_version is less than (3, 8).

  • bpo-40671: Prepare _hashlib for PEP 489 and use PyModule_AddType().

  • bpo-32309: Added a new coroutine asyncio.to_thread(). It is mainly used for running IO-bound functions in a separate thread to avoid blocking the event loop, and essentially works as a high-level version of run_in_executor() that can directly take keyword arguments.

  • bpo-40630: Added tracemalloc.reset_peak() to set the peak size of traced memory blocks to the current size, to measure the peak of specific pieces of code.

  • bpo-13097: ctypes now raises an ArgumentError when a callback is invoked with more than 1024 arguments.

  • bpo-23082: Updated the error message and docs of PurePath.relative_to() to better reflect the function behaviour.

  • bpo-39244: Fixed multiprocessing.context.get_all_start_methods to properly return the default method first on macOS.

  • bpo-39040: Fix parsing of invalid mime headers parameters by collapsing whitespace between encoded words in a bare-quote-string.

  • bpo-35714: struct.error is now raised if there is a null character in a struct format string.

  • bpo-36290: AST nodes are now raising TypeError on conflicting keyword arguments. Patch contributed by Rémi Lapeyre.

Tests

Build

  • bpo-40514: Remove --with-experimental-isolated-subinterpreters configure option in Python 3.9: the experiment continues in the master branch, but it's no longer needed in 3.9.

  • bpo-40683: Fixed an issue where the zoneinfo module and its tests were not included when Python is installed with make.

Windows

  • bpo-39631: Changes the registered MIME type for .py files on Windows to text/x-python instead of text/plain.

  • bpo-40677: Manually define IO_REPARSE_TAG_APPEXECLINK in case some old Windows SDK doesn't have it.

macOS

  • bpo-40741: Update macOS installer to use SQLite 3.32.2.

IDLE

  • bpo-39885: Make context menu Cut and Copy work again when right-clicking within a selection.

  • bpo-40723: Make test_idle pass when run after import.

C API

  • bpo-40910: Export explicitly the Py_GetArgcArgv() function to the C API and document the function. Previously, it was exported implicitly which no longer works since Python is built with -fvisibility=hidden.

  • bpo-40724: Allow defining buffer slots in type specs.

  • bpo-40826: PyOS_InterruptOccurred() now fails with a fatal error if it is called with the GIL released.

Python 3.9.0 beta 1

Release date: 2020-05-19

Security

Core and Builtins

  • bpo-40663: Correctly generate annotations where parentheses are omitted but required (e.g: Type[(str, int, *other))].

  • bpo-40596: Fixed str.isidentifier() for non-canonicalized strings containing non-BMP characters on Windows.

  • bpo-40593: Improved syntax errors for invalid characters in source code.

  • bpo-40585: Fixed a bug when using codeop.compile_command() that was causing exceptions to be swallowed with the new parser. Patch by Pablo Galindo

  • bpo-40566: Apply PEP 573 to abc.

  • bpo-40502: Initialize n->n_col_offset. (Patch by Joannah Nanjekye)

  • bpo-40527: Fix command line argument parsing: no longer write errors multiple times into stderr.

  • bpo-1635741: Port errno to multiphase initialization (PEP 489).

  • bpo-40523: Add pass-throughs for hash() and reversed() to weakref.proxy objects. Patch by Pablo Galindo.

  • bpo-1635741: Port syslog to multiphase initialization (PEP 489).

  • bpo-40246: Reporting a specialised error message for invalid string prefixes, which was introduced in bpo-40246, is being reverted due to backwards compatibility concerns for strings that immediately follow a reserved keyword without whitespace between them. Constructs like bg="#d00" if clear else"#fca" were failing to parse, which is not an acceptable breakage on such short notice.

  • bpo-40417: Fix imp module deprecation warning when PyImport_ReloadModule is called. Patch by Robert Rouhani.

  • bpo-40408: Fixed support of nested type variables in GenericAlias (e.g. list[list[T]]).

  • bpo-1635741: Port _stat module to multiphase initialization (PEP 489).

  • bpo-29587: Enable implicit exception chaining when calling generator.throw().

  • bpo-40328: Add tools for generating mappings headers for CJKCodecs.

  • bpo-40228: Setting frame.f_lineno is now robust w.r.t. changes in the source-to-bytecode compiler

  • bpo-38880: Added the ability to list interpreters associated with channel ends in the internal subinterpreters module.

  • bpo-37986: Improve performance of PyLong_FromDouble() for values that fit into long.

Library

  • bpo-40662: Fixed ast.get_source_segment() for ast nodes that have incomplete location information. Patch by Irit Katriel.

  • bpo-40665: Convert bisect to use Argument Clinic.

  • bpo-40536: Added the available_timezones() function to the zoneinfo module. Patch by Paul Ganssle.

  • bpo-40645: The hmac.HMAC exposes internal implementation details. The attributes digest_cons, inner, and outer are deprecated and will be removed in the future.

  • bpo-40645: The internal module _hashlib wraps and exposes OpenSSL's HMAC API. The new code will be used in Python 3.10 after the internal implementation details of the pure Python HMAC module are no longer part of the public API.

  • bpo-40637: Builtin hash modules can now be disabled or selectively enabled with configure --with-builtin-hashlib-hashes=sha3,blake1 or --without-builtin-hashlib-hashes.

  • bpo-37630: The hashlib module can now use SHA3 hashes and SHAKE XOF from OpenSSL when available.

  • bpo-40479: The hashlib now compiles with OpenSSL 3.0.0-alpha2.

  • bpo-40257: Revert changes to inspect.getdoc().

  • bpo-40607: When cancelling a task due to timeout, asyncio.wait_for() will now propagate the exception if an error happens during cancellation. Patch by Roman Skurikhin.

  • bpo-40612: Fix edge cases in SyntaxError formatting. If the offset is <= 0, no caret is printed. If the offset is > line length, the caret is printed pointing just after the last character.

  • bpo-40597: If text content lines are longer than policy.max_line_length, always use a content-encoding to make sure they are wrapped.

  • bpo-40571: Added functools.cache() as a simpler, more discoverable way to access the unbounded cache variant of lru_cache(maxsize=None).

  • bpo-40503: PEP 615, the zoneinfo module. Adds support for the IANA time zone database.

  • bpo-40397: Removed attributes __args__ and __parameters__ from special generic aliases like typing.List (not subscripted).

  • bpo-40549: Convert posixmodule.c ("posix" or "nt" module) to the multiphase initialization (PEP 489).

  • bpo-31033: Add a msg argument to Future.cancel() and Task.cancel().

  • bpo-40541: Added an optional counts parameter to random.sample().

  • bpo-40515: The ssl and hashlib modules now actively check that OpenSSL is build with thread support. Python 3.7.0 made thread support mandatory and no longer works safely with a no-thread builds.

  • bpo-31033: When a asyncio.Task is cancelled, the exception traceback now chains all the way back to where the task was first interrupted.

  • bpo-40504: functools.lru_cache() objects can now be the targets of weakrefs.

  • bpo-40559: Fix possible memory leak in the C implementation of asyncio.Task.

  • bpo-40480: fnmatch.fnmatch() could take exponential time in the presence of multiple * pattern characters. This was repaired by generating more elaborate regular expressions to avoid futile backtracking.

  • bpo-40495: compileall is now able to use hardlinks to prevent duplicates in a case when .pyc files for different optimization levels have the same content.

  • bpo-40457: The ssl module now support OpenSSL builds without TLS 1.0 and 1.1 methods.

  • bpo-40355: Improve error reporting in ast.literal_eval() in the presence of malformed ast.Dict nodes instead of silently ignoring any non-conforming elements. Patch by Curtis Bucher.

  • bpo-40465: Deprecated the optional random argument to random.shuffle().

  • bpo-40459: platform.win32_ver() now produces correct ptype strings instead of empty strings.

  • bpo-39435: The first argument of pickle.loads() is now positional-only.

  • bpo-39305: Update nntplib to merge nntplib.NNTP and nntplib._NNTPBase. Patch by Dong-hee Na.

  • bpo-32494: Update dbm.gnu to use gdbm_count if possible when calling len(). Patch by Dong-hee Na.

  • bpo-40453: Add isolated=True keyword-only parameter to _xxsubinterpreters.create(). An isolated subinterpreter cannot spawn threads, spawn a child process or call os.fork().

  • bpo-40286: Remove _random.Random.randbytes(): the C implementation of randbytes(). Implement the method in Python to ease subclassing: randbytes() now directly reuses getrandbits().

  • bpo-40394: Added default arguments to difflib.SequenceMatcher.find_longest_match().

  • bpo-39995: Fix a race condition in concurrent.futures._ThreadWakeup: access to _ThreadWakeup is now protected with the shutdown lock.

  • bpo-30966: Process.shutdown(wait=True) of concurrent.futures now closes explicitly the result queue.

  • bpo-30966: Add a new close() method to the SimpleQueue class to explicitly close the queue.

  • bpo-39966: Revert bpo-25597. unittest.mock.MagicMock with wraps' set uses default return values for magic methods.

  • bpo-39791: Added files() function to importlib.resources with support for subdirectories in package data, matching backport in importlib_resources 1.5.

  • bpo-40375: imaplib.IMAP4.unselect() is added. Patch by Dong-hee Na.

  • bpo-40389: repr() now returns typing.Optional[T] when called for typing.Union of two types, one of which is NoneType.

  • bpo-40291: Add support for CAN_J1939 sockets (available on Linux 5.4+)

  • bpo-40273: types.MappingProxyType is now reversible.

  • bpo-39075: The repr for types.SimpleNamespace is now insertion ordered rather than alphabetical.

  • bpo-40192: On AIX, thread_time() is now implemented with thread_cputime() which has nanosecond resolution, rather than clock_gettime(CLOCK_THREAD_CPUTIME_ID) which has a resolution of 10 ms. Patch by Batuhan Taskaya.

  • bpo-40025: Raise TypeError when _generate_next_value_ is defined after members. Patch by Ethan Onstott.

  • bpo-39058: In the argparse module, the repr for Namespace() and other argument holders now displayed in the order attributes were added. Formerly, it displayed in alphabetical order even though argument order is preserved the user visible parts of the module.

  • bpo-24416: The isocalendar() methods of datetime.date and datetime.datetime now return a named tuple instead of a tuple.

Documentation

  • bpo-34790: Add version of removal for explicit passing of coros to asyncio.wait()'s documentation

  • bpo-40561: Provide docstrings for webbrowser open functions.

  • bpo-40499: Mention that asyncio.wait() requires a non-empty set of awaitables.

  • bpo-39705: Tutorial example for sorted() in the Loop Techniques section is given a better explanation. Also a new example is included to explain sorted()'s basic behavior.

  • bpo-39435: Fix an incorrect signature for pickle.loads() in the docs

Tests

  • bpo-40055: distutils.tests now saves/restores warnings filters to leave them unchanged. Importing tests imports docutils which imports pkg_resources which adds a warnings filter.

  • bpo-40436: test_gdb and test.pythoninfo now check gdb command exit code.

Build

  • bpo-40653: Move _dirnameW out of HAVE_SYMLINK to fix a potential compiling issue.

  • bpo-40514: Add --with-experimental-isolated-subinterpreters build option to configure: better isolate subinterpreters, experimental build mode.

Windows

  • bpo-40650: Include winsock2.h in pytime.c for timeval.

  • bpo-40458: Increase reserved stack space to prevent overflow crash on Windows.

  • bpo-39148: Add IPv6 support to asyncio datagram endpoints in ProactorEventLoop. Change the raised exception for unknown address families to ValueError as it's not coming from Windows API.

macOS

  • bpo-34956: When building Python on macOS from source, _tkinter now links with non-system Tcl and Tk frameworks if they are installed in /Library/Frameworks, as had been the case on older releases of macOS. If a macOS SDK is explicitly configured, by using --enable-universalsdk= or -isysroot, only the SDK itself is searched. The default behavior can still be overridden with --with-tcltk-includes and --with-tcltk-libs.

  • bpo-35569: Expose RFC 3542 IPv6 socket options.

Tools/Demos

  • bpo-40479: Update multissltest helper to test with latest OpenSSL 1.0.2, 1.1.0, 1.1.1, and 3.0.0-alpha.

  • bpo-40431: Fix a syntax typo in turtledemo that now raises a SyntaxError.

  • bpo-40163: Fix multissltest tool. OpenSSL has changed download URL for old releases. The multissltest tool now tries to download from current and old download URLs.

C API

  • bpo-39465: Remove the _PyUnicode_ClearStaticStrings() function from the C API.

  • bpo-38787: Add PyCFunction_CheckExact() macro for exact type checks now that we allow subtypes of PyCFunction, as well as PyCMethod_CheckExact() and PyCMethod_Check() for the new PyCMethod subtype.

  • bpo-40545: Declare _PyErr_GetTopmostException() with PyAPI_FUNC() to properly export the function in the C API. The function remains private (_Py) prefix.

  • bpo-40412: Nullify inittab_copy during finalization, preventing future interpreter initializations in an embedded situation from crashing. Patch by Gregory Szorc.

  • bpo-40429: The PyThreadState_GetFrame() function now returns a strong reference to the frame.

  • bpo-40428: Remove the following functions from the C API. Call PyGC_Collect() explicitly to free all free lists.

    • PyAsyncGen_ClearFreeLists()

    • PyContext_ClearFreeList()

    • PyDict_ClearFreeList()

    • PyFloat_ClearFreeList()

    • PyFrame_ClearFreeList()

    • PyList_ClearFreeList()

    • PySet_ClearFreeList()

    • PyTuple_ClearFreeList()

  • bpo-40421: New PyFrame_GetBack() function: get the frame next outer frame.

  • bpo-40421: New PyFrame_GetCode() function: return a borrowed reference to the frame code.

  • bpo-40217: Ensure that instances of types created with PyType_FromSpecWithBases() will visit its class object when traversing references in the garbage collector (implemented as an extension of the provided tp_traverse). Patch by Pablo Galindo.

  • bpo-38787: Module C state is now accessible from C-defined heap type methods (PEP 573). Patch by Marcel Plch and Petr Viktorin.

Python 3.9.0 alpha 6

Release date: 2020-04-27

Security

  • bpo-40121: Fixes audit events raised on creating a new socket.

  • bpo-39073: Disallow CR or LF in email.headerregistry.Address arguments to guard against header injection attacks.

  • bpo-39503: CVE-2020-8492: The AbstractBasicAuthHandler class of the urllib.request module uses an inefficient regular expression which can be exploited by an attacker to cause a denial of service. Fix the regex to prevent the catastrophic backtracking. Vulnerability reported by Ben Caller and Matt Schwager.

Core and Builtins

  • bpo-40313: Improve the performance of bytes.hex().

  • bpo-40334: Switch to a new parser, based on PEG. For more details see PEP 617. To temporarily switch back to the old parser, use -X oldparser or PYTHONOLDPARSER=1. In Python 3.10 we will remove the old parser completely, including the parser module (already deprecated) and anything that depends on it.

  • bpo-40267: Fix the tokenizer to display the correct error message, when there is a SyntaxError on the last input character and no newline follows. It used to be unexpected EOF while parsing, while it should be invalid syntax.

  • bpo-39522: Correctly unparse explicit u prefix for strings when postponed evaluation for annotations activated. Patch by Batuhan Taskaya.

  • bpo-40246: Report a specialized error message, invalid string prefix, when the tokenizer encounters a string with an invalid prefix.

  • bpo-40082: Fix the signal handler: it now always uses the main interpreter, rather than trying to get the current Python thread state.

  • bpo-37388: str.encode() and str.decode() no longer check the encoding and errors in development mode or in debug mode during Python finalization. The codecs machinery can no longer work on very late calls to str.encode() and str.decode().

  • bpo-40077: Fix possible refleaks in _json, memo of PyScannerObject should be traversed.

  • bpo-37207: Speed up calls to dict() by using the PEP 590 vectorcall calling convention.

  • bpo-40141: Add column and line information to ast.keyword nodes. Patch by Pablo Galindo.

  • bpo-1635741: Port resource to multiphase initialization (PEP 489).

  • bpo-1635741: Port math to multiphase initialization (PEP 489).

  • bpo-1635741: Port _uuid module to multiphase initialization (PEP 489).

  • bpo-40077: Convert json module to use PyType_FromSpec().

  • bpo-40067: Improve the error message for multiple star expressions in an assignment. Patch by Furkan Onder

  • bpo-1635741: Port _functools module to multiphase initialization (PEP 489). Patch by Paulo Henrique Silva.

  • bpo-1635741: Port operator module to multiphase initialization (PEP 489). Patch by Paulo Henrique Silva.

  • bpo-20526: Fix PyThreadState_Clear(). PyThreadState.frame is a borrowed reference, not a strong reference: PyThreadState_Clear() must not call Py_CLEAR(tstate->frame).

  • bpo-1635741: Port time module to multiphase initialization (PEP 489). Patch by Paulo Henrique Silva.

  • bpo-1635741: Port _weakref extension module to multiphase initialization (PEP 489).

  • bpo-40020: Fix a leak and subsequent crash in parsetok.c caused by realloc misuse on a rare codepath.

  • bpo-39939: Added str.removeprefix and str.removesuffix methods and corresponding bytes, bytearray, and collections.UserString methods to remove affixes from a string if present. See PEP 616 for a full description. Patch by Dennis Sweeney.

  • bpo-39481: Implement PEP 585. This supports list[int], tuple[str, ...] etc.

  • bpo-32894: Support unparsing of infinity numbers in postponed annotations. Patch by Batuhan Taşkaya.

  • bpo-37207: Speed up calls to list() by using the PEP 590 vectorcall calling convention. Patch by Mark Shannon.

Library

  • bpo-40398: typing.get_args() now always returns an empty tuple for special generic aliases.

  • bpo-40396: Functions typing.get_origin(), typing.get_args() and typing.get_type_hints() support now generic aliases like list[int].

  • bpo-38061: Optimize the subprocess module on FreeBSD using closefrom(). A single close(fd) syscall is cheap, but when sysconf(_SC_OPEN_MAX) is high, the loop calling close(fd) on each file descriptor can take several milliseconds.

    The workaround on FreeBSD to improve performance was to load and mount the fdescfs kernel module, but this is not enabled by default.

    Initial patch by Ed Maste (emaste), Conrad Meyer (cem), Kyle Evans (kevans) and Kubilay Kocak (koobs): https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=242274

  • bpo-38061: On FreeBSD, os.closerange(fd_low, fd_high) now calls closefrom(fd_low) if fd_high is greater than or equal to sysconf(_SC_OPEN_MAX).

    Initial patch by Ed Maste (emaste), Conrad Meyer (cem), Kyle Evans (kevans) and Kubilay Kocak (koobs): https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=242274

  • bpo-40360: The lib2to3 module is pending deprecation due to PEP 617.

  • bpo-40138: Fix the Windows implementation of os.waitpid() for exit code larger than INT_MAX >> 8. The exit status is now interpreted as an unsigned number.

  • bpo-39942: Set "__main__" as the default module name when "__name__" is missing in typing.TypeVar. Patch by Weipeng Hong.

  • bpo-40275: The logging package is now imported lazily in unittest only when the assertLogs() assertion is used.

  • bpo-40275: The asyncio package is now imported lazily in unittest only when the IsolatedAsyncioTestCase class is used.

  • bpo-40330: In ShareableList.__setitem__(), check the size of a new string item after encoding it to utf-8, not before.

  • bpo-40148: Added pathlib.Path.with_stem() to create a new Path with the stem replaced.

  • bpo-40325: Deprecated support for set objects in random.sample().

  • bpo-40257: Improved help for the typing module. Docstrings are now shown for all special forms and special generic aliases (like Union and List). Using help() with generic alias like List[int] will show the help for the correspondent concrete type (list in this case).

  • bpo-40257: func:inspect.getdoc no longer returns docstring inherited from the type of the object or from parent class if it is a class if it is not defined in the object itself. In pydoc the documentation string is now shown not only for class, function, method etc, but for any object that has its own __doc__ attribute.

  • bpo-40287: Fixed SpooledTemporaryFile.seek() to return the position.

  • bpo-40290: Added zscore() to statistics.NormalDist().

  • bpo-40282: Allow random.getrandbits(0) to succeed and to return 0.

  • bpo-40286: Add random.randbytes() function and random.Random.randbytes() method to generate random bytes.

  • bpo-40277: collections.namedtuple() now provides a human-readable repr for its field accessors.

  • bpo-40270: The included copy of sqlite3 on Windows is now compiled with the json extension. This allows the use of functions such as json_object.

  • bpo-29255: Wait in KqueueSelector.select when no fds are registered

  • bpo-40260: Ensure modulefinder uses io.open_code() and respects coding comments.

  • bpo-40234: Allow again to spawn daemon threads in subinterpreters (revert change which denied them).

  • bpo-39207: Workers in ProcessPoolExecutor are now spawned on demand, only when there are no available idle workers to reuse. This optimizes startup overhead and reduces the amount of lost CPU time to idle workers. Patch by Kyle Stanley.

  • bpo-40091: Fix a hang at fork in the logging module: the new private _at_fork_reinit() method is now used to reinitialize locks at fork in the child process.

  • bpo-40149: Implement traverse and clear slots in _abc._abc_data type.

  • bpo-40208: Remove deprecated symtable.SymbolTable.has_exec().

  • bpo-40196: Fix a bug in the symtable module that was causing incorrectly report global variables as local. Patch by Pablo Galindo.

  • bpo-40190: Add support for _SC_AIX_REALMEM to posix.sysconf().

  • bpo-40182: Removed the _field_types attribute of the typing.NamedTuple class.

  • bpo-36517: Multiple inheritance with typing.NamedTuple now raises an error instead of silently ignoring other types.

  • bpo-40126: Fixed reverting multiple patches in unittest.mock. Patcher's __exit__() is now never called if its __enter__() is failed. Returning true from __exit__() silences now the exception.

  • bpo-40094: CGIHTTPRequestHandler of http.server now logs the CGI script exit code, rather than the CGI script exit status of os.waitpid(). For example, if the script is killed by signal 11, it now logs: "CGI script exit code -11."

  • bpo-40108: Improve the error message when triying to import a module using runpy and incorrently use the ".py" extension at the end of the module name. Patch by Pablo Galindo.

  • bpo-40094: Add os.waitstatus_to_exitcode() function: convert a wait status to an exit code.

  • bpo-40089: Fix threading._after_fork(): if fork was not called by a thread spawned by threading.Thread, threading._after_fork() now creates a _MainThread instance for _main_thread, instead of a _DummyThread instance.

  • bpo-40089: Add a private _at_fork_reinit() method to _thread.Lock, _thread.RLock, threading.RLock and threading.Condition classes: reinitialize the lock at fork in the child process, reset the lock to the unlocked state. Rename also the private _reset_internal_locks() method of threading.Event to _at_fork_reinit().

  • bpo-25780: Expose CAN_RAW_JOIN_FILTERS in the socket module.

  • bpo-39503: AbstractBasicAuthHandler of urllib.request now parses all WWW-Authenticate HTTP headers and accepts multiple challenges per header: use the realm of the first Basic challenge.

  • bpo-39812: Removed daemon threads from concurrent.futures by adding an internal threading._register_atexit(), which calls registered functions prior to joining all non-daemon threads. This allows for compatibility with subinterpreters, which don't support daemon threads.

  • bpo-40050: Fix importlib._bootstrap_external: avoid creating a new winreg builtin module if it's already available in sys.modules, and remove redundant imports.

  • bpo-40014: Fix os.getgrouplist(): if getgrouplist() function fails because the group list is too small, retry with a larger group list. On failure, the glibc implementation of getgrouplist() sets ngroups to the total number of groups. For other implementations, double the group list size.

  • bpo-40017: Add time.CLOCK_TAI constant if the operating system support it.

  • bpo-40016: In re docstring, clarify the relationship between inline and argument compile flags.

  • bpo-39953: Update internal table of OpenSSL error codes in the ssl module.

  • bpo-36144: Added PEP 584 operators to weakref.WeakValueDictionary.

  • bpo-36144: Added PEP 584 operators to weakref.WeakKeyDictionary.

  • bpo-38891: Fix linear runtime behaviour of the __getitem__ and __setitem__ methods in multiprocessing.shared_memory.ShareableList. This avoids quadratic performance when iterating a ShareableList. Patch by Thomas Krennwallner.

  • bpo-39682: Remove undocumented support for closing a pathlib.Path object via its context manager. The context manager magic methods remain, but they are now a no-op, making Path objects immutable.

  • bpo-36144: Added PEP 584 operators (| and |=) to collections.ChainMap.

  • bpo-39011: Normalization of line endings in ElementTree attributes was removed, as line endings which were replaced by entity numbers should be preserved in original form.

  • bpo-38410: Properly handle sys.audit() failures in sys.set_asyncgen_hooks().

  • bpo-36541: lib2to3 now recognizes named assignment expressions (the walrus operator, :=)

  • bpo-35967: In platform, delay the invocation of 'uname -p' until the processor attribute is requested.

  • bpo-35113: inspect.getsource() now returns correct source code for inner class with same name as module level class. Decorators are also returned as part of source of the class. Patch by Karthikeyan Singaravelan.

  • bpo-33262: Deprecate passing None as an argument for shlex.split()'s s parameter. Patch by Zackery Spytz.

  • bpo-31758: Prevent crashes when using an uninitialized _elementtree.XMLParser object. Patch by Oren Milman.

Documentation

  • bpo-27635: The pickle documentation incorrectly claimed that __new__ isn't called by default when unpickling.

  • bpo-39879: Updated 데이터 모델 docs to include dict() insertion order preservation. Patch by Furkan Onder and Samy Lahfa.

  • bpo-38387: Document PyDoc_STRVAR macro in the C-API reference.

  • bpo-13743: Some methods within xml.dom.minidom.Element class are now better documented.

Tests

  • bpo-31904: Set expected default encoding in test_c_locale_coercion.py for VxWorks RTOS.

  • bpo-40162: Update Travis CI configuration to OpenSSL 1.1.1f.

  • bpo-40146: Update OpenSSL to 1.1.1f in Azure Pipelines.

  • bpo-40094: Add test.support.wait_process() function.

  • bpo-40003: test.bisect_cmd now copies Python command line options like -O or -W. Moreover, emit a warning if test.bisect_cmd is used with -w/--verbose2 option.

  • bpo-39380: Add the encoding in ftplib.FTP and ftplib.FTP_TLS to the constructor as keyword-only and change the default from latin-1 to utf-8 to follow RFC 2640.

  • bpo-39793: Use the same domain when testing make_msgid. Patch by Batuhan Taskaya.

  • bpo-1812: Fix newline handling in doctest.testfile when loading from a package whose loader has a get_data method. Patch by Peter Donis.

Build

  • bpo-38360: Support single-argument form of macOS -isysroot flag.

  • bpo-40158: Fix CPython MSBuild Properties in NuGet Package (build/native/python.props)

  • bpo-38527: Fix configure check on Solaris for "float word ordering": sometimes, the correct "grep" command was not being used. Patch by Arnon Yaari.

Windows

  • bpo-40164: Updates Windows to OpenSSL 1.1.1f

  • bpo-8901: Ignore the Windows registry when the -E option is used.

macOS

  • bpo-38329: python.org macOS installers now update the Current version symlink of /Library/Frameworks/Python.framework/Versions for 3.9 installs. Previously, Current was only updated for Python 2.x installs. This should make it easier to embed Python 3 into other macOS applications.

  • bpo-40164: Update macOS installer builds to use OpenSSL 1.1.1g.

IDLE

  • bpo-38439: Add a 256×256 pixel IDLE icon to support more modern environments. Created by Andrew Clover. Delete the unused macOS idle.icns icon file.

  • bpo-38689: IDLE will no longer freeze when inspect.signature fails when fetching a calltip.

Tools/Demos

C API

Python 3.9.0 alpha 5

Release date: 2020-03-23

Security

  • bpo-38576: Disallow control characters in hostnames in http.client, addressing CVE-2019-18348. Such potentially malicious header injection URLs now cause a InvalidURL to be raised.

Core and Builtins

  • bpo-40010: Optimize pending calls in multithreaded applications. If a thread different than the main thread schedules a pending call (Py_AddPendingCall()), the bytecode evaluation loop is no longer interrupted at each bytecode instruction to check for pending calls which cannot be executed. Only the main thread can execute pending calls.

    Previously, the bytecode evaluation loop was interrupted at each instruction until the main thread executes pending calls.

  • bpo-1635741: Port _weakref extension module to multiphase initialization (PEP 489).

  • bpo-1635741: Port _collections module to multiphase initialization (PEP 489).

  • bpo-40010: Optimize signal handling in multithreaded applications. If a thread different than the main thread gets a signal, the bytecode evaluation loop is no longer interrupted at each bytecode instruction to check for pending signals which cannot be handled. Only the main thread of the main interpreter can handle signals.

    Previously, the bytecode evaluation loop was interrupted at each instruction until the main thread handles signals.

  • bpo-39984: If Py_AddPendingCall() is called in a subinterpreter, the function is now scheduled to be called from the subinterpreter, rather than being called from the main interpreter. Each subinterpreter now has its own list of scheduled calls.

  • bpo-1635741: Port _heapq module to multiphase initialization.

  • bpo-1635741: Port itertools module to multiphase initialization (PEP 489).

  • bpo-37207: Speed up calls to frozenset() by using the PEP 590 vectorcall calling convention. Patch by Dong-hee Na.

  • bpo-39984: subinterpreters: Move _PyRuntimeState.ceval.tracing_possible to PyInterpreterState.ceval.tracing_possible: each interpreter now has its own variable.

  • bpo-37207: Speed up calls to set() by using the PEP 590 vectorcall calling convention. Patch by Dong-hee Na.

  • bpo-1635741: Port _statistics module to multiphase initialization (PEP 489).

  • bpo-39968: Use inline function to replace extension modules' get_module_state macros.

  • bpo-39965: Correctly raise SyntaxError if await is used inside non-async functions and PyCF_ALLOW_TOP_LEVEL_AWAIT is set (like in the asyncio REPL). Patch by Pablo Galindo.

  • bpo-39562: Allow executing asynchronous comprehensions on the top level when the PyCF_ALLOW_TOP_LEVEL_AWAIT flag is given. Patch by Batuhan Taskaya.

  • bpo-37207: Speed up calls to tuple() by using the PEP 590 vectorcall calling convention. Patch by Dong-hee Na.

  • bpo-38373: Chaged list overallocation strategy. It no longer overallocates if the new size is closer to overalocated size than to the old size and adds padding.

  • bpo-39926: Update Unicode database to Unicode version 13.0.0.

  • bpo-19466: Clear the frames of daemon threads earlier during the Python shutdown to call objects destructors. So "unclosed file" resource warnings are now emitted for daemon threads in a more reliable way.

  • bpo-38894: Fix a bug that was causing incomplete results when calling pathlib.Path.glob in the presence of symlinks that point to files where the user does not have read access. Patch by Pablo Galindo and Matt Wozniski.

  • bpo-39877: Fix PyEval_RestoreThread() random crash at exit with daemon threads. It now accesses the _PyRuntime variable directly instead of using tstate->interp->runtime, since tstate can be a dangling pointer after Py_Finalize() has been called. Moreover, the daemon thread now exits before trying to take the GIL.

  • bpo-39871: Fix a possible SystemError in math.{atan2,copysign,remainder}() when the first argument cannot be converted to a float. Patch by Zackery Spytz.

  • bpo-39776: Fix race condition where threads created by PyGILState_Ensure() could get a duplicate id.

    This affects consumers of tstate->id like the contextvar caching machinery, which could return invalid cached objects under heavy thread load (observed in embedded scenarios).

  • bpo-39778: Fixed a crash due to incorrect handling of weak references in collections.OrderedDict classes. Patch by Pablo Galindo.

  • bpo-1635741: Port audioop extension module to multiphase initialization (PEP 489).

  • bpo-39702: Relax decorator grammar restrictions to allow any valid expression (PEP 614).

  • bpo-38091: Tweak import deadlock detection code to not deadlock itself.

  • bpo-1635741: Port _locale extension module to multiphase initialization (PEP 489).

  • bpo-39087: Optimize PyUnicode_AsUTF8() and PyUnicode_AsUTF8AndSize() slightly when they need to create internal UTF-8 cache.

  • bpo-39520: Fix unparsing of ext slices with no items (foo[:,]). Patch by Batuhan Taskaya.

  • bpo-39220: Do not optimize annotations if 'from __future__ import annotations' is used. Patch by Pablo Galindo.

  • bpo-35712: Using NotImplemented in a boolean context has been deprecated. Patch contributed by Josh Rosenberg.

  • bpo-22490: Don't leak environment variable __PYVENV_LAUNCHER__ into the interpreter session on macOS.

Library

  • bpo-39830: Add zipfile.Path to __all__ in the zipfile module.

  • bpo-40000: Improved error messages for validation of ast.Constant nodes. Patch by Batuhan Taskaya.

  • bpo-39999: __module__ of the AST node classes is now set to "ast" instead of "_ast". Added docstrings for dummy AST node classes and deprecated attributes.

  • bpo-39991: uuid.getnode() now skips IPv6 addresses with the same string length than a MAC address (17 characters): only use MAC addresses.

  • bpo-39988: Deprecated ast.AugLoad and ast.AugStore node classes because they are no longer used.

  • bpo-39656: Ensure bin/python3.# is always present in virtual environments on POSIX platforms - by Anthony Sottile.

  • bpo-39969: Deprecated ast.Param node class because it's no longer used. Patch by Batuhan Taskaya.

  • bpo-39360: Ensure all workers exit when finalizing a multiprocessing.Pool implicitly via the module finalization handlers of multiprocessing. This fixes a deadlock situation that can be experienced when the Pool is not properly finalized via the context manager or a call to multiprocessing.Pool.terminate. Patch by Batuhan Taskaya and Pablo Galindo.

  • bpo-35370: sys.settrace(), sys.setprofile() and _lsprof.Profiler.enable() now properly report PySys_Audit() error if "sys.setprofile" or "sys.settrace" audit event is denied.

  • bpo-39936: AIX: Fix _aix_support module when the subprocess is not available, when building Python from scratch. It now uses new private _bootsubprocess module, rather than having two implementations depending if subprocess is available or not. So _aix_support.aix_platform() result is now the same if subprocess is available or not.

  • bpo-36144: collections.OrderedDict now implements | and |= (PEP 584).

  • bpo-39652: The column name found in sqlite3.Cursor.description is now truncated on the first '[' only if the PARSE_COLNAMES option is set.

  • bpo-39915: Ensure unittest.mock.AsyncMock.await_args_list has call objects in the order of awaited arguments instead of using unittest.mock.Mock.call_args which has the last value of the call. Patch by Karthikeyan Singaravelan.

  • bpo-36144: Updated os.environ and os.environb to support PEP 584's merge (|) and update (|=) operators.

  • bpo-38662: The ensurepip module now invokes pip via the runpy module. Hence it is no longer tightly coupled with the internal API of the bundled pip version, allowing easier updates to a newer pip version both internally and for distributors.

  • bpo-38075: Fix the random.Random.seed() method when a bool is passed as the seed.

  • bpo-39916: More reliable use of os.scandir() in Path.glob(). It no longer emits a ResourceWarning when interrupted.

  • bpo-39850: multiprocessing now supports abstract socket addresses (if abstract sockets are supported in the running platform). When creating arbitrary addresses (like when default-constructing multiprocessing.connection.Listener objects) abstract sockets are preferred to avoid the case when the temporary-file-generated address is too large for an AF_UNIX socket address. Patch by Pablo Galindo.

  • bpo-36287: ast.dump() no longer outputs optional fields and attributes with default values. The default values for optional fields and attributes of AST nodes are now set as class attributes (e.g. Constant.kind is set to None).

  • bpo-39889: Fixed ast.unparse() for extended slices containing a single element (e.g. a[i:j,]). Remove redundant tuples when index with a tuple (e.g. a[i, j]).

  • bpo-39828: Fix json.tool to catch BrokenPipeError. Patch by Dong-hee Na.

  • bpo-13487: Avoid a possible "RuntimeError: dictionary changed size during iteration" from inspect.getmodule() when it tried to loop through sys.modules.

  • bpo-39674: Revert "bpo-37330: open() no longer accept 'U' in file mode". The "U" mode of open() is kept in Python 3.9 to ease transition from Python 2.7, but will be removed in Python 3.10.

  • bpo-28577: The hosts method on 32-bit prefix length IPv4Networks and 128-bit prefix IPv6Networks now returns a list containing the single Address instead of an empty list.

  • bpo-39826: Add getConnection method to logging HTTPHandler to enable custom connections.

  • bpo-39763: Reimplement distutils.spawn.spawn() function with the subprocess module.

  • bpo-39794: Add --without-decimal-contextvar build option. This enables a thread-local rather than a coroutine local context.

  • bpo-36144: collections.defaultdict now implements | (PEP 584).

  • bpo-39517: Fix runpy.run_path() when using pathlike objects

  • bpo-39775: Change inspect.Signature.parameters back to collections.OrderedDict. This was changed to dict in Python 3.9.0a4.

  • bpo-39678: Refactor queue_manager in concurrent.futures.ProcessPoolExecutor to make it easier to maintain.

  • bpo-39764: Fix AttributeError when calling get_stack on a PyAsyncGenObject Task

  • bpo-39769: The compileall.compile_dir() function's ddir parameter and the compileall command line flag -d no longer write the wrong pathname to the generated pyc file for submodules beneath the root of the directory tree being compiled. This fixes a regression introduced with Python 3.5.

  • bpo-36144: types.MappingProxyType objects now support the merge (|) operator from PEP 584.

  • bpo-38691: The importlib module now ignores the PYTHONCASEOK environment variable when the -E or -I command line options are being used.

  • bpo-39719: Remove tempfile.SpooledTemporaryFile.softspace() as files no longer have the softspace attribute in Python 3. Patch by Shantanu.

  • bpo-39667: Improve pathlib.Path compatibility on zipfile.Path and correct performance degradation as found in zipp 3.0.

  • bpo-39638: Keep ASDL signatures in the docstrings for AST nodes. Patch by Batuhan Taskaya

  • bpo-39639: Deprecated ast.Suite node class because it's no longer used. Patch by Batuhan Taskaya.

  • bpo-39609: Add thread_name_prefix to default asyncio executor

  • bpo-39548: Fix handling of header in urllib.request.AbstractDigestAuthHandler when the optional qop parameter is not present.

  • bpo-39509: HTTP status codes 103 EARLY_HINTS and 425 TOO_EARLY are added to http.HTTPStatus. Patch by Dong-hee Na.

  • bpo-39507: Adding HTTP status 418 "I'm a Teapot" to HTTPStatus in http library. Patch by Ross Rhodes.

  • bpo-39495: Remove default value from attrs parameter of xml.etree.ElementTree.TreeBuilder.start() for consistency between Python and C implementations.

  • bpo-38971: Open issue in the BPO indicated a desire to make the implementation of codecs.open() at parity with io.open(), which implements a try/except to assure file stream gets closed before an exception is raised.

  • bpo-38641: Added starred expressions support to return and yield statements for lib2to3. Patch by Vlad Emelianov.

  • bpo-37534: When using minidom module to generate XML documents the ability to add Standalone Document Declaration is added. All the changes are made to generate a document in compliance with Extensible Markup Language (XML) 1.0 (Fifth Edition) W3C Recommendation (available here: https://www.w3.org/TR/xml/#sec-prolog-dtd).

  • bpo-34788: Add support for scoped IPv6 addresses to ipaddress. Patch by Oleksandr Pavliuk.

  • bpo-34822: Simplified AST for subscription. Simple indices are now represented by their value, extended slices are represented as tuples. ast classes Index and ExtSlice are considered deprecated and will be removed in future Python versions. In the meantime, Index(value) now returns a value itself, ExtSlice(slices) returns Tuple(slices, Load()).

Documentation

  • bpo-39868: Updated the Language Reference for PEP 572.

  • bpo-13790: Change 'string' to 'specification' in format doc.

  • bpo-17422: The language reference no longer restricts default class namespaces to dicts only.

  • bpo-39530: Fix misleading documentation about mixed-type numeric comparisons.

  • bpo-39718: Update token documentation to reflect additions in Python 3.8

  • bpo-39677: Changed operand name of MAKE_FUNCTION from argc to flags for module dis

Tests

  • bpo-40019: test_gdb now skips tests if it detects that gdb failed to read debug information because the Python binary is optimized.

  • bpo-27807: test_site.test_startup_imports() is now skipped if a path of sys.path contains a .pth file.

  • bpo-26067: Do not fail test_shutil test_chown test when uid or gid of user cannot be resolved to a name.

  • bpo-39855: test_subprocess.test_user() now skips the test on an user name if the user name doesn't exist. For example, skip the test if the user "nobody" doesn't exist on Linux.

Build

  • bpo-39761: Fix build with DTrace but without additional DFLAGS.

  • bpo-39763: setup.py now uses a basic implementation of the subprocess module if the subprocess module is not available: before required C extension modules are built.

  • bpo-1294959: Add --with-platlibdir option to the configure script: name of the platform-specific library directory, stored in the new sys.platlibdir attribute. It is used to build the path of platform-specific extension modules and the path of the standard library. It is equal to "lib" on most platforms. On Fedora and SuSE, it is equal to "lib64" on 64-bit platforms. Patch by Jan Matějek, Matěj Cepl, Charalampos Stratakis and Victor Stinner.

Windows

  • bpo-39930: Ensures the required vcruntime140.dll is included in install packages.

  • bpo-39847: Avoid hang when computer is hibernated whilst waiting for a mutex (for lock-related objects from threading) around 49-day uptime.

  • bpo-38597: distutils will no longer statically link vcruntime140.dll when a redistributable version is unavailable. All future releases of CPython will include a copy of this DLL to ensure distributed extensions can continue to load.

  • bpo-38380: Update Windows builds to use SQLite 3.31.1

  • bpo-39789: Update Windows release build machines to Visual Studio 2019 (MSVC 14.2).

  • bpo-34803: Package for nuget.org now includes repository reference and bundled icon image.

macOS

  • bpo-38380: Update macOS builds to use SQLite 3.31.1

IDLE

  • bpo-27115: For 'Go to Line', use a Query box subclass with IDLE standard behavior and improved error checking.

  • bpo-39885: Since clicking to get an IDLE context menu moves the cursor, any text selection should be and now is cleared.

  • bpo-39852: Edit "Go to line" now clears any selection, preventing accidental deletion. It also updates Ln and Col on the status bar.

  • bpo-39781: Selecting code context lines no longer causes a jump.

Tools/Demos

  • bpo-36184: Port python-gdb.py to FreeBSD. python-gdb.py now checks for "take_gil" function name to check if a frame tries to acquire the GIL, instead of checking for "pthread_cond_timedwait" which is specific to Linux and can be a different condition than the GIL.

  • bpo-38080: Added support to fix getproxies in the lib2to3.fixes.fix_urllib module. Patch by José Roberto Meza Cabrera.

C API

Python 3.9.0 alpha 4

Release date: 2020-02-25

Security

Core and Builtins

  • bpo-39382: Fix a use-after-free in the single inheritance path of issubclass(), when the __bases__ of an object has a single reference, and so does its first item. Patch by Yonatan Goldschmidt.

  • bpo-39573: Update clinic tool to use Py_IS_TYPE(). Patch by Dong-hee Na.

  • bpo-39619: Enable use of os.chroot() on HP-UX systems.

  • bpo-39573: Add Py_IS_TYPE() static inline function to check whether the object o type is type.

  • bpo-39606: Fix regression caused by fix for bpo-39386, that prevented calling aclose on an async generator that had already been closed or exhausted.

  • bpo-39579: Change the ending column offset of Attribute nodes constructed in ast_for_dotted_name to point at the end of the current node and not at the end of the last NAME node.

  • bpo-1635741: Port _crypt extension module to multiphase initialization (PEP 489).

  • bpo-1635741: Port _contextvars extension module to multiphase initialization (PEP 489).

  • bpo-39510: Fix segfault in readinto() method on closed BufferedReader.

  • bpo-39502: Fix time.localtime() on 64-bit AIX to support years before 1902 and after 2038. Patch by M Felt.

  • bpo-39492: Fix a reference cycle in the C Pickler that was preventing the garbage collection of deleted, pickled objects.

  • bpo-39453: Fixed a possible crash in list.__contains__() when a list is changed during comparing items. Patch by Dong-hee Na.

  • bpo-39434: floor division of float operation now has a better performance. Also the message of ZeroDivisionError for this operation is updated. Patch by Dong-hee Na.

  • bpo-1635741: Port _codecs extension module to multiphase initialization (PEP 489).

  • bpo-1635741: Port _bz2 extension module to multiphase initialization (PEP 489).

  • bpo-1635741: Port _abc extension module to multiphase initialization (PEP 489).

  • bpo-39320: Replace two complex bytecodes for building dicts with two simpler ones. The new bytecodes DICT_MERGE and DICT_UPDATE have been added The old bytecodes BUILD_MAP_UNPACK and BUILD_MAP_UNPACK_WITH_CALL have been removed.

  • bpo-39219: Syntax errors raised in the tokenizer now always set correct "text" and "offset" attributes.

  • bpo-36051: Drop the GIL during large bytes.join operations. Patch by Bruce Merry.

  • bpo-38960: Fix DTrace build issues on FreeBSD. Patch by David Carlier.

  • bpo-37207: Speed up calls to range() by about 30%, by using the PEP 590 vectorcall calling convention. Patch by Mark Shannon.

  • bpo-36144: dict (and collections.UserDict) objects now support PEP 584's merge (|) and update (|=) operators. Patch by Brandt Bucher.

  • bpo-32856: Optimized the idiom for assignment a temporary variable in comprehensions. Now for y in [expr] in comprehensions is as fast as a simple assignment y = expr.

Library

  • bpo-30566: Fix IndexError when trying to decode an invalid string with punycode codec.

  • bpo-39649: Remove obsolete check for __args__ in bdb.Bdb.format_stack_entry.

  • bpo-39648: Expanded math.gcd() and math.lcm() to handle multiple arguments.

  • bpo-39681: Fix a regression where the C pickle module wouldn't allow unpickling from a file-like object that doesn't expose a readinto() method.

  • bpo-35950: Raise io.UnsupportedOperation in io.BufferedReader.truncate() when it is called on a read-only io.BufferedReader instance.

  • bpo-39479: Add math.lcm() function: least common multiple.

  • bpo-39674: Revert "Do not expose abstract collection classes in the collections module" change (bpo-25988). Aliases to ABC like collections.Mapping are kept in Python 3.9 to ease transition from Python 2.7, but will be removed in Python 3.10.

  • bpo-39104: Fix hanging ProcessPoolExcutor on shutdown(wait=False) when a task has failed pickling.

  • bpo-39627: Fixed TypedDict totality check for inherited keys.

  • bpo-39474: Fixed starting position of AST for expressions like (a)(b), (a)[b] and (a).b.

  • bpo-21016: The pydoc and trace modules now use the sysconfig module to get the path to the Python standard library, to support uncommon installation path like /usr/lib64/python3.9/ on Fedora. Patch by Jan Matějek.

  • bpo-39590: Collections.deque now holds strong references during deque.__contains__ and deque.count, fixing crashes.

  • bpo-39586: The distutils bdist_msi command is deprecated in Python 3.9, use bdist_wheel (wheel packages) instead.

  • bpo-39595: Improved performance of zipfile.Path for files with a large number of entries. Also improved performance and fixed minor issue as published with importlib_metadata 1.5.

  • bpo-39350: Fix regression in fractions.Fraction if the numerator and/or the denominator is an int subclass. The math.gcd() function is now used to normalize the numerator and denominator. math.gcd() always return a int type. Previously, the GCD type depended on numerator and denominator.

  • bpo-39567: Added audit for os.walk(), os.fwalk(), pathlib.Path.glob() and pathlib.Path.rglob().

  • bpo-39559: Remove unused, undocumented argument getters from uuid.getnode()

  • bpo-38149: sys.audit() is now called only once per call of glob.glob() and glob.iglob().

  • bpo-39546: Fix a regression in ArgumentParser where allow_abbrev=False was ignored for long options that used a prefix character other than "-".

  • bpo-39450: Striped whitespace from docstring before returning it from unittest.case.shortDescription().

  • bpo-12915: A new function resolve_name has been added to the pkgutil module. This resolves a string of the form 'a.b.c.d' or 'a.b:c.d' to an object. In the example, a.b is a package/module and c.d is an object within that package/module reached via recursive attribute access.

  • bpo-39353: The binascii.crc_hqx() function is no longer deprecated.

  • bpo-39493: Mark typing.IO.closed as a property

  • bpo-39491: Add typing.Annotated and include_extras parameter to typing.get_type_hints() as part of PEP 593. Patch by Till Varoquaux, documentation by Till Varoquaux and Konstantin Kashin.

  • bpo-39485: Fix a bug in unittest.mock.create_autospec() that would complain about the wrong number of arguments for custom descriptors defined in an extension module returning functions.

  • bpo-38932: Mock fully resets child objects on reset_mock(). Patch by Vegard Stikbakke

  • bpo-39082: Allow AsyncMock to correctly patch static/class methods

  • bpo-39432: Implement PEP-489 algorithm for non-ascii "PyInit_..." symbol names in distutils to make it export the correct init symbol also on Windows.

  • bpo-18819: Omit devmajor and devminor fields for non-device files in tarfile archives, enabling bit-for-bit compatibility with GNU tar(1).

  • bpo-39349: Added a new cancel_futures parameter to concurrent.futures.Executor.shutdown() that cancels all pending futures which have not started running, instead of waiting for them to complete before shutting down the executor.

  • bpo-39274: bool(fraction.Fraction) now returns a boolean even if (numerator != 0) does not return a boolean (ex: numpy number).

  • bpo-34793: Remove support for with (await asyncio.lock): and with (yield from asyncio.lock):. The same is correct for asyncio.Condition and asyncio.Semaphore.

  • bpo-25597: Ensure, if wraps is supplied to unittest.mock.MagicMock, it is used to calculate return values for the magic methods instead of using the default return values. Patch by Karthikeyan Singaravelan.

  • bpo-36350: inspect.Signature.parameters and inspect.BoundArguments.arguments are now dicts instead of OrderedDicts. Patch contributed by Rémi Lapeyre.

  • bpo-35727: Fix sys.exit() and sys.exit(None) exit code propagation when used in multiprocessing.Process.

  • bpo-32173: * Add lazycache function to __all__. * Use dict.clear to clear the cache. * Refactoring getline function and checkcache function.

Documentation

  • bpo-17422: The language reference now specifies restrictions on class namespaces. Adapted from a patch by Ethan Furman.

  • bpo-39572: Updated documentation of total flag of TypeDict.

  • bpo-39654: In pyclbr doc, update 'class' to 'module' where appropriate and add readmodule comment. Patch by Hakan Çelik.

  • bpo-39153: Clarify refcounting semantics for the following functions: - PyObject_SetItem - PyMapping_SetItemString - PyDict_SetItem - PyDict_SetItemString

  • bpo-39392: Explain that when filling with turtle, overlap regions may be left unfilled.

  • bpo-39369: Update mmap readline method description. The fact that the readline method does update the file position should not be ignored since this might give the impression for the programmer that it doesn't update it.

  • bpo-9056: Include subsection in TOC for PDF version of docs.

Tests

Build

  • bpo-39489: Remove COUNT_ALLOCS special build.

Windows

  • bpo-39553: Delete unused code related to SxS manifests.

  • bpo-39439: Honor the Python path when a virtualenv is active on Windows.

  • bpo-39393: Improve the error message when attempting to load a DLL with unresolved dependencies.

  • bpo-38883: home() and expanduser() on Windows now prefer USERPROFILE and no longer use HOME, which is not normally set for regular user accounts. This makes them again behave like os.path.expanduser(), which was changed to ignore HOME in 3.8, see bpo-36264.

  • bpo-39185: The build.bat script has additional options for very-quiet output (-q) and very-verbose output (-vv)

IDLE

  • bpo-39663: Add tests for pyparse find_good_parse_start().

  • bpo-39600: In the font configuration window, remove duplicated font names.

  • bpo-30780: Add remaining configdialog tests for buttons and highlights and keys tabs.

  • bpo-39388: IDLE Settings Cancel button now cancels pending changes

  • bpo-38792: Close an IDLE shell calltip if a KeyboardInterrupt or shell restart occurs. Patch by Zackery Spytz.

C API

  • bpo-35081: Move the bytes_methods.h header file to the internal C API as pycore_bytes_methods.h: it only contains private symbols (prefixed by _Py), except of the PyDoc_STRVAR_shared() macro.

  • bpo-35081: Move the dtoa.h header file to the internal C API as pycore_dtoa.h: it only contains private functions (prefixed by _Py). The math and cmath modules must now be compiled with the Py_BUILD_CORE macro defined.

  • bpo-39573: Add Py_SET_SIZE() function to set the size of an object.

  • bpo-39500: PyUnicode_IsIdentifier() does not call Py_FatalError() anymore if the string is not ready.

  • bpo-39573: Add Py_SET_TYPE() function to set the type of an object.

  • bpo-39573: Add a Py_SET_REFCNT() function to set the reference counter of an object.

  • bpo-39542: Convert PyType_HasFeature(), PyType_Check() and PyType_CheckExact() macros to static inline functions.

  • bpo-39542: In the limited C API, PyObject_INIT() and PyObject_INIT_VAR() are now defined as aliases to PyObject_Init() and PyObject_InitVar() to make their implementation opaque. It avoids to leak implementation details in the limited C API. Exclude the following functions from the limited C API: _Py_NewReference(), _Py_ForgetReference(), _PyTraceMalloc_NewReference() and _Py_GetRefTotal().

  • bpo-39542: Exclude trashcan mechanism from the limited C API: it requires access to PyTypeObject and PyThreadState structure fields, whereas these structures are opaque in the limited C API.

  • bpo-39511: The PyThreadState_Clear() function now calls the PyThreadState.on_delete callback. Previously, that happened in PyThreadState_Delete().

  • bpo-38076: Fix to clear the interpreter state only after clearing module globals to guarantee module state access from C Extensions during runtime destruction

  • bpo-39245: The Vectorcall API (PEP 590) was made public, adding the functions PyObject_Vectorcall, PyObject_VectorcallMethod, PyVectorcall_Function, PyObject_CallOneArg, PyObject_CallMethodNoArgs, PyObject_CallMethodOneArg, PyObject_FastCallDict, and the flag Py_TPFLAGS_HAVE_VECTORCALL.

Python 3.9.0 alpha 3

Release date: 2020-01-24

Core and Builtins

  • bpo-39427: Document all possibilities for the -X options in the command line help section. Patch by Pablo Galindo.

  • bpo-39421: Fix possible crashes when operating with the functions in the heapq module and custom comparison operators.

  • bpo-39386: Prevent double awaiting of async iterator.

  • bpo-17005: Add functools.TopologicalSorter to the functools module to offers functionality to perform topological sorting of graphs. Patch by Pablo Galindo, Tim Peters and Larry Hastings.

  • bpo-39320: Replace four complex bytecodes for building sequences with three simpler ones.

    The following four bytecodes have been removed:

    • BUILD_LIST_UNPACK

    • BUILD_TUPLE_UNPACK

    • BUILD_SET_UNPACK

    • BUILD_TUPLE_UNPACK_WITH_CALL

    The following three bytecodes have been added:

    • LIST_TO_TUPLE

    • LIST_EXTEND

    • SET_UPDATE

  • bpo-39336: Import loaders which publish immutable module objects can now publish immutable packages in addition to individual modules.

  • bpo-39322: Added a new function gc.is_finalized() to check if an object has been finalized by the garbage collector. Patch by Pablo Galindo.

  • bpo-39048: Improve the displayed error message when incorrect types are passed to async with statements by looking up the __aenter__() special method before the __aexit__() special method when entering an asynchronous context manager. Patch by Géry Ogam.

  • bpo-39235: Fix AST end location for lone generator expression in function call, e.g. f(i for i in a).

  • bpo-39209: Correctly handle multi-line tokens in interactive mode. Patch by Pablo Galindo.

  • bpo-1635741: Port _json extension module to multiphase initialization (PEP 489).

  • bpo-39216: Fix constant folding optimization for positional only arguments - by Anthony Sottile.

  • bpo-39215: Fix SystemError when nested function has annotation on positional-only argument - by Anthony Sottile.

  • bpo-39200: Correct the error message when calling the min() or max() with no arguments. Patch by Dong-hee Na.

  • bpo-39200: Correct the error message when trying to construct range objects with no arguments. Patch by Pablo Galindo.

  • bpo-39166: Fix incorrect line execution reporting in trace functions when tracing the last iteration of asynchronous for loops. Patch by Pablo Galindo.

  • bpo-39114: Fix incorrent line execution reporting in trace functions when tracing exception handlers with name binding. Patch by Pablo Galindo.

  • bpo-39156: Split the COMPARE_OP bytecode instruction into four distinct instructions.

    • COMPARE_OP for rich comparisons

    • IS_OP for 'is' and 'is not' tests

    • CONTAINS_OP for 'in' and 'is not' tests

    • JUMP_IF_NOT_EXC_MATCH for checking exceptions in 'try-except' statements.

    This improves the clarity of the interpreter and should provide a modest speedup.

  • bpo-38588: Fix possible crashes in dict and list when calling PyObject_RichCompareBool().

  • bpo-13601: By default, sys.stderr is line-buffered now, even if stderr is redirected to a file. You can still make sys.stderr unbuffered by passing the -u command-line option or setting the PYTHONUNBUFFERED environment variable.

    (Contributed by Jendrik Seipp in bpo-13601.)

  • bpo-38610: Fix possible crashes in several list methods by holding strong references to list elements when calling PyObject_RichCompareBool().

  • bpo-32021: Include brotli .br encoding in mimetypes encodings_map

Library

  • bpo-39430: Fixed race condition in lazy imports in tarfile.

  • bpo-39413: The os.unsetenv() function is now also available on Windows.

  • bpo-39390: Fixed a regression with the ignore callback of shutil.copytree(). The argument types are now str and List[str] again.

  • bpo-39395: The os.putenv() and os.unsetenv() functions are now always available.

  • bpo-39406: If setenv() C function is available, os.putenv() is now implemented with setenv() instead of putenv(), so Python doesn't have to handle the environment variable memory.

  • bpo-39396: Fix math.nextafter(-0.0, +0.0) on AIX 7.1.

  • bpo-29435: Allow tarfile.is_tarfile() to be used with file and file-like objects, like zipfile.is_zipfile(). Patch by William Woodruff.

  • bpo-39377: Removed encoding option from json.loads(). It has been deprecated since Python 3.1.

  • bpo-39389: Write accurate compression level metadata in gzip archives, rather than always signaling maximum compression.

  • bpo-39366: The previously deprecated xpath() and xgtitle() methods of nntplib.NNTP have been removed.

  • bpo-39357: Remove the buffering parameter of bz2.BZ2File. Since Python 3.0, it was ignored and using it was emitting DeprecationWarning. Pass an open file object, to control how the file is opened. The compresslevel parameter becomes keyword-only.

  • bpo-39353: Deprecate binhex4 and hexbin4 standards. Deprecate the binhex module and the following binascii functions: b2a_hqx(), a2b_hqx(), rlecode_hqx(), rledecode_hqx(), crc_hqx().

  • bpo-39351: Remove base64.encodestring() and base64.decodestring(), aliases deprecated since Python 3.1: use base64.encodebytes() and base64.decodebytes() instead.

  • bpo-39350: Remove fractions.gcd() function, deprecated since Python 3.5 (bpo-22486): use math.gcd() instead.

  • bpo-39329: LMTP constructor now has an optional timeout parameter. Patch by Dong-hee Na.

  • bpo-39313: Add a new exec_function option (--exec-function in the CLI) to RefactoringTool for making exec a function. Patch by Batuhan Taskaya.

  • bpo-39259: FTP_TLS and FTP_TLS now raise a ValueError if the given timeout for their constructor is zero to prevent the creation of a non-blocking socket. Patch by Dong-hee Na.

  • bpo-39259: SMTP and SMTP_SSL now raise a ValueError if the given timeout for their constructor is zero to prevent the creation of a non-blocking socket. Patch by Dong-hee Na.

  • bpo-39310: Add math.ulp(): return the value of the least significant bit of a float.

  • bpo-39297: Improved performance of importlib.metadata distribution discovery and resilients to inaccessible sys.path entries (importlib_metadata v1.4.0).

  • bpo-39259: NNTP and NNTP_SSL now raise a ValueError if the given timeout for their constructor is zero to prevent the creation of a non-blocking socket. Patch by Dong-hee Na.

  • bpo-38901: When you specify prompt='.' or equivalently python -m venv --prompt . ... the basename of the current directory is used to set the created venv's prompt when it's activated.

  • bpo-39288: Add math.nextafter(): return the next floating-point value after x towards y.

  • bpo-39259: POP3 and POP3_SSL now raise a ValueError if the given timeout for their constructor is zero to prevent the creation of a non-blocking socket. Patch by Dong-hee Na.

  • bpo-39242: Updated the Gmane domain from news.gmane.org to news.gmane.io which is used for examples of NNTP news reader server and nntplib tests.

  • bpo-35292: Proxy the SimpleHTTPRequestHandler.guess_type to mimetypes.guess_type so the mimetypes.init is called lazily to avoid unnecessary costs when http.server module is imported.

  • bpo-39239: The select.epoll.unregister() method no longer ignores the EBADF error.

  • bpo-38907: In http.server script, restore binding to IPv4 on Windows.

  • bpo-39152: Fix ttk.Scale.configure([name]) to return configuration tuple for name or all options. Giovanni Lombardo contributed part of the patch.

  • bpo-39198: If an exception were to be thrown in Logger.isEnabledFor (say, by asyncio timeouts or stopit) , the logging global lock may not be released appropriately, resulting in deadlock. This change wraps that block of code with try...finally to ensure the lock is released.

  • bpo-39191: Perform a check for running loop before starting a new task in loop.run_until_complete() to fail fast; it prevents the side effect of new task spawning before exception raising.

  • bpo-38871: Correctly parenthesize filter-based statements that contain lambda expressions in mod:lib2to3. Patch by Dong-hee Na.

  • bpo-39142: A change was made to logging.config.dictConfig to avoid converting instances of named tuples to ConvertingTuple. It's assumed that named tuples are too specialised to be treated like ordinary tuples; if a user of named tuples requires ConvertingTuple functionality, they will have to implement that themselves in their named tuple class.

  • bpo-39158: ast.literal_eval() now supports empty sets.

  • bpo-39129: Fix import path for asyncio.TimeoutError

  • bpo-39057: urllib.request.proxy_bypass_environment() now ignores leading dots and no longer ignores a trailing newline.

  • bpo-39056: Fixed handling invalid warning category in the -W option. No longer import the re module if it is not needed.

  • bpo-39055: base64.b64decode() with validate=True raises now a binascii.Error if the input ends with a single \n.

  • bpo-21600: Fix mock.patch.stopall() to stop active patches that were created with mock.patch.dict().

  • bpo-39019: Implement dummy __class_getitem__ for tempfile.SpooledTemporaryFile.

  • bpo-39019: Implement dummy __class_getitem__ for subprocess.Popen, subprocess.CompletedProcess

  • bpo-38914: Adjusted the wording of the warning issued by distutils' check command when the author and maintainer fields are supplied but no corresponding e-mail field (author_email or maintainer_email) is found. The wording now reflects the fact that these fields are suggested, but not required. Patch by Juergen Gmach.

  • bpo-38878: Fixed __subclasshook__ of os.PathLike to return a correct result upon inheritence. Patch by Bar Harel.

  • bpo-38615: IMAP4 and IMAP4_SSL now have an optional timeout parameter for their constructors. Also, the open() method now has an optional timeout parameter with this change. The overridden methods of IMAP4_SSL and IMAP4_stream were applied to this change. Patch by Dong-hee Na.

  • bpo-35182: Fixed Popen.communicate() subsequent call crash when the child process has already closed any piped standard stream, but still continues to be running. Patch by Andriy Maletsky.

  • bpo-38630: On Unix, subprocess.Popen.send_signal() now polls the process status. Polling reduces the risk of sending a signal to the wrong process if the process completed, the subprocess.Popen.returncode attribute is still None, and the pid has been reassigned (recycled) to a new different process.

  • bpo-38536: Removes trailing space in formatted currency with international=True and a locale with symbol following value. E.g. locale.currency(12.34, international=True) returned '12,34 EUR ' instead of '12,34 EUR'.

  • bpo-38473: Use signature from inner mock for autospecced methods attached with unittest.mock.attach_mock(). Patch by Karthikeyan Singaravelan.

  • bpo-38361: Fixed an issue where ident could include a leading path separator when syslog.openlog() was called without arguments.

  • bpo-38293: Add copy.copy() and copy.deepcopy() support to property() objects.

  • bpo-37958: Added the pstats.Stats.get_profile_dict() method to return the profile data as a StatsProfile instance.

  • bpo-28367: Termios magic constants for the following baud rates: - B500000 - B576000 - B921600 - B1000000 - B1152000 - B1500000 - B2000000 - B2500000 - B3000000 - B3500000 - B4000000 Patch by Andrey Smirnov

Documentation

Build

  • bpo-39395: On non-Windows platforms, the setenv() and unsetenv() functions are now required to build Python.

  • bpo-39160: Updated the documentation in /configure --help to show default values, reference documentation where required and add additional explanation where needed.

  • bpo-39144: The ctags and etags build targets both include Modules/_ctypes and Python standard library source files.

IDLE

  • bpo-39050: Make IDLE Settings dialog Help button work again.

  • bpo-34118: Tag memoryview, range, and tuple as classes, the same as list, etcetera, in the library manual built-in functions list.

  • bpo-32989: Add tests for editor newline_and_indent_event method. Remove dead code from pyparse find_good_parse_start method.

C API

  • bpo-39372: Clean header files of interfaces defined but with no implementation. The public API symbols being removed are: _PyBytes_InsertThousandsGroupingLocale, _PyBytes_InsertThousandsGrouping, _Py_InitializeFromArgs, _Py_InitializeFromWideArgs, _PyFloat_Repr, _PyFloat_Digits, _PyFloat_DigitsInit, PyFrame_ExtendStack, _PyAIterWrapper_Type, PyNullImporter_Type, PyCmpWrapper_Type, PySortWrapper_Type, PyNoArgsFunction.

  • bpo-39164: Add a private _PyErr_GetExcInfo() function to retrieve exception information of the specified Python thread state.

Python 3.9.0 alpha 2

Release date: 2019-12-18

Security

  • bpo-38945: Newline characters have been escaped when performing uu encoding to prevent them from overflowing into to content section of the encoded file. This prevents malicious or accidental modification of data during the decoding process.

  • bpo-37228: Due to significant security concerns, the reuse_address parameter of asyncio.loop.create_datagram_endpoint() is no longer supported. This is because of the behavior of SO_REUSEADDR in UDP. For more details, see the documentation for loop.create_datagram_endpoint(). (Contributed by Kyle Stanley, Antoine Pitrou, and Yury Selivanov in bpo-37228.)

  • bpo-38804: Fixes a ReDoS vulnerability in http.cookiejar. Patch by Ben Caller.

Core and Builtins

  • bpo-39028: Slightly improve the speed of keyword argument parsing with many kwargs by strengthening the assumption that kwargs are interned strings.

  • bpo-39080: Fix the value of end_col_offset for Starred Expression AST nodes when they are among the elements in the args attribute of Call AST nodes.

  • bpo-39031: When parsing an "elif" node, lineno and col_offset of the node now point to the "elif" keyword and not to its condition, making it consistent with the "if" node. Patch by Lysandros Nikolaou.

  • bpo-20443: In Python 3.9.0a1, sys.argv[0] was made an absolute path if a filename was specified on the command line. Revert this change, since most users expect sys.argv to be unmodified.

  • bpo-39008: PySys_Audit() now requires Py_ssize_t to be used for size arguments in the format string, regardless of whether PY_SSIZE_T_CLEAN was defined at include time.

  • bpo-38673: In REPL mode, don't switch to PS2 if the line starts with comment or whitespace. Based on work by Batuhan Taşkaya.

  • bpo-38922: Calling replace on a code object now raises the code.__new__ audit event.

  • bpo-38920: Add audit hooks for when sys.excepthook() and sys.unraisablehook() are invoked.

  • bpo-38892: Improve documentation for audit events table and functions.

  • bpo-38852: Set the thread stack size to 8 Mb for debug builds on android platforms.

  • bpo-38858: Each Python subinterpreter now has its own "small integer singletons": numbers in [-5; 257] range. It is no longer possible to change the number of small integers at build time by overriding NSMALLNEGINTS and NSMALLPOSINTS macros: macros should now be modified manually in pycore_pystate.h header file.

  • bpo-36854: The garbage collector state becomes per interpreter (PyInterpreterState.gc), rather than being global (_PyRuntimeState.gc).

  • bpo-38835: The PyFPE_START_PROTECT() and PyFPE_END_PROTECT() macros are empty: they have been doing nothing for the last year, so stop using them.

  • bpo-38328: Sped up the creation time of constant list and set displays. Patch by Brandt Bucher.

  • bpo-38707: MainThread.native_id is now correctly reset in child processes spawned using multiprocessing.Process, instead of retaining the parent's value.

  • bpo-38629: Added __floor__ and __ceil__ methods to float object. Patch by Batuhan Taşkaya.

  • bpo-27145: int + int and int - int operators can now return small integer singletons. Patch by hongweipeng.

  • bpo-38021: Provide a platform tag for AIX that is sufficient for PEP425 binary distribution identification. Patch by Michael Felt.

  • bpo-35409: Ignore GeneratorExit exceptions when throwing an exception into the aclose coroutine of an asynchronous generator.

  • bpo-33387: Removed WITH_CLEANUP_START, WITH_CLEANUP_FINISH, BEGIN_FINALLY, END_FINALLY, CALL_FINALLY and POP_FINALLY bytecodes. Replaced with RERAISE and WITH_EXCEPT_FINISH bytecodes. The compiler now generates different code for exceptional and non-exceptional branches for 'with' and 'try-except' statements. For 'try-finally' statements the 'finally' block is replicated for each exit from the 'try' body.

Library

  • bpo-39033: Fix NameError in zipimport. Patch by Karthikeyan Singaravelan.

  • bpo-39022: Update importlib.metadata to include improvements from importlib_metadata 1.3 including better serialization of EntryPoints and improved documentation for custom finders.

  • bpo-39006: Fix asyncio when the ssl module is missing: only check for ssl.SSLSocket instance if the ssl module is available.

  • bpo-38708: Fix a potential IndexError in email parser when parsing an empty msg-id.

  • bpo-38698: Add a new InvalidMessageID token to email parser to represent invalid Message-ID headers. Also, add defects when there is remaining value after parsing the header.

  • bpo-38994: Implement __class_getitem__ for os.PathLike, pathlib.Path.

  • bpo-38979: Return class from ContextVar.__class_getitem__ to simplify subclassing.

  • bpo-38978: Implement __class_getitem__ on asyncio objects (Future, Task, Queue). Patch by Batuhan Taskaya.

  • bpo-38916: array.array: Remove tostring() and fromstring() methods. They were aliases to tobytes() and frombytes(), deprecated since Python 3.2.

  • bpo-38986: Make repr of C accelerated TaskWakeupMethWrapper the same as of pure Python version.

  • bpo-38982: Fix asyncio PidfdChildWatcher: handle waitpid() error. If waitpid() is called elsewhere, waitpid() call fails with ChildProcessError: use return code 255 in this case, and log a warning. It ensures that the pidfd file descriptor is closed if this error occurs.

  • bpo-38529: Drop too noisy asyncio warning about deletion of a stream without explicit .close() call.

  • bpo-27413: Added ability to pass through ensure_ascii options to json.dumps in the json.tool command-line interface.

  • bpo-38634: The readline module now detects if Python is linked to libedit at runtime on all platforms. Previously, the check was only done on macOS.

  • bpo-33684: Fix json.tool failed to read a JSON file with non-ASCII characters when locale encoding is not UTF-8.

  • bpo-38698: Prevent UnboundLocalError to pop up in parse_message_id.

    parse_message_id() was improperly using a token defined inside an exception handler, which was raising UnboundLocalError on parsing an invalid value. Patch by Claudiu Popa.

  • bpo-38927: Use python -m pip instead of pip to upgrade dependencies in venv.

  • bpo-26730: Fix SpooledTemporaryFile.rollover() might corrupt the file when it is in text mode. Patch by Serhiy Storchaka.

  • bpo-38881: random.choices() now raises a ValueError when all the weights are zero.

  • bpo-38876: Raise pickle.UnpicklingError when loading an item from memo for invalid input.

    The previous code was raising a KeyError for both the Python and C implementation. This was caused by the specified index of an invalid input which did not exist in the memo structure, where the pickle stores what objects it has seen. The malformed input would have caused either a BINGET or LONG_BINGET load from the memo, leading to a KeyError as the determined index was bogus. Patch by Claudiu Popa

  • bpo-38688: Calling func:shutil.copytree to copy a directory tree from one directory to another subdirectory resulted in an endless loop and a RecursionError. A fix was added to consume an iterator and create the list of the entries to be copied, avoiding the recursion for newly created directories. Patch by Bruno P. Kinoshita.

  • bpo-38863: Improve is_cgi() function in http.server, which enables processing the case that cgi directory is a child of another directory other than root.

  • bpo-37838: typing.get_type_hints() properly handles functions decorated with functools.wraps().

  • bpo-38870: Expose ast.unparse() as a function of the ast module that can be used to unparse an ast.AST object and produce a string with code that would produce an equivalent ast.AST object when parsed. Patch by Pablo Galindo and Batuhan Taskaya.

  • bpo-38859: AsyncMock now returns StopAsyncIteration on the exhaustion of a side_effects iterable. Since PEP-479 its Impossible to raise a StopIteration exception from a coroutine.

  • bpo-38857: AsyncMock fix for return values that are awaitable types. This also covers side_effect iterable values that happened to be awaitable, and wraps callables that return an awaitable type. Before these awaitables were being awaited instead of being returned as is.

  • bpo-38834: typing.TypedDict subclasses now track which keys are optional using the __required_keys__ and __optional_keys__ attributes, to enable runtime validation by downstream projects. Patch by Zac Hatfield-Dodds.

  • bpo-38821: Fix unhandled exceptions in argparse when internationalizing error messages for arguments with nargs set to special (non-integer) values. Patch by Federico Bond.

  • bpo-38820: Make Python compatible with OpenSSL 3.0.0. ssl.SSLSocket.getpeercert() no longer returns IPv6 addresses with a trailing new line.

  • bpo-38811: Fix an unhandled exception in pathlib when os.link() is missing. Patch by Toke Høiland-Jørgensen.

  • bpo-38686: Added support for multiple qop values in urllib.request.AbstractDigestAuthHandler.

  • bpo-38712: Add the Linux-specific signal.pidfd_send_signal() function, which allows sending a signal to a process identified by a file descriptor rather than a pid.

  • bpo-38348: Add -i and --indent (indentation level), and --no-type-comments (type comments) command line options to ast parsing tool.

  • bpo-37523: Change zipfile.ZipExtFile to raise ValueError when trying to access the underlying file object after it has been closed. This new behavior is consistent with how accessing closed files is handled in other parts of Python.

  • bpo-38045: Improve the performance of enum._decompose() in enum. Patch by hongweipeng.

  • bpo-36820: Break cycle generated when saving an exception in socket.py, codeop.py and dyld.py as they keep alive not only the exception but user objects through the __traceback__ attribute. Patch by Mario Corchero.

  • bpo-36406: Handle namespace packages in doctest. Patch by Karthikeyan Singaravelan.

  • bpo-34776: Fix dataclasses to support forward references in type annotations

  • bpo-20928: ElementTree supports recursive XInclude processing. Patch by Stefan Behnel.

  • bpo-29636: Add whitespace options for formatting JSON with the json.tool CLI. The following mutually exclusive options are now supported: --indent for setting the indent level in spaces; --tab for indenting with tabs; --no-indent for suppressing newlines; and --compact for suppressing all whitespace. The default behavior remains the same as --indent=4.

Documentation

Tests

  • bpo-38546: Fix test_ressources_gced_in_workers() of test_concurrent_futures: explicitly stop the manager to prevent leaking a child process running in the background after the test completes.

  • bpo-38546: Multiprocessing and concurrent.futures tests now stop the resource tracker process when tests complete.

  • bpo-38614: Replace hardcoded timeout constants in tests with new test.support constants: LOOPBACK_TIMEOUT, INTERNET_TIMEOUT, SHORT_TIMEOUT and LONG_TIMEOUT. It becomes easier to adjust these four timeout constants for all tests at once, rather than having to adjust every single test file.

  • bpo-38547: Fix test_pty: if the process is the session leader, closing the master file descriptor raises a SIGHUP signal: simply ignore SIGHUP when running the tests.

  • bpo-38992: Fix a test for math.fsum() that was failing due to constant folding.

  • bpo-38991: test.support: run_python_until_end(), assert_python_ok() and assert_python_failure() functions no longer strip whitespaces from stderr. Remove test.support.strip_python_stderr() function.

  • bpo-38965: Fix test_faulthandler on GCC 10. Use the "volatile" keyword in faulthandler._stack_overflow() to prevent tail call optimization on any compiler, rather than relying on compiler specific pragma.

  • bpo-38875: test_capi: trashcan tests now require the test "cpu" resource.

  • bpo-38841: Skip asyncio test_create_datagram_endpoint_existing_sock_unix on platforms lacking a functional bind() for named unix domain sockets.

  • bpo-38692: Skip the test_posix.test_pidfd_open() test if os.pidfd_open() fails with a PermissionError. This situation can happen in a Linux sandbox using a syscall whitelist which doesn't allow the pidfd_open() syscall yet.

  • bpo-38839: Fix some unused functions in tests. Patch by Adam Johnson.

  • bpo-38669: Raise TypeError when passing target as a string with unittest.mock.patch.object().

  • bpo-37957: test.regrtest now can receive a list of test patterns to ignore (using the -i/--ignore argument) or a file with a list of patterns to ignore (using the --ignore-file argument). Patch by Pablo Galindo.

Build

  • bpo-37404: asyncio now raises TyperError when calling incompatible methods with an ssl.SSLSocket socket. Patch by Ido Michael.

  • bpo-36500: Added an optional "regen" project to the Visual Studio solution that will regenerate all grammar, tokens, and opcodes.

Windows

  • bpo-39007: Add auditing events to functions in winreg.

  • bpo-33125: Add support for building and releasing Windows ARM64 packages.

macOS

  • bpo-37931: Fixed a crash on OSX dynamic builds that occurred when re-initializing the posix module after a Py_Finalize if the environment had changed since the previous import posix. Patch by Benoît Hudson.

IDLE

  • bpo-38944: Escape key now closes IDLE completion windows. Patch by Johnny Najera.

  • bpo-38943: Fix IDLE autocomplete windows not always appearing on some systems. Patch by Johnny Najera.

  • bpo-38862: 'Strip Trailing Whitespace' on the Format menu removes extra newlines at the end of non-shell files.

  • bpo-38636: Fix IDLE Format menu tab toggle and file indent width. These functions (default shortcuts Alt-T and Alt-U) were mistakenly disabled in 3.7.5 and 3.8.0.

C API

  • bpo-38896: Remove PyUnicode_ClearFreeList() function: the Unicode free list has been removed in Python 3.3.

  • bpo-37340: Remove PyMethod_ClearFreeList() and PyCFunction_ClearFreeList() functions: the free lists of bound method objects have been removed.

  • bpo-38835: Exclude PyFPE_START_PROTECT() and PyFPE_END_PROTECT() macros of pyfpe.h from Py_LIMITED_API (stable API).

Python 3.9.0 alpha 1

Release date: 2019-11-19

Security

Core and Builtins

  • bpo-38631: Replace Py_FatalError() call with a regular RuntimeError exception in float.__getformat__().

  • bpo-38639: Optimized math.floor(), math.ceil() and math.trunc() for floats.

  • bpo-38640: Fixed a bug in the compiler that was causing to raise in the presence of break statements and continue statements inside always false while loops. Patch by Pablo Galindo.

  • bpo-38613: Optimized some set operations (e.g. |, ^, and -) of dict_keys. d.keys() | other was slower than set(d) | other but they are almost same performance for now.

  • bpo-28029: "".replace("", s, n) now returns s instead of an empty string for all non-zero n. There are similar changes for bytes and bytearray objects.

  • bpo-38535: Fixed line numbers and column offsets for AST nodes for calls without arguments in decorators.

  • bpo-38525: Fix a segmentation fault when using reverse iterators of empty dict objects. Patch by Dong-hee Na and Inada Naoki.

  • bpo-38465: bytearray, array and mmap objects allow now to export more than 2**31 buffers at a time.

  • bpo-38469: Fixed a bug where the scope of named expressions was not being resolved correctly in the presence of the global keyword. Patch by Pablo Galindo.

  • bpo-38437: Activate the GC_DEBUG macro for debug builds of the interpreter (when Py_DEBUG is set). Patch by Pablo Galindo.

  • bpo-38379: When the garbage collector makes a collection in which some objects resurrect (they are reachable from outside the isolated cycles after the finalizers have been executed), do not block the collection of all objects that are still unreachable. Patch by Pablo Galindo and Tim Peters.

  • bpo-38379: When cyclic garbage collection (gc) runs finalizers that resurrect unreachable objects, the current gc run ends, without collecting any cyclic trash. However, the statistics reported by collect() and get_stats() claimed that all cyclic trash found was collected, and that the resurrected objects were collected. Changed the stats to report that none were collected.

  • bpo-38392: In debug mode, PyObject_GC_Track() now calls tp_traverse() of the object type to ensure that the object is valid: test that objects visited by tp_traverse() are valid.

  • bpo-38210: Remove unecessary intersection and update set operation in dictview with empty set. (Contributed by Dong-hee Na in bpo-38210.)

  • bpo-38402: Check the error from the system's underlying crypt or crypt_r.

  • bpo-37474: On FreeBSD, Python no longer calls fedisableexcept() at startup to control the floating point control mode. The call became useless since FreeBSD 6: it became the default mode.

  • bpo-38006: Fix a bug due to the interaction of weakrefs and the cyclic garbage collector. We must clear any weakrefs in garbage in order to prevent their callbacks from executing and causing a crash.

  • bpo-38317: Fix warnings options priority: PyConfig.warnoptions has the highest priority, as stated in the PEP 587.

  • bpo-38310: Predict BUILD_MAP_UNPACK_WITH_CALL -> CALL_FUNCTION_EX opcode pairs in the main interpreter loop. Patch by Brandt Bucher.

  • bpo-36871: Improve error handling for the assert_has_calls and assert_has_awaits methods of mocks. Fixed a bug where any errors encountered while binding the expected calls to the mock's spec were silently swallowed, leading to misleading error output.

  • bpo-11410: Better control over symbol visibility is provided through use of the visibility attributes available in gcc >= 4.0, provided in a uniform way across POSIX and Windows. The POSIX build files have been updated to compile with -fvisibility=hidden, minimising exported symbols.

  • bpo-38219: Optimized the dict constructor and the update() method for the case when the argument is a dict.

  • bpo-38236: Python now dumps path configuration if it fails to import the Python codecs of the filesystem and stdio encodings.

  • bpo-38013: Allow to call async_generator_athrow().throw(...) even for non-started async generator helper. It fixes annoying warning at the end of asyncio.run() call.

  • bpo-38124: Fix an off-by-one error in PyState_AddModule that could cause out-of-bounds memory access.

  • bpo-38116: The select module is now PEP-384 compliant and no longer has static state

  • bpo-38113: ast module updated to PEP-384 and all statics removed

  • bpo-38076: The struct module is now PEP-384 compatible

  • bpo-38075: The random module is now PEP-384 compatible

  • bpo-38074: zlib module made PEP-384 compatible

  • bpo-38073: Make pwd extension module PEP-384 compatible

  • bpo-38072: grp module made PEP-384 compatible

  • bpo-38069: Make _posixsubprocess PEP-384 compatible

  • bpo-38071: Make termios extension module PEP-384 compatible

  • bpo-38005: Fixed comparing and creating of InterpreterID and ChannelID.

  • bpo-36946: Fix possible signed integer overflow when handling slices. Patch by hongweipeng.

  • bpo-37994: Fixed silencing arbitrary errors if an attribute lookup fails in several sites. Only AttributeError should be silenced.

  • bpo-8425: Optimize set difference_update for the case when the other set is much larger than the base set. (Suggested by Evgeny Kapun with code contributed by Michele Orrù).

  • bpo-37966: The implementation of is_normalized() has been greatly sped up on strings that aren't normalized, by implementing the full normalization-quick-check algorithm from the Unicode standard.

  • bpo-37947: Adjust correctly the recursion level in the symtable generation for named expressions. Patch by Pablo Galindo.

  • bpo-37812: The CHECK_SMALL_INT macro used inside Object/longobject.c has been replaced with an explicit return at each call site.

  • bpo-37751: Fix codecs.lookup() to normalize the encoding name the same way than encodings.normalize_encoding(), except that codecs.lookup() also converts the name to lower case.

  • bpo-37830: Fixed compilation of break and continue in the finally block when the corresponding try block contains return with a non-constant value.

  • bpo-20490: Improve import error message for partially initialized module on circular from imports - by Anthony Sottile.

  • bpo-37840: Fix handling of negative indices in sq_item of bytearray. Patch by Sergey Fedoseev.

  • bpo-37802: Slightly improve performance of PyLong_FromUnsignedLong(), PyLong_FromUnsignedLongLong() and PyLong_FromSize_t(). Patch by Sergey Fedoseev.

  • bpo-37409: Ensure explicit relative imports from interactive sessions and scripts (having no parent package) always raise ImportError, rather than treating the current module as the package. Patch by Ben Lewis.

  • bpo-32912: Reverted bpo-32912: emitting SyntaxWarning instead of DeprecationWarning for invalid escape sequences in string and bytes literals.

  • bpo-37757: PEP 572: As described in the PEP, assignment expressions now raise SyntaxError when their interaction with comprehension scoping results in an ambiguous target scope.

    The TargetScopeError subclass originally proposed by the PEP has been removed in favour of just raising regular syntax errors for the disallowed cases.

  • bpo-36279: Fix potential use of uninitialized memory in os.wait3().

  • bpo-36311: Decoding bytes objects larger than 2GiB is faster and no longer fails when a multibyte characters spans a chunk boundary.

  • bpo-34880: The assert statement now works properly if the AssertionError exception is being shadowed. Patch by Zackery Spytz.

  • bpo-37340: Removed object cache (free_list) for bound method objects. Temporary bound method objects are less used than before thanks to the LOAD_METHOD opcode and the _PyObject_VectorcallMethod C API.

  • bpo-37648: Fixed minor inconsistency in list.__contains__(), tuple.__contains__() and a few other places. The collection's item is now always at the left and the needle is on the right of ==.

  • bpo-37444: Update differing exception between builtins.__import__() and importlib.__import__().

  • bpo-37619: When adding a wrapper descriptor from one class to a different class (for example, setting __add__ = str.__add__ on an int subclass), an exception is correctly raised when the operator is called.

  • bpo-37593: Swap the positions of the posonlyargs and args parameters in the constructor of ast.parameters nodes.

  • bpo-37543: Optimized pymalloc for non PGO build.

  • bpo-37537: Compute allocated pymalloc blocks inside _Py_GetAllocatedBlocks(). This slows down _Py_GetAllocatedBlocks() but gives a small speedup to _PyObject_Malloc() and _PyObject_Free().

  • bpo-37467: Fix sys.excepthook() and PyErr_Display() if a filename is a bytes string. For example, for a SyntaxError exception where the filename attribute is a bytes string.

  • bpo-37433: Fix SyntaxError indicator printing too many spaces for multi-line strings - by Anthony Sottile.

  • bpo-37417: bytearray.extend() now correctly handles errors that arise during iteration. Patch by Brandt Bucher.

  • bpo-37414: The undocumented sys.callstats() function has been removed. Since Python 3.7, it was deprecated and always returned None. It required a special build option CALL_PROFILE which was already removed in Python 3.7.

  • bpo-37392: Remove sys.getcheckinterval() and sys.setcheckinterval() functions. They were deprecated since Python 3.2. Use sys.getswitchinterval() and sys.setswitchinterval() instead. Remove also check_interval field of the PyInterpreterState structure.

  • bpo-37388: In development mode and in debug build, encoding and errors arguments are now checked on string encoding and decoding operations. Examples: open(), str.encode() and bytes.decode().

    By default, for best performances, the errors argument is only checked at the first encoding/decoding error, and the encoding argument is sometimes ignored for empty strings.

  • bpo-37348: Optimized decoding short ASCII string with UTF-8 and ascii codecs. b"foo".decode() is about 15% faster. Patch by Inada Naoki.

  • bpo-24214: Improved support of the surrogatepass error handler in the UTF-8 and UTF-16 incremental decoders.

  • bpo-37330: open(), io.open(), codecs.open() and fileinput.FileInput no longer accept 'U' ("universal newline") in the file mode. This flag was deprecated since Python 3.3.

  • bpo-35224: Reverse evaluation order of key: value in dict comprehensions as proposed in PEP 572. I.e. in {k: v for ...}, k will be evaluated before v.

  • bpo-37316: Fix the PySys_Audit() call in mmap.mmap.

  • bpo-37300: Remove an unnecssary Py_XINCREF in classobject.c.

  • bpo-37269: Fix a bug in the peephole optimizer that was not treating correctly constant conditions with binary operators. Patch by Pablo Galindo.

  • bpo-20443: Python now gets the absolute path of the script filename specified on the command line (ex: "python3 script.py"): the __file__ attribute of the __main__ module and sys.path[0] become an absolute path, rather than a relative path.

  • bpo-37257: Python's small object allocator (obmalloc.c) now allows (no more than) one empty arena to remain available for immediate reuse, without returning it to the OS. This prevents thrashing in simple loops where an arena could be created and destroyed anew on each iteration.

  • bpo-37231: The dispatching of type slots to special methods (for example calling __mul__ when doing x * y) has been made faster.

  • bpo-36974: Implemented separate vectorcall functions for every calling convention of builtin functions and methods. This improves performance for calls.

  • bpo-37213: Handle correctly negative line offsets in the peephole optimizer. Patch by Pablo Galindo.

  • bpo-37219: Remove erroneous optimization for empty set differences.

  • bpo-15913: Implement PyBuffer_SizeFromFormat() function (previously documented but not implemented): call struct.calcsize(). Patch by Joannah Nanjekye.

  • bpo-36922: Slot functions optimize any callable with Py_TPFLAGS_METHOD_DESCRIPTOR instead of only instances of function.

  • bpo-36974: The slot tp_vectorcall_offset is inherited unconditionally to support super().__call__() when the base class uses vectorcall.

  • bpo-37160: threading.get_native_id() now also supports NetBSD.

  • bpo-37077: Add threading.get_native_id() support for AIX. Patch by M. Felt

  • bpo-36781: sum() has been optimized for boolean values.

  • bpo-34556: Add --upgrade-deps to venv module. Patch by Cooper Ry Lees

  • bpo-20523: pdb.Pdb supports ~/.pdbrc in Windows 7. Patch by Tim Hopper and Dan Lidral-Porter.

  • bpo-35551: Updated encodings: - Removed the "tis260" encoding, which was an alias for the nonexistent "tactis" codec. - Added "mac_centeuro" as an alias for the mac_latin2 encoding.

  • bpo-19072: The classmethod decorator can now wrap other descriptors such as property objects. Adapted from a patch written by Graham Dumpleton.

  • bpo-27575: Improve speed of dictview intersection by directly using set intersection logic. Patch by David Su.

  • bpo-30773: Prohibit parallel running of aclose() / asend() / athrow(). Fix ag_running to reflect the actual running status of the AG.

Library

  • bpo-36589: The curses.update_lines_cols() function now returns None instead of 1 on success.

  • bpo-38807: Update TypeError messages for os.path.join() to include os.PathLike objects as acceptable input types.

  • bpo-38724: Add a repr for subprocess.Popen objects. Patch by Andrey Doroschenko.

  • bpo-38786: pydoc now recognizes and parses HTTPS URLs. Patch by python273.

  • bpo-38785: Prevent asyncio from crashing if parent __init__ is not called from a constructor of object derived from asyncio.Future.

  • bpo-38723: pdb now uses io.open_code() to trigger auditing events.

  • bpo-27805: Allow opening pipes and other non-seekable files in append mode with open().

  • bpo-38438: Simplify the argparse usage message for nargs="*".

  • bpo-38761: WeakSet is now registered as a collections.abc.MutableSet.

  • bpo-38716: logging: change RotatingHandler namer and rotator to class-level attributes. This stops __init__ from setting them to None in the case where a subclass defines them with eponymous methods.

  • bpo-38713: Add os.P_PIDFD constant, which may be passed to os.waitid() to wait on a Linux process file descriptor.

  • bpo-38692: Add asyncio.PidfdChildWatcher, a Linux-specific child watcher implementation that polls process file descriptors.

  • bpo-38692: Expose the Linux pidfd_open syscall as os.pidfd_open().

  • bpo-38602: Added constants F_OFD_GETLK, F_OFD_SETLK and F_OFD_SETLKW to the fcntl module. Patch by Dong-hee Na.

  • bpo-38334: Fixed seeking backward on an encrypted zipfile.ZipExtFile.

  • bpo-38312: Add curses.get_escdelay(), curses.set_escdelay(), curses.get_tabsize(), and curses.set_tabsize() functions - by Anthony Sottile.

  • bpo-38586: Now fileConfig() correcty sets the .name of handlers loaded.

  • bpo-38565: Add new cache_parameters() method for functools.lru_cache() to better support pickling.

  • bpo-34679: asynci.ProactorEventLoop.close() now only calls signal.set_wakeup_fd() in the main thread.

  • bpo-31202: The case the result of pathlib.WindowsPath.glob() matches now the case of the pattern for literal parts.

  • bpo-36321: Remove misspelled attribute. The 3.8 changelog noted that this would be removed in 3.9.

  • bpo-38521: Fixed erroneous equality comparison in statistics.NormalDist().

  • bpo-38493: Added CLD_KILLED and CLD_STOPPED for si_code. Patch by Dong-hee Na.

  • bpo-38478: Fixed a bug in inspect.signature.bind() that was causing it to fail when handling a keyword argument with same name as positional-only parameter. Patch by Pablo Galindo.

  • bpo-33604: Fixed hmac.new and hmac.HMAC to raise TypeError instead of ValueError when the digestmod parameter, now required in 3.8, is omitted. Also clarified the hmac module documentation and docstrings.

  • bpo-38378: Parameters out and in of os.sendfile() was renamed to out_fd and in_fd.

  • bpo-38417: Added support for setting the umask in the child process to the subprocess module on POSIX systems.

  • bpo-38449: Revert GH-15522, which introduces a regression in mimetypes.guess_type() due to improper handling of filenames as urls.

  • bpo-38431: Fix __repr__ method for dataclasses.InitVar to support typing objects, patch by Samuel Colvin.

  • bpo-38109: Add missing stat.S_IFDOOR, stat.S_IFPORT, stat.S_IFWHT, stat.S_ISDOOR(), stat.S_ISPORT(), and stat.S_ISWHT() values to the Python implementation of stat.

  • bpo-38422: Clarify docstrings of pathlib suffix(es)

  • bpo-38405: Nested subclasses of typing.NamedTuple are now pickleable.

  • bpo-38332: Prevent KeyError thrown by _encoded_words.decode() when given an encoded-word with invalid content-type encoding from propagating all the way to email.message.get().

  • bpo-38371: Deprecated the split() method in _tkinter.TkappType in favour of the splitlist() method which has more consistent and predicable behavior.

  • bpo-38341: Add smtplib.SMTPNotSupportedError to the smtplib exported names.

  • bpo-38319: sendfile() used in socket and shutil modules was raising OverflowError for files >= 2GiB on 32-bit architectures. (patch by Giampaolo Rodola)

  • bpo-38242: Revert the new asyncio Streams API

  • bpo-13153: OS native encoding is now used for converting between Python strings and Tcl objects. This allows to display, copy and paste to clipboard emoji and other non-BMP characters. Converting strings from Tcl to Python and back now never fails (except MemoryError).

  • bpo-38019: Correctly handle pause/resume reading of closed asyncio unix pipe.

  • bpo-38163: Child mocks will now detect their type as either synchronous or asynchronous, asynchronous child mocks will be AsyncMocks and synchronous child mocks will be either MagicMock or Mock (depending on their parent type).

  • bpo-38161: Removes _AwaitEvent from AsyncMock.

  • bpo-38216: Allow the rare code that wants to send invalid http requests from the http.client library a way to do so. The fixes for bpo-30458 led to breakage for some projects that were relying on this ability to test their own behavior in the face of bad requests.

  • bpo-28286: Deprecate opening GzipFile for writing implicitly. Always specify the mode argument for writing.

  • bpo-38108: Any synchronous magic methods on an AsyncMock now return a MagicMock. Any asynchronous magic methods on a MagicMock now return an AsyncMock.

  • bpo-38265: Update the length parameter of os.pread() to accept Py_ssize_t instead of int.

  • bpo-38112: compileall has a higher default recursion limit and new command-line arguments for path manipulation, symlinks handling, and multiple optimization levels.

  • bpo-38248: asyncio: Fix inconsistent immediate Task cancellation

  • bpo-38237: The arguments for the builtin pow function are more descriptive. They can now also be passed in as keywords.

  • bpo-34002: Improve efficiency in parts of email package by changing while-pop to a for loop, using isdisjoint instead of set intersections.

  • bpo-38191: Constructors of NamedTuple and TypedDict types now accept arbitrary keyword argument names, including "cls", "self", "typename", "_typename", "fields" and "_fields".

  • bpo-38155: Add __all__ to datetime. Patch by Tahia Khan.

  • bpo-38185: Fixed case-insensitive string comparison in sqlite3.Row indexing.

  • bpo-38136: Changes AsyncMock call count and await count to be two different counters. Now await count only counts when a coroutine has been awaited, not when it has been called, and vice-versa. Update the documentation around this.

  • bpo-37828: Fix default mock name in unittest.mock.Mock.assert_called() exceptions. Patch by Abraham Toriz Cruz.

  • bpo-38175: Fix a memory leak in comparison of sqlite3.Row objects.

  • bpo-33936: _hashlib no longer calls obsolete OpenSSL initialization function with OpenSSL 1.1.0+.

  • bpo-34706: Preserve subclassing in inspect.Signature.from_callable.

  • bpo-38153: Names of hashing algorithms frome OpenSSL are now normalized to follow Python's naming conventions. For example OpenSSL uses sha3-512 instead of sha3_512 or blake2b512 instead of blake2b.

  • bpo-38115: Fix a bug in dis.findlinestarts() where it would return invalid bytecode offsets. Document that a code object's co_lnotab can contain invalid bytecode offsets.

  • bpo-38148: Add slots to asyncio transport classes, which can reduce memory usage.

  • bpo-38142: The _hashlib OpenSSL wrapper extension module is now PEP-384 compliant.

  • bpo-9216: hashlib constructors now support usedforsecurity flag to signal that a hashing algorithm is not used in a security context.

  • bpo-36991: Fixes a potential incorrect AttributeError exception escaping ZipFile.extract() in some unsupported input error situations.

  • bpo-38134: Remove obsolete copy of PBKDF2_HMAC_fast. All supported OpenSSL versions contain a fast implementation.

  • bpo-38132: The OpenSSL hashlib wrapper uses a simpler implementation. Several Macros and pointless caches are gone. The hash name now comes from OpenSSL's EVP. The algorithm name stays the same, except it is now always lower case.

  • bpo-38008: Fix parent class check in protocols to correctly identify the module that provides a builtin protocol, instead of assuming they all come from the collections.abc module

  • bpo-34037: For asyncio, add a new coroutine loop.shutdown_default_executor(). The new coroutine provides an API to schedule an executor shutdown that waits on the threadpool to finish closing. Also, asyncio.run() has been updated to utilize the new coroutine. Patch by Kyle Stanley.

  • bpo-37405: Fixed regression bug for socket.getsockname() for non-CAN_ISOTP AF_CAN address family sockets by returning a 1-tuple instead of string.

  • bpo-38121: Update parameter names on functions in importlib.metadata matching the changes in the 0.22 release of importlib_metadata.

  • bpo-38110: The os.closewalk() implementation now uses the libc fdwalk() API on platforms where it is available.

  • bpo-38093: Fixes AsyncMock so it doesn't crash when used with AsyncContextManagers or AsyncIterators.

  • bpo-37488: Add warning to datetime.utctimetuple(), datetime.utcnow() and datetime.utcfromtimestamp() .

  • bpo-35640: Allow passing a path-like object as directory argument to the http.server.SimpleHTTPRequestHandler class. Patch by Géry Ogam.

  • bpo-38086: Update importlib.metadata with changes from importlib_metadata 0.21.

  • bpo-37251: Remove __code__ check in AsyncMock that incorrectly evaluated function specs as async objects but failed to evaluate classes with __await__ but no __code__ attribute defined as async objects.

  • bpo-38037: Fix reference counters in the signal module.

  • bpo-38066: Hide internal asyncio.Stream methods: feed_eof(), feed_data(), set_exception() and set_transport().

  • bpo-38059: inspect.py now uses sys.exit() instead of exit()

  • bpo-38049: Added command-line interface for the ast module.

  • bpo-37953: In typing, improved the __hash__ and __eq__ methods for ForwardReferences.

  • bpo-38026: Fixed inspect.getattr_static() used isinstance while it should avoid dynamic lookup.

  • bpo-35923: Update importlib.machinery.BuiltinImporter to use loader._ORIGIN instead of a hardcoded value. Patch by Dong-hee Na.

  • bpo-38010: In importlib.metadata sync with importlib_metadata 0.20, clarifying behavior of files() and fixing issue where only one requirement was returned for requires() on dist-info packages.

  • bpo-38006: weakref.WeakValueDictionary defines a local remove() function used as callback for weak references. This function was created with a closure. Modify the implementation to avoid the closure.

  • bpo-37995: Added the indent option to ast.dump() which allows it to produce a multiline indented output.

  • bpo-34410: Fixed a crash in the tee() iterator when re-enter it. RuntimeError is now raised in this case.

  • bpo-37140: Fix a ctypes regression of Python 3.8. When a ctypes.Structure is passed by copy to a function, ctypes internals created a temporary object which had the side effect of calling the structure finalizer (__del__) twice. The Python semantics requires a finalizer to be called exactly once. Fix ctypes internals to no longer call the finalizer twice.

  • bpo-37587: _json.scanstring is now up to 3x faster when there are many backslash escaped characters in the JSON string.

  • bpo-37834: Prevent shutil.rmtree exception when built on non-Windows system without fd system call support, like older versions of macOS.

  • bpo-10978: Semaphores and BoundedSemaphores can now release more than one waiting thread at a time.

  • bpo-37972: Subscripts to the unittest.mock.call objects now receive the same chaining mechanism as any other custom attributes, so that the following usage no longer raises a TypeError:

    call().foo().__getitem__('bar')

    Patch by blhsing

  • bpo-37965: Fix C compiler warning caused by distutils.ccompiler.CCompiler.has_function.

  • bpo-37964: Add F_GETPATH command to fcntl.

  • bpo-37960: repr() of buffered and text streams now silences only expected exceptions when get the value of "name" and "mode" attributes.

  • bpo-37961: Add a total_nframe field to the traces collected by the tracemalloc module. This field indicates the original number of frames before it was truncated.

  • bpo-37951: Most features of the subprocess module now work again in subinterpreters. Only preexec_fn is restricted in subinterpreters.

  • bpo-36205: Fix the rusage implementation of time.process_time() to correctly report the sum of the system and user CPU time.

  • bpo-37950: Fix ast.dump() when call with incompletely initialized node.

  • bpo-34679: Restores instantiation of Windows IOCP event loops from the non-main thread.

  • bpo-36917: Add default implementation of the ast.NodeVisitor.visit_Constant() method which emits a deprecation warning and calls corresponding methody visit_Num(), visit_Str(), etc.

  • bpo-37798: Update test_statistics.py to verify that the statistics module works well for both C and Python implementations. Patch by Dong-hee Na

  • bpo-26589: Added a new status code to the http module: 451 UNAVAILABLE_FOR_LEGAL_REASONS

  • bpo-37915: Fix a segmentation fault that appeared when comparing instances of datetime.timezone and datetime.tzinfo objects. Patch by Pablo Galindo.

  • bpo-32554: Deprecate having random.seed() call hash on arbitrary types.

  • bpo-9938: Add optional keyword argument exit_on_error for ArgumentParser.

  • bpo-37851: The faulthandler module no longer allocates its alternative stack at Python startup. Now the stack is only allocated at the first faulthandler usage.

  • bpo-32793: Fix a duplicated debug message when smtplib.SMTP.connect() is called.

  • bpo-37885: venv: Don't generate unset variable warning on deactivate.

  • bpo-37868: Fix dataclasses.is_dataclass when given an instance that never raises AttributeError in __getattr__. That is, an object that returns something for __dataclass_fields__ even if it's not a dataclass.

  • bpo-37811: Fix socket module's socket.connect(address) function being unable to establish connection in case of interrupted system call. The problem was observed on all OSes which poll(2) system call can take only non-negative integers and -1 as a timeout value.

  • bpo-37863: Optimizations for Fraction.__hash__ suggested by Tim Peters.

  • bpo-21131: Fix faulthandler.register(chain=True) stack. faulthandler now allocates a dedicated stack of SIGSTKSZ*2 bytes, instead of just SIGSTKSZ bytes. Calling the previous signal handler in faulthandler signal handler uses more than SIGSTKSZ bytes of stack memory on some platforms.

  • bpo-37798: Add C fastpath for statistics.NormalDist.inv_cdf() Patch by Dong-hee Na

  • bpo-37804: Remove the deprecated method threading.Thread.isAlive(). Patch by Dong-hee Na.

  • bpo-37819: Add Fraction.as_integer_ratio() to match the corresponding methods in bool, int, float, and decimal.

  • bpo-14465: Add an xml.etree.ElementTree.indent() function for pretty-printing XML trees. Contributed by Stefan Behnel.

  • bpo-37810: Fix difflib ? hint in diff output when dealing with tabs. Patch by Anthony Sottile.

  • bpo-37772: In zipfile.Path, when adding implicit dirs, ensure that ancestral directories are added and that duplicates are excluded.

  • bpo-18578: Renamed and documented test.bytecode_helper as test.support.bytecode_helper. Patch by Joannah Nanjekye.

  • bpo-37785: Fix xgettext warnings in argparse.

  • bpo-34488: writelines() method of io.BytesIO is now slightly faster when many small lines are passed. Patch by Sergey Fedoseev.

  • bpo-37449: ensurepip now uses importlib.resources.read_binary() to read data instead of pkgutil.get_data(). Patch by Joannah Nanjekye.

  • bpo-28292: Mark calendar.py helper functions as being private. The follows PEP 8 guidance to maintain the style conventions in the module and it addresses a known case of user confusion.

  • bpo-18049: Add definition of THREAD_STACK_SIZE for AIX in Python/thread_pthread.h The default thread stacksize caused crashes with the default recursion limit Patch by M Felt

  • bpo-37742: The logging.getLogger() API now returns the root logger when passed the name 'root', whereas previously it returned a non-root logger named 'root'. This could affect cases where user code explicitly wants a non-root logger named 'root', or instantiates a logger using logging.getLogger(__name__) in some top-level module called 'root.py'.

  • bpo-37738: Fix the implementation of curses addch(str, color_pair): pass the color pair to setcchar(), instead of always passing 0 as the color pair.

  • bpo-37723: Fix performance regression on regular expression parsing with huge character sets. Patch by Yann Vaginay.

  • bpo-35943: The function PyImport_GetModule() now ensures any module it returns is fully initialized. Patch by Joannah Nanjekye.

  • bpo-32178: Fix IndexError in email package when trying to parse invalid address fields starting with :.

  • bpo-37268: The parser module is deprecated and will be removed in future versions of Python.

  • bpo-11953: Completing WSA* error codes in socket.

  • bpo-37685: Fixed comparisons of datetime.timedelta and datetime.timezone.

  • bpo-37697: Syncronize importlib.metadata with importlib_metadata 0.19, improving handling of EGG-INFO files and fixing a crash when entry point names contained colons.

  • bpo-37695: Correct curses.unget_wch() error message. Patch by Anthony Sottile.

  • bpo-37689: Add is_relative_to() in PurePath to determine whether or not one path is relative to another.

  • bpo-29553: Fixed argparse.ArgumentParser.format_usage() for mutually exclusive groups. Patch by Andrew Nester.

  • bpo-37691: Let math.dist() accept coordinates as sequences (or iterables) rather than just tuples.

  • bpo-37685: Fixed __eq__, __lt__ etc implementations in some classes. They now return NotImplemented for unsupported type of the other operand. This allows the other operand to play role (for example the equality comparison with ANY will return True).

  • bpo-37354: Make Activate.ps1 Powershell script static to allow for signing it.

  • bpo-37664: Update wheels bundled with ensurepip (pip 19.2.3 and setuptools 41.2.0)

  • bpo-37663: Bring consistency to venv shell activation scripts by always using __VENV_PROMPT__.

  • bpo-37642: Allowed the pure Python implementation of datetime.timezone to represent sub-minute offsets close to minimum and maximum boundaries, specifically in the ranges (23:59, 24:00) and (-23:59, 24:00). Patch by Ngalim Siregar

  • bpo-36161: In posix, use ttyname_r instead of ttyname for thread safety.

  • bpo-36324: Make internal attributes for statistics.NormalDist() private.

  • bpo-37555: Fix NonCallableMock._call_matcher returning tuple instead of _Call object when self._spec_signature exists. Patch by Elizabeth Uselton

  • bpo-29446: Make from tkinter import * import only the expected objects.

  • bpo-16970: Adding a value error when an invalid value in passed to nargs Patch by Robert Leenders

  • bpo-34443: Exceptions from enum now use the __qualname of the enum class in the exception message instead of the __name__.

  • bpo-37491: Fix IndexError when parsing email headers with unexpectedly ending bare-quoted string value. Patch by Abhilash Raj.

  • bpo-37587: Make json.loads faster for long strings. (Patch by Marco Paolini)

  • bpo-18378: Recognize "UTF-8" as a valid value for LC_CTYPE in locale._parse_localename.

  • bpo-37579: Return NotImplemented in Python implementation of __eq__ for timedelta and time when the other object being compared is not of the same type to match C implementation. Patch by Karthikeyan Singaravelan.

  • bpo-21478: Record calls to parent when autospecced object is attached to a mock using unittest.mock.attach_mock(). Patch by Karthikeyan Singaravelan.

  • bpo-37531: "python3 -m test -jN --timeout=TIMEOUT" now kills a worker process if it runs longer than TIMEOUT seconds.

  • bpo-37482: Fix serialization of display name in originator or destination address fields with both encoded words and special chars.

  • bpo-36993: Improve error reporting for corrupt zip files with bad zip64 extra data. Patch by Daniel Hillier.

  • bpo-37502: pickle.loads() no longer raises TypeError when the buffers argument is set to None

  • bpo-37520: Correct behavior for zipfile.Path.parent when the path object identifies a subdirectory.

  • bpo-18374: Fix the .col_offset attribute of nested ast.BinOp instances which had a too large value in some situations.

  • bpo-37424: Fixes a possible hang when using a timeout on subprocess.run() while capturing output. If the child process spawned its own children or otherwise connected its stdout or stderr handles with another process, we could hang after the timeout was reached and our child was killed when attempting to read final output from the pipes.

  • bpo-37421: Fix multiprocessing.util.get_temp_dir() finalizer: clear also the 'tempdir' configuration of the current process, so next call to get_temp_dir() will create a new temporary directory, rather than reusing the removed temporary directory.

  • bpo-37481: The distutils bdist_wininst command is deprecated in Python 3.8, use bdist_wheel (wheel packages) instead.

  • bpo-37479: When Enum.__str__ is overridden in a derived class, the override will be used by Enum.__format__ regardless of whether mixin classes are present.

  • bpo-37440: http.client now enables TLS 1.3 post-handshake authentication for default context or if a cert_file is passed to HTTPSConnection.

  • bpo-37437: Update vendorized expat version to 2.2.7.

  • bpo-37428: SSLContext.post_handshake_auth = True no longer sets SSL_VERIFY_POST_HANDSHAKE verify flag for client connections. Although the option is documented as ignored for clients, OpenSSL implicitly enables cert chain validation when the flag is set.

  • bpo-37420: os.sched_setaffinity() now correctly handles errors that arise during iteration over its mask argument. Patch by Brandt Bucher.

  • bpo-37412: The os.getcwdb() function now uses the UTF-8 encoding on Windows, rather than the ANSI code page: see PEP 529 for the rationale. The function is no longer deprecated on Windows.

  • bpo-37406: The sqlite3 module now raises TypeError, rather than ValueError, if operation argument type is not str: execute(), executemany() and calling a connection.

  • bpo-29412: Fix IndexError in parsing a header value ending unexpectedly. Patch by Abhilash Raj.

  • bpo-36546: The dist argument for statistics.quantiles() is now positional only. The current name doesn't reflect that the argument can be either a dataset or a distribution. Marking the parameter as positional avoids confusion and makes it possible to change the name later.

  • bpo-37394: Fix a bug that was causing the queue module to fail if the accelerator module was not available. Patch by Pablo Galindo.

  • bpo-37376: pprint now has support for types.SimpleNamespace. Patch by Carl Bordum Hansen.

  • bpo-26967: An ArgumentParser with allow_abbrev=False no longer disables grouping of short flags, such as -vv, but only disables abbreviation of long flags as documented. Patch by Zac Hatfield-Dodds.

  • bpo-37212: unittest.mock.call() now preserves the order of keyword arguments in repr output. Patch by Karthikeyan Singaravelan.

  • bpo-37372: Fix error unpickling datetime.time objects from Python 2 with seconds>=24. Patch by Justin Blanchard.

  • bpo-37345: Add formal support for UDPLITE sockets. Support was present before, but it is now easier to detect support with hasattr(socket, 'IPPROTO_UDPLITE') and there are constants defined for each of the values needed: socket.IPPROTO_UDPLITE, UDPLITE_SEND_CSCOV, and UDPLITE_RECV_CSCOV. Patch by Gabe Appleton.

  • bpo-37358: Optimized functools.partial by using vectorcall.

  • bpo-37347: sqlite3.Connection.create_aggregate(), sqlite3.Connection.create_function(), sqlite3.Connection.set_authorizer(), sqlite3.Connection.set_progress_handler() sqlite3.Connection.set_trace_callback() methods lead to segfaults if some of these methods are called twice with an equal object but not the same. Now callbacks are stored more carefully. Patch by Aleksandr Balezin.

  • bpo-37163: The obj argument of dataclasses.replace() is positional-only now.

  • bpo-37085: Add the optional Linux SocketCAN Broadcast Manager constants, used as flags to configure the BCM behaviour, in the socket module. Patch by Karl Ding.

  • bpo-37328: HTMLParser.unescape is removed. It was undocumented and deprecated since Python 3.4.

  • bpo-37305: Add .webmanifest -> application/manifest+json to list of recognized file types and content type headers

  • bpo-37320: aifc.openfp() alias to aifc.open(), sunau.openfp() alias to sunau.open(), and wave.openfp() alias to wave.open() have been removed. They were deprecated since Python 3.7.

  • bpo-37315: Deprecated accepting floats with integral value (like 5.0) in math.factorial().

  • bpo-37312: _dummy_thread and dummy_threading modules have been removed. These modules were deprecated since Python 3.7 which requires threading support.

  • bpo-33972: Email with single part but content-type set to multipart/* doesn't raise AttributeError anymore.

  • bpo-37280: Use threadpool for reading from file for sendfile fallback mode.

  • bpo-37279: Fix asyncio sendfile support when sendfile sends extra data in fallback mode.

  • bpo-19865: ctypes.create_unicode_buffer() now also supports non-BMP characters on platforms with 16-bit wchar_t (for example, Windows and AIX).

  • bpo-37266: In a subinterpreter, spawning a daemon thread now raises an exception. Daemon threads were never supported in subinterpreters. Previously, the subinterpreter finalization crashed with a Pyton fatal error if a daemon thread was still running.

  • bpo-37210: Allow pure Python implementation of pickle to work even when the C _pickle module is unavailable.

  • bpo-21872: Fix lzma: module decompresses data incompletely. When decompressing a FORMAT_ALONE format file, and it doesn't have the end marker, sometimes the last one to dozens bytes can't be output. Patch by Ma Lin.

  • bpo-35922: Fix RobotFileParser.crawl_delay() and RobotFileParser.request_rate() to return None rather than raise AttributeError when no relevant rule is defined in the robots.txt file. Patch by Rémi Lapeyre.

  • bpo-35766: Change the format of feature_version to be a (major, minor) tuple.

  • bpo-36607: Eliminate RuntimeError raised by asyncio.all_tasks() if internal tasks weak set is changed by another thread during iteration.

  • bpo-18748: _pyio.IOBase destructor now does nothing if getting the closed attribute fails to better mimick _io.IOBase finalizer.

  • bpo-36402: Fix a race condition at Python shutdown when waiting for threads. Wait until the Python thread state of all non-daemon threads get deleted (join all non-daemon threads), rather than just wait until non-daemon Python threads complete.

  • bpo-37206: Default values which cannot be represented as Python objects no longer improperly represented as None in function signatures.

  • bpo-37111: Added encoding and errors keyword parameters to logging.basicConfig.

  • bpo-12144: Ensure cookies with expires attribute are handled in CookieJar.make_cookies().

  • bpo-34886: Fix an unintended ValueError from subprocess.run() when checking for conflicting input and stdin or capture_output and stdout or stderr args when they were explicitly provided but with None values within a passed in **kwargs dict rather than as passed directly by name. Patch contributed by Rémi Lapeyre.

  • bpo-37173: The exception message for inspect.getfile() now correctly reports the passed class rather than the builtins module.

  • bpo-37178: Give math.perm() a one argument form that means the same as math.factorial().

  • bpo-37178: For math.perm(n, k), let k default to n, giving the same result as factorial.

  • bpo-37165: Converted _collections._count_elements to use the Argument Clinic.

  • bpo-34767: Do not always create a collections.deque in asyncio.Lock.

  • bpo-37158: Speed-up statistics.fmean() by switching from a function to a generator.

  • bpo-34282: Remove Enum._convert method, deprecated in 3.8.

  • bpo-37150: argparse._ActionsContainer.add_argument now throws error, if someone accidentally pass FileType class object instead of instance of FileType as type argument

  • bpo-28724: The socket module now has the socket.send_fds() and socket.recv.fds() methods. Contributed by Joannah Nanjekye, Shinya Okano and Victor Stinner.

  • bpo-35621: Support running asyncio subprocesses when execution event loop in a thread on UNIX.

  • bpo-36520: Lengthy email headers with UTF-8 characters are now properly encoded when they are folded. Patch by Jeffrey Kintscher.

  • bpo-30835: Fixed a bug in email parsing where a message with invalid bytes in content-transfer-encoding of a multipart message can cause an AttributeError. Patch by Andrew Donnellan.

  • bpo-31163: pathlib.Path instance's rename and replace methods now return the new Path instance.

  • bpo-25068: urllib.request.ProxyHandler now lowercases the keys of the passed dictionary.

  • bpo-26185: Fix repr() on empty ZipInfo object. Patch by Mickaël Schoentgen.

  • bpo-21315: Email headers containing RFC2047 encoded words are parsed despite the missing whitespace, and a defect registered. Also missing trailing whitespace after encoded words is now registered as a defect.

  • bpo-31904: Port test_datetime to VxWorks: skip zoneinfo tests on VxWorks

  • bpo-35805: Add parser for Message-ID header and add it to default HeaderRegistry. This should prevent folding of Message-ID using RFC 2048 encoded words.

  • bpo-36871: Ensure method signature is used instead of constructor signature of a class while asserting mock object against method calls. Patch by Karthikeyan Singaravelan.

  • bpo-35070: posix.getgrouplist() now works correctly when the user belongs to NGROUPS_MAX supplemental groups. Patch by Jeffrey Kintscher.

  • bpo-31783: Fix race condition in ThreadPoolExecutor when worker threads are created during interpreter shutdown.

  • bpo-36582: Fix UserString.encode() to correctly return bytes rather than a UserString instance.

  • bpo-32424: Deprecate xml.etree.ElementTree.Element.copy() in favor of copy.copy().

    Patch by Gordon P. Hemsley

  • bpo-36564: Fix infinite loop in email header folding logic that would be triggered when an email policy's max_line_length is not long enough to include the required markup and any values in the message. Patch by Paul Ganssle

  • bpo-36543: Removed methods Element.getchildren(), Element.getiterator() and ElementTree.getiterator() and the xml.etree.cElementTree module.

  • bpo-36409: Remove the old plistlib API deprecated in Python 3.4

  • bpo-36302: distutils sorts source file lists so that Extension .so files build more reproducibly by default

  • bpo-36250: Ignore ValueError from signal with interaction in non-main thread.

  • bpo-36046: Added user, group and extra_groups parameters to the subprocess.Popen constructor. Patch by Patrick McLean.

  • bpo-32627: Fix compile error when _uuid headers conflicting included.

  • bpo-35800: Deprecate smtpd.MailmanProxy ready for future removal.

  • bpo-35168: shlex.shlex.punctuation_chars is now a read-only property.

  • bpo-8538: Add support for boolean actions like --foo and --no-foo to argparse. Patch contributed by Rémi Lapeyre.

  • bpo-20504: Fixes a bug in cgi module when a multipart/form-data request has no Content-Length header.

  • bpo-25988: The abstract base classes in collections.abc no longer are exposed in the regular collections module.

  • bpo-11122: Distutils won't check for rpmbuild in specified paths only.

  • bpo-34775: Division handling of PurePath now returns NotImplemented instead of raising a TypeError when passed something other than an instance of str or PurePath. Patch by Roger Aiudi.

  • bpo-34749: binascii.a2b_base64() is now up to 2 times faster. Patch by Sergey Fedoseev.

  • bpo-34519: Add additional aliases for HP Roman 8. Patch by Michael Osipov.

  • bpo-28009: Fix uuid.getnode() on platforms with '.' as MAC Addr delimiter as well fix for MAC Addr format that omits a leading 0 in MAC Addr values. Currently, AIX is the only know platform with these settings. Patch by Michael Felt.

  • bpo-30618: Add readlink(). Patch by Girts Folkmanis.

  • bpo-32498: Made urllib.parse.unquote() accept bytes in addition to strings. Patch by Stein Karlsen.

  • bpo-33348: lib2to3 now recognizes expressions after * and ** like in f(*[] or []).

  • bpo-32689: Update shutil.move() function to allow for Path objects to be used as source argument. Patch by Emily Morehouse and Maxwell "5.13b" McKinnon.

  • bpo-32820: Added __format__ to IPv4 and IPv6 classes. Always outputs a fully zero- padded string. Supports b/x/n modifiers (bin/hex/native format). Native format for IPv4 is bin, native format for IPv6 is hex. Also supports '#' and '_' modifiers.

  • bpo-27657: Fix urllib.parse.urlparse() with numeric paths. A string like "path:80" is no longer parsed as a path but as a scheme ("path") and a path ("80").

  • bpo-4963: Fixed non-deterministic behavior related to mimetypes extension mapping and module reinitialization.

Documentation

  • bpo-21767: Explicitly mention abc support in functools.singledispatch

  • bpo-38816: Provides more details about the interaction between fork() and CPython's runtime, focusing just on the C-API. This includes cautions about where fork() should and shouldn't be called.

  • bpo-38351: Modernize email examples from %-formatting to f-strings.

  • bpo-38778: Document the fact that RuntimeError is raised if os.fork() is called in a subinterpreter.

  • bpo-38592: Add Brazilian Portuguese to the language switcher at Python Documentation website.

  • bpo-38294: Add list of no-longer-escaped chars to re.escape documentation

  • bpo-38053: Modernized the plistlib documentation

  • bpo-26868: Fix example usage of PyModule_AddObject() to properly handle errors.

  • bpo-36797: Fix a dead link in the distutils API Reference.

  • bpo-37977: Warn more strongly and clearly about pickle insecurity

  • bpo-37979: Added a link to dateutil.parser.isoparse in the datetime.fromisoformat documentation. Patch by Paul Ganssle

  • bpo-12707: Deprecate info(), geturl(), getcode() methods in favor of the headers, url, and status properties, respectively, for HTTPResponse and addinfourl. Also deprecate the code attribute of addinfourl in favor of the status attribute. Patch by Ashwin Ramaswami

  • bpo-37937: Mention frame.f_trace in sys.settrace() docs.

  • bpo-37878: Make PyThreadState_DeleteCurrent() Internal.

  • bpo-37759: Beginning edits to Whatsnew 3.8

  • bpo-37726: Stop recommending getopt in the tutorial for command line argument parsing and promote argparse.

  • bpo-32910: Remove implementation-specific behaviour of how venv's Deactivate works.

  • bpo-37256: Fix wording of arguments for Request in urllib.request

  • bpo-37284: Add a brief note to indicate that any new sys.implementation required attributes must go through the PEP process.

  • bpo-30088: Documented that mailbox.Maildir constructor doesn't attempt to verify the maildir folder layout correctness. Patch by Sviatoslav Sydorenko.

  • bpo-37521: Fix importlib examples to insert any newly created modules via importlib.util.module_from_spec() immediately into sys.modules instead of after calling loader.exec_module().

    Thanks to Benjamin Mintz for finding the bug.

  • bpo-37456: Slash ('/') is now part of syntax.

  • bpo-37487: Fix PyList_GetItem index description to include 0.

  • bpo-37149: Replace the dead link to the Tkinter 8.5 reference by John Shipman, New Mexico Tech, with a link to the archive.org copy.

  • bpo-37478: Added possible exceptions to the description of os.chdir().

  • bpo-34903: Documented that in datetime.datetime.strptime(), the leading zero in some two-digit formats is optional. Patch by Mike Gleen.

  • bpo-36260: Add decompression pitfalls to zipfile module documentation.

  • bpo-37004: In the documentation for difflib, a note was added explicitly warning that the results of SequenceMatcher's ratio method may depend on the order of the input strings.

  • bpo-36960: Restructured the datetime docs in the interest of making them more user-friendly and improving readability. Patch by Brad Solomon.

  • bpo-36487: Make C-API docs clear about what the "main" interpreter is.

  • bpo-23460: The documentation for decimal string formatting using the :g specifier has been updated to reflect the correct exponential notation cutoff point. Original patch contributed by Tuomas Suutari.

  • bpo-35803: Document and test that tempfile functions may accept a path-like object for the dir argument. Patch by Anthony Sottile.

  • bpo-33944: Added a note about the intended use of code in .pth files.

  • bpo-34293: Fix the Doc/Makefile regarding PAPER environment variable and PDF builds

  • bpo-25237: Add documentation for tkinter modules

Tests

  • bpo-38614: Fix test_communicate() of test_asyncio.test_subprocess: use support.LONG_TIMEOUT (5 minutes), instead of just 1 minute.

  • bpo-38614: Add timeout constants to test.support: LOOPBACK_TIMEOUT, INTERNET_TIMEOUT, SHORT_TIMEOUT and LONG_TIMEOUT.

  • bpo-38502: test.regrtest now uses process groups in the multiprocessing mode (-jN command line option) if process groups are available: if os.setsid() and os.killpg() functions are available.

  • bpo-35998: Fix a race condition in test_asyncio.test_start_tls_server_1(). Previously, there was a race condition between the test main() function which replaces the protocol and the test ServerProto protocol which sends ANSWER once it gets HELLO. Now, only the test main() function is responsible to send data, ServerProto no longer sends data.

  • bpo-38470: Fix test_compileall.test_compile_dir_maxlevels() on Windows without long path support: only create 3 subdirectories instead of between 20 and 100 subdirectories.

  • bpo-37531: On timeout, regrtest no longer attempts to call popen.communicate() again: it can hang until all child processes using stdout and stderr pipes completes. Kill the worker process and ignores its output. Change also the faulthandler timeout of the main process from 1 minute to 5 minutes, for Python slowest buildbots.

  • bpo-38239: Fix test_gdb for Link Time Optimization (LTO) builds.

  • bpo-38275: test_ssl now handles disabled TLS/SSL versions better. OpenSSL's crypto policy and run-time settings are recognized and tests for disabled versions are skipped. Tests also accept more TLS minimum_versions for platforms that override OpenSSL's default with strict settings.

  • bpo-38271: The private keys for test_ssl were encrypted with 3DES in traditional PKCS#5 format. 3DES and the digest algorithm of PKCS#5 are blocked by some strict crypto policies. Use PKCS#8 format with AES256 encryption instead.

  • bpo-38270: test.support now has a helper function to check for availibility of a hash digest function. Several tests are refactored avoid MD5 and use SHA256 instead. Other tests are marked to use MD5 and skipped when MD5 is disabled.

  • bpo-37123: Multiprocessing test test_mymanager() now also expects -SIGTERM, not only exitcode 0. BaseManager._finalize_manager() sends SIGTERM to the manager process if it takes longer than 1 second to stop, which happens on slow buildbots.

  • bpo-38212: Multiprocessing tests: increase test_queue_feeder_donot_stop_onexc() timeout from 1 to 60 seconds.

  • bpo-38117: Test with OpenSSL 1.1.1d

  • bpo-38018: Increase code coverage for multiprocessing.shared_memory.

  • bpo-37805: Add tests for json.dump(..., skipkeys=True). Patch by Dong-hee Na.

  • bpo-37531: Enhance regrtest multiprocess timeout: write a message when killing a worker process, catch popen.kill() and popen.wait() exceptions, put a timeout on the second call to popen.communicate().

  • bpo-37876: Add tests for ROT-13 codec.

  • bpo-36833: Added tests for PyDateTime_xxx_GET_xxx() macros of the C API of the datetime module. Patch by Joannah Nanjekye.

  • bpo-37558: Fix test_shared_memory_cleaned_after_process_termination name handling

  • bpo-37526: Add test.support.catch_threading_exception(): context manager catching threading.Thread exception using threading.excepthook().

  • bpo-37421: test_concurrent_futures now explicitly stops the ForkServer instance if it's running.

  • bpo-37421: multiprocessing tests now stop the ForkServer instance if it's running: close the "alive" file descriptor to ask the server to stop and then remove its UNIX address.

  • bpo-37421: test_distutils.test_build_ext() is now able to remove the temporary directory on Windows: don't import the newly built C extension ("xx") in the current process, but test it in a separated process.

  • bpo-37421: test_concurrent_futures now cleans up multiprocessing to remove immediately temporary directories created by multiprocessing.util.get_temp_dir().

  • bpo-37421: test_winconsoleio doesn't leak a temporary file anymore: use tempfile.TemporaryFile() to remove it when the test completes.

  • bpo-37421: multiprocessing tests now explicitly call _run_finalizers() to immediately remove temporary directories created by tests.

  • bpo-37421: urllib.request tests now call urlcleanup() to remove temporary files created by urlretrieve() tests and to clear the _opener global variable set by urlopen() and functions calling indirectly urlopen().

  • bpo-37472: Remove Lib/test/outstanding_bugs.py.

  • bpo-37199: Fix test failures when IPv6 is unavailable or disabled.

  • bpo-19696: Replace deprecated method "random.choose" with "random.choice" in "test_pkg_import.py".

  • bpo-37335: Remove no longer necessary code from c locale coercion tests

  • bpo-37421: Fix test_shutil to no longer leak temporary files.

  • bpo-37411: Fix test_wsgiref.testEnviron() to no longer depend on the environment variables (don't fail if "X" variable is set).

  • bpo-37400: Fix test_os.test_chown(): use os.getgroups() rather than grp.getgrall() to get groups. Rename also the test to test_chown_gid().

  • bpo-37359: Add --cleanup option to python3 -m test to remove test_python_* directories of previous failed jobs. Add "make cleantest" to run python3 -m test --cleanup.

  • bpo-37362: test_gdb no longer fails if it gets an "unexpected" message on stderr: it now ignores stderr. The purpose of test_gdb is to test that python-gdb.py commands work as expected, not to test gdb.

  • bpo-35998: Avoid TimeoutError in test_asyncio: test_start_tls_server_1()

  • bpo-37278: Fix test_asyncio ProactorLoopCtrlC: join the thread to prevent leaking a running thread and leaking a reference.

  • bpo-37261: Fix test.support.catch_unraisable_exception(): its __exit__() method now ignores unraisable exception raised when clearing its unraisable attribute.

  • bpo-37069: regrtest now uses sys.unraisablehook() to mark a test as "environment altered" (ENV_CHANGED) if it emits an "unraisable exception". Moreover, regrtest logs a warning in this case.

    Use python3 -m test --fail-env-changed to catch unraisable exceptions in tests.

  • bpo-37252: Fix assertions in test_close and test_events_mask_overflow devpoll tests.

  • bpo-37169: Rewrite _PyObject_IsFreed() unit tests.

  • bpo-37153: test_venv.test_multiprocessing() now explicitly calls pool.terminate() to wait until the pool completes.

  • bpo-34001: Make test_ssl pass with LibreSSL. LibreSSL handles minimum and maximum TLS version differently than OpenSSL.

  • bpo-36919: Make test_source_encoding.test_issue2301 implementation independent. The test will work now for both CPython and IronPython.

  • bpo-30202: Update test.test_importlib.test_abc to test find_spec().

  • bpo-28009: Modify the test_uuid logic to test when a program is available AND can be used to obtain a MACADDR as basis for an UUID. Patch by M. Felt

  • bpo-34596: Fallback to a default reason when unittest.skip() is uncalled. Patch by Naitree Zhu.

Build

  • bpo-38809: On Windows, build scripts will now recognize and use python.exe from an active virtual env.

  • bpo-38684: Fix _hashlib build when Blake2 is disabled, but OpenSSL supports it.

  • bpo-38468: Misc/python-config.in now uses getvar() for all still existing sysconfig.get_config_var() calls. Patch by Joannah Nanjekye.

  • bpo-37415: Fix stdatomic.h header check for ICC compiler: the ICC implementation lacks atomic_uintptr_t type which is needed by Python.

  • bpo-38301: In Solaris family, we must be sure to use -D_REENTRANT. Patch by Jesús Cea Avión.

  • bpo-36002: Locate llvm-profdata and llvm-ar binaries using AC_PATH_TOOL rather than AC_PATH_TARGET_TOOL.

  • bpo-37936: The .gitignore file systematically keeps "rooted", with a non-trailing slash, all the rules that are meant to apply to files in a specific place in the repo. Previously, when the intended file to ignore happened to be at the root of the repo, we'd most often accidentally also ignore files and directories with the same name anywhere in the tree.

  • bpo-37760: The Tools/unicode/makeunicodedata.py script, which is used for converting information from the Unicode Character Database into generated code and data used by the methods of str and by the unicodedata module, now handles each character's data as a dataclass with named attributes, rather than a length-18 list of different fields.

  • bpo-37936: The .gitignore file no longer applies to any files that are in fact tracked in the Git repository. Patch by Greg Price.

  • bpo-37725: Change "clean" makefile target to also clean the program guided optimization (PGO) data. Previously you would have to use "make clean" and "make profile-removal", or "make clobber".

  • bpo-37707: Mark some individual tests to skip when --pgo is used. The tests marked increase the PGO task time significantly and likely don't help improve optimization of the final executable.

  • bpo-36044: Reduce the number of unit tests run for the PGO generation task. This speeds up the task by a factor of about 15x. Running the full unit test suite is slow. This change may result in a slightly less optimized build since not as many code branches will be executed. If you are willing to wait for the much slower build, the old behavior can be restored using './configure [..] PROFILE_TASK="-m test --pgo-extended"'. We make no guarantees as to which PGO task set produces a faster build. Users who care should run their own relevant benchmarks as results can depend on the environment, workload, and compiler tool chain.

  • bpo-37468: make install no longer installs wininst-*.exe files used by distutils bdist_wininst: bdist_wininst only works on Windows.

  • bpo-37189: Many PyRun_XXX() functions like PyRun_String() were no longer exported in libpython38.dll by mistake. Export them again to fix the ABI compatibility.

  • bpo-25361: Enables use of SSE2 instructions in Windows 32-bit build.

  • bpo-36210: Update optional extension module detection for AIX. ossaudiodev and spwd are not applicable for AIX, and are no longer reported as missing. 3rd-party packaging of ncurses (with ASIS support) conflicts with officially supported AIX curses library, so configure AIX to use libcurses.a. However, skip trying to build _curses_panel.

    patch by M Felt

Windows

  • bpo-38589: Fixes HTML Help shortcut when Windows is not installed to C drive

  • bpo-38453: Ensure ntpath.realpath() correctly resolves relative paths.

  • bpo-38519: Restores the internal C headers that were missing from the nuget.org and Microsoft Store packages.

  • bpo-38492: Remove pythonw.exe dependency on the Microsoft C++ runtime.

  • bpo-38344: Fix error message in activate.bat

  • bpo-38359: Ensures pyw.exe launcher reads correct registry key.

  • bpo-38355: Fixes ntpath.realpath failing on sys.executable.

  • bpo-38117: Update bundled OpenSSL to 1.1.1d

  • bpo-38092: Reduce overhead when using multiprocessing in a Windows virtual environment.

  • bpo-38133: Allow py.exe launcher to locate installations from the Microsoft Store and improve display of active virtual environments.

  • bpo-38114: The pip.ini is no longer included in the Nuget package.

  • bpo-32592: Set Windows 8 as the minimum required version for API support

  • bpo-36634: os.cpu_count() now returns active processors rather than maximum processors.

  • bpo-36634: venv activate.bat now works when the existing variables contain double quote characters.

  • bpo-38081: Prevent error calling os.path.realpath() on 'NUL'.

  • bpo-38087: Fix case sensitivity in test_pathlib and test_ntpath.

  • bpo-38088: Fixes distutils not finding vcruntime140.dll with only the v142 toolset installed.

  • bpo-37283: Ensure command-line and unattend.xml setting override previously detected states in Windows installer.

  • bpo-38030: Fixes os.stat() failing for block devices on Windows

  • bpo-38020: Fixes potential crash when calling os.readlink() (or indirectly through realpath()) on a file that is not a supported link.

  • bpo-37705: Improve the implementation of winerror_to_errno().

  • bpo-37549: os.dup() no longer fails for standard streams on Windows 7.

  • bpo-1311: The nul file on Windows now returns True from exists() and a valid result from os.stat() with S_IFCHR set.

  • bpo-9949: Enable support for following symlinks in os.realpath().

  • bpo-37834: Treat all name surrogate reparse points on Windows in os.lstat() and other reparse points as regular files in os.stat().

  • bpo-36266: Add the module name in the formatted error message when DLL load fail happens during module import in _PyImport_FindSharedFuncptrWindows(). Patch by Srinivas Nyayapati.

  • bpo-25172: Trying to import the crypt module on Windows will result in an ImportError with a message explaining that the module isn't supported on Windows. On other platforms, if the underlying _crypt module is not available, the ImportError will include a message explaining the problem.

  • bpo-37778: Fixes the icons used for file associations to the Microsoft Store package.

  • bpo-37734: Fix use of registry values to launch Python from Microsoft Store app.

  • bpo-37702: Fix memory leak on Windows in creating an SSLContext object or running urllib.request.urlopen('https://...').

  • bpo-37672: Switch Windows Store package's pip to use bundled pip.ini instead of PIP_USER variable.

  • bpo-10945: Officially drop support for creating bdist_wininst installers on non-Windows systems.

  • bpo-37445: Include the FORMAT_MESSAGE_IGNORE_INSERTS flag in FormatMessageW() calls.

  • bpo-37369: Fixes path for sys.executable when running from the Microsoft Store.

  • bpo-37380: Don't collect unfinished processes with subprocess._active on Windows to cleanup later. Patch by Ruslan Kuprieiev.

  • bpo-37351: Removes libpython38.a from standard Windows distribution.

  • bpo-35360: Update Windows builds to use SQLite 3.28.0.

  • bpo-37267: On Windows, os.dup() no longer creates an inheritable fd when handling a character file.

  • bpo-36779: Ensure time.tzname is correct on Windows when the active code page is set to CP_UTF7 or CP_UTF8.

  • bpo-32587: Make winreg.REG_MULTI_SZ support zero-length strings.

  • bpo-28269: Replace use of strcasecmp() for the system function _stricmp(). Patch by Minmin Gong.

  • bpo-36590: Add native Bluetooth RFCOMM support to socket module.

macOS

  • bpo-38117: Updated OpenSSL to 1.1.1d in macOS installer.

  • bpo-38089: Move Azure Pipelines to latest VM versions and make macOS tests optional

  • bpo-18049: Increase the default stack size of threads from 5MB to 16MB on macOS, to match the stack size of the main thread. This avoids crashes on deep recursion in threads.

  • bpo-34602: Avoid test suite failures on macOS by no longer calling resource.setrlimit to increase the process stack size limit at runtime. The runtime change is no longer needed since the interpreter is being built with a larger default stack size.

  • bpo-35360: Update macOS installer to use SQLite 3.28.0.

  • bpo-34631: Updated OpenSSL to 1.1.1c in macOS installer.

IDLE

  • bpo-26353: Stop adding newline when saving an IDLE shell window.

  • bpo-4630: Add an option to toggle IDLE's cursor blink for shell, editor, and output windows. See Settings, General, Window Preferences, Cursor Blink. Patch by Zackery Spytz.

  • bpo-38598: Do not try to compile IDLE shell or output windows

  • bpo-36698: IDLE no longer fails when write non-encodable characters to stderr. It now escapes them with a backslash, as the regular Python interpreter. Added the errors field to the standard streams.

  • bpo-35379: When exiting IDLE, catch any AttributeError. One happens when EditorWindow.close is called twice. Printing a traceback, when IDLE is run from a terminal, is useless and annoying.

  • bpo-38183: To avoid problems, test_idle ignores the user config directory. It no longer tries to create or access .idlerc or any files within. Users must run IDLE to discover problems with saving settings.

  • bpo-38077: IDLE no longer adds 'argv' to the user namespace when initializing it. This bug only affected 3.7.4 and 3.8.0b2 to 3.8.0b4.

  • bpo-38041: Shell restart lines now fill the window width, always start with '=', and avoid wrapping unnecessarily. The line will still wrap if the included file name is long relative to the width.

  • bpo-35771: To avoid occasional spurious test_idle failures on slower machines, increase the hover_delay in test_tooltip.

  • bpo-37824: Properly handle user input warnings in IDLE shell. Cease turning SyntaxWarnings into SyntaxErrors.

  • bpo-37929: IDLE Settings dialog now closes properly when there is no shell window.

  • bpo-37902: Add mousewheel scrolling for IDLE module, path, and stack browsers. Patch by George Zhang.

  • bpo-37849: Fixed completions list appearing too high or low when shown above the current line.

  • bpo-36419: Refactor IDLE autocomplete and improve testing.

  • bpo-37748: Reorder the Run menu. Put the most common choice, Run Module, at the top.

  • bpo-37692: Improve highlight config sample with example shell interaction and better labels for shell elements.

  • bpo-37628: Settings dialog no longer expands with font size.

  • bpo-37627: Initialize the Customize Run dialog with the command line arguments most recently entered before. The user can optionally edit before submitting them.

  • bpo-33610: Fix code context not showing the correct context when first toggled on.

  • bpo-37530: Optimize code context to reduce unneeded background activity. Font and highlight changes now occur along with text changes instead of after a random delay.

  • bpo-27452: Cleanup config.py by inlining RemoveFile and simplifying the handling of file in CreateConfigHandlers.

  • bpo-37325: Fix tab focus traversal order for help source and custom run dialogs.

  • bpo-37321: Both subprocess connection error messages now refer to the 'Startup failure' section of the IDLE doc.

  • bpo-17535: Add optional line numbers for IDLE editor windows. Windows open without line numbers unless set otherwise in the General tab of the configuration dialog.

  • bpo-26806: To compensate for stack frames added by IDLE and avoid possible problems with low recursion limits, add 30 to limits in the user code execution process. Subtract 30 when reporting recursion limits to make this addition mostly transparent.

  • bpo-37177: Properly 'attach' search dialogs to their main window so that they behave like other dialogs and do not get hidden behind their main window.

  • bpo-37039: Adjust "Zoom Height" to individual screens by momentarily maximizing the window on first use with a particular screen. Changing screen settings may invalidate the saved height. While a window is maximized, "Zoom Height" has no effect.

  • bpo-35763: Make calltip reminder about '/' meaning positional-only less obtrusive by only adding it when there is room on the first line.

  • bpo-5680: Add 'Run... Customized' to the Run menu to run a module with customized settings. Any 'command line arguments' entered are added to sys.argv. One can suppress the normal Shell main module restart.

  • bpo-36390: Gather Format menu functions into format.py. Combine paragraph.py, rstrip.py, and format methods from editor.py.

Tools/Demos

  • bpo-38118: Update Valgrind suppression file to ignore a false alarm in PyUnicode_Decode() when using GCC builtin strcmp().

  • bpo-38347: pathfix.py: Assume all files that end on '.py' are Python scripts when working recursively.

  • bpo-37803: pdb's --help and --version long options now work.

  • bpo-37942: Improve ArgumentClinic converter for floats.

  • bpo-37704: Remove Tools/scripts/h2py.py: use cffi to access a C API in Python.

  • bpo-37675: 2to3 now works when run from a zipped standard library.

  • bpo-37034: Argument Clinic now uses the argument name on errors with keyword-only argument instead of their position. Patch contributed by Rémi Lapeyre.

  • bpo-37064: Add option -k to pathscript.py script: preserve shebang flags. Add option -a to pathscript.py script: add flags.

C API

  • bpo-37633: Re-export some function compatibility wrappers for macros in pythonrun.h.

  • bpo-38644: Provide Py_EnterRecursiveCall() and Py_LeaveRecursiveCall() as regular functions for the limited API. Previously, there were defined as macros, but these macros didn't work with the limited API which cannot access PyThreadState.recursion_depth field. Remove _Py_CheckRecursionLimit from the stable ABI.

  • bpo-38650: The global variable PyStructSequence_UnnamedField is now a constant and refers to a constant string.

  • bpo-38540: Fixed possible leak in PyArg_Parse() and similar functions for format units "es#" and "et#" when the macro PY_SSIZE_T_CLEAN is not defined.

  • bpo-38395: Fix a crash in weakref.proxy objects due to incorrect lifetime management when calling some associated methods that may delete the last reference to object being referenced by the proxy. Patch by Pablo Galindo.

  • bpo-36389: The _PyObject_CheckConsistency() function is now also available in release mode. For example, it can be used to debug a crash in the visit_decref() function of the GC.

  • bpo-38266: Revert the removal of PyThreadState_DeleteCurrent() with documentation.

  • bpo-38303: Update audioop extension module to use the stable ABI (PEP-384). Patch by Tyler Kieft.

  • bpo-38234: Py_SetPath() now sets sys.executable to the program full path (Py_GetProgramFullPath()) rather than to the program name (Py_GetProgramName()).

  • bpo-38234: Python ignored arguments passed to Py_SetPath(), Py_SetPythonHome() and Py_SetProgramName(): fix Python initialization to use specified arguments.

  • bpo-38205: The Py_UNREACHABLE() macro now calls Py_FatalError().

  • bpo-38140: Make dict and weakref offsets opaque for C heap types by passing the offsets through PyMemberDef

  • bpo-15088: The C function PyGen_NeedsFinalizing has been removed. It was not documented, tested or used anywhere within CPython after the implementation of PEP 442. Patch by Joannah Nanjekye. (Patch by Joannah Nanjekye)

  • bpo-36763: Options added by PySys_AddXOption() are now handled the same way than PyConfig.xoptions and command line -X options.

  • bpo-37926: Fix a crash in PySys_SetArgvEx(0, NULL, 0).

  • bpo-37879: Fix subtype_dealloc to suppress the type decref when the base type is a C heap type

  • bpo-37645: Add _PyObject_FunctionStr() to get a user-friendly string representation of a function-like object. Patch by Jeroen Demeyer.

  • bpo-29548: The functions PyEval_CallObject, PyEval_CallFunction, PyEval_CallMethod and PyEval_CallObjectWithKeywords are deprecated. Use PyObject_Call() and its variants instead.

  • bpo-37151: PyCFunction_Call is now a deprecated alias of PyObject_Call().

  • bpo-37540: The vectorcall protocol now requires that the caller passes only strings as keyword names.

  • bpo-37207: The vectorcall protocol is now enabled for type objects: set tp_vectorcall to a vectorcall function to be used instead of tp_new and tp_init when calling the class itself.

  • bpo-21120: Exclude Python-ast.h, ast.h and asdl.h from the limited API.

  • bpo-37483: Add new function _PyObject_CallOneArg for calling an object with one positional argument.

  • bpo-36763: Add PyConfig_SetWideStringList() function.

  • bpo-37337: Add fast functions for calling methods: _PyObject_VectorcallMethod(), _PyObject_CallMethodNoArgs() and _PyObject_CallMethodOneArg().

  • bpo-28805: The METH_FASTCALL calling convention has been documented.

  • bpo-37221: The new function PyCode_NewWithPosOnlyArgs() allows to create code objects like PyCode_New(), but with an extra posonlyargcount parameter for indicating the number of positonal-only arguments.

  • bpo-37215: Fix dtrace issue introduce by bpo-36842

  • bpo-37194: Add a new public PyObject_CallNoArgs() function to the C API: call a callable Python object without any arguments. It is the most efficient way to call a callback without any argument. On x86-64, for example, PyObject_CallFunctionObjArgs(func, NULL) allocates 960 bytes on the stack per call, whereas PyObject_CallNoArgs(func) only allocates 624 bytes per call.

  • bpo-37170: Fix the cast on error in PyLong_AsUnsignedLongLongMask().

  • bpo-35381: Convert posixmodule.c statically allocated types DirEntryType and ScandirIteratorType to heap-allocated types.

  • bpo-34331: Use singular/plural noun in error message when instantiating an abstract class with non-overriden abstract method(s).

Python 3.8.0 beta 1

Release date: 2019-06-04

Security

  • bpo-35907: CVE-2019-9948: Avoid file reading by disallowing local-file:// and local_file:// URL schemes in URLopener().open() and URLopener().retrieve() of urllib.request.

  • bpo-33529: Prevent fold function used in email header encoding from entering infinite loop when there are too many non-ASCII characters in a header.

  • bpo-33164: Updated blake2 implementation which uses secure memset implementation provided by platform.

Core and Builtins

  • bpo-35814: Allow unpacking in the right hand side of annotated assignments. In particular, t: Tuple[int, ...] = x, y, *z is now allowed.

  • bpo-37126: All structseq objects are now tracked by the garbage collector. Patch by Pablo Galindo.

  • bpo-37122: Make the co_argcount attribute of code objects represent the total number of positional arguments (including positional-only arguments). The value of co_posonlyargcount can be used to distinguish which arguments are positional only, and the difference (co_argcount - co_posonlyargcount) is the number of positional-or-keyword arguments. Patch by Pablo Galindo.

  • bpo-20092: Constructors of int, float and complex will now use the __index__() special method, if available and the corresponding method __int__(), __float__() or __complex__() is not available.

  • bpo-37087: Add native thread ID (TID) support to OpenBSD.

  • bpo-26219: Implemented per opcode cache mechanism and LOAD_GLOBAL instruction use it. LOAD_GLOBAL is now about 40% faster. Contributed by Yury Selivanov, and Inada Naoki.

  • bpo-37072: Fix crash in PyAST_FromNodeObject() when flags is NULL.

  • bpo-37029: Freeing a great many small objects could take time quadratic in the number of arenas, due to using linear search to keep obmalloc.c's list of usable arenas sorted by order of number of free memory pools. This is accomplished without search now, leaving the worst-case time linear in the number of arenas. For programs where this quite visibly matters (typically with more than 100 thousand small objects alive simultaneously), this can greatly reduce the time needed to release their memory.

  • bpo-26423: Fix possible overflow in wrap_lenfunc() when sizeof(long) < sizeof(Py_ssize_t) (e.g., 64-bit Windows).

  • bpo-37050: Improve the AST for "debug" f-strings, which use '=' to print out the source of the expression being evaluated. Delete expr_text from the FormattedValue node, and instead use a Constant string node (possibly merged with adjacent constant expressions inside the f-string).

  • bpo-22385: The bytes.hex, bytearray.hex, and memoryview.hex methods as well as the binascii.hexlify and b2a_hex functions now have the ability to include an optional separator between hex bytes. This functionality was inspired by MicroPython's hexlify implementation.

  • bpo-26836: Add os.memfd_create().

  • bpo-37032: Added new replace() method to the code type (types.CodeType).

  • bpo-37007: Implement socket.if_nameindex(), socket.if_nametoindex(), and socket.if_indextoname() on Windows.

  • bpo-36829: PyErr_WriteUnraisable() now creates a traceback object if there is no current traceback. Moreover, call PyErr_NormalizeException() and PyException_SetTraceback() to normalize the exception value. Ignore any error.

  • bpo-36878: Only accept text after # type: ignore if the first character is ASCII. This is to disallow things like # type: ignoreé.

  • bpo-36878: Store text appearing after a # type: ignore comment in the AST. For example a type ignore like # type: ignore[E1000] will have the string "[E1000]" stored in its AST node.

  • bpo-2180: Treat line continuation at EOF as a SyntaxError by Anthony Sottile.

  • bpo-36907: Fix a crash when calling a C function with a keyword dict (f(**kwargs)) and changing the dict kwargs while that function is running.

  • bpo-36946: Fix possible signed integer overflow when handling slices.

  • bpo-36826: Add NamedExpression kind support to ast_unparse.c

  • bpo-1875: A SyntaxError is now raised if a code blocks that will be optimized away (e.g. if conditions that are always false) contains syntax errors. Patch by Pablo Galindo.

  • bpo-36027: Allow computation of modular inverses via three-argument pow: the second argument is now permitted to be negative in the case where the first and third arguments are relatively prime.

  • bpo-36861: Update the Unicode database to version 12.1.0.

  • bpo-28866: Avoid caching attributes of classes which type defines mro() to avoid a hard cache invalidation problem.

  • bpo-36851: The FrameType stack is now correctly cleaned up if the execution ends with a return and the stack is not empty.

  • bpo-34616: The compile() builtin functions now support the ast.PyCF_ALLOW_TOP_LEVEL_AWAIT flag, which allow to compile sources that contains top-level await, async with or async for. This is useful to evaluate async-code from with an already async functions; for example in a custom REPL.

  • bpo-36842: Implement PEP 578, adding sys.audit, io.open_code and related APIs.

  • bpo-27639: Correct return type for UserList slicing operations. Patch by Michael Blahay, Erick Cervantes, and vaultah

  • bpo-36737: Move PyRuntimeState.warnings into per-interpreter state (via "module state").

  • bpo-36793: Removed __str__ implementations from builtin types bool, int, float, complex and few classes from the standard library. They now inherit __str__() from object.

  • bpo-36817: Add a = feature f-strings for debugging. This can precede !s, !r, or !a. It produces the text of the expression, followed by an equal sign, followed by the repr of the value of the expression. So f'{3*9+15=}' would be equal to the string '3*9+15=42'. If = is specified, the default conversion is set to !r, unless a format spec is given, in which case the formatting behavior is unchanged, and __format__ will be used.

  • bpo-24048: Save the live exception during import.c's remove_module().

  • bpo-27987: pymalloc returns memory blocks aligned by 16 bytes, instead of 8 bytes, on 64-bit platforms to conform x86-64 ABI. Recent compilers assume this alignment more often. Patch by Inada Naoki.

  • bpo-36601: A long-since-meaningless check for getpid() == main_pid was removed from Python's internal C signal handler.

  • bpo-36594: Fix incorrect use of %p in format strings. Patch by Zackery Spytz.

  • bpo-36045: builtins.help() now prefixes async for async functions

  • bpo-36084: Add native thread ID (TID) to threading.Thread objects (supported platforms: Windows, FreeBSD, Linux, macOS)

  • bpo-36035: Added fix for broken symlinks in combination with pathlib

  • bpo-35983: Added new trashcan macros to deal with a double deallocation that could occur when the tp_dealloc of a subclass calls the tp_dealloc of a base class and that base class uses the trashcan mechanism. Patch by Jeroen Demeyer.

  • bpo-20602: Do not clear sys.flags and sys.float_info during shutdown. Patch by Zackery Spytz.

  • bpo-26826: Expose copy_file_range() as a low level API in the os module.

  • bpo-32388: Remove cross-version binary compatibility requirement in tp_flags.

  • bpo-31862: Port binascii to PEP 489 multiphase initialization. Patch by Marcel Plch.

Library

  • bpo-37128: Added math.perm().

  • bpo-37120: Add SSLContext.num_tickets to control the number of TLSv1.3 session tickets.

  • bpo-12202: Fix the error handling in msilib.SummaryInformation.GetProperty(). Patch by Zackery Spytz.

  • bpo-26835: The fcntl module now contains file sealing constants for sealing of memfds.

  • bpo-29262: Add get_origin() and get_args() introspection helpers to typing module.

  • bpo-12639: msilib.Directory.start_component() no longer fails if keyfile is not None.

  • bpo-36999: Add the asyncio.Task.get_coro() method to publicly expose the tasks's coroutine object.

  • bpo-35246: Make asyncio.create_subprocess_exec() accept path-like arguments.

  • bpo-35279: Change default max_workers of ThreadPoolExecutor from cpu_count() * 5 to min(32, cpu_count() + 4)). Previous value was unreasonably large on many cores machines.

  • bpo-37076: _thread.start_new_thread() now logs uncaught exception raised by the function using sys.unraisablehook(), rather than sys.excepthook(), so the hook gets access to the function which raised the exception.

  • bpo-33725: On macOS, the multiprocessing module now uses spawn start method by default.

  • bpo-37054: Fix destructor _pyio.BytesIO and _pyio.TextIOWrapper: initialize their _buffer attribute as soon as possible (in the class body), because it's used by __del__() which calls close().

  • bpo-37058: PEP 544: Add Protocol and @runtime_checkable to the typing module.

  • bpo-36933: The functions sys.set_coroutine_wrapper and sys.get_coroutine_wrapper that were deprecated and marked for removal in 3.8 have been removed.

  • bpo-37047: Handle late binding and attribute access in unittest.mock.AsyncMock setup for autospeccing. Document newly implemented async methods in unittest.mock.MagicMock.

  • bpo-37049: PEP 589: Add TypedDict to the typing module.

  • bpo-37046: PEP 586: Add Literal to the typing module.

  • bpo-37045: PEP 591: Add Final qualifier and @final decorator to the typing module.

  • bpo-37035: Don't log OSError based exceptions if a fatal error has occurred in asyncio transport. Peer can generate almost any OSError, user cannot avoid these exceptions by fixing own code. Errors are still propagated to user code, it's just logging them is pointless and pollute asyncio logs.

  • bpo-37001: symtable.symtable() now accepts the same input types for source code as the built-in compile() function. Patch by Dino Viehland.

  • bpo-37028: Implement asyncio REPL

  • bpo-37027: Return safe to use proxy socket object from transport.get_extra_info('socket')

  • bpo-32528: Make asyncio.CancelledError a BaseException.

    This will address the common mistake many asyncio users make: an "except Exception" clause breaking Tasks cancellation.

    In addition to this change, we stop inheriting asyncio.TimeoutError and asyncio.InvalidStateError from their concurrent.futures.* counterparts. There's no point for these exceptions to share the inheritance chain.

  • bpo-1230540: Add a new threading.excepthook() function which handles uncaught threading.Thread.run() exception. It can be overridden to control how uncaught threading.Thread.run() exceptions are handled.

  • bpo-36996: Handle unittest.mock.patch() used as a decorator on async functions.

  • bpo-37008: Add support for calling next() with the mock resulting from unittest.mock.mock_open()

  • bpo-27737: Allow whitespace only header encoding in email.header - by Batuhan Taskaya

  • bpo-36969: PDB command args now display positional only arguments. Patch contributed by Rémi Lapeyre.

  • bpo-36969: PDB command args now display keyword only arguments. Patch contributed by Rémi Lapeyre.

  • bpo-36983: Add missing names to typing.__all__: ChainMap, ForwardRef, OrderedDict - by Anthony Sottile.

  • bpo-36972: Add SupportsIndex protocol to the typing module to allow type checking to detect classes that can be passed to hex(), oct() and bin().

  • bpo-32972: Implement unittest.IsolatedAsyncioTestCase to help testing asyncio-based code.

  • bpo-36952: fileinput.input() and fileinput.FileInput bufsize argument has been removed (was deprecated and ignored since Python 3.6), and as a result the mode and openhook arguments have been made keyword-only.

  • bpo-36952: Starting with Python 3.3, importing ABCs from collections is deprecated, and import should be done from collections.abc. Still being able to import from collections was marked for removal in 3.8, but has been delayed to 3.9; documentation and DeprecationWarning clarified.

  • bpo-36949: Implement __repr__ for WeakSet objects.

  • bpo-36948: Fix NameError in urllib.request.URLopener.retrieve(). Patch by Karthikeyan Singaravelan.

  • bpo-33524: Fix the folding of email header when the max_line_length is 0 or None and the header contains non-ascii characters. Contributed by Licht Takeuchi (@Licht-T).

  • bpo-24564: shutil.copystat() now ignores errno.EINVAL on os.setxattr() which may occur when copying files on filesystems without extended attributes support.

    Original patch by Giampaolo Rodola, updated by Ying Wang.

  • bpo-36888: Python child processes can now access the status of their parent process using multiprocessing.process.parent_process

  • bpo-36921: Deprecate @coroutine for sake of async def.

  • bpo-25652: Fix bug in __rmod__ of UserString - by Batuhan Taskaya.

  • bpo-36916: Remove a message about an unhandled exception in a task when writer.write() is used without await and writer.drain() fails with an exception.

  • bpo-36889: Introduce asyncio.Stream class that merges asyncio.StreamReader and asyncio.StreamWriter functionality. asyncio.Stream can work in readonly, writeonly and readwrite modes. Provide asyncio.connect(), asyncio.connect_unix(), asyncio.connect_read_pipe() and asyncio.connect_write_pipe() factories to open asyncio.Stream connections. Provide asyncio.StreamServer and UnixStreamServer to serve servers with asyncio.Stream API. Modify asyncio.create_subprocess_shell() and asyncio.create_subprocess_exec() to use asyncio.Stream instead of deprecated StreamReader and StreamWriter. Deprecate asyncio.StreamReader and asyncio.StreamWriter. Deprecate usage of private classes, e.g. asyncio.FlowControlMixing and asyncio.StreamReaderProtocol outside of asyncio package.

  • bpo-36845: Added validation of integer prefixes to the construction of IP networks and interfaces in the ipaddress module.

  • bpo-23378: Add an extend action to argparser.

  • bpo-36867: Fix a bug making a SharedMemoryManager instance and its parent process use two separate resource_tracker processes.

  • bpo-23896: Adds a grammar to lib2to3.pygram that contains exec as a function not as statement.

  • bpo-36895: The function time.clock() was deprecated in 3.3 in favor of time.perf_counter() and marked for removal in 3.8, it has removed.

  • bpo-35545: Fix asyncio discarding IPv6 scopes when ensuring hostname resolutions internally

  • bpo-36887: Add new function math.isqrt() to compute integer square roots.

  • bpo-34632: Introduce the importlib.metadata module with (provisional) support for reading metadata from third-party packages.

  • bpo-36878: When using type_comments=True in ast.parse, treat # type: ignore followed by a non-alphanumeric character and then arbitrary text as a type ignore, instead of requiring nothing but whitespace or another comment. This is to permit formations such as # type: ignore[E1000].

  • bpo-36778: cp65001 encoding (Windows code page 65001) becomes an alias to utf_8 encoding.

  • bpo-36867: The multiprocessing.resource_tracker replaces the multiprocessing.semaphore_tracker module. Other than semaphores, resource_tracker also tracks shared_memory segments.

  • bpo-30262: The Cache and Statement objects of the sqlite3 module are not exposed to the user. Patch by Aviv Palivoda.

  • bpo-24538: In shutil.copystat(), first copy extended file attributes and then file permissions, since extended attributes can only be set on the destination while it is still writeable.

  • bpo-36829: Add new sys.unraisablehook() function which can be overridden to control how "unraisable exceptions" are handled. It is called when an exception has occurred but there is no way for Python to handle it. For example, when a destructor raises an exception or during garbage collection (gc.collect()).

  • bpo-36832: Introducing zipfile.Path, a pathlib-compatible wrapper for traversing zip files.

  • bpo-36814: Fix an issue where os.posix_spawnp() would incorrectly raise a TypeError when file_actions is None.

  • bpo-33110: Handle exceptions raised by functions added by concurrent.futures add_done_callback correctly when the Future has already completed.

  • bpo-26903: Limit max_workers in ProcessPoolExecutor to 61 to work around a WaitForMultipleObjects limitation.

  • bpo-36813: Fix QueueListener to call queue.task_done() upon stopping. Patch by Bar Harel.

  • bpo-36806: Forbid creation of asyncio stream objects like StreamReader, StreamWriter, Process, and their protocols outside of asyncio package.

  • bpo-36802: Provide both sync and async calls for StreamWriter.write() and StreamWriter.close()

  • bpo-36801: Properly handle SSL connection closing in asyncio StreamWriter.drain() call.

  • bpo-36785: Implement PEP 574 (pickle protocol 5 with out-of-band buffers).

  • bpo-36772: functools.lru_cache() can now be used as a straight decorator in addition to its existing usage as a function that returns a decorator.

  • bpo-6584: Add a BadGzipFile exception to the gzip module.

  • bpo-36748: Optimized write buffering in C implementation of TextIOWrapper. Writing ASCII string to TextIOWrapper with ascii, latin1, or utf-8 encoding is about 20% faster. Patch by Inada Naoki.

  • bpo-8138: Don't mark wsgiref.simple_server.SimpleServer as multi-threaded since wsgiref.simple_server.WSGIServer is single-threaded.

  • bpo-22640: py_compile.compile() now supports silent mode. Patch by Joannah Nanjekye

  • bpo-29183: Fix double exceptions in wsgiref.handlers.BaseHandler by calling its close() method only when no exception is raised.

  • bpo-36548: Improved the repr of regular expression flags.

  • bpo-36542: The signature of Python functions can now be overridden by specifying the __text_signature__ attribute.

  • bpo-36533: Reinitialize logging.Handler locks in forked child processes instead of attempting to acquire them all in the parent before forking only to be released in the child process. The acquire/release pattern was leading to deadlocks in code that has implemented any form of chained logging handlers that depend upon one another as the lock acquisition order cannot be guaranteed.

  • bpo-35252: Throw a TypeError instead of an AssertionError when using an invalid type annotation with singledispatch.

  • bpo-35900: Allow reduction methods to return a 6-item tuple where the 6th item specifies a custom state-setting method that's called instead of the regular __setstate__ method.

  • bpo-35900: enable custom reduction callback registration for functions and classes in _pickle.c, using the new Pickler's attribute reducer_override

  • bpo-36368: Fix a bug crashing SharedMemoryManager instances in interactive sessions after a ctrl-c (KeyboardInterrupt) was sent

  • bpo-31904: Fix mmap fail for VxWorks

  • bpo-27497: csv.DictWriter.writeheader() now returns the return value of the underlying csv.Writer.writerow() method. Patch contributed by Ashish Nitin Patil.

  • bpo-36239: Parsing .mo files now ignores comments starting and ending with #-#-#-#-#.

  • bpo-26707: Enable plistlib to read and write binary plist files that were created as a KeyedArchive file. Specifically, this allows the plistlib to process 0x80 tokens as UID objects.

  • bpo-31904: Add posix module support for VxWorks.

  • bpo-35125: Asyncio: Remove inner callback on outer cancellation in shield

  • bpo-35721: Fix asyncio.SelectorEventLoop.subprocess_exec() leaks file descriptors if Popen fails and called with stdin=subprocess.PIPE. Patch by Niklas Fiekas.

  • bpo-31855: unittest.mock.mock_open() results now respects the argument of read([size]). Patch contributed by Rémi Lapeyre.

  • bpo-35431: Implement math.comb() that returns binomial coefficient, that computes the number of ways to choose k items from n items without repetition and without order. Patch by Yash Aggarwal and Keller Fuchs.

  • bpo-26660: Fixed permission errors in TemporaryDirectory clean up. Previously TemporaryDirectory.cleanup() failed when non-writeable or non-searchable files or directories were created inside a temporary directory.

  • bpo-34271: Add debugging helpers to ssl module. It's now possible to dump key material and to trace TLS protocol. The default and stdlib contexts also support SSLKEYLOGFILE env var.

  • bpo-26467: Added AsyncMock to support using unittest to mock asyncio coroutines. Patch by Lisa Roach.

  • bpo-33569: dataclasses.InitVar: Exposes the type used to create the init var.

  • bpo-34424: Fix serialization of messages containing encoded strings when the policy.linesep is set to a multi-character string. Patch by Jens Troeger.

  • bpo-34303: Performance of functools.reduce() is slightly improved. Patch by Sergey Fedoseev.

  • bpo-33361: Fix a bug in codecs.StreamRecoder where seeking might leave old data in a buffer and break subsequent read calls. Patch by Ammar Askar.

  • bpo-22454: The shlex module now exposes shlex.join(), the inverse of shlex.split(). Patch by Bo Bayles.

  • bpo-31922: asyncio.AbstractEventLoop.create_datagram_endpoint(): Do not connect UDP socket when broadcast is allowed. This allows to receive replies after a UDP broadcast.

  • bpo-24882: Change ThreadPoolExecutor to use existing idle threads before spinning up new ones.

  • bpo-31961: Added support for bytes and path-like objects in subprocess.Popen() on Windows. The args parameter now accepts a path-like object if shell is False and a sequence containing bytes and path-like objects. The executable parameter now accepts a bytes and path-like object. The cwd parameter now accepts a bytes object. Based on patch by Anders Lorentsen.

  • bpo-33123: pathlib.Path.unlink now accepts a missing_ok parameter to avoid a FileNotFoundError from being raised. Patch by Robert Buchholz.

  • bpo-32941: Allow mmap.mmap objects to access the madvise() system call (through mmap.mmap.madvise()).

  • bpo-22102: Added support for ZIP files with disks set to 0. Such files are commonly created by builtin tools on Windows when use ZIP64 extension. Patch by Francisco Facioni.

  • bpo-32515: trace.py can now run modules via python3 -m trace -t --module module_name

  • bpo-32299: Changed unittest.mock.patch.dict() to return the patched dictionary when used as context manager. Patch by Vadim Tsander.

  • bpo-27141: Added a __copy__() to collections.UserList and collections.UserDict in order to correctly implement shallow copying of the objects. Patch by Bar Harel.

  • bpo-31829: \r, \0 and \x1a (end-of-file on Windows) are now escaped in protocol 0 pickles of Unicode strings. This allows to load them without loss from files open in text mode in Python 2.

  • bpo-23395: _thread.interrupt_main() now avoids setting the Python error status if the SIGINT signal is ignored or not handled by Python.

Documentation

  • bpo-36896: Clarify that some types have unstable constructor signature between Python versions.

  • bpo-36686: Improve documentation of the stdin, stdout, and stderr arguments of the asyncio.subprocess_exec function to specify which values are supported. Also mention that decoding as text is not supported.

    Add a few tests to verify that the various values passed to the std* arguments actually work.

  • bpo-36984: Improve version added references in typing module - by Anthony Sottile.

  • bpo-36868: What's new now mentions SSLContext.hostname_checks_common_name instead of SSLContext.host_flags.

  • bpo-35924: Add a note to the curses.addstr() documentation to warn that multiline strings can cause segfaults because of an ncurses bug.

  • bpo-36783: Added C API Documentation for Time_FromTimeAndFold and PyDateTime_FromDateAndTimeAndFold as per PEP 495. Patch by Edison Abahurire.

  • bpo-36797: More of the legacy distutils documentation has been either pruned, or else more clearly marked as being retained solely until the setuptools documentation covers it independently.

  • bpo-22865: Add detail to the documentation on the pty.spawn function.

  • bpo-35397: Remove deprecation and document urllib.parse.unwrap(). Patch contributed by Rémi Lapeyre.

  • bpo-32995: Added the context variable in glossary.

  • bpo-33519: Clarify that copy() is not part of the MutableSequence ABC.

  • bpo-33482: Make codecs.StreamRecoder.writelines take a list of bytes.

  • bpo-25735: Added documentation for func factorial to indicate that returns integer values

  • bpo-20285: Expand object.__doc__ (docstring) to make it clearer. Modify pydoc.py so that help(object) lists object methods (for other classes, help omits methods of the object base class.)

Tests

  • bpo-37069: Modify test_coroutines, test_cprofile, test_generators, test_raise, test_ssl and test_yield_from to use test.support.catch_unraisable_exception() rather than test.support.captured_stderr().

  • bpo-37098: Fix test_memfd_create on older Linux Kernels.

  • bpo-37081: Test with OpenSSL 1.1.1c

  • bpo-36829: Add test.support.catch_unraisable_exception(): context manager catching unraisable exception using sys.unraisablehook().

  • bpo-36915: The main regrtest process now always removes all temporary directories of worker processes even if they crash or if they are killed on KeyboardInterrupt (CTRL+c).

  • bpo-36719: "python3 -m test -jN ..." now continues the execution of next tests when a worker process crash (CHILD_ERROR state). Previously, the test suite stopped immediately. Use --failfast to stop at the first error.

  • bpo-36816: Update Lib/test/selfsigned_pythontestdotnet.pem to match self-signed.pythontest.net's new TLS certificate.

  • bpo-35925: Skip httplib and nntplib networking tests when they would otherwise fail due to a modern OS or distro with a default OpenSSL policy of rejecting connections to servers with weak certificates.

  • bpo-36782: Add tests for several C API functions in the datetime module. Patch by Edison Abahurire.

  • bpo-36342: Fix test_multiprocessing in test_venv if platform lacks functioning sem_open.

Build

  • bpo-36721: To embed Python into an application, a new --embed option must be passed to python3-config --libs --embed to get -lpython3.8 (link the application to libpython). To support both 3.8 and older, try python3-config --libs --embed first and fallback to python3-config --libs (without --embed) if the previous command fails.

    Add a pkg-config python-3.8-embed module to embed Python into an application: pkg-config python-3.8-embed --libs includes -lpython3.8. To support both 3.8 and older, try pkg-config python-X.Y-embed --libs first and fallback to pkg-config python-X.Y --libs (without --embed) if the previous command fails (replace X.Y with the Python version).

    On the other hand, pkg-config python3.8 --libs no longer contains -lpython3.8. C extensions must not be linked to libpython (except on Android, case handled by the script); this change is backward incompatible on purpose.

  • bpo-36786: "make install" now runs compileall in parallel.

Windows

  • bpo-36965: include of STATUS_CONTROL_C_EXIT without depending on MSC compiler

  • bpo-35926: Update to OpenSSL 1.1.1b for Windows.

  • bpo-29883: Add Windows support for UDP transports for the Proactor Event Loop. Patch by Adam Meily.

  • bpo-33407: The Py_DEPRECATED() macro has been implemented for MSVC.

macOS

  • bpo-36231: Support building Python on macOS without /usr/include installed. As of macOS 10.14, system header files are only available within an SDK provided by either the Command Line Tools or the Xcode app.

IDLE

  • bpo-35610: Replace now redundant .context_use_ps1 with .prompt_last_line. This finishes change started in bpo-31858.

  • bpo-37038: Make idlelib.run runnable; add test clause.

  • bpo-36958: Print any argument other than None or int passed to SystemExit or sys.exit().

  • bpo-36807: When saving a file, call os.fsync() so bits are flushed to e.g. USB drive.

  • bpo-32411: In browser.py, remove extraneous sorting by line number since dictionary was created in line number order.

Tools/Demos

  • bpo-37053: Handle strings like u"bar" correctly in Tools/parser/unparse.py. Patch by Chih-Hsuan Yen.

C API

  • bpo-36763: Implement the PEP 587 "Python Initialization Configuration".

  • bpo-36379: Fix crashes when attempting to use the modulo parameter when __ipow__ is implemented in C.

  • bpo-37107: Update PyObject_CallMethodObjArgs() and _PyObject_CallMethodIdObjArgs to use _PyObject_GetMethod to avoid creating a bound method object in many cases. Patch by Michael J. Sullivan.

  • bpo-36974: Implement PEP 590: Vectorcall: a fast calling protocol for CPython. This is a new protocol to optimize calls of custom callable objects.

  • bpo-36763: Py_Main() now returns the exitcode rather than calling Py_Exit(exitcode) when calling PyErr_Print() if the current exception type is SystemExit.

  • bpo-36922: Add new type flag Py_TPFLAGS_METHOD_DESCRIPTOR for objects behaving like unbound methods. These are objects supporting the optimization given by the LOAD_METHOD/CALL_METHOD opcodes. See PEP 590.

  • bpo-36728: The PyEval_ReInitThreads() function has been removed from the C API. It should not be called explicitly: use PyOS_AfterFork_Child() instead.

Python 3.8.0 alpha 4

Release date: 2019-05-06

Security

  • bpo-36742: Fixes mishandling of pre-normalization characters in urlsplit().

  • bpo-30458: Address CVE-2019-9740 by disallowing URL paths with embedded whitespace or control characters through into the underlying http client request. Such potentially malicious header injection URLs now cause an http.client.InvalidURL exception to be raised.

  • bpo-35755: shutil.which() now uses os.confstr("CS_PATH") if available and if the PATH environment variable is not set. Remove also the current directory from posixpath.defpath. On Unix, shutil.which() and the subprocess module no longer search the executable in the current directory if the PATH environment variable is not set.

Core and Builtins

  • bpo-36722: In debug build, import now also looks for C extensions compiled in release mode and for C extensions compiled in the stable ABI.

  • bpo-32849: Fix Python Initialization code on FreeBSD to detect properly when stdin file descriptor (fd 0) is invalid.

  • bpo-36623: Remove parser headers and related function declarations that lack implementations after the removal of pgen.

  • bpo-20180: dict.pop() is now up to 33% faster thanks to Argument Clinic. Patch by Inada Naoki.

  • bpo-36611: Debug memory allocators: disable serialno field by default from debug hooks on Python memory allocators to reduce the memory footprint by 5%. Enable tracemalloc to get the traceback where a memory block has been allocated when a fatal memory error is logged to decide where to put a breakpoint. Compile Python with PYMEM_DEBUG_SERIALNO defined to get back the field.

  • bpo-36588: On AIX, sys.platform doesn't contain the major version anymore. Always return 'aix', instead of 'aix3' .. 'aix7'. Since older Python versions include the version number, it is recommended to always use sys.platform.startswith('aix'). Contributed by M. Felt.

  • bpo-36549: Change str.capitalize to use titlecase for the first character instead of uppercase.

  • bpo-36540: Implement PEP 570 (Python positional-only parameters). Patch by Pablo Galindo.

  • bpo-36475: PyEval_AcquireLock() and PyEval_AcquireThread() now terminate the current thread if called while the interpreter is finalizing, making them consistent with PyEval_RestoreThread(), Py_END_ALLOW_THREADS(), and PyGILState_Ensure().

  • bpo-36504: Fix signed integer overflow in _ctypes.c's PyCArrayType_new().

  • bpo-20844: Fix running script with encoding cookie and LF line ending may fail on Windows.

  • bpo-24214: Fixed support of the surrogatepass error handler in the UTF-8 incremental decoder.

  • bpo-36452: Changing dict keys during iteration of the dict itself, keys(), values(), or items() will now be detected in certain corner cases where keys are deleted/added so that the number of keys isn't changed. A RuntimeError will be raised after len(dict) iterations. Contributed by Thomas Perl.

  • bpo-36459: Fix a possible double PyMem_FREE() due to tokenizer.c's tok_nextc().

  • bpo-36433: Fixed TypeError message in classmethoddescr_call.

  • bpo-36430: Fix a possible reference leak in itertools.count().

  • bpo-36440: Include node names in ParserError messages, instead of numeric IDs. Patch by A. Skrobov.

  • bpo-36143: Regenerate keyword from the Grammar and Tokens file using pgen. Patch by Pablo Galindo.

  • bpo-18372: Add missing PyObject_GC_Track() calls in the pickle module. Patch by Zackery Spytz.

Library

  • bpo-35952: Fix pythoninfo when the compiler is missing.

  • bpo-28238: The .find*() methods of xml.etree.ElementTree can now search for wildcards like {*}tag and {ns}* that match a tag in any namespace or all tags in a namespace. Patch by Stefan Behnel.

  • bpo-26978: pathlib.path.link_to() is now implemented. It creates a hard link pointing to a path.

  • bpo-1613500: fileinput.FileInput now uses the input file mode to correctly set the output file mode (previously it was hardcoded to 'w') when inplace=True is passed to its constructor.

  • bpo-36734: Fix compilation of faulthandler.c on HP-UX. Initialize stack_t current_stack to zero using memset().

  • bpo-13611: The xml.etree.ElementTree packages gained support for C14N 2.0 serialisation. Patch by Stefan Behnel.

  • bpo-36669: Add missing matrix multiplication operator support to weakref.proxy.

  • bpo-36676: The XMLParser() in xml.etree.ElementTree provides namespace prefix context to the parser target if it defines the callback methods "start_ns()" and/or "end_ns()". Patch by Stefan Behnel.

  • bpo-36673: The TreeBuilder and XMLPullParser in xml.etree.ElementTree gained support for parsing comments and processing instructions. Patch by Stefan Behnel.

  • bpo-36650: The C version of functools.lru_cache() was treating calls with an empty **kwargs dictionary as being distinct from calls with no keywords at all. This did not result in an incorrect answer, but it did trigger an unexpected cache miss.

  • bpo-28552: Fix distutils.sysconfig if sys.executable is None or an empty string: use os.getcwd() to initialize project_base. Fix also the distutils build command: don't use sys.executable if it is None or an empty string.

  • bpo-35755: shutil.which() and distutils.spawn.find_executable() now use os.confstr("CS_PATH") if available instead of os.defpath, if the PATH environment variable is not set. Moreover, don't use os.confstr("CS_PATH") nor os.defpath if the PATH environment variable is set to an empty string.

  • bpo-25430: improve performance of IPNetwork.__contains__()

  • bpo-30485: Path expressions in xml.etree.ElementTree can now avoid explicit namespace prefixes for tags (or the "{namespace}tag" notation) by passing a default namespace with an empty string prefix.

  • bpo-36613: Fix asyncio wait() not removing callback if exception

  • bpo-36598: Fix isinstance check for Mock objects with spec when the code is executed under tracing. Patch by Karthikeyan Singaravelan.

  • bpo-18748: In development mode (-X dev) and in debug build, the io.IOBase destructor now logs close() exceptions. These exceptions are silent by default in release mode.

  • bpo-36575: The _lsprof module now uses internal timer same to time.perf_counter() by default. gettimeofday(2) was used on Unix. New timer has better resolution on most Unix platforms and timings are no longer impacted by system clock updates since perf_counter() is monotonic. Patch by Inada Naoki.

  • bpo-33461: json.loads now emits DeprecationWarning when encoding option is specified. Patch by Matthias Bussonnier.

  • bpo-36559: The random module now prefers the lean internal _sha512 module over hashlib for seed(version=2) to optimize import time.

  • bpo-17561: Set backlog=None as the default for socket.create_server.

  • bpo-34373: Fix time.mktime() error handling on AIX for year before 1970.

  • bpo-36232: Improve error message when trying to open existing DBM database that actually doesn't exist. Patch by Marco Rougeth.

  • bpo-36546: Add statistics.quantiles()

  • bpo-36050: Optimized http.client.HTTPResponse.read() for large response. Patch by Inada Naoki.

  • bpo-36522: If debuglevel is set to >0 in http.client, print all values for headers with multiple values for the same header name. Patch by Matt Houglum.

  • bpo-36492: Deprecated passing required arguments like func as keyword arguments in functions which should accept arbitrary keyword arguments and pass them to other function. Arbitrary keyword arguments (even with names "self" and "func") can now be passed to these functions if the required arguments are passed as positional arguments.

  • bpo-27181: Add statistics.geometric_mean().

  • bpo-30427: os.path.normcase() relies on os.fspath() to check the type of its argument. Redundant checks have been removed from its posixpath.normcase() and ntpath.normcase() implementations. Patch by Wolfgang Maier.

  • bpo-36385: Stop rejecting IPv4 octets for being ambiguously octal. Leading zeros are ignored, and no longer are assumed to specify octal octets. Octets are always decimal numbers. Octets must still be no more than three digits, including leading zeroes.

  • bpo-36434: Errors during writing to a ZIP file no longer prevent to properly close it.

  • bpo-36407: Fixed wrong indentation writing for CDATA section in xml.dom.minidom. Patch by Vladimir Surjaninov.

  • bpo-36326: inspect.getdoc() can now find docstrings for member objects when __slots__ is a dictionary.

  • bpo-36366: Calling stop() on an unstarted or stopped unittest.mock.patch() object will now return None instead of raising RuntimeError, making the method idempotent. Patch by Karthikeyan Singaravelan.

  • bpo-36348: The imap.IMAP4.logout() method no longer ignores silently arbitrary exceptions.

  • bpo-31904: Add time module support and fix test_time faiures for VxWorks.

  • bpo-36227: Added support for keyword arguments default_namespace and xml_declaration in functions ElementTree.tostring() and ElementTree.tostringlist().

  • bpo-36004: Added new alternate constructors datetime.date.fromisocalendar() and datetime.datetime.fromisocalendar(), which construct date objects from ISO year, week number and weekday; these are the inverse of each class's isocalendar method. Patch by Paul Ganssle.

  • bpo-35936: modulefinder no longer depends on the deprecated imp module, and the initializer for modulefinder.ModuleFinder now has immutable default arguments. Patch by Brandt Bucher.

  • bpo-35376: modulefinder correctly handles modules that have the same name as a bad package. Patch by Brandt Bucher.

  • bpo-17396: modulefinder no longer crashes when encountering syntax errors in followed imports. Patch by Brandt Bucher.

  • bpo-35934: Added create_server() and has_dualstack_ipv6() convenience functions to automate the necessary tasks usually involved when creating a server socket, including accepting both IPv4 and IPv6 connections on the same socket. (Contributed by Giampaolo Rodola in bpo-17561.)

  • bpo-23078: Add support for classmethod() and staticmethod() to unittest.mock.create_autospec(). Initial patch by Felipe Ochoa.

  • bpo-35416: Fix potential resource warnings in distutils. Patch by Mickaël Schoentgen.

  • bpo-25451: Add transparency methods to tkinter.PhotoImage. Patch by Zackery Spytz.

  • bpo-35082: Don't return deleted attributes when calling dir on a unittest.mock.Mock.

  • bpo-34547: wsgiref.handlers.BaseHandler now handles abrupt client connection terminations gracefully. Patch by Petter Strandmark.

  • bpo-31658: xml.sax.parse() now supports path-like. Patch by Mickaël Schoentgen.

  • bpo-34139: Remove stale unix datagram socket before binding

  • bpo-33530: Implemented Happy Eyeballs in asyncio.create_connection(). Added two new arguments, happy_eyeballs_delay and interleave, to specify Happy Eyeballs behavior.

  • bpo-33291: Do not raise AttributeError when calling the inspect functions isgeneratorfunction, iscoroutinefunction, isasyncgenfunction on a method created from an arbitrary callable. Instead, return False.

  • bpo-31310: Fix the multiprocessing.semaphore_tracker so it is reused by child processes

  • bpo-31292: Fix setup.py check --restructuredtext for files containing include directives.

Documentation

  • bpo-36625: Remove obsolete comments from docstrings in fractions.Fraction

  • bpo-30840: Document relative imports

  • bpo-36523: Add docstring for io.IOBase.writelines().

  • bpo-36425: New documentation translation: Simplified Chinese.

  • bpo-36345: Avoid the duplication of code from Tools/scripts/serve.py in using the literalinclude directive for the basic wsgiref-based web server in the documentation of wsgiref. Contributed by Stéphane Wirtel.

  • bpo-36345: Using the code of the Tools/scripts/serve.py script as an example in the wsgiref documentation. Contributed by Stéphane Wirtel.

  • bpo-36157: Added Documention for PyInterpreterState_Main().

  • bpo-33043: Updates the docs.python.org page with the addition of a 'Contributing to Docs' link at the end of the page (between 'Reporting Bugs' and 'About Documentation'). Updates the 'Found a Bug' page with additional links and information in the Documentation Bugs section.

  • bpo-35581: @typing.type_check_only now allows type stubs to mark functions and classes not available during runtime.

  • bpo-33832: Add glossary entry for 'magic method'.

  • bpo-32913: Added re.Match.groupdict example to regex HOWTO.

Tests

  • bpo-36719: regrtest now always detects uncollectable objects. Previously, the check was only enabled by --findleaks. The check now also works with -jN/--multiprocess N. --findleaks becomes a deprecated alias to --fail-env-changed.

  • bpo-36725: When using multiprocessing mode (-jN), regrtest now better reports errors if a worker process fails, and it exits immediately on a worker thread failure or when interrupted.

  • bpo-36454: Change test_time.test_monotonic() to test only the lower bound of elapsed time after a sleep command rather than the upper bound. This prevents unnecessary test failures on slow buildbots. Patch by Victor Stinner.

  • bpo-32424: Improve test coverage for xml.etree.ElementTree. Patch by Gordon P. Hemsley.

  • bpo-32424: Fix typo in test_cyclic_gc() test for xml.etree.ElementTree. Patch by Gordon P. Hemsley.

  • bpo-36635: Add a new _testinternalcapi module to test the internal C API.

  • bpo-36629: Fix test_imap4_host_default_value() of test_imaplib: catch also errno.ENETUNREACH error.

  • bpo-36611: Fix test_sys.test_getallocatedblocks() when tracemalloc is enabled.

  • bpo-36560: Fix reference leak hunting in regrtest: compute also deltas (of reference count, allocated memory blocks, file descriptor count) during warmup, to ensure that everything is initialized before starting to hunt reference leaks.

  • bpo-36565: Fix reference hunting (python3 -m test -R 3:3) when Python has no built-in abc module.

  • bpo-31904: Port test_resource to VxWorks: skip tests cases setting RLIMIT_FSIZE and RLIMIT_CPU.

  • bpo-31904: Fix test_tabnanny on VxWorks: adjust ENOENT error message.

  • bpo-36436: Fix _testcapi.pymem_buffer_overflow(): handle memory allocation failure.

  • bpo-31904: Fix test_utf8_mode on VxWorks: Python always use UTF-8 on VxWorks.

  • bpo-36341: Fix tests that may fail with PermissionError upon calling bind() on AF_UNIX sockets.

Build

  • bpo-36747: Remove the stale scriptsinstall Makefile target.

  • bpo-21536: On Unix, C extensions are no longer linked to libpython except on Android and Cygwin.

    It is now possible for a statically linked Python to load a C extension built using a shared library Python.

    When Python is embedded, libpython must not be loaded with RTLD_LOCAL, but RTLD_GLOBAL instead. Previously, using RTLD_LOCAL, it was already not possible to load C extensions which were not linked to libpython, such as C extensions of the standard library built by the *shared* section of Modules/Setup.

    distutils, python-config and python-config.py have been modified.

  • bpo-36707: ./configure --with-pymalloc no longer adds the m flag to SOABI (sys.implementation.cache_tag). Enabling or disabling pymalloc has no impact on the ABI.

  • bpo-36635: Change PyAPI_FUNC(type), PyAPI_DATA(type) and PyMODINIT_FUNC macros of pyport.h when Py_BUILD_CORE_MODULE is defined. The Py_BUILD_CORE_MODULE define must be now be used to build a C extension as a dynamic library accessing Python internals: export the PyInit_xxx() function in DLL exports on Windows.

  • bpo-31904: Don't build the _crypt extension on VxWorks.

  • bpo-36618: Add -fmax-type-align=8 to CFLAGS when clang compiler is detected. The pymalloc memory allocator aligns memory on 8 bytes. On x86-64, clang expects alignment on 16 bytes by default and so uses MOVAPS instruction which can lead to segmentation fault. Instruct clang that Python is limited to alignment on 8 bytes to use MOVUPS instruction instead: slower but don't trigger a SIGSEGV if the memory is not aligned on 16 bytes. Sadly, the flag must be added to CFLAGS and not just CFLAGS_NODIST, since third party C extensions can have the same issue.

  • bpo-36605: make tags and make TAGS now also parse Modules/_io/*.c and Modules/_io/*.h.

  • bpo-36465: Release builds and debug builds are now ABI compatible: defining the Py_DEBUG macro no longer implies the Py_TRACE_REFS macro, which introduces the only ABI incompatibility. The Py_TRACE_REFS macro, which adds the sys.getobjects() function and the PYTHONDUMPREFS environment variable, can be set using the new ./configure --with-trace-refs build option.

  • bpo-36577: setup.py now correctly reports missing OpenSSL headers and libraries again.

  • bpo-36544: Fix regression introduced in bpo-36146 refactoring setup.py

  • bpo-36508: python-config --ldflags no longer includes flags of the LINKFORSHARED variable. The LINKFORSHARED variable must only be used to build executables.

  • bpo-36503: Remove references to "aix3" and "aix4". Patch by M. Felt.

Windows

  • bpo-35920: Added platform.win32_edition() and platform.win32_is_iot(). Added support for cross-compiling packages for Windows ARM32. Skip tests that are not expected to work on Windows IoT Core ARM32.

  • bpo-36649: Remove trailing spaces for registry keys when installed via the Store.

  • bpo-34144: Fixed activate.bat to correctly update codepage when chcp.com returns dots in output. Patch by Lorenz Mende.

  • bpo-36509: Added preset-iot layout for Windows IoT ARM containers. This layout doesn't contain UI components like tkinter or IDLE. It also doesn't contain files to support on-target builds since Windows ARM32 builds must be cross-compiled when using MSVC.

  • bpo-35941: enum_certificates function of the ssl module now returns certificates from all available certificate stores inside windows in a query instead of returning only certificates from the system wide certificate store. This includes certificates from these certificate stores: local machine, local machine enterprise, local machine group policy, current user, current user group policy, services, users. ssl.enum_crls() function is changed in the same way to return all certificate revocation lists inside the windows certificate revocation list stores.

  • bpo-36441: Fixes creating a venv when debug binaries are installed.

  • bpo-36085: Enable better DLL resolution on Windows by using safe DLL search paths and adding os.add_dll_directory().

  • bpo-36010: Add the venv standard library module to the nuget distribution for Windows.

  • bpo-29515: Add the following socket module constants on Windows: IPPROTO_AH IPPROTO_CBT IPPROTO_DSTOPTS IPPROTO_EGP IPPROTO_ESP IPPROTO_FRAGMENT IPPROTO_GGP IPPROTO_HOPOPTS IPPROTO_ICLFXBM IPPROTO_ICMPV6 IPPROTO_IDP IPPROTO_IGMP IPPROTO_IGP IPPROTO_IPV4 IPPROTO_IPV6 IPPROTO_L2TP IPPROTO_MAX IPPROTO_ND IPPROTO_NONE IPPROTO_PGM IPPROTO_PIM IPPROTO_PUP IPPROTO_RDP IPPROTO_ROUTING IPPROTO_SCTP IPPROTO_ST

  • bpo-35947: Added current version of libffi to cpython-source-deps. Change _ctypes to use current version of libffi on Windows.

  • bpo-34060: Report system load when running test suite on Windows. Patch by Ammar Askar. Based on prior work by Jeremy Kloth.

  • bpo-31512: With the Windows 10 Creators Update, non-elevated users can now create symlinks as long as the computer has Developer Mode enabled.

macOS

  • bpo-34602: Avoid failures setting macOS stack resource limit with resource.setrlimit. This reverts an earlier fix for bpo-18075 which forced a non-default stack size when building the interpreter executable on macOS.

IDLE

  • bpo-36429: Fix starting IDLE with pyshell. Add idlelib.pyshell alias at top; remove pyshell alias at bottom. Remove obsolete __name__=='__main__' command.

Tools/Demos

  • bpo-14546: Fix the argument handling in Tools/scripts/lll.py.

C API

  • bpo-36763: Fix memory leak in Py_SetStandardStreamEncoding(): release memory if the function is called twice.

  • bpo-36641: PyDoc_VAR(name) and PyDoc_STRVAR(name,str) now create static const char name[] instead of static char name[]. Patch by Inada Naoki.

  • bpo-36389: Change the value of CLEANBYTE, DEADDYTE and FORBIDDENBYTE internal constants used by debug hooks on Python memory allocators (PyMem_SetupDebugHooks() function). Byte patterns 0xCB, 0xDB and 0xFB have been replaced with 0xCD, 0xDD and 0xFD to use the same values than Windows CRT debug malloc() and free().

  • bpo-36443: Since Python 3.7.0, calling Py_DecodeLocale() before Py_Initialize() produces mojibake if the LC_CTYPE locale is coerced and/or if the UTF-8 Mode is enabled by the user configuration. The LC_CTYPE coercion and UTF-8 Mode are now disabled by default to fix the mojibake issue. They must now be enabled explicitly (opt-in) using the new _Py_PreInitialize() API with _PyPreConfig.

  • bpo-36025: Fixed an accidental change to the datetime C API where the arguments to the PyDate_FromTimestamp() function were incorrectly interpreted as a single timestamp rather than an arguments tuple, which causes existing code to start raising TypeError. The backwards-incompatible change was only present in alpha releases of Python 3.8. Patch by Paul Ganssle.

  • bpo-35810: Modify PyObject_Init to correctly increase the refcount of heap- allocated Type objects. Also fix the refcounts of the heap-allocated types that were either doing this manually or not decreasing the type's refcount in tp_dealloc

Python 3.8.0 alpha 3

Release date: 2019-03-25

Security

  • bpo-36216: Changes urlsplit() to raise ValueError when the URL contains characters that decompose under IDNA encoding (NFKC-normalization) into characters that affect how the URL is parsed.

  • bpo-35121: Don't send cookies of domain A without Domain attribute to domain B when domain A is a suffix match of domain B while using a cookiejar with http.cookiejar.DefaultCookiePolicy policy. Patch by Karthikeyan Singaravelan.

Core and Builtins

  • bpo-36421: Fix a possible double decref in _ctypes.c's PyCArrayType_new().

  • bpo-36412: Fix a possible crash when creating a new dictionary.

  • bpo-36398: Fix a possible crash in structseq_repr().

  • bpo-36256: Fix bug in parsermodule when parsing a state in a DFA that has two or more arcs with labels of the same type. Patch by Pablo Galindo.

  • bpo-36365: repr(structseq) is no longer limited to 512 bytes.

  • bpo-36374: Fix a possible null pointer dereference in merge_consts_recursive(). Patch by Zackery Spytz.

  • bpo-36236: At Python initialization, the current directory is no longer prepended to sys.path if it has been removed.

  • bpo-36352: Python initialization now fails with an error, rather than silently truncating paths, if a path is too long.

  • bpo-36301: Python initialization now fails if decoding pybuilddir.txt configuration file fails at startup.

  • bpo-36333: Fix leak in _PyRuntimeState_Fini. Contributed by Stéphane Wirtel.

  • bpo-36332: The builtin compile() can now handle AST objects that contain assignment expressions. Patch by Pablo Galindo.

  • bpo-36282: Improved error message for too much positional arguments in some builtin functions.

  • bpo-30040: New empty dict uses fewer memory for now. It used more memory than empty dict created by dict.clear(). And empty dict creation and deletion is about 2x faster. Patch by Inada Naoki.

  • bpo-36262: Fix an unlikely memory leak on conversion from string to float in the function _Py_dg_strtod() used by float(str), complex(str), pickle.load(), marshal.load(), etc.

  • bpo-36252: Update Unicode databases to version 12.0.0.

  • bpo-36218: Fix a segfault occurring when sorting a list of heterogeneous values. Patch contributed by Rémi Lapeyre and Elliot Gorokhovsky.

  • bpo-36188: Cleaned up left-over vestiges of Python 2 unbound method handling in method objects and documentation. Patch by Martijn Pieters

  • bpo-36124: Add a new interpreter-specific dict and expose it in the C-API via PyInterpreterState_GetDict(). This parallels PyThreadState_GetDict(). However, extension modules should continue using PyModule_GetState() for their own internal per-interpreter state.

  • bpo-35975: Add a feature_version flag to ast.parse() (documented) and compile() (hidden) that allows tweaking the parser to support older versions of the grammar. In particular, if feature_version is 5 or 6, the hacks for the async and await keyword from PEP 492 are reinstated. (For 7 or higher, these are unconditionally treated as keywords, but they are still special tokens rather than NAME tokens that the parser driver recognizes.)

  • bpo-31904: Use UTF-8 as the system encoding on VxWorks.

  • bpo-36048: The __index__() special method will be used instead of __int__() for implicit conversion of Python numbers to C integers. Using the __int__() method in implicit conversions has been deprecated.

  • bpo-35808: Retire pgen and use a modified version of pgen2 to generate the parser. Patch by Pablo Galindo.

Library

  • bpo-36401: The class documentation created by pydoc now has a separate section for readonly properties.

  • bpo-36320: The typing.NamedTuple() class has deprecated the _field_types attribute in favor of the __annotations__ attribute which carried the same information. Also, both attributes were converted from OrderedDict to a regular dict.

  • bpo-34745: Fix asyncio ssl memory issues caused by circular references

  • bpo-36324: Add method to statistics.NormalDist for computing the inverse cumulative normal distribution.

  • bpo-36321: collections.namedtuple() misspelled the name of an attribute. To be consistent with typing.NamedTuple, the attribute name should have been "_field_defaults" instead of "_fields_defaults". For backwards compatibility, both spellings are now created. The misspelled version may be removed in the future.

  • bpo-36297: "unicode_internal" codec is removed. It was deprecated since Python 3.3. Patch by Inada Naoki.

  • bpo-36298: Raise ModuleNotFoundError in pyclbr when a module can't be found. Thanks to 'mental' for the bug report.

  • bpo-36268: Switch the default format used for writing tars with mod:tarfile to the modern POSIX.1-2001 pax standard, from the vendor-specific GNU. Contributed by C.A.M. Gerlach.

  • bpo-36285: Fix integer overflows in the array module. Patch by Stephan Hohe.

  • bpo-31904: Add _signal module support for VxWorks.

  • bpo-36272: logging does not silently ignore RecursionError anymore. Patch contributed by Rémi Lapeyre.

  • bpo-36280: Add a kind field to ast.Constant. It is 'u' if the literal has a 'u' prefix (i.e. a Python 2 style unicode literal), else None.

  • bpo-35931: The pdb debug command now gracefully handles all exceptions.

  • bpo-36251: Fix format strings used for stderrprinter and re.Match reprs. Patch by Stephan Hohe.

  • bpo-36235: Fix CFLAGS in customize_compiler() of distutils.sysconfig: when the CFLAGS environment variable is defined, don't override CFLAGS variable with the OPT variable anymore. Initial patch written by David Malcolm.

  • bpo-35807: Update ensurepip to install pip 19.0.3 and setuptools 40.8.0.

  • bpo-36139: Release GIL when closing mmap objects.

  • bpo-36179: Fix two unlikely reference leaks in _hashopenssl. The leaks only occur in out-of-memory cases.

  • bpo-36169: Add overlap() method to statistics.NormalDist. Computes the overlapping coefficient for two normal distributions.

  • bpo-36103: Default buffer size used by shutil.copyfileobj() is changed from 16 KiB to 64 KiB on non-Windows platform to reduce system call overhead. Contributed by Inada Naoki.

  • bpo-36130: Fix pdb with skip=... when stepping into a frame without a __name__ global. Patch by Anthony Sottile.

  • bpo-35652: shutil.copytree(copy_function=...) erroneously pass DirEntry instead of a path string.

  • bpo-35178: Ensure custom warnings.formatwarning() function can receive line as positional argument. Based on patch by Tashrif Billah.

  • bpo-36106: Resolve potential name clash with libm's sinpi(). Patch by Dmitrii Pasechnik.

  • bpo-36091: Clean up reference to async generator in Lib/types. Patch by Henry Chen.

  • bpo-36043: FileCookieJar supports path-like object. Contributed by Stéphane Wirtel

  • bpo-35899: Enum has been fixed to correctly handle empty strings and strings with non-Latin characters (ie. 'α', 'א') without crashing. Original patch contributed by Maxwell. Assisted by Stéphane Wirtel.

  • bpo-21269: Add args and kwargs properties to mock call objects. Contributed by Kumar Akshay.

  • bpo-30670: pprint.pp has been added to pretty-print objects with dictionary keys being sorted with their insertion order by default. Parameter sort_dicts has been added to pprint.pprint, pprint.pformat and pprint.PrettyPrinter. Contributed by Rémi Lapeyre.

  • bpo-35843: Implement __getitem__ for _NamespacePath. Patch by Anthony Sottile.

  • bpo-35802: Clean up code which checked presence of os.stat / os.lstat / os.chmod which are always present. Patch by Anthony Sottile.

  • bpo-35715: Librates the return value of a ProcessPoolExecutor _process_worker after it's no longer needed to free memory

  • bpo-35493: Use multiprocessing.connection.wait() instead of polling each 0.2 seconds for worker updates in multiprocessing.Pool. Patch by Pablo Galindo.

  • bpo-35661: Store the venv prompt in pyvenv.cfg.

  • bpo-35121: Don't set cookie for a request when the request path is a prefix match of the cookie's path attribute but doesn't end with "/". Patch by Karthikeyan Singaravelan.

  • bpo-21478: Calls to a child function created with unittest.mock.create_autospec() should propagate to the parent. Patch by Karthikeyan Singaravelan.

  • bpo-35198: Fix C++ extension compilation on AIX

Documentation

  • bpo-36329: Declare the path of the Python binary for the usage of Tools/scripts/serve.py when executing make -C Doc/ serve. Contributed by Stéphane Wirtel

  • bpo-36138: Improve documentation about converting datetime.timedelta to scalars.

  • bpo-21314: A new entry was added to the Core Language Section of the Programming FAQ, which explaines the usage of slash(/) in the signature of a function. Patch by Lysandros Nikolaou

Tests

  • bpo-36234: test_posix.PosixUidGidTests: add tests for invalid uid/gid type (str). Initial patch written by David Malcolm.

  • bpo-29571: Fix test_re.test_locale_flag(): use locale.getpreferredencoding() rather than locale.getlocale() to get the locale encoding. With some locales, locale.getlocale() returns the wrong encoding.

  • bpo-36123: Fix race condition in test_socket.

Build

  • bpo-36356: Fix leaks that led to build failure when configured with address sanitizer.

  • bpo-36146: Add TEST_EXTENSIONS constant to setup.py to allow to not build test extensions like _testcapi.

  • bpo-36146: Fix setup.py on macOS: only add /usr/include/ffi to include directories of _ctypes, not for all extensions.

  • bpo-31904: Enable build system to cross-build for VxWorks RTOS.

Windows

  • bpo-36312: Fixed decoders for the following code pages: 50220, 50221, 50222, 50225, 50227, 50229, 57002 through 57011, 65000 and 42.

  • bpo-36264: Don't honor POSIX HOME in os.path.expanduser on windows. Patch by Anthony Sottile.

  • bpo-24643: Fix name collisions due to #define timezone _timezone in PC/pyconfig.h.

IDLE

  • bpo-36405: Use dict unpacking in idlelib.

  • bpo-36396: Remove fgBg param of idlelib.config.GetHighlight(). This param was only used twice and changed the return type.

  • bpo-36176: Fix IDLE autocomplete & calltip popup colors. Prevent conflicts with Linux dark themes (and slightly darken calltip background).

  • bpo-23205: For the grep module, add tests for findfiles, refactor findfiles to be a module-level function, and refactor findfiles to use os.walk.

  • bpo-23216: Add docstrings to IDLE search modules.

  • bpo-36152: Remove colorizer.ColorDelegator.close_when_done and the corresponding argument of .close(). In IDLE, both have always been None or False since 2007.

  • bpo-32129: Avoid blurry IDLE application icon on macOS with Tk 8.6. Patch by Kevin Walzer.

  • bpo-36096: Refactor class variables to instance variables in colorizer.

  • bpo-30348: Increase test coverage of idlelib.autocomplete by 30%. Patch by Louie Lu

Tools/Demos

  • bpo-35132: Fix py-list and py-bt commands of python-gdb.py on gdb7.

  • bpo-32217: Fix freeze script on Windows.

C API

  • bpo-36381: Raise DeprecationWarning when '#' formats are used for building or parsing values without PY_SSIZE_T_CLEAN.

  • bpo-36142: The whole coreconfig.h header is now excluded from Py_LIMITED_API. Move functions definitions into a new internal pycore_coreconfig.h header.

Python 3.8.0 alpha 2

Release date: 2019-02-25

Core and Builtins

  • bpo-36052: Raise a SyntaxError when assigning a value to __debug__ with the Assignment Operator. Contributed by Stéphane Wirtel and Pablo Galindo.

  • bpo-36012: Doubled the speed of class variable writes. When a non-dunder attribute was updated, there was an unnecessary call to update slots.

  • bpo-35942: The error message emitted when returning invalid types from __fspath__ in interfaces that allow passing PathLike objects has been improved and now it does explain the origin of the error.

  • bpo-36016: gc.get_objects can now receive an optional parameter indicating a generation to get objects from. Patch by Pablo Galindo.

  • bpo-1054041: When the main interpreter exits due to an uncaught KeyboardInterrupt, the process now exits in the appropriate manner for its parent process to detect that a SIGINT or ^C terminated the process. This allows shells and batch scripts to understand that the user has asked them to stop.

  • bpo-35992: Fix __class_getitem__() not being called on a class with a custom non-subscriptable metaclass.

  • bpo-35993: Fix a crash on fork when using subinterpreters. Contributed by Stéphane Wirtel

  • bpo-35991: Fix a potential double free in Modules/_randommodule.c.

  • bpo-35961: Fix a crash in slice_richcompare(): use strong references rather than stolen references for the two temporary internal tuples.

  • bpo-35911: Enable the creation of cell objects by adding a cell.__new__ method, and expose the type cell in Lib/types.py under the name CellType. Patch by Pierre Glaser.

  • bpo-12822: Use monotonic clock for pthread_cond_timedwait when pthread_condattr_setclock and CLOCK_MONOTONIC are available.

  • bpo-15248: The compiler emits now syntax warnings in the case when a comma is likely missed before tuple or list.

  • bpo-35886: The implementation of PyInterpreterState has been moved into the internal header files (guarded by Py_BUILD_CORE).

  • bpo-31506: Clarify the errors reported when object.__new__ and object.__init__ receive more than one argument. Contributed by Sanyam Khurana.

  • bpo-35724: Signal-handling is now guaranteed to happen relative to the main interpreter.

  • bpo-33608: We added a new internal _Py_AddPendingCall() that operates relative to the provided interpreter. This allows us to use the existing implementation to ask another interpreter to do work that cannot be done in the current interpreter, like decref an object the other interpreter owns. The existing Py_AddPendingCall() only operates relative to the main interpreter.

  • bpo-33989: Fix a possible crash in list.sort() when sorting objects with ob_type->tp_richcompare == NULL. Patch by Zackery Spytz.

Library

  • bpo-35512: unittest.mock.patch.dict() used as a decorator with string target resolves the target during function call instead of during decorator construction. Patch by Karthikeyan Singaravelan.

  • bpo-36018: Add statistics.NormalDist, a tool for creating and manipulating normal distributions of random variable. Features a composite class that treats the mean and standard deviation of measurement data as single entity.

  • bpo-35904: Added statistics.fmean() as a faster, floating point variant of the existing mean() function.

  • bpo-35918: Removed broken has_key method from multiprocessing.managers.SyncManager.dict. Contributed by Rémi Lapeyre.

  • bpo-18283: Add support for bytes to shutil.which().

  • bpo-35960: Fix dataclasses.field() throwing away empty mapping objects passed as metadata.

  • bpo-35500: Write expected and actual call parameters on separate lines in unittest.mock.Mock.assert_called_with() assertion errors. Contributed by Susan Su.

  • bpo-35931: The pdb debug command now gracefully handles syntax errors.

  • bpo-24209: In http.server script, rely on getaddrinfo to bind to preferred address based on the bind parameter. Now default bind or binding to a name may bind to IPv6 or dual-stack, depending on the environment.

  • bpo-35321: Set __spec__.origin of _frozen_importlib to frozen so that it matches the behavior of _frozen_importlib_external. Patch by Nina Zakharenko.

  • bpo-35378: Fix a reference issue inside multiprocessing.Pool that caused the pool to remain alive if it was deleted without being closed or terminated explicitly. A new strong reference is added to the pool iterators to link the lifetime of the pool to the lifetime of its iterators so the pool does not get destroyed if a pool iterator is still alive.

  • bpo-34294: re module, fix wrong capturing groups in rare cases. re.search(), re.findall(), re.sub() and other functions that scan through string looking for a match, should reset capturing groups between two match attempts. Patch by Ma Lin.

  • bpo-35615: weakref: Fix a RuntimeError when copying a WeakKeyDictionary or a WeakValueDictionary, due to some keys or values disappearing while iterating.

  • bpo-35606: Implement math.prod() as analogous function to sum() that returns the product of a 'start' value (default: 1) times an iterable of numbers. Patch by Pablo Galindo.

  • bpo-32417: Performing arithmetic between datetime.datetime subclasses and datetime.timedelta now returns an object of the same type as the datetime.datetime subclass. As a result, datetime.datetime.astimezone() and alternate constructors like datetime.datetime.now() and datetime.fromtimestamp() called with a tz argument now also retain their subclass.

  • bpo-35153: Add headers optional keyword-only parameter to xmlrpc.client.ServerProxy, xmlrpc.client.Transport and xmlrpc.client.SafeTransport. Patch by Cédric Krier.

  • bpo-34572: Fix C implementation of pickle.loads to use importlib's locking mechanisms, and thereby avoid using partially-loaded modules. Patch by Tim Burgess.

Documentation

  • bpo-36083: Fix formatting of --check-hash-based-pycs options in the manpage Synopsis.

  • bpo-36007: Bump minimum sphinx version to 1.8. Patch by Anthony Sottile.

  • bpo-22062: Update documentation and docstrings for pathlib. Original patch by Mike Short.

Tests

  • bpo-27313: Avoid test_ttk_guionly ComboboxTest failure with macOS Cocoa Tk.

  • bpo-36019: Add test.support.TEST_HTTP_URL and replace references of http://www.example.com by this new constant. Contributed by Stéphane Wirtel.

  • bpo-36037: Fix test_ssl for strict OpenSSL configuration like RHEL8 strict crypto policy. Use older TLS version for minimum TLS version of the server SSL context if needed, to test TLS version older than default minimum TLS version.

  • bpo-35798: Added test.support.check_syntax_warning().

  • bpo-35505: Make test_imap4_host_default_value independent on whether the local IMAP server is running.

  • bpo-35917: multiprocessing: provide unit tests for SyncManager and SharedMemoryManager classes + all the shareable types which are supposed to be supported by them. (patch by Giampaolo Rodola)

  • bpo-35704: Skip test_shutil.test_unpack_archive_xztar to prevent a MemoryError on 32-bit AIX when MAXDATA setting is less than 0x20000000.

    Patch by Michael Felt (aixtools)

  • bpo-34720: Assert m_state != NULL to mimic GC traversal functions that do not correctly handle module creation when the module state has not been created.

Windows

  • bpo-35976: Added ARM build support to Windows build files in PCBuild.

  • bpo-35692: pathlib no longer raises when checking file and directory existence on drives that are not ready

  • bpo-35872: Uses the base Python executable when invoking venv in a virtual environment

  • bpo-35873: Prevents venv paths being inherited by child processes

  • bpo-35299: Fix sysconfig detection of the source directory and distutils handling of pyconfig.h during PGO profiling

IDLE

  • bpo-24310: IDLE -- Document settings dialog font tab sample.

  • bpo-35833: Revise IDLE doc for control codes sent to Shell. Add a code example block.

  • bpo-35689: Add docstrings and unittests for colorizer.py.

Python 3.8.0 alpha 1

Release date: 2019-02-03

Security

  • bpo-35746: [CVE-2019-5010] Fix a NULL pointer deref in ssl module. The cert parser did not handle CRL distribution points with empty DP or URI correctly. A malicious or buggy certificate can result into segfault. Vulnerability (TALOS-2018-0758) reported by Colin Read and Nicolas Edet of Cisco.

  • bpo-34812: The -I command line option (run Python in isolated mode) is now also copied by the multiprocessing and distutils modules when spawning child processes. Previously, only -E and -s options (enabled by -I) were copied.

  • bpo-34791: The xml.sax and xml.dom.domreg no longer use environment variables to override parser implementations when sys.flags.ignore_environment is set by -E or -I arguments.

  • bpo-17239: The xml.sax and xml.dom.minidom parsers no longer processes external entities by default. External DTD and ENTITY declarations no longer load files or create network connections.

  • bpo-34623: CVE-2018-14647: The C accelerated _elementtree module now initializes hash randomization salt from _Py_HashSecret instead of libexpat's default CSPRNG.

  • bpo-34405: Updated to OpenSSL 1.1.0i for Windows builds.

  • bpo-33871: Fixed sending the part of the file in os.sendfile() on macOS. Using the trailers argument could cause sending more bytes from the input file than was specified.

  • bpo-32533: Fixed thread-safety of error handling in _ssl.

  • bpo-33136: Harden ssl module against LibreSSL CVE-2018-8970. X509_VERIFY_PARAM_set1_host() is called with an explicit namelen. A new test ensures that NULL bytes are not allowed.

  • bpo-33001: Minimal fix to prevent buffer overrun in os.symlink on Windows

  • bpo-32981: Regexes in difflib and poplib were vulnerable to catastrophic backtracking. These regexes formed potential DOS vectors (REDOS). They have been refactored. This resolves CVE-2018-1060 and CVE-2018-1061. Patch by Jamie Davis.

  • bpo-28414: The ssl module now allows users to perform their own IDN en/decoding when using SNI.

Core and Builtins

  • bpo-35877: Make parenthesis optional for named expressions in while statement. Patch by Karthikeyan Singaravelan.

  • bpo-35814: Allow same right hand side expressions in annotated assignments as in normal ones. In particular, x: Tuple[int, int] = 1, 2 (without parentheses on the right) is now allowed.

  • bpo-35766: Add the option to parse PEP 484 type comments in the ast module. (Off by default.) This is merging the key functionality of the third party fork thereof, [typed_ast](https://github.com/python/typed_ast).

  • bpo-35713: Reorganize Python initialization to get working exceptions and sys.stderr earlier.

  • bpo-33416: Add end line and end column position information to the Python AST nodes. This is a C-level backwards incompatible change.

  • bpo-35720: Fixed a minor memory leak in pymain_parse_cmdline_impl function in Modules/main.c

  • bpo-35634: func(**kwargs) will now raise an error when kwargs is a mapping containing multiple entries with the same key. An error was already raised when other keyword arguments are passed before **kwargs since Python 3.6.

  • bpo-35623: Fix a crash when sorting very long lists. Patch by Stephan Hohe.

  • bpo-35214: clang Memory Sanitizer build instrumentation was added to work around false positives from posix, socket, time, test_io, and test_faulthandler.

  • bpo-35560: Fix an assertion error in format() in debug build for floating point formatting with "n" format, zero padding and small width. Release build is not impacted. Patch by Karthikeyan Singaravelan.

  • bpo-35552: Format characters %s and %V in PyUnicode_FromFormat() and %s in PyBytes_FromFormat() no longer read memory past the limit if precision is specified.

  • bpo-35504: Fix segfaults and SystemErrors when deleting certain attributes. Patch by Zackery Spytz.

  • bpo-35504: Fixed a SystemError when delete the characters_written attribute of an OSError.

  • bpo-35494: Improved syntax error messages for unbalanced parentheses in f-string.

  • bpo-35444: Fixed error handling in pickling methods when fail to look up builtin "getattr". Sped up pickling iterators.

  • bpo-35436: Fix various issues with memory allocation error handling. Patch by Zackery Spytz.

  • bpo-35423: Separate the signal handling trigger in the eval loop from the "pending calls" machinery. There is no semantic change and the difference in performance is insignificant.

  • bpo-35357: Internal attributes' names of unittest.mock._Call and unittest.mock.MagicProxy (name, parent & from_kall) are now prefixed with _mock_ in order to prevent clashes with widely used object attributes. Fixed minor typo in test function name.

  • bpo-35372: Fixed the code page decoder for input longer than 2 GiB containing undecodable bytes.

  • bpo-35336: Fix PYTHONCOERCECLOCALE=1 environment variable: only coerce the C locale if the LC_CTYPE locale is "C".

  • bpo-31241: The lineno and col_offset attributes of AST nodes for list comprehensions, generator expressions and tuples are now point to the opening parenthesis or square brace. For tuples without parenthesis they point to the position of the first item.

  • bpo-33954: For str.format(), float.__format__() and complex.__format__() methods for non-ASCII decimal point when using the "n" formatter.

  • bpo-35269: Fix a possible segfault involving a newly-created coroutine. Patch by Zackery Spytz.

  • bpo-35224: Implement PEP 572 (assignment expressions). Patch by Emily Morehouse.

  • bpo-32492: Speed up namedtuple attribute access by 1.6x using a C fast-path for the name descriptors. Patch by Pablo Galindo.

  • bpo-35214: Fixed an out of bounds memory access when parsing a truncated unicode escape sequence at the end of a string such as '\N'. It would read one byte beyond the end of the memory allocation.

  • bpo-35214: The interpreter and extension modules have had annotations added so that they work properly under clang's Memory Sanitizer. A new configure flag --with-memory-sanitizer has been added to make test builds of this nature easier to perform.

  • bpo-35193: Fix an off by one error in the bytecode peephole optimizer where it could read bytes beyond the end of bounds of an array when removing unreachable code. This bug was present in every release of Python 3.6 and 3.7 until now.

  • bpo-35169: Improved error messages for forbidden assignments.

  • bpo-34022: Fix handling of hash-based bytecode files in zipimport. Patch by Elvis Pranskevichus.

  • bpo-28401: Debug builds will no longer to attempt to import extension modules built for the ABI as they were never compatible to begin with. Patch by Stefano Rivera.

  • bpo-29341: Clarify in the docstrings of os methods that path-like objects are also accepted as input parameters.

  • bpo-35050: socket: Fix off-by-one bug in length check for AF_ALG name and type.

  • bpo-29743: Raise ValueError instead of OverflowError in case of a negative _length_ in a ctypes.Array subclass. Also raise TypeError instead of AttributeError for non-integer _length_. Original patch by Oren Milman.

  • bpo-16806: Fix lineno and col_offset for multi-line string tokens.

  • bpo-35029: SyntaxWarning raised as an exception at code generation time will be now replaced with a SyntaxError for better error reporting.

  • bpo-34983: Expose symtable.Symbol.is_nonlocal() in the symtable module. Patch by Pablo Galindo.

  • bpo-34974: bytes and bytearray constructors no longer convert unexpected exceptions (e.g. MemoryError and KeyboardInterrupt) to TypeError.

  • bpo-34939: Allow annotated names in module namespace that are declared global before the annotation happens. Patch by Pablo Galindo.

  • bpo-34973: Fixed crash in bytes() when the list argument is mutated while it is iterated.

  • bpo-34876: The lineno and col_offset attributes of the AST for decorated function and class refer now to the position of the corresponding def, async def and class instead of the position of the first decorator. This leads to more correct line reporting in tracing. This is the only case when the position of child AST nodes can precede the position of the parent AST node.

  • bpo-34879: Fix a possible null pointer dereference in bytesobject.c. Patch by Zackery Spytz.

  • bpo-34784: Fix the implementation of PyStructSequence_NewType in order to create heap allocated StructSequences.

  • bpo-32912: A SyntaxWarning is now emitted instead of a DeprecationWarning for invalid escape sequences in string and bytes literals.

  • bpo-34854: Fixed a crash in compiling string annotations containing a lambda with a keyword-only argument that doesn't have a default value.

  • bpo-34850: The compiler now produces a SyntaxWarning when identity checks (is and is not) are used with certain types of literals (e.g. strings, ints). These can often work by accident in CPython, but are not guaranteed by the language spec. The warning advises users to use equality tests (== and !=) instead.

  • bpo-34824: Fix a possible null pointer dereference in Modules/_ssl.c. Patch by Zackery Spytz.

  • bpo-30156: The C function property_descr_get() uses a "cached" tuple to optimize function calls. But this tuple can be discovered in debug mode with sys.getobjects(). Remove the optimization, it's not really worth it and it causes 3 different crashes last years.

  • bpo-34762: Fix contextvars C API to use PyObject* pointer types.

  • bpo-34751: The hash function for tuples is now based on xxHash which gives better collision results on (formerly) pathological cases. Additionally, on 64-bit systems it improves tuple hashes in general. Patch by Jeroen Demeyer with substantial contributions by Tim Peters.

  • bpo-34735: Fix a memory leak in Modules/timemodule.c. Patch by Zackery Spytz.

  • bpo-34683: Fixed a bug where some SyntaxError error pointed to locations that were off-by-one.

  • bpo-34651: Only allow the main interpreter to fork. The avoids the possibility of affecting the main interpreter, which is critical to operation of the runtime.

  • bpo-34653: Remove unused function PyParser_SimpleParseStringFilename.

  • bpo-32236: Warn that line buffering is not supported if open() is called with binary mode and buffering=1.

  • bpo-34641: Further restrict the syntax of the left-hand side of keyword arguments in function calls. In particular, f((keyword)=arg) is now disallowed.

  • bpo-34637: Make the start argument to sum() visible as a keyword argument.

  • bpo-1621: Do not assume signed integer overflow behavior (C undefined behavior) when performing set hash table resizing.

  • bpo-34588: Fix an off-by-one in the recursive call pruning feature of traceback formatting.

  • bpo-34485: On Windows, the LC_CTYPE is now set to the user preferred locale at startup. Previously, the LC_CTYPE locale was "C" at startup, but changed when calling setlocale(LC_CTYPE, "") or setlocale(LC_ALL, "").

  • bpo-34485: Standard streams like sys.stdout now use the "surrogateescape" error handler, instead of "strict", on the POSIX locale (when the C locale is not coerced and the UTF-8 Mode is disabled).

  • bpo-34485: Fix the error handler of standard streams like sys.stdout: PYTHONIOENCODING=":" is now ignored instead of setting the error handler to "strict".

  • bpo-34485: Python now gets the locale encoding with C code to initialize the encoding of standard streams like sys.stdout. Moreover, the encoding is now initialized to the Python codec name to get a normalized encoding name and to ensure that the codec is loaded. The change avoids importing _bootlocale and _locale modules at startup by default.

  • bpo-34527: On FreeBSD, Py_DecodeLocale() and Py_EncodeLocale() now also forces the ASCII encoding if the LC_CTYPE locale is "POSIX", not only if the LC_CTYPE locale is "C".

  • bpo-34527: The UTF-8 Mode is now also enabled by the "POSIX" locale, not only by the "C" locale.

  • bpo-34403: On HP-UX with C or POSIX locale, sys.getfilesystemencoding() now returns "ascii" instead of "roman8" (when the UTF-8 Mode is disabled and the C locale is not coerced).

  • bpo-34523: The Python filesystem encoding is now read earlier during the Python initialization.

  • bpo-12458: Tracebacks show now correct line number for subexpressions in multiline expressions. Tracebacks show now the line number of the first line for multiline expressions instead of the line number of the last subexpression.

  • bpo-34408: Prevent a null pointer dereference and resource leakage in PyInterpreterState_New().

  • bpo-34400: Fix undefined behavior in parsetok.c. Patch by Zackery Spytz.

  • bpo-33073: Added as_integer_ratio to ints to make them more interoperable with floats.

  • bpo-34377: Update valgrind suppression list to use _PyObject_Free/_PyObject_Realloc instead of PyObject_Free/PyObject_Realloc.

  • bpo-34353: Added the "socket" option in the stat.filemode() Python implementation to match the C implementation.

  • bpo-34320: Fix dict(od) didn't copy iteration order of OrderedDict.

  • bpo-34113: Fixed crash on debug builds when opcode stack was adjusted with negative numbers. Patch by Constantin Petrisor.

  • bpo-34100: Compiler now merges constants in tuples and frozensets recursively. Code attributes like co_names are merged too.

  • bpo-34151: Performance of list concatenation, repetition and slicing operations is slightly improved. Patch by Sergey Fedoseev.

  • bpo-34170: -X dev: it is now possible to override the memory allocator using PYTHONMALLOC even if the developer mode is enabled.

  • bpo-33237: Improved AttributeError message for partially initialized module.

  • bpo-34149: Fix min and max functions to get default behavior when key is None.

  • bpo-34125: Profiling of unbound built-in methods now works when **kwargs is given.

  • bpo-34141: Optimized pickling atomic types (None, bool, int, float, bytes, str).

  • bpo-34126: Fix crashes when profiling certain invalid calls of unbound methods. Patch by Jeroen Demeyer.

  • bpo-24618: Fixed reading invalid memory when create the code object with too small varnames tuple or too large argument counts.

  • bpo-34068: In io.IOBase.close(), ensure that the closed attribute is not set with a live exception. Patch by Zackery Spytz and Serhiy Storchaka.

  • bpo-34087: Fix buffer overflow while converting unicode to numeric values.

  • bpo-34080: Fixed a memory leak in the compiler when it raised some uncommon errors during tokenizing.

  • bpo-34066: Disabled interruption by Ctrl-C between calling open() and entering a with block in with open().

  • bpo-34042: Fix dict.copy() to maintain correct total refcount (as reported by sys.gettotalrefcount()).

  • bpo-33418: Fix potential memory leak in function object when it creates reference cycle.

  • bpo-33985: Implement contextvars.ContextVar.name attribute.

  • bpo-33956: Update vendored Expat library copy to version 2.2.5.

  • bpo-24596: Decref the module object in PyRun_SimpleFileExFlags() before calling PyErr_Print(). Patch by Zackery Spytz.

  • bpo-33451: Close directly executed pyc files before calling PyEval_EvalCode().

  • bpo-1617161: The hash of BuiltinMethodType instances (methods of built-in classes) now depends on the hash of the identity of __self__ instead of its value. The hash and equality of ModuleType and MethodWrapperType instances (methods of user-defined classes and some methods of built-in classes like str.__add__) now depend on the hash and equality of the identity of __self__ instead of its value. MethodWrapperType instances no longer support ordering.

  • bpo-33824: Fix "LC_ALL=C python3.7 -V": reset properly the command line parser when the encoding changes after reading the Python configuration.

  • bpo-33803: Fix a crash in hamt.c caused by enabling GC tracking for an object that hadn't all of its fields set to NULL.

  • bpo-33738: Seven macro incompatibilities with the Limited API were fixed, and the macros PyIter_Check(), PyIndex_Check() and PyExceptionClass_Name() were added as functions. A script for automatic macro checks was added.

  • bpo-33786: Fix asynchronous generators to handle GeneratorExit in athrow() correctly

  • bpo-30167: PyRun_SimpleFileExFlags removes __cached__ from module in addition to __file__.

  • bpo-33706: Fix a crash in Python initialization when parsing the command line options. Thanks Christoph Gohlke for the bug report and the fix!

  • bpo-33597: Reduce PyGC_Head size from 3 words to 2 words.

  • bpo-30654: Fixed reset of the SIGINT handler to SIG_DFL on interpreter shutdown even when there was a custom handler set previously. Patch by Philipp Kerling.

  • bpo-33622: Fixed a leak when the garbage collector fails to add an object with the __del__ method or referenced by it into the gc.garbage list. PyGC_Collect() can now be called when an exception is set and preserves it.

  • bpo-33462: Make dict and dict views reversible. Patch by Rémi Lapeyre.

  • bpo-23722: A RuntimeError is now raised when the custom metaclass doesn't provide the __classcell__ entry in the namespace passed to type.__new__. A DeprecationWarning was emitted in Python 3.6--3.7.

  • bpo-33499: Add PYTHONPYCACHEPREFIX environment variable and -X pycache_prefix command-line option to set an alternate root directory for writing module bytecode cache files.

  • bpo-25711: The zipimport module has been rewritten in pure Python.

  • bpo-33509: Fix module_globals parameter of warnings.warn_explicit(): don't crash if module_globals is not a dict.

  • bpo-31849: Fix signed/unsigned comparison warning in pyhash.c.

  • bpo-33475: Fixed miscellaneous bugs in converting annotations to strings and optimized parentheses in the string representation.

  • bpo-20104: Added support for the setpgroup, resetids, setsigmask, setsigdef and scheduler parameters of posix_spawn. Patch by Pablo Galindo.

  • bpo-33391: Fix a leak in set_symmetric_difference().

  • bpo-33363: Raise a SyntaxError for async with and async for statements outside of async functions.

  • bpo-28055: Fix unaligned accesses in siphash24(). Patch by Rolf Eike Beer.

  • bpo-33128: Fix a bug that causes PathFinder to appear twice on sys.meta_path. Patch by Pablo Galindo Salgado.

  • bpo-33331: Modules imported last are now cleared first at interpreter shutdown.

  • bpo-33312: Fixed clang ubsan (undefined behavior sanitizer) warnings in dictobject.c by adjusting how the internal struct _dictkeysobject shared keys structure is declared.

  • bpo-33305: Improved syntax error messages for invalid numerical literals.

  • bpo-33306: Improved syntax error messages for unbalanced parentheses.

  • bpo-33234: The list constructor will pre-size and not over-allocate when the input length is known.

  • bpo-33270: Intern the names for all anonymous code objects. Patch by Zackery Spytz.

  • bpo-30455: The C and Python code and the documentation related to tokens are now generated from a single source file Grammar/Tokens.

  • bpo-33176: Add a toreadonly() method to memoryviews.

  • bpo-33231: Fix potential memory leak in normalizestring().

  • bpo-33205: Change dict growth function from round_up_to_power_2(used*2+hashtable_size/2) to round_up_to_power_2(used*3). Previously, dict is shrinked only when used == 0. Now dict has more chance to be shrinked.

  • bpo-29922: Improved error messages in 'async with' when __aenter__() or __aexit__() return non-awaitable object.

  • bpo-33199: Fix ma_version_tag in dict implementation is uninitialized when copying from key-sharing dict.

  • bpo-33053: When using the -m switch, sys.path[0] is now explicitly expanded as the starting working directory, rather than being left as the empty path (which allows imports from the current working directory at the time of the import)

  • bpo-33138: Changed standard error message for non-pickleable and non-copyable types. It now says "cannot pickle" instead of "can't pickle" or "cannot serialize".

  • bpo-33018: Improve consistency of errors raised by issubclass() when called with a non-class and an abstract base class as the first and second arguments, respectively. Patch by Josh Bronson.

  • bpo-33083: math.factorial no longer accepts arguments that are not int-like. Patch by Pablo Galindo.

  • bpo-33041: Added new opcode END_ASYNC_FOR and fixes the following issues:

    • Setting global StopAsyncIteration no longer breaks async for loops.

    • Jumping into an async for loop is now disabled.

    • Jumping out of an async for loop no longer corrupts the stack.

  • bpo-25750: Fix rare Python crash due to bad refcounting in type_getattro() if a descriptor deletes itself from the class. Patch by Jeroen Demeyer.

  • bpo-33041: Fixed bytecode generation for "async for" with a complex target. A StopAsyncIteration raised on assigning or unpacking will be now propagated instead of stopping the iteration.

  • bpo-33026: Fixed jumping out of "with" block by setting f_lineno.

  • bpo-33005: Fix a crash on fork when using a custom memory allocator (ex: using PYTHONMALLOC env var). _PyGILState_Reinit() and _PyInterpreterState_Enable() now use the default RAW memory allocator to allocate a new interpreters mutex on fork.

  • bpo-32911: Due to unexpected compatibility issues discovered during downstream beta testing, reverted bpo-29463. docstring field is removed from Module, ClassDef, FunctionDef, and AsyncFunctionDef ast nodes which was added in 3.7a1. Docstring expression is restored as a first statement in their body. Based on patch by Inada Naoki.

  • bpo-17288: Prevent jumps from 'return' and 'exception' trace events.

  • bpo-32946: Importing names from already imported module with "from ... import ..." is now 30% faster if the module is not a package.

  • bpo-32932: Make error message more revealing when there are non-str objects in __all__.

  • bpo-32925: Optimized iterating and containing test for literal lists consisting of non-constants: x in [a, b] and for x in [a, b]. The case of all constant elements already was optimized.

  • bpo-32889: Update Valgrind suppression list to account for the rename of Py_ADDRESS_IN_RANG to address_in_range.

  • bpo-32836: Don't use temporary variables in cases of list/dict/set comprehensions

  • bpo-31356: Remove the new API added in bpo-31356 (gc.ensure_disabled() context manager).

  • bpo-32305: For namespace packages, ensure that both __file__ and __spec__.origin are set to None.

  • bpo-32303: Make sure __spec__.loader matches __loader__ for namespace packages.

  • bpo-32711: Fix the warning messages for Python/ast_unparse.c. Patch by Stéphane Wirtel

  • bpo-32583: Fix possible crashing in builtin Unicode decoders caused by write out-of-bound errors when using customized decode error handlers.

  • bpo-32489: A continue statement is now allowed in the finally clause.

  • bpo-17611: Simplified the interpreter loop by moving the logic of unrolling the stack of blocks into the compiler. The compiler emits now explicit instructions for adjusting the stack of values and calling the cleaning up code for break, continue and return.

    Removed opcodes BREAK_LOOP, CONTINUE_LOOP, SETUP_LOOP and SETUP_EXCEPT. Added new opcodes ROT_FOUR, BEGIN_FINALLY and CALL_FINALLY and POP_FINALLY. Changed the behavior of END_FINALLY and WITH_CLEANUP_START.

  • bpo-32285: New function unicodedata.is_normalized, which can check whether a string is in a specific normal form.

  • bpo-10544: Yield expressions are now disallowed in comprehensions and generator expressions except the expression for the outermost iterable.

  • bpo-32117: Iterable unpacking is now allowed without parentheses in yield and return statements, e.g. yield 1, 2, 3, *rest. Thanks to David Cuthbert for the change and Jordan Chapman for added tests.

  • bpo-31902: Fix the col_offset attribute for ast nodes ast.AsyncFor, ast.AsyncFunctionDef, and ast.AsyncWith. Previously, col_offset pointed to the keyword after async.

  • bpo-25862: Fix assertion failures in the tell() method of io.TextIOWrapper. Patch by Zackery Spytz.

  • bpo-21983: Fix a crash in ctypes.cast() in case the type argument is a ctypes structured data type. Patch by Eryk Sun and Oren Milman.

  • bpo-31577: Fix a crash in os.utime() in case of a bad ns argument. Patch by Oren Milman.

  • bpo-29832: Remove references to 'getsockaddrarg' from various socket error messages. Patch by Oren Milman.

Library

  • bpo-35845: Add 'order' parameter to memoryview.tobytes().

  • bpo-35864: The _asdict() method for collections.namedtuple now returns a regular dict instead of an OrderedDict.

  • bpo-35537: An ExitStack is now used internally within subprocess.POpen to clean up pipe file handles. No behavior change in normal operation. But if closing one handle were ever to cause an exception, the others will now be closed instead of leaked. (patch by Giampaolo Rodola)

  • bpo-35847: RISC-V needed the CTYPES_PASS_BY_REF_HACK. Fixes ctypes Structure test_pass_by_value.

  • bpo-35813: Shared memory submodule added to multiprocessing to avoid need for serialization between processes

  • bpo-35780: Fix lru_cache() errors arising in recursive, reentrant, or multi-threaded code. These errors could result in orphan links and in the cache being trapped in a state with fewer than the specified maximum number of links. Fix handling of negative maxsize which should have been treated as zero. Fix errors in toggling the "full" status flag. Fix misordering of links when errors are encountered. Sync-up the C code and pure Python code for the space saving path in functions with a single positional argument. In this common case, the space overhead of an lru cache entry is reduced by almost half. Fix counting of cache misses. In error cases, the miss count was out of sync with the actual number of times the underlying user function was called.

  • bpo-35537: os.posix_spawn() and os.posix_spawnp() now have a setsid parameter.

  • bpo-23846: asyncio.ProactorEventLoop now catches and logs send errors when the self-pipe is full.

  • bpo-34323: asyncio: Enhance IocpProactor.close() log: wait 1 second before the first log, then log every second. Log also the number of seconds since close() was called.

  • bpo-35674: Add a new os.posix_spawnp() function. Patch by Joannah Nanjekye.

  • bpo-35733: ast.Constant(boolean) no longer an instance of ast.Num. Patch by Anthony Sottile.

  • bpo-35726: QueueHandler.prepare() now makes a copy of the record before modifying and enqueueing it, to avoid affecting other handlers in the chain.

  • bpo-35719: Sped up multi-argument math functions atan2(), copysign(), remainder() and hypot() by 1.3--2.5 times.

  • bpo-35717: Fix KeyError exception raised when using enums and compile. Patch contributed by Rémi Lapeyre.

  • bpo-35699: Fixed detection of Visual Studio Build Tools 2017 in distutils

  • bpo-32710: Fix memory leaks in asyncio ProactorEventLoop on overlapped operation failure.

  • bpo-35702: The time.CLOCK_UPTIME_RAW constant is now available for macOS 10.12.

  • bpo-32710: Fix a memory leak in asyncio in the ProactorEventLoop when ReadFile() or WSASend() overlapped operation fail immediately: release the internal buffer.

  • bpo-35682: Fix asyncio.ProactorEventLoop.sendfile(): don't attempt to set the result of an internal future if it's already done.

  • bpo-35283: Add a deprecated warning for the threading.Thread.isAlive() method. Patch by Dong-hee Na.

  • bpo-35664: Improve operator.itemgetter() performance by 33% with optimized argument handling and with adding a fast path for the common case of a single non-negative integer index into a tuple (which is the typical use case in the standard library).

  • bpo-35643: Fixed a SyntaxWarning: invalid escape sequence in Modules/_sha3/cleanup.py. Patch by Mickaël Schoentgen.

  • bpo-35619: Improved support of custom data descriptors in help() and pydoc.

  • bpo-28503: The crypt module now internally uses the crypt_r() library function instead of crypt() when available.

  • bpo-35614: Fixed help() on metaclasses. Patch by Sanyam Khurana.

  • bpo-35568: Expose raise(signum) as raise_signal

  • bpo-35588: The floor division and modulo operations and the divmod() function on fractions.Fraction types are 2--4x faster. Patch by Stefan Behnel.

  • bpo-35585: Speed-up building enums by value, e.g. http.HTTPStatus(200).

  • bpo-30561: random.gammavariate(1.0, beta) now computes the same result as random.expovariate(1.0 / beta). This synchronizes the two algorithms and eliminates some idiosyncrasies in the old implementation. It does however produce a difference stream of random variables than it used to.

  • bpo-35537: The subprocess module can now use the os.posix_spawn() function in some cases for better performance.

  • bpo-35526: Delaying the 'joke' of barry_as_FLUFL.mandatory to Python version 4.0

  • bpo-35523: Remove ctypes callback workaround: no longer create a callback at startup. Avoid SELinux alert on import ctypes and import uuid.

  • bpo-31784: uuid.uuid1() now calls time.time_ns() rather than int(time.time() * 1e9).

  • bpo-35513: TextTestRunner of unittest.runner now uses time.perf_counter() rather than time.time() to measure the execution time of a test: time.time() can go backwards, whereas time.perf_counter() is monotonic.

  • bpo-35502: Fixed reference leaks in xml.etree.ElementTree.TreeBuilder in case of unfinished building of the tree (in particular when an error was raised during parsing XML).

  • bpo-35348: Make platform.architecture() parsing of file command output more reliable: add the -b option to the file command to omit the filename, force the usage of the C locale, and search also the "shared object" pattern.

  • bpo-35491: multiprocessing: Add Pool.__repr__() and enhance BaseProcess.__repr__() (add pid and parent pid) to ease debugging. Pool state constant values are now strings instead of integers, for example RUN value becomes 'RUN' instead of 0.

  • bpo-35477: multiprocessing.Pool.__enter__() now fails if the pool is not running: with pool: fails if used more than once.

  • bpo-31446: Copy command line that was passed to CreateProcessW since this function can change the content of the input buffer.

  • bpo-35471: Python 2.4 dropped MacOS 9 support. The macpath module was deprecated in Python 3.7. The module is now removed.

  • bpo-23057: Unblock Proactor event loop when keyboard interrupt is received on Windows

  • bpo-35052: Fix xml.dom.minidom cloneNode() on a document with an entity: pass the correct arguments to the user data handler of an entity.

  • bpo-20239: Allow repeated assignment deletion of unittest.mock.Mock attributes. Patch by Pablo Galindo.

  • bpo-17185: Set __signature__ on mock for inspect to get signature. Patch by Karthikeyan Singaravelan.

  • bpo-35445: Memory errors during creating posix.environ no longer ignored.

  • bpo-35415: Validate fileno= argument to socket.socket().

  • bpo-35424: multiprocessing.Pool destructor now emits ResourceWarning if the pool is still running.

  • bpo-35330: When a Mock instance was used to wrap an object, if side_effect is used in one of the mocks of it methods, don't call the original implementation and return the result of using the side effect the same way that it is done with return_value.

  • bpo-35346: Drop Mac OS 9 and Rhapsody support from the platform module. Rhapsody last release was in 2000. Mac OS 9 last release was in 2001.

  • bpo-10496: check_environ() of distutils.utils now catches KeyError on calling pwd.getpwuid(): don't create the HOME environment variable in this case.

  • bpo-10496: posixpath.expanduser() now returns the input path unchanged if the HOME environment variable is not set and the current user has no home directory (if the current user identifier doesn't exist in the password database). This change fix the site module if the current user doesn't exist in the password database (if the user has no home directory).

  • bpo-35389: platform.libc_ver() now uses os.confstr('CS_GNU_LIBC_VERSION') if available and the executable parameter is not set.

  • bpo-35394: Add empty slots to asyncio abstract protocols.

  • bpo-35310: Fix a bug in select.select() where, in some cases, the file descriptor sequences were returned unmodified after a signal interruption, even though the file descriptors might not be ready yet. select.select() will now always return empty lists if a timeout has occurred. Patch by Oran Avraham.

  • bpo-35380: Enable TCP_NODELAY on Windows for proactor asyncio event loop.

  • bpo-35341: Add generic version of collections.OrderedDict to the typing module. Patch by Ismo Toijala.

  • bpo-35371: Fixed possible crash in os.utime() on Windows when pass incorrect arguments.

  • bpo-35346: platform.uname() now redirects stderr to os.devnull when running external programs like cmd /c ver.

  • bpo-35066: Previously, calling the strftime() method on a datetime object with a trailing '%' in the format string would result in an exception. However, this only occurred when the datetime C module was being used; the python implementation did not match this behavior. Datetime is now PEP-399 compliant, and will not throw an exception on a trailing '%'.

  • bpo-35345: The function platform.popen has been removed, it was deprecated since Python 3.3: use os.popen() instead.

  • bpo-35344: On macOS, platform.platform() now uses platform.mac_ver(), if it returns a non-empty release string, to get the macOS version rather than the darwin version.

  • bpo-35312: Make lib2to3.pgen2.parse.ParseError round-trip pickle-able. Patch by Anthony Sottile.

  • bpo-35308: Fix regression in webbrowser where default browsers may be preferred over browsers in the BROWSER environment variable.

  • bpo-24746: Avoid stripping trailing whitespace in doctest fancy diff. Original patch by R. David Murray & Jairo Trad. Enhanced by Sanyam Khurana.

  • bpo-28604: locale.localeconv() now sets temporarily the LC_CTYPE locale to the LC_MONETARY locale if the two locales are different and monetary strings are non-ASCII. This temporary change affects other threads.

  • bpo-35277: Update ensurepip to install pip 18.1 and setuptools 40.6.2.

  • bpo-24209: Adds IPv6 support when invoking http.server directly.

  • bpo-35226: Recursively check arguments when testing for equality of unittest.mock.call objects and add note that tracking of parameters used to create ancestors of mocks in mock_calls is not possible.

  • bpo-29564: The warnings module now suggests to enable tracemalloc if the source is specified, the tracemalloc module is available, but tracemalloc is not tracing memory allocations.

  • bpo-35189: Modify the following fnctl function to retry if interrupted by a signal (EINTR): flock, lockf, fnctl

  • bpo-30064: Use add_done_callback() in sock_* asyncio API to unsubscribe reader/writer early on calcellation.

  • bpo-35186: Removed the "built with" comment added when setup.py upload is used with either bdist_rpm or bdist_dumb.

  • bpo-35152: Allow sending more than 2 GB at once on a multiprocessing connection on non-Windows systems.

  • bpo-35062: Fix incorrect parsing of _io.IncrementalNewlineDecoder's translate argument.

  • bpo-35065: Remove StreamReaderProtocol._untrack_reader. The call to _untrack_reader is currently performed too soon, causing the protocol to forget about the reader before connection_lost can run and feed the EOF to the reader.

  • bpo-34160: ElementTree and minidom now preserve the attribute order specified by the user.

  • bpo-35079: Improve difflib.SequenceManager.get_matching_blocks doc by adding 'non-overlapping' and changing '!=' to '<'.

  • bpo-33710: Deprecated l*gettext() functions and methods in the gettext module. They return encoded bytes instead of Unicode strings and are artifacts from Python 2 times. Also deprecated functions and methods related to setting the charset for l*gettext() functions and methods.

  • bpo-35017: socketserver.BaseServer.serve_forever() now exits immediately if it's shutdown() method is called while it is polling for new events.

  • bpo-35024: importlib no longer logs wrote redundantly after (created|could not create) is already logged. Patch by Quentin Agren.

  • bpo-35047: unittest.mock now includes mock calls in exception messages if assert_not_called, assert_called_once, or assert_called_once_with fails. Patch by Petter Strandmark.

  • bpo-31047: Fix ntpath.abspath regression where it didn't remove a trailing separator on Windows. Patch by Tim Graham.

  • bpo-35053: tracemalloc now tries to update the traceback when an object is reused from a "free list" (optimization for faster object creation, used by the builtin list type for example).

  • bpo-31553: Add the --json-lines option to json.tool. Patch by hongweipeng.

  • bpo-34794: Fixed a leak in Tkinter when pass the Python wrapper around Tcl_Obj back to Tcl/Tk.

  • bpo-34909: Enum: fix grandchildren subclassing when parent mixed with concrete data types.

  • bpo-35022: unittest.mock.MagicMock now supports the __fspath__ method (from os.PathLike).

  • bpo-35008: Fixed references leaks when call the __setstate__() method of xml.etree.ElementTree.Element in the C implementation for already initialized element.

  • bpo-23420: Verify the value for the parameter '-s' of the cProfile CLI. Patch by Robert Kuska

  • bpo-33947: dataclasses now handle recursive reprs without raising RecursionError.

  • bpo-34890: Make inspect.iscoroutinefunction(), inspect.isgeneratorfunction() and inspect.isasyncgenfunction() work with functools.partial(). Patch by Pablo Galindo.

  • bpo-34521: Use socket.CMSG_SPACE() to calculate ancillary data size instead of socket.CMSG_LEN() in multiprocessing.reduction.recvfds() as RFC 3542 requires the use of the former for portable applications.

  • bpo-31522: The mailbox.mbox.get_string function from_ parameter can now successfully be set to a non-default value.

  • bpo-34970: Protect tasks weak set manipulation in asyncio.all_tasks()

  • bpo-34969: gzip: Add --fast, --best on the gzip CLI, these parameters will be used for the fast compression method (quick) or the best method compress (slower, but smaller file). Also, change the default compression level to 6 (tradeoff).

  • bpo-16965: The 2to3 execfile fixer now opens the file with mode 'rb'. Patch by Zackery Spytz.

  • bpo-34966: pydoc now supports aliases not only to methods defined in the end class, but also to inherited methods. The docstring is not duplicated for aliases.

  • bpo-34926: mimetypes.MimeTypes.guess_type() now accepts path-like object in addition to url strings. Patch by Mayank Asthana.

  • bpo-23831: Add moveto() method to the tkinter.Canvas widget. Patch by Juliette Monsel.

  • bpo-34941: Methods find(), findtext() and findall() of the Element class in the xml.etree.ElementTree module are now able to find children which are instances of Element subclasses.

  • bpo-32680: smtplib.SMTP objects now always have a sock attribute present

  • bpo-34769: Fix for async generators not finalizing when event loop is in debug mode and garbage collector runs in another thread.

  • bpo-34936: Fix TclError in tkinter.Spinbox.selection_element(). Patch by Juliette Monsel.

  • bpo-34829: Add methods selection_from, selection_range, selection_present and selection_to to the tkinter.Spinbox for consistency with the tkinter.Entry widget. Patch by Juliette Monsel.

  • bpo-34911: Added secure_protocols argument to http.cookiejar.DefaultCookiePolicy to allow for tweaking of protocols and also to add support by default for wss, the secure websocket protocol.

  • bpo-34922: Fixed integer overflow in the digest() and hexdigest() methods for the SHAKE algorithm in the hashlib module.

  • bpo-34925: 25% speedup in argument parsing for the functions in the bisect module.

  • bpo-34900: Fixed unittest.TestCase.debug() when used to call test methods with subtests. Patch by Bruno Oliveira.

  • bpo-34844: logging.Formatter enhancement - Ensure styles and fmt matches in logging.Formatter - Added validate method in each format style class: StrFormatStyle, PercentStyle, StringTemplateStyle. - This method is called in the constructor of logging.Formatter class - Also re-raise the KeyError in the format method of each style class, so it would a bit clear that it's an error with the invalid format fields.

  • bpo-34897: Adjust test.support.missing_compiler_executable check so that a nominal command name of "" is ignored. Patch by Michael Felt.

  • bpo-34871: Fix inspect module polluted sys.modules when parsing __text_signature__ of callable.

  • bpo-34898: Add mtime argument to gzip.compress for reproducible output. Patch by Guo Ci Teo.

  • bpo-28441: On Cygwin and MinGW, ensure that sys.executable always includes the full filename in the path, including the .exe suffix (unless it is a symbolic link).

  • bpo-34866: Adding max_num_fields to cgi.FieldStorage to make DOS attacks harder by limiting the number of MiniFieldStorage objects created by FieldStorage.

  • bpo-34711: http.server ensures it reports HTTPStatus.NOT_FOUND when the local path ends with "/" and is not a directory, even if the underlying OS (e.g. AIX) accepts such paths as a valid file reference. Patch by Michael Felt.

  • bpo-34872: Fix self-cancellation in C implementation of asyncio.Task

  • bpo-34849: Don't log waiting for selector.select in asyncio loop iteration. The waiting is pretty normal for any asyncio program, logging its time just adds a noise to logs without any useful information provided.

  • bpo-34022: The SOURCE_DATE_EPOCH environment variable no longer overrides the value of the invalidation_mode argument to py_compile.compile(), and determines its default value instead.

  • bpo-34819: Use a monotonic clock to compute timeouts in Executor.map() and as_completed(), in order to prevent timeouts from deviating when the system clock is adjusted.

  • bpo-34758: Add .wasm -> application/wasm to list of recognized file types and content type headers

  • bpo-34789: xml.sax.make_parser() now accepts any iterable as its parser_list argument. Patch by Andrés Delfino.

  • bpo-34334: In QueueHandler, clear exc_text from LogRecord to prevent traceback from being written twice.

  • bpo-34687: On Windows, asyncio now uses ProactorEventLoop, instead of SelectorEventLoop, by default.

  • bpo-5950: Support reading zip files with archive comments in zipimport.

  • bpo-32892: The parser now represents all constants as ast.Constant instead of using specific constant AST types (Num, Str, Bytes, NameConstant and Ellipsis). These classes are considered deprecated and will be removed in future Python versions.

  • bpo-34728: Add deprecation warning when loop is used in methods: asyncio.sleep, asyncio.wait and asyncio.wait_for.

  • bpo-34738: ZIP files created by distutils will now include entries for directories.

  • bpo-34659: Add an optional initial argument to itertools.accumulate().

  • bpo-29577: Support multiple mixin classes when creating Enums.

  • bpo-34670: Add SSLContext.post_handshake_auth and SSLSocket.verify_client_post_handshake for TLS 1.3's post handshake authentication feature.

  • bpo-32718: The Activate.ps1 script from venv works with PowerShell Core 6.1 and is now available under all operating systems.

  • bpo-31177: Fix bug that prevented using reset_mock on mock instances with deleted attributes

  • bpo-34672: Add a workaround, so the 'Z' time.strftime() specifier on the musl C library can work in some cases.

  • bpo-34666: Implement asyncio.StreamWriter.awrite and asyncio.StreamWriter.aclose() coroutines. Methods are needed for providing a consistent stream API with control flow switched on by default.

  • bpo-6721: Acquire the logging module's commonly used internal locks while fork()ing to avoid deadlocks in the child process.

  • bpo-34658: Fix a rare interpreter unhandled exception state SystemError only seen when using subprocess with a preexec_fn while an after_parent handler has been registered with os.register_at_fork and the fork system call fails.

  • bpo-34652: Ensure os.lchmod() is never defined on Linux.

  • bpo-34638: Store a weak reference to stream reader to break strong references loop between reader and protocol. It allows to detect and close the socket if the stream is deleted (garbage collected) without close() call.

  • bpo-34536: Enum._missing_: raise ValueError if None returned and TypeError if non-member is returned.

  • bpo-34636: Speed up re scanning of many non-matching characters for s w and d within bytes objects. (microoptimization)

  • bpo-24412: Add addModuleCleanup() and addClassCleanup() to unittest to support cleanups for setUpModule() and setUpClass(). Patch by Lisa Roach.

  • bpo-34630: Don't log SSL certificate errors in asyncio code (connection error logging is skipped already).

  • bpo-32490: Prevent filename duplication in subprocess exception messages. Patch by Zackery Spytz.

  • bpo-34363: dataclasses.asdict() and .astuple() now handle namedtuples correctly.

  • bpo-34625: Update vendorized expat library version to 2.2.6.

  • bpo-32270: The subprocess module no longer mistakenly closes redirected fds even when they were in pass_fds when outside of the default {0, 1, 2} set.

  • bpo-34622: Create a dedicated asyncio.CancelledError, asyncio.InvalidStateError and asyncio.TimeoutError exception classes. Inherit them from corresponding exceptions from concurrent.futures package. Extract asyncio exceptions into a separate file.

  • bpo-34610: Fixed iterator of multiprocessing.managers.DictProxy.

  • bpo-34421: Fix distutils logging for non-ASCII strings. This caused installation issues on Windows.

  • bpo-34604: Fix possible mojibake in the error message of pwd.getpwnam and grp.getgrnam using string representation because of invisible characters or trailing whitespaces. Patch by William Grzybowski.

  • bpo-30977: Make uuid.UUID use __slots__ to reduce its memory footprint. Based on original patch by Wouter Bolsterlee.

  • bpo-34574: OrderedDict iterators are not exhausted during pickling anymore. Patch by Sergey Fedoseev.

  • bpo-8110: Refactored subprocess to check for Windows-specific modules rather than sys.platform == 'win32'.

  • bpo-34530: distutils.spawn.find_executable() now falls back on os.defpath if the PATH environment variable is not set.

  • bpo-34563: On Windows, fix multiprocessing.Connection for very large read: fix _winapi.PeekNamedPipe() and _winapi.ReadFile() for read larger than INT_MAX (usually 2^31-1).

  • bpo-34558: Correct typo in Lib/ctypes/_aix.py

  • bpo-34282: Move Enum._convert to EnumMeta._convert_ and fix enum members getting shadowed by parent attributes.

  • bpo-22872: When the queue is closed, ValueError is now raised by multiprocessing.Queue.put() and multiprocessing.Queue.get() instead of AssertionError and OSError, respectively. Patch by Zackery Spytz.

  • bpo-34515: Fix parsing non-ASCII identifiers in lib2to3.pgen2.tokenize (PEP 3131).

  • bpo-13312: Avoids a possible integer underflow (undefined behavior) in the time module's year handling code when passed a very low negative year value.

  • bpo-34472: Improved compatibility for streamed files in zipfile. Previously an optional signature was not being written and certain ZIP applications were not supported. Patch by Silas Sewell.

  • bpo-34454: Fix the .fromisoformat() methods of datetime types crashing when given unicode with non-UTF-8-encodable code points. Specifically, datetime.fromisoformat() now accepts surrogate unicode code points used as the separator. Report and tests by Alexey Izbyshev, patch by Paul Ganssle.

  • bpo-6700: Fix inspect.getsourcelines for module level frames/tracebacks. Patch by Vladimir Matveev.

  • bpo-34171: Running the trace module no longer creates the trace.cover file.

  • bpo-34441: Fix crash when an ABC-derived class with invalid __subclasses__ is passed as the second argument to issubclass(). Patch by Alexey Izbyshev.

  • bpo-34427: Fix infinite loop in a.extend(a) for MutableSequence subclasses.

  • bpo-34412: Make signal.strsignal() work on HP-UX. Patch by Michael Osipov.

  • bpo-20849: shutil.copytree now accepts a new dirs_exist_ok keyword argument. Patch by Josh Bronson.

  • bpo-31715: Associate .mjs file extension with application/javascript MIME Type.

  • bpo-34384: os.readlink() now accepts path-like and bytes objects on Windows.

  • bpo-22602: The UTF-7 decoder now raises UnicodeDecodeError for ill-formed sequences starting with "+" (as specified in RFC 2152). Patch by Zackery Spytz.

  • bpo-2122: The mmap.flush() method now returns None on success, raises an exception on error under all platforms.

  • bpo-34341: Appending to the ZIP archive with the ZIP64 extension no longer grows the size of extra fields of existing entries.

  • bpo-34333: Fix %-formatting in pathlib.PurePath.with_suffix() when formatting an error message.

  • bpo-18540: The imaplib.IMAP4 and imaplib.IMAP4_SSL classes now resolve to the local host IP correctly when the default value of host parameter ('') is used.

  • bpo-26502: Implement traceback.FrameSummary.__len__() method to preserve compatibility with the old tuple API.

  • bpo-34318: assertRaises(), assertRaisesRegex(), assertWarns() and assertWarnsRegex() no longer success if the passed callable is None. They no longer ignore unknown keyword arguments in the context manager mode. A DeprecationWarning was raised in these cases since Python 3.5.

  • bpo-9372: Deprecate __getitem__() methods of xml.dom.pulldom.DOMEventStream, wsgiref.util.FileWrapper and fileinput.FileInput.

  • bpo-33613: Fix a race condition in multiprocessing.semaphore_tracker when the tracker receives SIGINT before it can register signal handlers for ignoring it.

  • bpo-34248: Report filename in the exception raised when the database file cannot be opened by dbm.gnu.open() and dbm.ndbm.open() due to OS-related error. Patch by Zsolt Cserna.

  • bpo-33089: Add math.dist() to compute the Euclidean distance between two points.

  • bpo-34246: smtplib.SMTP.send_message() no longer modifies the content of the mail_options argument. Patch by Pablo S. Blum de Aguiar.

  • bpo-31047: Fix ntpath.abspath for invalid paths on windows. Patch by Franz Woellert.

  • bpo-32321: Add pure Python fallback for functools.reduce. Patch by Robert Wright.

  • bpo-34270: The default asyncio task class now always has a name which can be get or set using two new methods (get_name() and set_name()) and is visible in the repr() output. An initial name can also be set using the new name keyword argument to asyncio.create_task() or the create_task() method of the event loop. If no initial name is set, the default Task implementation generates a name like Task-1 using a monotonic counter.

  • bpo-34263: asyncio's event loop will not pass timeouts longer than one day to epoll/select etc.

  • bpo-34035: Fix several AttributeError in zipfile seek() methods. Patch by Mickaël Schoentgen.

  • bpo-32215: Fix performance regression in sqlite3 when a DML statement appeared in a different line than the rest of the SQL query.

  • bpo-34075: Deprecate passing non-ThreadPoolExecutor instances to AbstractEventLoop.set_default_executor().

  • bpo-34251: Restore msilib.Win64 to preserve backwards compatibility since it's already used by distutils' bdist_msi command.

  • bpo-19891: Ignore errors caused by missing / non-writable homedir while writing history during exit of an interactive session. Patch by Anthony Sottile.

  • bpo-33089: Enhanced math.hypot() to support more than two dimensions.

  • bpo-34228: tracemalloc: PYTHONTRACEMALLOC=0 environment variable and -X tracemalloc=0 command line option are now allowed to disable explicitly tracemalloc at startup.

  • bpo-13041: Use shutil.get_terminal_size() to calculate the terminal width correctly in the argparse.HelpFormatter class. Initial patch by Zbyszek Jędrzejewski-Szmek.

  • bpo-34213: Allow frozen dataclasses to have a field named "object". Previously this conflicted with an internal use of "object".

  • bpo-34052: sqlite3.Connection.create_aggregate(), sqlite3.Connection.create_function(), sqlite3.Connection.set_authorizer(), sqlite3.Connection.set_progress_handler() methods raises TypeError when unhashable objects are passed as callable. These methods now don't pass such objects to SQLite API. Previous behavior could lead to segfaults. Patch by Sergey Fedoseev.

  • bpo-34197: Attributes skipinitialspace, doublequote and strict of the dialect attribute of the csv reader are now bool instances instead of integers 0 or 1.

  • bpo-32788: Errors other than TypeError raised in methods __adapt__() and __conform__() in the sqlite3 module are now propagated to the user.

  • bpo-21446: The reload fixer now uses importlib.reload() instead of deprecated imp.reload().

  • bpo-940286: pydoc's Helper.showtopic() method now prints the cross references of a topic correctly.

  • bpo-34164: base64.b32decode() could raise UnboundLocalError or OverflowError for incorrect padding. Now it always raises base64.Error in these cases.

  • bpo-33729: Fixed issues with arguments parsing in hashlib.

  • bpo-34097: ZipFile can zip files older than 1980-01-01 and newer than 2107-12-31 using a new strict_timestamps parameter at the cost of setting the timestamp to the limit.

  • bpo-34108: Remove extraneous CR in 2to3 refactor.

  • bpo-34070: Make sure to only check if the handle is a tty, when opening a file with buffering=-1.

  • bpo-27494: Reverted bpo-27494. 2to3 rejects now a trailing comma in generator expressions.

  • bpo-33967: functools.singledispatch now raises TypeError instead of IndexError when no positional arguments are passed.

  • bpo-34041: Add the parameter deterministic to the sqlite3.Connection.create_function() method. Patch by Sergey Fedoseev.

  • bpo-34056: Ensure the loader shim created by imp.load_module always returns bytes from its get_data() function. This fixes using imp.load_module with PEP 552 hash-based pycs.

  • bpo-34054: The multiprocessing module now uses the monotonic clock time.monotonic() instead of the system clock time.time() to implement timeout.

  • bpo-34043: Optimize tarfile uncompress performance about 15% when gzip is used.

  • bpo-34044: subprocess.Popen now copies the startupinfo argument to leave it unchanged: it will modify the copy, so that the same STARTUPINFO object can be used multiple times.

  • bpo-34010: Fixed a performance regression for reading streams with tarfile. The buffered read should use a list, instead of appending to a bytes object.

  • bpo-34019: webbrowser: Correct the arguments passed to Opera Browser when opening a new URL using the webbrowser module. Patch by Bumsik Kim.

  • bpo-34003: csv.DictReader now creates dicts instead of OrderedDicts. Patch by Michael Selik.

  • bpo-33978: Closed existing logging handlers before reconfiguration via fileConfig and dictConfig. Patch by Karthikeyan Singaravelan.

  • bpo-14117: Make minor tweaks to turtledemo. The 'wikipedia' example is now 'rosette', describing what it draws. The 'penrose' print output is reduced. The'1024' output of 'tree' is eliminated.

  • bpo-33974: Fixed passing lists and tuples of strings containing special characters ", \, {, } and \n as options to ttk widgets.

  • bpo-27500: Fix getaddrinfo to resolve IPv6 addresses correctly.

  • bpo-24567: Improve random.choices() to handle subnormal input weights that could occasionally trigger an IndexError.

  • bpo-33871: Fixed integer overflow in os.readv(), os.writev(), os.preadv() and os.pwritev() and in os.sendfile() with headers or trailers arguments (on BSD-based OSes and macOS).

  • bpo-25007: Add copy.copy() and copy.deepcopy() support to zlib compressors and decompressors. Patch by Zackery Spytz.

  • bpo-33929: multiprocessing: Fix a race condition in Popen of multiprocessing.popen_spawn_win32. The child process now duplicates the read end of pipe instead of "stealing" it. Previously, the read end of pipe was "stolen" by the child process, but it leaked a handle if the child process had been terminated before it could steal the handle from the parent process.

  • bpo-33899: Tokenize module now implicitly emits a NEWLINE when provided with input that does not have a trailing new line. This behavior now matches what the C tokenizer does internally. Contributed by Ammar Askar.

  • bpo-33897: Added a 'force' keyword argument to logging.basicConfig().

  • bpo-33695: shutil.copytree() uses os.scandir() function and all copy functions depending from it use cached os.stat() values. The speedup for copying a directory with 8000 files is around +9% on Linux, +20% on Windows and + 30% on a Windows SMB share. Also the number of os.stat() syscalls is reduced by 38% making shutil.copytree() especially faster on network filesystems. (Contributed by Giampaolo Rodola' in bpo-33695.)

  • bpo-33916: bz2 and lzma: When Decompressor.__init__() is called twice, free the old lock to not leak memory.

  • bpo-32568: Make select.epoll() and its documentation consistent regarding sizehint and flags.

  • bpo-33833: Fixed bug in asyncio where ProactorSocketTransport logs AssertionError if force closed during write.

  • bpo-33663: Convert content length to string before putting to header.

  • bpo-33721: os.path functions that return a boolean result like exists(), lexists(), isdir(), isfile(), islink(), and ismount(), and pathlib.Path methods that return a boolean result like exists(), is_dir(), is_file(), is_mount(), is_symlink(), is_block_device(), is_char_device(), is_fifo(), is_socket() now return False instead of raising ValueError or its subclasses UnicodeEncodeError and UnicodeDecodeError for paths that contain characters or bytes unrepresentable at the OS level.

  • bpo-26544: Fixed implementation of platform.libc_ver(). It almost always returned version '2.9' for glibc.

  • bpo-33843: Remove deprecated cgi.escape, cgi.parse_qs and cgi.parse_qsl.

  • bpo-33842: Remove tarfile.filemode which is deprecated since Python 3.3.

  • bpo-30167: Prevent site.main() exception if PYTHONSTARTUP is set. Patch by Steve Weber.

  • bpo-33805: Improve error message of dataclasses.replace() when an InitVar is not specified

  • bpo-33687: Fix the call to os.chmod() for uu.decode() if a mode is given or decoded. Patch by Timo Furrer.

  • bpo-33812: Datetime instance d with non-None tzinfo, but with d.tzinfo.utcoffset(d) returning None is now treated as naive by the astimezone() method.

  • bpo-32108: In configparser, don't clear section when it is assigned to itself.

  • bpo-27397: Make email module properly handle invalid-length base64 strings.

  • bpo-33578: Implement multibyte encoder/decoder state methods

  • bpo-30805: Avoid race condition with debug logging

  • bpo-33476: Fix _header_value_parser.py when address group is missing final ';'. Contributed by Enrique Perez-Terron

  • bpo-33694: asyncio: Fix a race condition causing data loss on pause_reading()/resume_reading() when using the ProactorEventLoop.

  • bpo-32493: Correct test for uuid_enc_be availability in configure.ac. Patch by Michael Felt.

  • bpo-33792: Add asyncio.WindowsSelectorEventLoopPolicy and asyncio.WindowsProactorEventLoopPolicy.

  • bpo-33274: W3C DOM Level 1 specifies return value of Element.removeAttributeNode() as "The Attr node that was removed." xml.dom.minidom now complies with this requirement.

  • bpo-33778: Update unicodedata's database to Unicode version 11.0.0.

  • bpo-33165: Added a stacklevel parameter to logging calls to allow use of wrapper/helper functions for logging APIs.

  • bpo-33770: improve base64 exception message for encoded inputs of invalid length

  • bpo-33769: asyncio/start_tls: Fix error message; cancel callbacks in case of an unhandled error; mark SSLTransport as closed if it is aborted.

  • bpo-33767: The concatenation (+) and repetition (*) sequence operations now raise TypeError instead of SystemError when performed on mmap.mmap objects. Patch by Zackery Spytz.

  • bpo-33734: asyncio/ssl: Fix AttributeError, increase default handshake timeout

  • bpo-31014: Fixed creating a controller for webbrowser when a user specifies a path to an entry in the BROWSER environment variable. Based on patch by John Still.

  • bpo-2504: Add gettext.pgettext() and variants.

  • bpo-33197: Add description property for _ParameterKind

  • bpo-32751: When cancelling the task due to a timeout, asyncio.wait_for() will now wait until the cancellation is complete.

  • bpo-32684: Fix gather to propagate cancellation of itself even with return_exceptions.

  • bpo-33654: Support protocol type switching in SSLTransport.set_protocol().

  • bpo-33674: Pause the transport as early as possible to further reduce the risk of data_received() being called before connection_made().

  • bpo-33671: shutil.copyfile(), shutil.copy(), shutil.copy2(), shutil.copytree() and shutil.move() use platform-specific fast-copy syscalls on Linux and macOS in order to copy the file more efficiently. On Windows shutil.copyfile() uses a bigger default buffer size (1 MiB instead of 16 KiB) and a memoryview()-based variant of shutil.copyfileobj() is used. The speedup for copying a 512MiB file is about +26% on Linux, +50% on macOS and +40% on Windows. Also, much less CPU cycles are consumed. (Contributed by Giampaolo Rodola' in bpo-25427.)

  • bpo-33674: Fix a race condition in SSLProtocol.connection_made() of asyncio.sslproto: start immediately the handshake instead of using call_soon(). Previously, data_received() could be called before the handshake started, causing the handshake to hang or fail.

  • bpo-31647: Fixed bug where calling write_eof() on a _SelectorSocketTransport after it's already closed raises AttributeError.

  • bpo-32610: Make asyncio.all_tasks() return only pending tasks.

  • bpo-32410: Avoid blocking on file IO in sendfile fallback code

  • bpo-33469: Fix RuntimeError after closing loop that used run_in_executor

  • bpo-33672: Fix Task.__repr__ crash with Cython's bogus coroutines

  • bpo-33654: Fix transport.set_protocol() to support switching between asyncio.Protocol and asyncio.BufferedProtocol. Fix loop.start_tls() to work with asyncio.BufferedProtocols.

  • bpo-33652: Pickles of type variables and subscripted generics are now future-proof and compatible with older Python versions.

  • bpo-32493: Fixed uuid.uuid1() on FreeBSD.

  • bpo-33238: Add InvalidStateError to concurrent.futures. Future.set_result and Future.set_exception now raise InvalidStateError if the futures are not pending or running. Patch by Jason Haydaman.

  • bpo-33618: Finalize and document preliminary and experimental TLS 1.3 support with OpenSSL 1.1.1

  • bpo-33625: Release GIL on grp.getgrnam, grp.getgrgid, pwd.getpwnam and pwd.getpwuid if reentrant variants of these functions are available. Patch by William Grzybowski.

  • bpo-33623: Fix possible SIGSGV when asyncio.Future is created in __del__

  • bpo-11874: Use a better regex when breaking usage into wrappable parts. Avoids bogus assertion errors from custom metavar strings.

  • bpo-30877: Fixed a bug in the Python implementation of the JSON decoder that prevented the cache of parsed strings from clearing after finishing the decoding. Based on patch by c-fos.

  • bpo-33604: Remove HMAC default to md5 marked for removal in 3.8 (removal originally planned in 3.6, bump to 3.8 in gh-7062).

  • bpo-33582: Emit a deprecation warning for inspect.formatargspec

  • bpo-21145: Add functools.cached_property decorator, for computed properties cached for the life of the instance.

  • bpo-33570: Change TLS 1.3 cipher suite settings for compatibility with OpenSSL 1.1.1-pre6 and newer. OpenSSL 1.1.1 will have TLS 1.3 ciphers enabled by default.

  • bpo-28556: Do not simplify arguments to typing.Union. Now Union[Manager, Employee] is not simplified to Employee at runtime. Such simplification previously caused several bugs and limited possibilities for introspection.

  • bpo-12486: tokenize.generate_tokens() is now documented as a public API to tokenize unicode strings. It was previously present but undocumented.

  • bpo-33540: Add a new block_on_close class attribute to ForkingMixIn and ThreadingMixIn classes of socketserver.

  • bpo-33548: tempfile._candidate_tempdir_list should consider common TEMP locations

  • bpo-33109: argparse subparsers are once again not required by default, reverting the change in behavior introduced by bpo-26510 in 3.7.0a2.

  • bpo-33541: Remove unused private method _strptime.LocaleTime.__pad (a.k.a. _LocaleTime__pad).

  • bpo-33536: dataclasses.make_dataclass now checks for invalid field names and duplicate fields. Also, added a check for invalid field specifications.

  • bpo-33542: Prevent uuid.get_node from using a DUID instead of a MAC on Windows. Patch by Zvi Effron

  • bpo-26819: Fix race condition with ReadTransport.resume_reading in Windows proactor event loop.

  • Fix failure in typing.get_type_hints() when ClassVar was provided as a string forward reference.

  • bpo-33516: unittest.mock.MagicMock now supports the __round__ magic method.

  • bpo-28612: Added support for Site Maps to urllib's RobotFileParser as RobotFileParser.site_maps(). Patch by Lady Red, based on patch by Peter Wirtz.

  • bpo-28167: Remove platform.linux_distribution, which was deprecated since 3.5.

  • bpo-33504: Switch the default dictionary implementation for configparser from collections.OrderedDict to the standard dict type.

  • bpo-33505: Optimize asyncio.ensure_future() by reordering if checks: 1.17x faster.

  • bpo-33497: Add errors param to cgi.parse_multipart and make an encoding in FieldStorage use the given errors (needed for Twisted). Patch by Amber Brown.

  • bpo-29235: The cProfile.Profile class can now be used as a context manager. Patch by Scott Sanderson.

  • bpo-33495: Change dataclasses.Fields repr to use the repr of each of its members, instead of str. This makes it more clear what each field actually represents. This is especially true for the 'type' member.

  • bpo-26103: Correct inspect.isdatadescriptor to look for __set__ or __delete__. Patch by Aaron Hall.

  • bpo-29209: Removed the doctype() method and the html parameter of the constructor of XMLParser. The doctype() method defined in a subclass will no longer be called. Deprecated methods getchildren() and getiterator() in the ElementTree module emit now a DeprecationWarning instead of PendingDeprecationWarning.

  • bpo-33453: Fix dataclasses to work if using literal string type annotations or if using PEP 563 "Postponed Evaluation of Annotations". Only specific string prefixes are detected for both ClassVar ("ClassVar" and "typing.ClassVar") and InitVar ("InitVar" and "dataclasses.InitVar").

  • bpo-28556: Minor fixes in typing module: add annotations to NamedTuple.__new__, pass *args and **kwds in Generic.__new__. Original PRs by Paulius Šarka and Chad Dombrova.

  • bpo-33365: Print the header values besides the header keys instead just the header keys if debuglevel is set to >0 in http.client. Patch by Marco Strigl.

  • bpo-20087: Updated alias mapping with glibc 2.27 supported locales.

  • bpo-33422: Fix trailing quotation marks getting deleted when looking up byte/string literals on pydoc. Patch by Andrés Delfino.

  • bpo-28167: The function platform.linux_distribution and platform.dist now trigger a DeprecationWarning and have been marked for removal in Python 3.8

  • bpo-33281: Fix ctypes.util.find_library regression on macOS.

  • bpo-33311: Text and html output generated by cgitb does not display parentheses if the current call is done directly in the module. Patch by Stéphane Blondon.

  • bpo-27300: The file classes in tempfile now accept an errors parameter that complements the already existing encoding. Patch by Stephan Hohe.

  • bpo-32933: unittest.mock.mock_open() now supports iteration over the file contents. Patch by Tony Flury.

  • bpo-33217: Raise TypeError when looking up non-Enum objects in Enum classes and Enum members.

  • bpo-33197: Update error message when constructing invalid inspect.Parameters Patch by Dong-hee Na.

  • bpo-33383: Fixed crash in the get() method of the dbm.ndbm database object when it is called with a single argument.

  • bpo-33375: The warnings module now finds the Python file associated with a warning from the code object, rather than the frame's global namespace. This is consistent with how tracebacks and pdb find filenames, and should work better for dynamically executed code.

  • bpo-33336: imaplib now allows MOVE command in IMAP4.uid() (RFC 6851: IMAP MOVE Extension) and potentially as a name of supported method of IMAP4 object.

  • bpo-32455: Added jump parameter to dis.stack_effect().

  • bpo-27485: Rename and deprecate undocumented functions in urllib.parse().

  • bpo-33332: Add signal.valid_signals() to expose the POSIX sigfillset() functionality.

  • bpo-33251: ConfigParser.items() was fixed so that key-value pairs passed in via vars are not included in the resulting output.

  • bpo-33329: Fix multiprocessing regression on newer glibcs

  • bpo-33334: dis.stack_effect() now supports all defined opcodes including NOP and EXTENDED_ARG.

  • bpo-991266: Fix quoting of the Comment attribute of http.cookies.SimpleCookie.

  • bpo-33131: Upgrade bundled version of pip to 10.0.1.

  • bpo-33308: Fixed a crash in the parser module when converting an ST object to a tree of tuples or lists with line_info=False and col_info=True.

  • bpo-23403: lib2to3 now uses pickle protocol 4 for pre-computed grammars.

  • bpo-33266: lib2to3 now recognizes rf'...' strings.

  • bpo-11594: Ensure line-endings are respected when using lib2to3.

  • bpo-33254: Have importlib.resources.contents() and importlib.abc.ResourceReader.contents() return an iterable instead of an iterator.

  • bpo-33265: contextlib.ExitStack and contextlib.AsyncExitStack now use a method instead of a wrapper function for exit callbacks.

  • bpo-33263: Fix FD leak in _SelectorSocketTransport Patch by Vlad Starostin.

  • bpo-33256: Fix display of <module> call in the html produced by cgitb.html(). Patch by Stéphane Blondon.

  • bpo-33144: random.Random() and its subclassing mechanism got optimized to check only once at class/subclass instantiation time whether its getrandbits() method can be relied on by other methods, including randrange(), for the generation of arbitrarily large random integers. Patch by Wolfgang Maier.

  • bpo-33185: Fixed regression when running pydoc with the -m switch. (The regression was introduced in 3.7.0b3 by the resolution of bpo-33053)

    This fix also changed pydoc to add os.getcwd() to sys.path when necessary, rather than adding ".".

  • bpo-29613: Added support for the SameSite cookie flag to the http.cookies module.

  • bpo-33169: Delete entries of None in sys.path_importer_cache when importlib.machinery.invalidate_caches() is called.

  • bpo-33203: random.Random.choice() now raises IndexError for empty sequences consistently even when called from subclasses without a getrandbits() implementation.

  • bpo-33224: Update difflib.mdiff() for PEP 479. Convert an uncaught StopIteration in a generator into a return-statement.

  • bpo-33209: End framing at the end of C implementation of pickle.Pickler.dump().

  • bpo-32861: The urllib.robotparser's __str__ representation now includes wildcard entries and the "Crawl-delay" and "Request-rate" fields. Also removes extra newlines that were being appended to the end of the string. Patch by Michael Lazar.

  • bpo-23403: DEFAULT_PROTOCOL in pickle was bumped to 4. Protocol 4 is described in PEP 3154 and available since Python 3.4. It offers better performance and smaller size compared to protocol 3 introduced in Python 3.0.

  • bpo-20104: Improved error handling and fixed a reference leak in os.posix_spawn().

  • bpo-33106: Deleting a key from a read-only dbm database raises module specific error instead of KeyError.

  • bpo-33175: In dataclasses, Field.__set_name__ now looks up the __set_name__ special method on the class, not the instance, of the default value.

  • bpo-32380: Create functools.singledispatchmethod to support generic single dispatch on descriptors and methods.

  • bpo-33141: Have Field objects pass through __set_name__ to their default values, if they have their own __set_name__.

  • bpo-33096: Allow ttk.Treeview.insert to insert iid that has a false boolean value. Note iid=0 and iid=False would be same. Patch by Garvit Khatri.

  • bpo-32873: Treat type variables and special typing forms as immutable by copy and pickle. This fixes several minor issues and inconsistencies, and improves backwards compatibility with Python 3.6.

  • bpo-33134: When computing dataclass's __hash__, use the lookup table to contain the function which returns the __hash__ value. This is an improvement over looking up a string, and then testing that string to see what to do.

  • bpo-33127: The ssl module now compiles with LibreSSL 2.7.1.

  • bpo-32505: Raise TypeError if a member variable of a dataclass is of type Field, but doesn't have a type annotation.

  • bpo-33078: Fix the failure on OSX caused by the tests relying on sem_getvalue

  • bpo-33116: Add 'Field' to dataclasses.__all__.

  • bpo-32896: Fix an error where subclassing a dataclass with a field that uses a default_factory would generate an incorrect class.

  • bpo-33100: Dataclasses: If a field has a default value that's a MemberDescriptorType, then it's from that field being in __slots__, not an actual default value.

  • bpo-32953: If a non-dataclass inherits from a frozen dataclass, allow attributes to be added to the derived class. Only attributes from the frozen dataclass cannot be assigned to. Require all dataclasses in a hierarchy to be either all frozen or all non-frozen.

  • bpo-33097: Raise RuntimeError when executor.submit is called during interpreter shutdown.

  • bpo-32968: Modulo and floor division involving Fraction and float should return float.

  • bpo-33061: Add missing NoReturn to __all__ in typing.py

  • bpo-33078: Fix the size handling in multiprocessing.Queue when a pickling error occurs.

  • bpo-33064: lib2to3 now properly supports trailing commas after *args and **kwargs in function signatures.

  • bpo-33056: FIX properly close leaking fds in concurrent.futures.ProcessPoolExecutor.

  • bpo-33021: Release the GIL during fstat() calls, avoiding hang of all threads when calling mmap.mmap(), os.urandom(), and random.seed(). Patch by Nir Soffer.

  • bpo-31804: Avoid failing in multiprocessing.Process if the standard streams are closed or None at exit.

  • bpo-33034: Providing an explicit error message when casting the port property to anything that is not an integer value using urlparse() and urlsplit(). Patch by Matt Eaton.

  • bpo-30249: Improve struct.unpack_from() exception messages for problems with the buffer size and offset.

  • bpo-33037: Skip sending/receiving data after SSL transport closing.

  • bpo-27683: Fix a regression in ipaddress that result of hosts() is empty when the network is constructed by a tuple containing an integer mask and only 1 bit left for addresses.

  • bpo-22674: Add the strsignal() function in the signal module that returns the system description of the given signal, as returned by strsignal(3).

  • bpo-32999: Fix C implementation of ABC.__subclasscheck__(cls, subclass) crashed when subclass is not a type object.

  • bpo-33009: Fix inspect.signature() for single-parameter partialmethods.

  • bpo-32969: Expose several missing constants in zlib and fix corresponding documentation.

  • bpo-32056: Improved exceptions raised for invalid number of channels and sample width when read an audio file in modules aifc, wave and sunau.

  • bpo-32970: Improved disassembly of the MAKE_FUNCTION instruction.

  • bpo-32844: Fix wrong redirection of a low descriptor (0 or 1) to stderr in subprocess if another low descriptor is closed.

  • bpo-32960: For dataclasses, disallow inheriting frozen from non-frozen classes, and also disallow inheriting non-frozen from frozen classes. This restriction will be relaxed at a future date.

  • bpo-32713: Fixed tarfile.itn handling of out-of-bounds float values. Patch by Joffrey Fuhrer.

  • bpo-32257: The ssl module now contains OP_NO_RENEGOTIATION constant, available with OpenSSL 1.1.0h or 1.1.1.

  • bpo-32951: Direct instantiation of SSLSocket and SSLObject objects is now prohibited. The constructors were never documented, tested, or designed as public constructors. Users were suppose to use ssl.wrap_socket() or SSLContext.

  • bpo-32929: Remove the tri-state parameter "hash", and add the boolean "unsafe_hash". If unsafe_hash is True, add a __hash__ function, but if a __hash__ exists, raise TypeError. If unsafe_hash is False, add a __hash__ based on the values of eq= and frozen=. The unsafe_hash=False behavior is the same as the old hash=None behavior. unsafe_hash=False is the default, just as hash=None used to be.

  • bpo-32947: Add OP_ENABLE_MIDDLEBOX_COMPAT and test workaround for TLSv1.3 for future compatibility with OpenSSL 1.1.1.

  • bpo-32146: Document the interaction between frozen executables and the spawn and forkserver start methods in multiprocessing.

  • bpo-30622: The ssl module now detects missing NPN support in LibreSSL.

  • bpo-32922: dbm.open() now encodes filename with the filesystem encoding rather than default encoding.

  • bpo-32759: Free unused arenas in multiprocessing.heap.

  • bpo-32859: In os.dup2, don't check every call whether the dup3 syscall exists or not.

  • bpo-32556: nt._getfinalpathname, nt._getvolumepathname and nt._getdiskusage now correctly convert from bytes.

  • bpo-21060: Rewrite confusing message from setup.py upload from "No dist file created in earlier command" to the more helpful "Must create and upload files in one command".

  • bpo-32857: In tkinter, after_cancel(None) now raises a ValueError instead of canceling the first scheduled function. Patch by Cheryl Sabella.

  • bpo-32852: Make sure sys.argv remains as a list when running trace.

  • bpo-31333: _abc module is added. It is a speedup module with C implementations for various functions and methods in abc. Creating an ABC subclass and calling isinstance or issubclass with an ABC subclass are up to 1.5x faster. In addition, this makes Python start-up up to 10% faster.

    Note that the new implementation hides internal registry and caches, previously accessible via private attributes _abc_registry, _abc_cache, and _abc_negative_cache. There are three debugging helper methods that can be used instead _dump_registry, _abc_registry_clear, and _abc_caches_clear.

  • bpo-32841: Fixed asyncio.Condition issue which silently ignored cancellation after notifying and cancelling a conditional lock. Patch by Bar Harel.

  • bpo-32819: ssl.match_hostname() has been simplified and no longer depends on re and ipaddress module for wildcard and IP addresses. Error reporting for invalid wildcards has been improved.

  • bpo-19675: multiprocessing.Pool no longer leaks processes if its initialization fails.

  • bpo-32394: socket: Remove TCP_FASTOPEN,TCP_KEEPCNT,TCP_KEEPIDLE,TCP_KEEPINTVL flags on older version Windows during run-time.

  • bpo-31787: Fixed refleaks of __init__() methods in various modules. (Contributed by Oren Milman)

  • bpo-30157: Fixed guessing quote and delimiter in csv.Sniffer.sniff() when only the last field is quoted. Patch by Jake Davis.

  • bpo-30688: Added support of \N{name} escapes in regular expressions. Based on patch by Jonathan Eunice.

  • bpo-32792: collections.ChainMap() preserves the order of the underlying mappings.

  • bpo-32775: fnmatch.translate() no longer produces patterns which contain set operations. Sets starting with '[' or containing '--', '&&', '~~' or '||' will be interpreted differently in regular expressions in future versions. Currently they emit warnings. fnmatch.translate() now avoids producing patterns containing such sets by accident.

  • bpo-32622: Implement native fast sendfile for Windows proactor event loop.

  • bpo-32777: Fix a rare but potential pre-exec child process deadlock in subprocess on POSIX systems when marking file descriptors inheritable on exec in the child process. This bug appears to have been introduced in 3.4.

  • bpo-32647: The ctypes module used to depend on indirect linking for dlopen. The shared extension is now explicitly linked against libdl on platforms with dl.

  • bpo-32749: A dbm.dumb database opened with flags 'r' is now read-only. dbm.dumb.open() with flags 'r' and 'w' no longer creates a database if it does not exist.

  • bpo-32741: Implement asyncio.TimerHandle.when() method.

  • bpo-32691: Use mod_spec.parent when running modules with pdb

  • bpo-32734: Fixed asyncio.Lock() safety issue which allowed acquiring and locking the same lock multiple times, without it being free. Patch by Bar Harel.

  • bpo-32727: Do not include name field in SMTP envelope from address. Patch by Stéphane Wirtel

  • bpo-31453: Add TLSVersion constants and SSLContext.maximum_version / minimum_version attributes. The new API wraps OpenSSL 1.1 https://www.openssl.org/docs/man1.1.0/ssl/SSL_CTX_set_min_proto_version.html feature.

  • bpo-24334: Internal implementation details of ssl module were cleaned up. The SSLSocket has one less layer of indirection. Owner and session information are now handled by the SSLSocket and SSLObject constructor. Channel binding implementation has been simplified.

  • bpo-31848: Fix the error handling in Aifc_read.initfp() when the SSND chunk is not found. Patch by Zackery Spytz.

  • bpo-32585: Add Ttk spinbox widget to tkinter.ttk. Patch by Alan D Moore.

  • bpo-32512: profile CLI accepts -m module_name as an alternative to script path.

  • bpo-8525: help() on a type now displays builtin subclasses. This is intended primarily to help with notification of more specific exception subclasses.

    Patch by Sanyam Khurana.

  • bpo-31639: http.server now exposes a ThreadingHTTPServer class and uses it when the module is run with -m to cope with web browsers pre-opening sockets.

  • bpo-29877: compileall: import ProcessPoolExecutor only when needed, preventing hangs on low resource platforms

  • bpo-32221: Various functions returning tuple containing IPv6 addresses now omit %scope part since the same information is already encoded in scopeid tuple item. Especially this speeds up socket.recvfrom() when it receives multicast packet since useless resolving of network interface name is omitted.

  • bpo-32147: binascii.unhexlify() is now up to 2 times faster. Patch by Sergey Fedoseev.

  • bpo-30693: The TarFile class now recurses directories in a reproducible way.

  • bpo-30693: The ZipFile class now recurses directories in a reproducible way.

  • bpo-31680: Added curses.ncurses_version.

  • bpo-31908: Fix output of cover files for trace module command-line tool. Previously emitted cover files only when --missing option was used. Patch by Michael Selik.

  • bpo-31608: Raise a TypeError instead of crashing if a collections.deque subclass returns a non-deque from __new__. Patch by Oren Milman.

  • bpo-31425: Add support for sockets of the AF_QIPCRTR address family, supported by the Linux kernel. This is used to communicate with services, such as GPS or radio, running on Qualcomm devices. Patch by Bjorn Andersson.

  • bpo-22005: Implemented unpickling instances of datetime, date and time pickled by Python 2. encoding='latin1' should be used for successful decoding.

  • bpo-27645: sqlite3.Connection now exposes a backup method, if the underlying SQLite library is at version 3.6.11 or higher. Patch by Lele Gaifax.

  • bpo-16865: Support arrays >=2GiB in ctypes. Patch by Segev Finer.

  • bpo-31508: Removed support of arguments in tkinter.ttk.Treeview.selection. It was deprecated in 3.6. Use specialized methods like selection_set for changing the selection.

  • bpo-29456: Fix bugs in hangul normalization: u1176, u11a7 and u11c3

Documentation

  • bpo-21257: Document http.client.parse_headers().

  • bpo-34764: Improve example of iter() with 2nd sentinel argument.

  • bpo-35564: Explicitly set master_doc variable in conf.py for compliance with Sphinx 2.0

  • bpo-35511: Specified that profile.Profile class doesn't not support enable or disable methods. Also, elaborated that Profile object as a context manager is only supported in cProfile module.

  • bpo-10536: Enhance the gettext docs. Patch by Éric Araujo

  • bpo-35089: Remove mention of typing.io and typing.re. Their types should be imported from typing directly.

  • bpo-35038: Fix the documentation about an unexisting f_restricted attribute in the frame object. Patch by Stéphane Wirtel

  • bpo-35042: Replace PEP XYZ by the pep role and allow to use the direct links to the PEPs.

  • bpo-35044: Fix the documentation with the role exc for the appropriated exception. Patch by Stéphane Wirtel

  • bpo-35035: Rename documentation for email.utils to email.utils.rst.

  • bpo-34967: Use app.add_object_type() instead of the deprecated Sphinx function app.description_unit()

  • bpo-34913: Add documentation about the new command line interface of the gzip module.

  • bpo-32174: chm document displays non-ASCII charaters properly on some MBCS Windows systems.

  • bpo-11233: Create availability directive for documentation. Original patch by Georg Brandl.

  • bpo-34790: Document how passing coroutines to asyncio.wait() can be confusing.

  • bpo-34552: Make clear that == operator sometimes is equivalent to is. The <, <=, > and >= operators are only defined where they make sense.

  • bpo-28617: Fixed info in the stdtypes docs concerning the types that support membership tests.

  • bpo-20177: Migrate datetime.date.fromtimestamp to Argument Clinic. Patch by Tim Hoffmann.

  • bpo-34065: Fix wrongly written basicConfig documentation markup syntax

  • bpo-33460: replaced ellipsis with correct error codes in tutorial chapter 3.

  • bpo-33847: Add '@' operator entry to index.

  • bpo-33409: Clarified the relationship between PEP 538's PYTHONCOERCECLOCALE and PEP 540's PYTHONUTF8 mode.

  • bpo-33197: Add versionadded tag to the documentation of ParameterKind.description

  • bpo-17045: Improve the C-API doc for PyTypeObject. This includes adding several quick-reference tables and a lot of missing slot/typedef entries. The existing entries were also cleaned up with a slightly more consistent format.

  • bpo-33736: Improve the documentation of asyncio.open_connection(), asyncio.start_server() and their UNIX socket counterparts.

  • bpo-23859: Document that asyncio.wait() does not cancel its futures on timeout.

  • bpo-32436: Document PEP 567 changes to asyncio.

  • bpo-33604: Update HMAC md5 default to a DeprecationWarning, bump removal to 3.8.

  • bpo-33594: Document getargspec, from_function and from_builtin as deprecated in their respective docstring, and include version since deprecation in DeprecationWarning message.

  • bpo-33503: Fix broken pypi link

  • bpo-33421: Add missing documentation for typing.AsyncContextManager.

  • bpo-33487: BZ2file now emit a DeprecationWarning when buffering=None is passed, the deprecation message and documentation also now explicitly state it is deprecated since 3.0.

  • bpo-33378: Add Korean language switcher for https://docs.python.org/3/

  • bpo-33276: Clarify that the __path__ attribute on modules cannot be just any value.

  • bpo-33201: Modernize documentation for writing C extension types.

  • bpo-33195: Deprecate Py_UNICODE usage in c-api/arg document. Py_UNICODE related APIs are deprecated since Python 3.3, but it is missed in the document.

  • bpo-33126: Document PyBuffer_ToContiguous().

  • bpo-27212: Modify documentation for the islice() recipe to consume initial values up to the start index.

  • bpo-28247: Update zipapp documentation to describe how to make standalone applications.

  • bpo-18802: Documentation changes for ipaddress. Patch by Jon Foster and Berker Peksag.

  • bpo-27428: Update documentation to clarify that WindowsRegistryFinder implements MetaPathFinder. (Patch by Himanshu Lakhara)

  • bpo-28124: The ssl module function ssl.wrap_socket() has been de-emphasized and deprecated in favor of the more secure and efficient SSLContext.wrap_socket() method.

  • bpo-17232: Clarify docs for -O and -OO. Patch by Terry Reedy.

  • bpo-32436: Add documentation for the contextvars module (PEP 567).

  • bpo-32800: Update link to w3c doc for xml default namespaces.

  • bpo-11015: Update test.support documentation.

  • bpo-32613: Update the faq/windows.html to use the py command from PEP 397 instead of python.

  • bpo-8722: Document __getattr__() behavior when property get() method raises AttributeError.

  • bpo-32614: Modify RE examples in documentation to use raw strings to prevent DeprecationWarning and add text to REGEX HOWTO to highlight the deprecation.

  • bpo-20709: Remove the paragraph where we explain that os.utime() does not support a directory as path under Windows. Patch by Jan-Philip Gehrcke

  • bpo-32722: Remove the bad example in the tutorial of the Generator Expression. Patch by Stéphane Wirtel

  • bpo-31972: Improve docstrings for pathlib.PurePath subclasses.

  • bpo-30607: Use the externalized python-docs-theme package when building the documentation.

  • bpo-8243: Add a note about curses.addch and curses.addstr exception behavior when writing outside a window, or pad.

  • bpo-32337: Update documentation related with dict order.

  • bpo-25041: Document AF_PACKET in the socket module.

  • bpo-31432: Clarify meaning of CERT_NONE, CERT_OPTIONAL, and CERT_REQUIRED flags for ssl.SSLContext.verify_mode.

Tests

  • bpo-35772: Fix sparse file tests of test_tarfile on ppc64 with the tmpfs filesystem. Fix the function testing if the filesystem supports sparse files: create a file which contains data and "holes", instead of creating a file which contains no data. tmpfs effective block size is a page size (tmpfs lives in the page cache). RHEL uses 64 KiB pages on aarch64, ppc64, ppc64le, only s390x and x86_64 use 4 KiB pages, whereas the test punch holes of 4 KiB.

  • bpo-35045: Make ssl tests less strict and also accept TLSv1 as system default. The changes unbreaks test_min_max_version on Fedora 29.

  • bpo-32710: test_asyncio/test_sendfile.py now resets the event loop policy using tearDownModule() as done in other tests, to prevent a warning when running tests on Windows.

  • bpo-33717: test.pythoninfo now logs information of all clocks, not only time.time() and time.perf_counter().

  • bpo-35488: Add a test to pathlib's Path.match() to verify it does not support glob-style ** recursive pattern matching.

  • bpo-31731: Fix a race condition in check_interrupted_write() of test_io: create directly the thread with SIGALRM signal blocked, rather than blocking the signal later from the thread. Previously, it was possible that the thread gets the signal before the signal is blocked.

  • bpo-35424: Fix test_multiprocessing_main_handling: use multiprocessing.Pool with a context manager and then explicitly join the pool.

  • bpo-35519: Rename test.bisect module to test.bisect_cmd to avoid conflict with bisect module when running directly a test like ./python Lib/test/test_xmlrpc.py.

  • bpo-35513: Replace time.time() with time.monotonic() in tests to measure time delta.

  • bpo-34279: test.support.run_unittest() no longer raise TestDidNotRun if the test result contains skipped tests. The exception is now only raised if no test have been run and no test have been skipped.

  • bpo-35412: Add testcase to test_future4: check unicode literal.

  • bpo-26704: Added test demonstrating double-patching of an instance method. Patch by Anthony Sottile.

  • bpo-33725: test_multiprocessing_fork may crash on recent versions of macOS. Until the issue is resolved, skip the test on macOS.

  • bpo-35352: Modify test_asyncio to use the certificate set from the test directory.

  • bpo-35317: Fix mktime() overflow error in test_email: run test_localtime_daylight_true_dst_true() and test_localtime_daylight_false_dst_true() with a specific timezone.

  • bpo-21263: After several reports that test_gdb does not work properly on macOS and since gdb is not shipped by default anymore, test_gdb is now skipped on macOS when LLVM Clang has been used to compile Python. Patch by Lysandros Nikolaou

  • bpo-34279: regrtest issue a warning when no tests have been executed in a particular test file. Also, a new final result state is issued if no test have been executed across all test files. Patch by Pablo Galindo.

  • bpo-34962: make docstest in Doc now passes., and is enforced in CI

  • bpo-23596: Use argparse for the command line of the gzip module. Patch by Antony Lee

  • bpo-34537: Fix test_gdb.test_strings() when LC_ALL=C and GDB was compiled with Python 3.6 or earlier.

  • bpo-34587: test_socket: Remove RDSTest.testCongestion(). The test tries to fill the receiver's socket buffer and expects an error. But the RDS protocol doesn't require that. Moreover, the Linux implementation of RDS expects that the producer of the messages reduces its rate, it's not the role of the receiver to trigger an error. The test fails on Fedora 28 by design, so just remove it.

  • bpo-34661: Fix test_shutil if unzip doesn't support -t.

  • bpo-34200: Fixed non-deterministic flakiness of test_pkg by not using the scary test.support.module_cleanup() logic to save and restore sys.modules contents between test cases.

  • bpo-34569: The experimental PEP 554 data channels now correctly pass negative PyLong objects between subinterpreters on 32-bit systems. Patch by Michael Felt.

  • bpo-34594: Fix usage of hardcoded errno values in the tests.

  • bpo-34579: Fix test_embed for AIX Patch by Michael Felt

  • bpo-34542: Use 3072 RSA keys and SHA-256 signature for test certs and keys.

  • bpo-11193: Remove special condition for AIX in test_subprocess.test_undecodable_env

  • bpo-34347: Fix test_utf8_mode.test_cmd_line for AIX

  • bpo-34490: On AIX with AF_UNIX family sockets getsockname() does not provide 'sockname', so skip calls to transport.get_extra_info('sockname')

  • bpo-34391: Fix ftplib test for TLS 1.3 by reading from data socket.

  • bpo-11192: Fix test_socket on AIX 6.1 and later IPv6 zone id supports only supported by inet_pton6_zone() Switch to runtime-based platform.system() to establish current platform rather than build-time based sys.platform()

  • bpo-34399: Update all RSA keys and DH params to use at least 2048 bits.

  • bpo-34373: Fix test_mktime and test_pthread_getcpuclickid tests for AIX Add range checking for _PyTime_localtime for AIX Patch by Michael Felt

  • bpo-11191: Skip the distutils test 'test_search_cpp' when using XLC as compiler patch by aixtools (Michael Felt)

  • Improved an error message when mock assert_has_calls fails.

  • bpo-33746: Fix test_unittest when run in verbose mode.

  • bpo-33901: Fix test_dbm_gnu on macOS with gdbm 1.15: add a larger value to make sure that the file size changes.

  • bpo-33873: Fix a bug in regrtest that caused an extra test to run if --huntrleaks/-R was used. Exit with error in case that invalid parameters are specified to --huntrleaks/-R (at least one warmup run and one repetition must be used).

  • bpo-33562: Check that a global asyncio event loop policy is not left behind by any tests.

  • bpo-33655: Ignore test_posix_fallocate failures on BSD platforms that might be due to running on ZFS.

  • bpo-32962: Fixed test_gdb when Python is compiled with flags -mcet -fcf-protection -O0.

  • bpo-33358: Fix test_embed.test_pre_initialization_sys_options() when the interpreter is built with --enable-shared.

  • bpo-32872: Avoid regrtest compatibility issue with namespace packages.

  • bpo-32517: Fix failing test_asyncio on macOS 10.12.2+ due to transport of KqueueSelector loop was not being closed.

  • bpo-32663: Making sure the SMTPUTF8SimTests class of tests gets run in test_smtplib.py.

  • bpo-27643: Test_C test case needs "signed short" bitfields, but the IBM XLC compiler (on AIX) does not support this Skip the code and test when AIX and XLC are used

    Applicable to Python2-2.7 and later

  • bpo-19417: Add test_bdb.py.

  • bpo-31809: Add tests to verify connection with secp ECDH curves.

Build

  • bpo-34691: The _contextvars module is now built into the core Python library on Windows.

  • bpo-35683: Improved Azure Pipelines build steps and now verifying layouts correctly

  • bpo-35642: Remove asynciomodule.c from pythoncore.vcxproj

  • bpo-35550: Fix incorrect Solaris #ifdef checks to look for __sun && __SVR4 instead of sun when compiling.

  • bpo-35499: make profile-opt no longer replaces CFLAGS_NODIST with CFLAGS. It now adds profile-guided optimization (PGO) flags to CFLAGS_NODIST: existing CFLAGS_NODIST flags are kept.

  • bpo-35257: Avoid leaking the linker flags from Link Time Optimizations (LTO) into distutils when compiling C extensions.

  • bpo-35351: When building Python with clang and LTO, LTO flags are no longer passed into CFLAGS to build third-party C extensions through distutils.

  • bpo-35139: Fix a compiler error when statically linking pyexpat in Modules/Setup.

  • bpo-35059: PCbuild: Set InlineFunctionExpansion to OnlyExplicitInline ("/Ob1" option) in pyproject.props in Debug mode to expand functions marked as inline. This change should make Python compiled in Debug mode a little bit faster on Windows.

  • bpo-35011: Restores the use of pyexpatns.h to isolate our embedded copy of the expat C library so that its symbols do not conflict at link or dynamic loading time with an embedding application or other extension modules with their own version of libexpat.

  • bpo-28015: Have --with-lto works correctly with clang.

  • bpo-34765: Update the outdated install-sh file to the latest revision from automake v1.16.1

  • bpo-34585: Check for floating-point byte order in configure.ac using compilation tests instead of executing code, so that these checks work in cross-compiled builds.

  • bpo-34710: Fixed SSL module build with OpenSSL & pedantic CFLAGS.

  • bpo-34582: Add JUnit XML output for regression tests and update Azure DevOps builds.

  • bpo-34081: Make Sphinx warnings as errors in the Docs Makefile.

  • bpo-34555: Fix for case where it was not possible to have both HAVE_LINUX_VM_SOCKETS_H and HAVE_SOCKADDR_ALG be undefined.

  • bpo-33015: Fix an undefined behaviour in the pthread implementation of PyThread_start_new_thread(): add a function wrapper to always return NULL.

  • bpo-34245: The Python shared library is now installed with write permission (mode 0755), which is the standard way of installing such libraries.

  • bpo-34121: Fix detection of C11 atomic support on clang.

  • bpo-32430: Rename Modules/Setup.dist to Modules/Setup, and remove the necessity to copy the former manually to the latter when updating the local source tree.

  • bpo-30345: Add -g to LDFLAGS when compiling with LTO to get debug symbols.

  • bpo-5755: Move -Wstrict-prototypes option to CFLAGS_NODIST from OPT. This option emitted annoying warnings when building extension modules written in C++.

  • bpo-33614: Ensures module definition files for the stable ABI on Windows are correctly regenerated.

  • bpo-33648: The --with-c-locale-warning configuration flag has been removed. It has had no effect for about a year.

  • bpo-33522: Enable CI builds on Visual Studio Team Services at https://python.visualstudio.com/cpython

  • bpo-33512: configure's check for "long double" has been simplified

  • bpo-33483: C compiler is now correctly detected from the standard environment variables. --without-gcc and --with-icc options have been removed.

  • bpo-33394: Enable the verbose build for extension modules, when GNU make is passed macros on the command line.

  • bpo-33393: Update config.guess and config.sub files.

  • bpo-33377: Add new triplets for mips r6 and riscv variants (used in extension suffixes).

  • bpo-32232: By default, modules configured in Modules/Setup are no longer built with -DPy_BUILD_CORE. Instead, modules that specifically need that preprocessor definition include it in their individual entries.

  • bpo-33182: The embedding tests can once again be built with clang 6.0

  • bpo-33163: Upgrade pip to 9.0.3 and setuptools to v39.0.1.

  • bpo-33012: gcc 8 has added a new warning heuristic to detect invalid function casts and a stock python build seems to hit that warning quite often. The most common is the cast of a METH_NOARGS function (that uses just one argument) to a PyCFunction. Fix this by adding a dummy argument to all functions that implement METH_NOARGS.

  • bpo-32898: Fix the python debug build when using COUNT_ALLOCS.

  • bpo-29442: Replace optparse with argparse in setup.py

Windows

  • bpo-35890: Fix API calling consistency of GetVersionEx and wcstok.

  • bpo-32560: The py launcher now forwards its STARTUPINFO structure to child processes.

  • bpo-35854: Fix EnvBuilder and --symlinks in venv on Windows

  • bpo-35811: Avoid propagating venv settings when launching via py.exe

  • bpo-35797: Fix default executable used by the multiprocessing module

  • bpo-35758: Allow building on ARM with MSVC.

  • bpo-29734: Fix handle leaks in os.stat on Windows.

  • bpo-35596: Use unchecked PYCs for the embeddable distro to avoid zipimport restrictions.

  • bpo-35596: Fix vcruntime140.dll being added to embeddable distro multiple times.

  • bpo-35402: Update Windows build to use Tcl and Tk 8.6.9

  • bpo-35401: Updates Windows build to OpenSSL 1.1.0j

  • bpo-34977: venv on Windows will now use a python.exe redirector rather than copying the actual binaries from the base environment.

  • bpo-34977: Adds support for building a Windows App Store package

  • bpo-35067: Remove _distutils_findvs module and use vswhere.exe instead.

  • bpo-32557: Allow shutil.disk_usage to take a file path on Windows

  • bpo-34770: Fix a possible null pointer dereference in pyshellext.cpp.

  • bpo-34603: Fix returning structs from functions produced by MSVC

  • bpo-34581: Guard MSVC-specific code in socketmodule.c with #ifdef _MSC_VER.

  • bpo-34532: Fixes exit code of list version arguments for py.exe.

  • bpo-34062: Fixed the '--list' and '--list-paths' arguments for the py.exe launcher

  • bpo-34225: Ensure INCLUDE and LIB directories do not end with a backslash.

  • bpo-34011: A suite of code has been changed which copied across DLLs and init.tcl from the running Python location into a venv being created. These copies are needed only when running from a Python source build, and the copying code is now only run when that is the case, rather than whenever a venv is created.

  • bpo-34006: Revert line length limit for Windows help docs. The line-length limit is not needed because the pages appear in a separate app rather than on a browser tab. It can also interact badly with the DPI setting.

  • bpo-31546: Restore running PyOS_InputHook while waiting for user input at the prompt. The restores integration of interactive GUI windows (such as Matplotlib figures) with the prompt on Windows.

  • bpo-30237: Output error when ReadConsole is canceled by CancelSynchronousIo instead of crashing.

  • bpo-33895: GIL is released while calling functions that acquire Windows loader lock.

  • bpo-33720: Reduces maximum marshal recursion depth on release builds.

  • bpo-29097: Fix bug where datetime.fromtimestamp() erroneously throws an OSError on Windows for values between 0 and 86400. Patch by Ammar Askar.

  • bpo-33316: PyThread_release_lock always fails

  • bpo-33184: Update Windows installer to use OpenSSL 1.1.0h.

  • bpo-32890: Fix usage of GetLastError() instead of errno in os.execve() and os.truncate().

  • bpo-33016: Fix potential use of uninitialized memory in nt._getfinalpathname

  • bpo-32903: Fix a memory leak in os.chdir() on Windows if the current directory is set to a UNC path.

  • bpo-32901: Update Tcl and Tk versions to 8.6.8

  • bpo-31966: Fixed WindowsConsoleIO.write() for writing empty data.

  • bpo-32409: Ensures activate.bat can handle Unicode contents.

  • bpo-32457: Improves handling of denormalized executable path when launching Python.

  • bpo-32370: Use the correct encoding for ipconfig output in the uuid module. Patch by Segev Finer.

  • bpo-29248: Fix os.readlink() on Windows, which was mistakenly treating the PrintNameOffset field of the reparse data buffer as a number of characters instead of bytes. Patch by Craig Holmquist and SSE4.

  • bpo-1104: Correctly handle string length in msilib.SummaryInfo.GetProperty() to prevent it from truncating the last character.

macOS

  • bpo-35401: Update macOS installer to use OpenSSL 1.1.0j.

  • bpo-35025: Properly guard the use of the CLOCK_GETTIME et al. macros in timemodule on macOS.

  • bpo-24658: On macOS, fix reading from and writing into a file with a size larger than 2 GiB.

  • bpo-34405: Update to OpenSSL 1.1.0i for macOS installer builds.

  • bpo-33635: In macOS stat on some file descriptors (/dev/fd/3 f.e) will result in bad file descriptor OSError. Guard against this exception was added in is_dir, is_file and similar methods. DirEntry.is_dir can also throw this exception so _RecursiveWildcardSelector._iterate_directories was also extended with the same error ignoring pattern.

  • bpo-13631: The .editrc file in user's home directory is now processed correctly during the readline initialization through editline emulation on macOS.

  • bpo-33184: Update macOS installer build to use OpenSSL 1.1.0h.

  • bpo-32726: Build and link with private copy of Tcl/Tk 8.6 for the macOS 10.6+ installer. The 10.9+ installer variant already does this. This means that the Python 3.7 provided by the python.org macOS installers no longer need or use any external versions of Tcl/Tk, either system-provided or user-installed, such as ActiveTcl.

  • bpo-32901: Update macOS 10.9+ installer to Tcl/Tk 8.6.8.

  • bpo-31903: In _scproxy, drop the GIL when calling into SystemConfiguration to avoid deadlocks.

IDLE

  • bpo-35770: IDLE macosx deletes Options => Configure IDLE. It previously deleted Window => Zoom Height by mistake. (Zoom Height is now on the Options menu). On Mac, the settings dialog is accessed via Preferences on the IDLE menu.

  • bpo-35769: Change IDLE's new file name from 'Untitled' to 'untitled'

  • bpo-35660: Fix imports in idlelib.window.

  • bpo-35641: Proper format calltip when the function has no docstring.

  • bpo-33987: Use ttk Frame for ttk widgets.

  • bpo-34055: Fix erroneous 'smart' indents and newlines in IDLE Shell.

  • bpo-35591: Find Selection now works when selection not found.

  • bpo-35196: Speed up squeezer line counting.

  • bpo-35598: Update config_key: use PEP 8 names and ttk widgets, make some objects global, and add tests.

  • bpo-28097: Add Previous/Next History entries to Shell menu.

  • bpo-35208: Squeezer now properly counts wrapped lines before newlines.

  • bpo-35555: Gray out Code Context menu entry when it's not applicable.

  • bpo-35521: Document the IDLE editor code context feature. Add some internal references within the IDLE doc.

  • bpo-22703: The Code Context menu label now toggles between Show/Hide Code Context. The Zoom Height menu now toggles between Zoom/Restore Height. Zoom Height has moved from the Window menu to the Options menu.

  • bpo-35213: Where appropriate, use 'macOS' in idlelib.

  • bpo-34864: On macOS, warn if the system preference "Prefer tabs when opening documents" is set to "Always".

  • bpo-34864: Document two IDLE on MacOS issues. The System Preferences Dock "prefer tabs always" setting disables some IDLE features. Menus are a bit different than as described for Windows and Linux.

  • bpo-35202: Remove unused imports from lib/idlelib

  • bpo-33000: Document that IDLE's shell has no line limit. A program that runs indefinitely can overfill memory.

  • bpo-23220: Explain how IDLE's Shell displays output.

  • bpo-35099: Improve the doc about IDLE running user code. The section is renamed from "IDLE -- console differences" is renamed "Running user code". It mostly covers the implications of using custom sys.stdxxx objects.

  • bpo-35097: Add IDLE doc subsection explaining editor windows. Topics include opening, title and status bar, .py* extension, and running.

  • bpo-35093: Document the IDLE document viewer in the IDLE doc. Add a paragraph in "Help and preferences", "Help sources" subsection.

  • bpo-35088: Update idlelib.help.copy_string docstring. We now use git and backporting instead of hg and forward merging.

  • bpo-35087: Update idlelib help files for the current doc build. The main change is the elimination of chapter-section numbers.

  • bpo-34548: Use configured color theme for read-only text views.

  • bpo-1529353: Enable "squeezing" of long outputs in the shell, to avoid performance degradation and to clean up the history without losing it. Squeezed outputs may be copied, viewed in a separate window, and "unsqueezed".

  • bpo-34047: Fixed mousewheel scrolling direction on macOS.

  • bpo-34275: Make IDLE calltips always visible on Mac. Some MacOS-tk combinations need .update_idletasks(). Patch by Kevin Walzer.

  • bpo-34120: Fix unresponsiveness after closing certain windows and dialogs.