Changelog

Python 3.9.6 final

Release date: 2021-06-28

Security

• bpo-44022: mod:http.client now avoids infinitely reading potential HTTP headers after a 100 Continue status response from the server.

Core and Builtins

• bpo-44409: Fix error location information for tokenizer errors raised on initialization of the tokenizer. Patch by Pablo Galindo.

• bpo-43667: Improve Unicode support in non-UTF locales on Oracle Solaris. This issue does not affect other Solaris systems.

• bpo-44168: Fix error message in the parser involving keyword arguments with invalid expressions. Patch by Pablo Galindo

• bpo-44114: Fix incorrect dictkeys_reversed and dictitems_reversed function signatures in C code, which broke webassembly builds.

• bpo-44070: No longer eagerly makes import filenames absolute, except for extension modules, which was introduced in 3.9.5.

• bpo-28146: Fix a confusing error message in str.format().

• bpo-11105: When compiling ast.AST objects with recursive references through compile(), the interpreter doesn’t crash anymore instead it raises a RecursionError.

Library

• bpo-44516: Update vendored pip to 21.1.3

• bpo-44482: Fix very unlikely resource leak in glob in alternate Python implementations.

• bpo-44439: Fix in bz2.BZ2File.write() / lzma.LZMAFile.write() methods, when the input data is an object that supports the buffer protocol, the file length may be wrong.

• bpo-44434: _thread.start_new_thread() no longer calls PyThread_exit_thread() explicitly at the thread exit, the call was redundant. On Linux with the glibc, pthread_exit() aborts the whole process if dlopen() fails to open libgcc_s.so file (ex: EMFILE error). Patch by Victor Stinner.

• bpo-44422: The threading.enumerate() function now uses a reentrant lock to prevent a hang on reentrant call. Patch by Victor Stinner.

• bpo-44395: Fix as_string() to pass unixfrom properly. Patch by Dong-hee Na.

• bpo-44342: [Enum] Be more robust in searching for pickle support before making an enum class unpicklable.

• bpo-44356: [Enum] Allow multiple data-type mixins if they are all the same.

• bpo-44254: On Mac, give turtledemo button text a color that works on both light or dark background. Programmers cannot control the latter.

• bpo-44145: hmac computations were not releasing the GIL while calling the OpenSSL HMAC_Update C API (a new feature in 3.9). This unintentionally prevented parallel computation as other hashlib algorithms support.

• bpo-37788: Fix a reference leak when a Thread object is never joined.

• bpo-44061: Fix regression in previous release when calling pkgutil.iter_modules() with a list of pathlib.Path objects

• bpo-36515: The hashlib module no longer does unaligned memory accesses when compiled for ARM platforms.

• bpo-44018: random.seed() no longer mutates bytearray inputs.

• bpo-38352: Add IO, BinaryIO, TextIO, Match, and Pattern to typing.__all__. Patch by Jelle Zijlstra.

• bpo-43972: When http.server.SimpleHTTPRequestHandler sends a 301 (Moved Permanently) for a directory path not ending with /, add a Content-Length: 0 header. This improves the behavior for certain clients.

• bpo-28528: Fix a bug in pdb where checkline() raises AttributeError if it is called after reset().

• bpo-43776: When subprocess.Popen args are provided as a string or as pathlib.Path, the Popen instance repr now shows the right thing.

• bpo-43666: AIX: Lib/_aix_support.get_platform() may fail in an AIX WPAR. The fileset bos.rte appears to have a builddate in both LPAR and WPAR so this fileset is queried rather than bos.mp64. To prevent a similiar situation (no builddate in ODM) a value (9988) sufficient for completing a build is provided. Patch by M Felt.

• bpo-43650: Fix MemoryError in shutil.unpack_archive() which fails inside shutil._unpack_zipfile() on large files. Patch by Igor Bolshakov.

• bpo-43318: Fix a bug where pdb does not always echo cleared breakpoints.

• bpo-43295: datetime.datetime.strptime() now raises ValueError instead of IndexError when matching 'z' with the %z format specifier.

• bpo-37022: pdb now displays exceptions from repr() with its p and pp commands.

Documentation

• bpo-40620: Convert examples in tutorial controlflow.rst section 4.3 to be interpreter-demo style.

• bpo-13814: In the Design FAQ, answer “Why don’t generators support the with statement?”

• bpo-44392: Added a new section in the C API documentation for types used in type hinting. Documented Py_GenericAlias and Py_GenericAliasType.

• bpo-38291: Mark typing.io and typing.re as deprecated since Python 3.8 in the documentation. They were never properly supported by type checkers.

• bpo-44322: Document that SyntaxError args have a details tuple and that details are adjusted for errors in f-string field replacement expressions.

• bpo-44195: Corrected references to TraversableResources in docs. There is no TraversableReader.

• bpo-41963: Document that ConfigParser strips off comments when reading configuration files.

• bpo-44072: Correct where in the numeric ABC hierarchy ** support is added, i.e., in numbers.Complex, not numbers.Integral.

• bpo-43558: Add the remark to dataclasses documentation that the __init__() of any base class has to be called in __post_init__(), along with a code example.

• bpo-41621: Document that collections.defaultdict parameter default_factory defaults to None and is positional-only.

Tests

• bpo-44287: Fix asyncio test_popen() of test_windows_utils by using a longer timeout. Use military grade battle-tested test.support.SHORT_TIMEOUT timeout rather than a hardcoded timeout of 10 seconds: it’s 30 seconds by default, but it is made longer on slow buildbots. Patch by Victor Stinner.

• bpo-44363: Account for address sanitizer in test_capi. test_capi now passes when run GCC address sanitizer.

Build

• bpo-44381: The Windows build now accepts EnableControlFlowGuard set to guard to enable CFG.

Windows

• bpo-41299: Fix 16ms jitter when using timeouts in threading, such as with threading.Lock.acquire() or threading.Condition.wait().

macOS

• bpo-43568: Relax unnecessarily restrictive MACOSX_DEPLOYMENT_TARGET check when building extension modules for macOS. Patch by Joshua Root.

• bpo-43109: Allow –with-lto configure option to work with Apple-supplied Xcode or Command Line Tools.

IDLE

• bpo-40128: Mostly fix completions on macOS when not using tcl/tk 8.6.11 (as with 3.9). The added update_idletask call should be harmless and possibly helpful otherwise.

• bpo-33962: Move the indent space setting from the Font tab to the new Windows tab. Patch by Mark Roseman and Terry Jan Reedy.

• bpo-40468: Split the settings dialog General tab into Windows and Shell/ED tabs. Move help sources, which extend the Help menu, to the Extensions tab. Make space for new options and shorten the dialog. The latter makes the dialog better fit small screens.

• bpo-41611: Avoid uncaught exceptions in AutoCompleteWindow.winconfig_event().

• bpo-41611: Fix IDLE sometimes freezing upon tab-completion on macOS.

Tools/Demos

• bpo-44074: Make patchcheck automatically detect the correct base branch name (previously it was hardcoded to ‘master’)

C API

• bpo-44441: Py_RunMain() now resets PyImport_Inittab to its initial value at exit. It must be possible to call PyImport_AppendInittab() or PyImport_ExtendInittab() at each Python initialization. Patch by Victor Stinner.

• bpo-42083: Fix crash in PyStructSequence_NewType() when passed NULL in the documentation string slot.

Python 3.9.5 final

Release date: 2021-05-03

Security

• bpo-43434: Creating a sqlite3.Connection object now also produces a sqlite3.connect auditing event. Previously this event was only produced by sqlite3.connect() calls. Patch by Erlend E. Aasland.

• bpo-43882: The presence of newline or tab characters in parts of a URL could allow some forms of attacks.

  Following the controlling specification for URLs defined by WHATWG urllib.parse() now removes ASCII newlines and tabs from URLs, preventing such attacks.

• bpo-43472: Ensures interpreter-level audit hooks receive the cpython.PyInterpreterState_New event when called through the _xxsubinterpreters module.

• bpo-36384: ipaddress module no longer accepts any leading zeros in IPv4 address strings. Leading zeros are ambiguous and interpreted as octal notation by some libraries. For example the legacy function socket.inet_aton() treats leading zeros as octal notatation. glibc implementation of modern inet_pton() does not accept any leading zeros. For a while the ipaddress module used to accept ambiguous leading zeros.

• bpo-43075: Fix Regular Expression Denial of Service (ReDoS) vulnerability in urllib.request.AbstractBasicAuthHandler. The ReDoS-vulnerable regex has quadratic worst-case complexity and it allows cause a denial of service when identifying crafted invalid RFCs. This ReDoS issue is on the client side and needs remote attackers to control the HTTP server.

• bpo-42800: Audit hooks are now fired for frame.f_code, traceback.tb_frame, and generator code/frame attribute access.

Core and Builtins

• bpo-43105: Importlib now resolves relative paths when creating module spec objects from file locations.

• bpo-42924: Fix bytearray repetition incorrectly copying data from the start of the buffer, even if the data is offset within the buffer (e.g. after reassigning a slice at the start of the bytearray to a shorter byte string).

Library

• bpo-43993: Update bundled pip to 21.1.1.

• bpo-43937: Fixed the turtle module working with non-default root window.

• bpo-43930: Update bundled pip to 21.1 and setuptools to 56.0.0

• bpo-43920: OpenSSL 3.0.0: load_verify_locations() now returns a consistent error message when cadata contains no valid certificate.

• bpo-43607: urllib can now convert Windows paths with \\?\ prefixes into URL paths.

• bpo-43284: platform.win32_ver derives the windows version from sys.getwindowsversion().platform_version which in turn derives the version from kernel32.dll (which can be of a different version than Windows itself). Therefore change the platform.win32_ver to determine the version using the platform module’s _syscmd_ver private function to return an accurate version.

• bpo-42248: [Enum] ensure exceptions raised in _missing_ are released.

• bpo-43799: OpenSSL 3.0.0: define OPENSSL_API_COMPAT 1.1.1 to suppress deprecation warnings. Python requires OpenSSL 1.1.1 APIs.

• bpo-43794: Add ssl.OP_IGNORE_UNEXPECTED_EOF constants (OpenSSL 3.0.0)

• bpo-43789: OpenSSL 3.0.0: Don’t call the password callback function a second time when first call has signaled an error condition.

• bpo-43788: The header files for ssl error codes are now OpenSSL version-specific. Exceptions will now show correct reason and library codes. The make_ssl_data.py script has been rewritten to use OpenSSL’s text file with error codes.

• bpo-43655: tkinter dialog windows are now recognized as dialogs by window managers on macOS and X Window.

• bpo-43534: turtle.textinput() and turtle.numinput() create now a transient window working on behalf of the canvas window.

• bpo-43522: Fix problem with hostname_checks_common_name. OpenSSL does not copy hostflags from struct SSL_CTX to struct SSL.

• bpo-42967: Allow bytes separator argument in urllib.parse.parse_qs and urllib.parse.parse_qsl when parsing str query strings. Previously, this raised a TypeError.

• bpo-43176: Fixed processing of a dataclass that inherits from a frozen dataclass with no fields. It is now correctly detected as an error.

• bpo-41735: Fix thread locks in zlib module may go wrong in rare case. Patch by Ma Lin.

• bpo-36470: Fix dataclasses with InitVars and replace(). Patch by Claudiu Popa.

• bpo-32745: Fix a regression in the handling of ctypes’ ctypes.c_wchar_p type: embedded null characters would cause a ValueError to be raised. Patch by Zackery Spytz.

Documentation

• bpo-43959: The documentation on the PyContextVar C-API was clarified.

• bpo-43938: Update dataclasses documentation to express that FrozenInstanceError is derived from AttributeError.

• bpo-43755: Update documentation to reflect that unparenthesized lambda expressions can no longer be the expression part in an if clause in comprehensions and generator expressions since Python 3.9.

• bpo-43739: Fixing the example code in Doc/extending/extending.rst to declare and initialize the pmodule variable to be of the right type.

Tests

• bpo-43961: Fix test_logging.test_namer_rotator_inheritance() on Windows: use os.replace() rather than os.rename(). Patch by Victor Stinner.

• bpo-43842: Fix a race condition in the SMTP test of test_logging. Don’t close a file descriptor (socket) from a different thread while asyncore.loop() is polling the file descriptor. Patch by Victor Stinner.

• bpo-43811: Tests multiple OpenSSL versions on GitHub Actions. Use ccache to speed up testing.

• bpo-43791: OpenSSL 3.0.0: Disable testing of legacy protocols TLS 1.0 and 1.1. Tests are failing with TLSV1_ALERT_INTERNAL_ERROR.

Windows

• bpo-35306: Avoid raising errors from pathlib.Path.exists() when passed an invalid filename.

• bpo-38822: Fixed os.stat() failing on inaccessible directories with a trailing slash, rather than falling back to the parent directory’s metadata. This implicitly affected os.path.exists() and os.path.isdir().

• bpo-26227: Fixed decoding of host names in socket.gethostbyaddr() and socket.gethostbyname_ex().

• bpo-40432: Updated pegen regeneration script on Windows to find and use Python 3.8 or higher. Prior to this, pegen regeneration already required 3.8 or higher, but the script may have used lower versions of Python.

• bpo-43745: Actually updates Windows release to OpenSSL 1.1.1k. Earlier releases were mislabelled and actually included 1.1.1i again.

• bpo-43492: Upgrade Windows installer to use SQLite 3.35.5.

macOS

• bpo-42119: Fix check for macOS SDK paths when building Python. Narrow search to match contents of SDKs, namely only files in /System/Library, /System/IOSSupport, and /usr other than /usr/local. Previously, anything under /System was assumed to be in an SDK which causes problems with the new file system layout in 10.15+ where user file systems may appear to be mounted under /System. Paths in /Library were also incorrectly treated as SDK locations.

• bpo-44009: Provide “python3.x-intel64” executable to allow reliably forcing macOS universal2 framework builds to run under Rosetta 2 Intel-64 emulation on Apple Silicon Macs. This can be useful for testing or when universal2 wheels are not yet available.

• bpo-43492: Update macOS installer to use SQLite 3.35.4.

IDLE

• bpo-43655: IDLE dialog windows are now recognized as dialogs by window managers on macOS and X Window.

Python 3.9.4 final

Release date: 2021-04-04

Core and Builtins

• bpo-43710: Reverted the fix for https://bugs.python.org/issue42500 as it changed the PyThreadState struct size and broke the 3.9.x ABI in the 3.9.3 release (visible on 32-bit platforms using binaries compiled using an earlier version of Python 3.9.x headers).

Library

• bpo-26053: Fixed bug where the pdb interactive run command echoed the args from the shell command line, even if those have been overridden at the pdb prompt.

Python 3.9.3 final

Release date: 2021-04-02

Security

• bpo-42988: CVE-2021-3426: Remove the getfile feature of the pydoc module which could be abused to read arbitrary files on the disk (directory traversal vulnerability). Moreover, even source code of Python modules can contain sensitive data like passwords. Vulnerability reported by David Schwörer.

• bpo-43285: ftplib no longer trusts the IP address value returned from the server in response to the PASV command by default. This prevents a malicious FTP server from using the response to probe IPv4 address and port combinations on the client network.

  Code that requires the former vulnerable behavior may set a trust_server_pasv_ipv4_address attribute on their ftplib.FTP instances to True to re-enable it.

• bpo-43439: Add audit hooks for gc.get_objects(), gc.get_referrers() and gc.get_referents(). Patch by Pablo Galindo.

Core and Builtins

• bpo-43660: Fix crash that happens when replacing sys.stderr with a callable that can remove the object while an exception is being printed. Patch by Pablo Galindo.

• bpo-43555: Report the column offset for SyntaxError for invalid line continuation characters. Patch by Pablo Galindo.

• bpo-43517: Fix misdetection of circular imports when using from pkg.mod import attr, which caused false positives in non-trivial multi-threaded code.

• bpo-35883: Python no longer fails at startup with a fatal error if a command line argument contains an invalid Unicode character. The Py_DecodeLocale() function now escapes byte sequences which would be decoded as Unicode characters outside the [U+0000; U+10ffff] range.

• bpo-43406: Fix a possible race condition where PyErr_CheckSignals tries to execute a non-Python signal handler.

• bpo-42500: Improve handling of exceptions near recursion limit. Converts a number of Fatal Errors in RecursionErrors.

Library

• bpo-43433: xmlrpc.client.ServerProxy no longer ignores query and fragment in the URL of the server.

• bpo-35930: Raising an exception raised in a “future” instance will create reference cycles.

• bpo-43577: Fix deadlock when using ssl.SSLContext debug callback with ssl.SSLContext.sni_callback().

• bpo-43521: ast.unparse can now render NaNs and empty sets.

• bpo-43423: subprocess.communicate() no longer raises an IndexError when there is an empty stdout or stderr IO buffer during a timeout on Windows.

• bpo-27820: Fixed long-standing bug of smtplib.SMTP where doing AUTH LOGIN with initial_response_ok=False will fail.

  The cause is that SMTP.auth_login _always_ returns a password if provided with a challenge string, thus non-compliant with the standard for AUTH LOGIN.

  Also fixes bug with the test for smtpd.

• bpo-43332: Improves the networking efficiency of http.client when using a proxy via set_tunnel(). Fewer small send calls are made during connection setup.

• bpo-43399: Fix ElementTree.extend not working on iterators when using the Python implementation

• bpo-43316: The python -m gzip command line application now properly fails when detecting an unsupported extension. It exits with a non-zero exit code and prints an error message to stderr.

• bpo-43260: Fix TextIOWrapper can not flush internal buffer forever after very large text is written.

• bpo-42782: Fail fast in shutil.move() to avoid creating destination directories on failure.

• bpo-37193: Fixed memory leak in socketserver.ThreadingMixIn introduced in Python 3.7.

Documentation

• bpo-43199: Answer “Why is there no goto?” in the Design and History FAQ.

• bpo-43407: Clarified that a result from time.monotonic(), time.perf_counter(), time.process_time(), or time.thread_time() can be compared with the result from any following call to the same function - not just the next immediate call.

• bpo-27646: Clarify that ‘yield from <expr>’ works with any iterable, not just iterators.

• bpo-36346: Update some deprecated unicode APIs which are documented as “will be removed in 4.0” to “3.12”. See PEP 623 for detail.

Tests

• bpo-37945: Fix test_getsetlocale_issue1813() of test_locale: skip the test if setlocale() fails. Patch by Victor Stinner.

• bpo-41561: Add workaround for Ubuntu’s custom OpenSSL security level policy.

• bpo-43288: Fix test_importlib to correctly skip Unicode file tests if the fileystem does not support them.

Build

• bpo-43631: Update macOS, Windows, and CI to OpenSSL 1.1.1k.

• bpo-43617: Improve configure.ac: Check for presence of autoconf-archive package and remove our copies of M4 macros.

macOS

• bpo-41837: Update macOS installer build to use OpenSSL 1.1.1j.

IDLE

• bpo-42225: Document that IDLE can fail on Unix either from misconfigured IP masquerage rules or failure displaying complex colored (non-ascii) characters.

• bpo-43283: Document why printing to IDLE’s Shell is often slower than printing to a system terminal and that it can be made faster by pre-formatting a single string before printing.

Python 3.9.2 final

Release date: 2021-02-19

Windows

• bpo-43155: PyCMethod_New() is now present in python3.lib.

Python 3.9.2 release candidate 1

Release date: 2021-02-16

Security

• bpo-42967: Fix web cache poisoning vulnerability by defaulting the query args separator to &, and allowing the user to choose a custom separator.

• bpo-42938: Avoid static buffers when computing the repr of ctypes.c_double and ctypes.c_longdouble values.

Core and Builtins

• bpo-42819: readline: Explicitly disable bracketed paste in the interactive interpreter, even if it’s set in the inputrc, is enabled by default (eg GNU Readline 8.1), or a user calls readline.read_init_file(). The Python REPL has not implemented bracketed paste support. Also, bracketed mode writes the "\x1b[?2004h" escape sequence into stdout which causes test failures in applications that don’t support it. It can still be explicitly enabled by calling readline.parse_and_bind("set enable-bracketed-paste on"). Patch by Dustin Rodrigues.

• bpo-42806: Fix the column offsets for f-strings ast nodes surrounded by parentheses and for nodes that spawn multiple lines. Patch by Pablo Galindo.

• bpo-40631: Fix regression where a single parenthesized starred expression was a valid assignment target.

• bpo-32381: Fix encoding name when running a .pyc file on Windows: PyRun_SimpleFileExFlags() now uses the correct encoding to decode the filename.

• bpo-42536: Several built-in and standard library types now ensure that their internal result tuples are always tracked by the garbage collector:

  • collections.OrderedDict.items()

  • dict.items()

  • enumerate()

  • functools.reduce()

  • itertools.combinations()

  • itertools.combinations_with_replacement()

  • itertools.permutations()

  • itertools.product()

  • itertools.zip_longest()

  • zip()

  Previously, they could have become untracked by a prior garbage collection. Patch by Brandt Bucher.

• bpo-42195: The __args__ of the parameterized generics for typing.Callable and collections.abc.Callable are now consistent. The __args__ for collections.abc.Callable are now flattened while typing.Callable’s have not changed. To allow this change, types.GenericAlias can now be subclassed and collections.abc.Callable’s __class_getitem__ will now return a subclass of types.GenericAlias. Tests for typing were also updated to not subclass things like Callable[..., T] as that is not a valid base class. Finally, both types no longer validate their argtypes, in Callable[[argtypes], resulttype] to prepare for PEP 612. Patch by Ken Jin.

Library

• bpo-43102: The namedtuple __new__ method had its __builtins__ set to None instead of an actual dictionary. This created problems for introspection tools.

• bpo-43108: Fixed a reference leak in the curses module. Patch by Pablo Galindo

• bpo-42944: Fix random.Random.sample when counts argument is not None.

• bpo-42931: Add randbytes() to random.__all__.

• bpo-42780: Fix os.set_inheritable() for O_PATH file descriptors on Linux.

• bpo-42851: remove __init_subclass__ support for Enum members

• bpo-41748: Fix HTMLParser parsing rules for element attributes containing commas with spaces. Patch by Karl Dubost.

• bpo-42759: Fixed equality comparison of tkinter.Variable and tkinter.font.Font. Objects which belong to different Tcl interpreters are now always different, even if they have the same name.

• bpo-42756: Configure LMTP Unix-domain socket to use socket global default timeout when a timeout is not explicitly provided.

• bpo-23328: Allow / character in username, password fields on _PROXY envars.

• bpo-42655: subprocess extra_groups is now correctly passed into setgroups() system call.

• bpo-42727: EnumMeta.__prepare__ now accepts **kwds to properly support __init_subclass__

• bpo-42681: Fixed range checks for color and pair numbers in curses.

• bpo-37961: Fix crash in tracemalloc.Traceback.__repr__() (regressed in Python 3.9).

• bpo-42630: tkinter functions and constructors which need a default root window raise now RuntimeError with descriptive message instead of obscure AttributeError or NameError if it is not created yet or cannot be created automatically.

• bpo-42644: logging.disable will now validate the types and value of its parameter. It also now accepts strings representing the levels (as does loging.setLevel) instead of only the numerical values.

• bpo-36541: Fixed lib2to3.pgen2 to be able to parse PEP-570 positional only argument syntax.

• bpo-42517: Enum: private names will raise a DeprecationWarning; in 3.10 they will become normal attributes

• bpo-42678: Enum: call __init_subclass__ after members have been added

• bpo-42532: Remove unexpected call of __bool__ when passing a spec_arg argument to a Mock.

• bpo-42388: Fix subprocess.check_output(…, input=None) behavior when text=True to be consistent with that of the documentation and universal_newlines=True.

• bpo-34463: Fixed discrepancy between traceback and the interpreter in formatting of SyntaxError with lineno not set (traceback was changed to match interpreter).

• bpo-42375: subprocess module update for DragonFlyBSD support.

• bpo-42384: Make pdb populate sys.path[0] exactly the same as regular python execution.

• bpo-42383: Fix pdb: previously pdb would fail to restart the debugging target if it was specified using a relative path and the current directory changed.

• bpo-42318: Fixed support of non-BMP characters in tkinter on macOS.

• bpo-42163: Restore compatibility for uname_result around deepcopy and _replace.

• bpo-39825: Windows: Change sysconfig.get_config_var('EXT_SUFFIX') to the expected full platform_tag.extension format. Previously it was hard-coded to .pyd, now it is compatible with distutils.sysconfig and will result in something like .cp38-win_amd64.pyd. This brings windows into conformance with the other platforms.

• bpo-42059: typing.TypedDict types created using the alternative call-style syntax now correctly respect the total keyword argument when setting their __required_keys__ and __optional_keys__ class attributes.

• bpo-39101: Fixed tests using IsolatedAsyncioTestCase from hanging on BaseExceptions.

• bpo-42005: Fix CLI of cProfile and profile to catch BrokenPipeError.

• bpo-41907: fix format() behavior for IntFlag

• bpo-41889: Enum: fix regression involving inheriting a multiply-inherited enum

• bpo-41891: Ensure asyncio.wait_for waits for task completion

• bpo-41604: Don’t decrement the reference count of the previous user_ptr when set_panel_userptr fails.

• bpo-40219: Lowered tkinter.ttk.LabeledScale dummy widget to prevent hiding part of the content label.

• bpo-40084: Fix Enum.__dir__: dir(Enum.member) now includes attributes as well as methods.

• bpo-39068: Fix initialization race condition in a85encode() and b85encode() in base64. Patch by Brandon Stansbury.

• bpo-33289: Correct call to tkinter.colorchooser to return RGB triplet of ints instead of floats. Patch by Cheryl Sabella.

Documentation

• bpo-40304: Fix doc for type(name, bases, dict). Patch by Boris Verkhovskiy and Éric Araujo.

• bpo-42811: Updated importlib.utils.resolve_name() doc to use __spec__.parent instead of __package__. (Thanks Yair Frid.)

• bpo-17140: Add documentation for the multiprocessing.pool.ThreadPool class.

Tests

• bpo-42794: Update test_nntplib to use offical group name of news.aioe.org for testing. Patch by Dong-hee Na.

• bpo-40810: In sqlite3, fix CheckTraceCallbackContent for SQLite pre 3.7.15.

Build

• bpo-43174: Windows build now uses /utf-8 compiler option.

• bpo-42692: Fix __builtin_available check on older compilers. Patch by Joshua Root.

• bpo-42604: Now all platforms use a value for the “EXT_SUFFIX” build variable derived from SOABI (for instance in freeBSD, “EXT_SUFFIX” is now “.cpython-310d.so” instead of “.so”). Previosuly only Linux, Mac and VxWorks were using a value for “EXT_SUFFIX” that included “SOABI”.

• bpo-42598: Fix implicit function declarations in configure which could have resulted in incorrect configuration checks. Patch contributed by Joshua Root.

• bpo-29076: Add fish shell support to macOS installer.

Windows

• bpo-41837: Updated Windows installer to include OpenSSL 1.1.1i

• bpo-42584: Upgrade Windows installer to use SQLite 3.34.0.

macOS

• bpo-42504: Ensure that the value of sysconfig.get_config_var(‘MACOSX_DEPLOYMENT_TARGET’) is always a string, even in when the value is parsable as an integer.

• bpo-42361: Update macOS installer build to use Tcl/Tk 8.6.11 (rc2, expected to be final release).

• bpo-41837: Update macOS installer build to use OpenSSL 1.1.1i.

• bpo-42584: Update macOS installer to use SQLite 3.34.0.

IDLE

• bpo-43008: Make IDLE invoke sys.excepthook() in normal, 2-process mode. Patch by Ken Hilton.

• bpo-33065: Fix problem debugging user classes with __repr__ method.

• bpo-23544: Disable Debug=>Stack Viewer when user code is running or Debugger is active, to prevent hang or crash. Patch by Zackery Spytz.

• bpo-32631: Finish zzdummy example extension module: make menu entries work; add docstrings and tests with 100% coverage.

Tools/Demos

• bpo-42726: Fixed Python 3 compatibility issue with gdb/libpython.py handling of attribute dictionaries.

• bpo-42613: Fix freeze.py tool to use the prope config and library directories. Patch by Victor Stinner.

C API

• bpo-43030: Fixed a compiler warning in Py_UNICODE_ISSPACE() on platforms with signed wchar_t.

• bpo-42591: Export the Py_FrozenMain() function: fix a Python 3.9.0 regression. Python 3.9 uses -fvisibility=hidden and the function was not exported explicitly and so not exported.

• bpo-40052: Fix an alignment build warning/error in function PyVectorcall_Function(). Patch by Andreas Schneider, Antoine Pitrou and Petr Viktorin.

Python 3.9.1 final

Release date: 2020-12-07

Core and Builtins

• bpo-42576: types.GenericAlias will now raise a TypeError when attempting to initialize with a keyword argument. Previously, this would cause the interpreter to crash if the interpreter was compiled with debug symbols. This does not affect interpreters compiled for release. Patch by Ken Jin.

Library

• bpo-5054: CGIHTTPRequestHandler.run_cgi() HTTP_ACCEPT improperly parsed. Replace the special purpose getallmatchingheaders with generic get_all method and add relevant tests.

  Original Patch by Martin Panter. Modified by Senthil Kumaran.

• bpo-17735: inspect.findsource() now raises OSError instead of IndexError when co_lineno of a code object is greater than the file length. This can happen, for example, when a file is edited after it was imported. PR by Irit Katriel.

• bpo-42116: Fix handling of trailing comments by inspect.getsource().

• bpo-42487: ChainMap.__iter__ no longer calls __getitem__ on underlying maps

• bpo-42482: TracebackException no longer holds a reference to the exception’s traceback object. Consequently, instances of TracebackException for equivalent but non-equal exceptions now compare as equal.

• bpo-42406: We fixed an issue in pickle.whichmodule in which importing multiprocessing could change the how pickle identifies which module an object belongs to, potentially breaking the unpickling of those objects.

• bpo-34215: Clarify the error message for asyncio.IncompleteReadError when expected is None.

• bpo-12800: Extracting a symlink from a tarball should succeed and overwrite the symlink if it already exists. The fix is to remove the existing file or symlink before extraction. Based on patch by Chris AtLee, Jeffrey Kintscher, and Senthil Kumaran.

Tests

• bpo-41473: Reenable test_gdb on gdb 9.2 and newer: https://bugzilla.redhat.com/show_bug.cgi?id=1866884 bug is fixed in gdb 10.1.

• bpo-42553: Fix test_asyncio.test_call_later() race condition: don’t measure asyncio performance in the call_later() unit test. The test failed randomly on the CI.

macOS

• bpo-41116: If no explicit macOS SDK was specified, setup.py should check for Tcl and TK frameworks in /Library/Frameworks; the previous commit inadvertently broke that test.

• bpo-42504: Fix build on macOS Big Sur when MACOSX_DEPLOYMENT_TARGET=11

IDLE

• bpo-42508: Keep IDLE running on macOS. Remove obsolete workaround that prevented running files with shortcuts when using new universal2 installers built on macOS 11.

Python 3.9.1 release candidate 1

Release date: 2020-11-24

Security

• bpo-42103: Prevented potential DoS attack via CPU and RAM exhaustion when processing malformed Apple Property List files in binary format.

• bpo-42051: The plistlib module no longer accepts entity declarations in XML plist files to avoid XML vulnerabilities. This should not affect users as entity declarations are not used in regular plist files.

• bpo-40791: Add volatile to the accumulator variable in hmac.compare_digest, making constant-time-defeating optimizations less likely.

Core and Builtins

• bpo-41686: On Windows, the SIGINT event, _PyOS_SigintEvent(), is now created even if Python is configured to not install signal handlers (if PyConfig.install_signal_handlers equals to 0, or Py_InitializeEx(0)).

• bpo-42381: Allow assignment expressions in set literals and set comprehensions as per PEP 572. Patch by Pablo Galindo.

• bpo-42374: Fix a regression introduced by the new parser, where an unparenthesized walrus operator was not allowed within generator expressions.

• bpo-42296: On Windows, fix a regression in signal handling which prevented to interrupt a program using CTRL+C. The signal handler can be run in a thread different than the Python thread, in which case the test deciding if the thread can handle signals is wrong.

• bpo-42332: types.GenericAlias objects can now be the targets of weakrefs.

• bpo-42218: Fixed a bug in the PEG parser that was causing crashes in debug mode. Now errors are checked in left-recursive rules to avoid cases where such errors do not get handled in time and appear as long-distance crashes in other places.

• bpo-42214: Fixed a possible crash in the PEG parser when checking for the ‘!=’ token in the barry_as_flufl rule. Patch by Pablo Galindo.

• bpo-42143: Fix handling of errors during creation of PyFunctionObject, which resulted in operations on uninitialized memory. Patch by Yonatan Goldschmidt.

• bpo-41659: Fix a bug in the parser, where a curly brace following a primary didn’t fail immediately. This led to invalid expressions like a {b} to throw a SyntaxError with a wrong offset, or invalid expressions ending with a curly brace like a { to not fail immediately in the REPL.

• bpo-42150: Fix possible buffer overflow in the new parser when checking for continuation lines. Patch by Pablo Galindo.

• bpo-42123: Run the parser two times. On the first run, disable all the rules that only generate better error messages to gain performance. If there’s a parse failure, run the parser a second time with those enabled.

• bpo-42057: Fix peephole optimizer misoptimize conditional jump + JUMP_IF_NOT_EXC_MATCH pair.

• bpo-41984: The garbage collector now tracks all user-defined classes. Patch by Brandt Bucher.

• bpo-41993: Fixed potential issues with removing not completely initialized module from sys.modules when import fails.

• bpo-41979: Star-unpacking is now allowed for with item’s targets in the PEG parser.

• bpo-41909: Fixed stack overflow in issubclass() and isinstance() when getting the __bases__ attribute leads to infinite recursion.

• bpo-41894: When loading a native module and a load failure occurs, prevent a possible UnicodeDecodeError when not running in a UTF-8 locale by decoding the load error message using the current locale’s encoding.

• bpo-39934: Correctly count control blocks in ‘except’ in compiler. Ensures that a syntax error, rather a fatal error, occurs for deeply nested, named exception handlers.

Library

• bpo-42328: Fixed tkinter.ttk.Style.map(). The function accepts now the representation of the default state as empty sequence (as returned by Style.map()). The structure of the result is now the same on all platform and does not depend on the value of wantobjects.

• bpo-42345: Fix various issues with typing.Literal parameter handling (flatten, deduplicate, use type to cache key). Patch provided by Yurii Karabas.

• bpo-42350: Fix the threading.Thread class at fork: do nothing if the thread is already stopped (ex: fork called at Python exit). Previously, an error was logged in the child process.

• bpo-42014: The onerror callback from shutil.rmtree now receives correct function when os.open fails.

• bpo-42237: Fix os.sendfile() on illumos.

• bpo-42249: Fixed writing binary Plist files larger than 4 GiB.

• bpo-35455: On Solaris, thread_time() is now implemented with gethrvtime() because clock_gettime(CLOCK_THREAD_CPUTIME_ID) is not always available. Patch by Jakub Kulik.

• bpo-42233: The repr() of typing types containing Generic Alias Types previously did not show the parameterized types in the GenericAlias. They have now been changed to do so.

• bpo-41754: webbrowser: Ignore NotADirectoryError when calling xdg-settings.

• bpo-29566: binhex.binhex() consisently writes macOS 9 line endings.

• bpo-42183: Fix a stack overflow error for asyncio Task or Future repr().

  The overflow occurs under some circumstances when a Task or Future recursively returns itself.

• bpo-42146: Fix memory leak in subprocess.Popen() in case an uid (gid) specified in user (group, extra_groups) overflows uid_t (gid_t).

• bpo-42140: Improve asyncio.wait function to create the futures set just one time.

• bpo-42103: InvalidFileException and RecursionError are now the only errors caused by loading malformed binary Plist file (previously ValueError and TypeError could be raised in some specific cases).

• bpo-41052: Pickling heap types implemented in C with protocols 0 and 1 raises now an error instead of producing incorrect data.

• bpo-41491: plistlib: fix parsing XML plists with hexadecimal integer values

• bpo-42065: Fix an incorrectly formatted error from _codecs.charmap_decode() when called with a mapped value outside the range of valid Unicode code points. PR by Max Bernstein.

• bpo-41966: Fix pickling pure Python datetime.time subclasses. Patch by Dean Inwood.

• bpo-41976: Fixed a bug that was causing ctypes.util.find_library() to return None when triying to locate a library in an environment when gcc>=9 is available and ldconfig is not. Patch by Pablo Galindo

• bpo-41900: C14N 2.0 serialisation in xml.etree.ElementTree failed for unprefixed attributes when a default namespace was defined.

• bpo-41840: Fix a bug in the symtable module that was causing module-scope global variables to not be reported as both local and global. Patch by Pablo Galindo.

• bpo-41831: str() for the type attribute of the tkinter.Event object always returns now the numeric code returned by Tk instead of the name of the event type.

• bpo-41817: fix tkinter.EventType Enum so all members are strings, and none are tuples

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

• bpo-41316: Fix the tarfile module to write only basename of TAR file to GZIP compression header.

• bpo-16396: Allow ctypes.wintypes to be imported on non-Windows systems.

• bpo-40592: shutil.which() now ignores empty entries in PATHEXT instead of treating them as a match.

• bpo-40550: Fix time-of-check/time-of-action issue in subprocess.Popen.send_signal.

• bpo-40492: Fix --outfile for cProfile / profile not writing the output file in the original directory when the program being profiled changes the working directory. PR by Anthony Sottile.

• bpo-40105: ZipFile truncates files to avoid corruption when a shorter comment is provided in append (“a”) mode. Patch by Jan Mazur.

• bpo-27321: Fixed KeyError exception when flattening an email to a string attempts to replace a non-existent Content-Transfer-Encoding header.

Documentation

• bpo-42153: Fix the URL for the IMAP protocol documents.

• bpo-42061: Document __format__ functionality for IP addresses.

• bpo-41910: Document the default implementation of object.__eq__.

• bpo-42010: Clarify that subscription expressions are also valid for certain classes and types in the standard library, and for user-defined classes and types if the classmethod __class_getitem__() is provided.

• bpo-41805: Documented generic alias type and types.GenericAlias. Also added an entry in glossary for generic types.

• bpo-41774: In Programming FAQ “Sequences (Tuples/Lists)” section, add “How do you remove multiple items from a list”.

• bpo-35293: Fix RemovedInSphinx40Warning when building the documentation. Patch by Dong-hee Na.

• bpo-41726: Update the refcounts info of PyType_FromModuleAndSpec.

• bpo-39693: Fix tarfile’s extractfile documentation

• bpo-39416: Document some restrictions on the default string representations of numeric classes.

Tests

• bpo-40754: Include _testinternalcapi module in Windows installer for test suite

• bpo-41739: Fix test_logging.test_race_between_set_target_and_flush(): the test now waits until all threads complete to avoid leaking running threads.

• bpo-41970: Avoid a test failure in test_lib2to3 if the module has already imported at the time the test executes. Patch by Pablo Galindo.

• bpo-41944: Tests for CJK codecs no longer call eval() on content received via HTTP.

• bpo-41939: Fix test_site.test_license_exists_at_url(): call urllib.request.urlcleanup() to reset the global urllib.request._opener. Patch by Victor Stinner.

• bpo-41561: test_ssl: skip test_min_max_version_mismatch when TLS 1.0 is not available

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

• bpo-41306: Fixed a failure in test_tk.test_widgets.ScaleTest happening when executing the test with Tk 8.6.10.

Build

• bpo-42398: Fix a race condition in “make regen-all” when make -jN option is used to run jobs in parallel. The clinic.py script now only use atomic write to write files. Moveover, generated files are now left unchanged if the content does not change, to not change the file modification time.

• bpo-41617: Fix building pycore_bitutils.h internal header on old clang version without __builtin_bswap16() (ex: Xcode 4.6.3 on Mac OS X 10.7). Patch by Joshua Root and Victor Stinner.

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

• bpo-40998: Addressed three compiler warnings found by undefined behavior sanitizer (ubsan).

Windows

• bpo-42120: Remove macro definition of copysign (to _copysign) in headers.

• bpo-38439: Updates the icons for IDLE in the Windows Store package.

• bpo-41744: Fixes automatic import of props file when using the Nuget package.

• bpo-41557: Update Windows installer to use SQLite 3.33.0.

• bpo-38324: Avoid Unicode errors when accessing certain locale data on Windows.

macOS

• bpo-41116: Ensure distutils.unixxcompiler.find_library_file can find system provided libraries on macOS 11.

• bpo-41100: Add support for macOS 11 and Apple Silicon systems.

  It is now possible to build “Universal 2” binaries using “–enable-universalsdk –with-universal-archs=universal2”.

  Binaries build on later macOS versions can be deployed back to older versions (tested up to macOS 10.9), when using the correct deployment target. This is tested using Xcode 11 and later.

• bpo-38443: The --enable-universalsdk and --with-universal-archs options for the configure script now check that the specified architectures can be used.

• bpo-41471: Ignore invalid prefix lengths in system proxy excludes.

• bpo-41557: Update macOS installer to use SQLite 3.33.0.

IDLE

• bpo-42426: Fix reporting offset of the RE error in searchengine.

• bpo-42415: Get docstrings for IDLE calltips more often by using inspect.getdoc.

• bpo-33987: Mostly finish using ttk widgets, mainly for editor, settings, and searches. Some patches by Mark Roseman.

• bpo-41775: Use ‘IDLE Shell’ as shell title

• bpo-35764: Rewrite the Calltips doc section.

• bpo-40181: In calltips, stop reminding that ‘/’ marks the end of positional-only arguments.

• bpo-40511: Typing opening and closing parentheses inside the parentheses of a function call will no longer cause unnecessary “flashing” off and on of an existing open call-tip, e.g. when typed in a string literal.

• bpo-38439: Add a 256×256 pixel IDLE icon to the Windows .ico file. Created by Andrew Clover. Remove the low-color gif variations from the .ico file.

C API

• bpo-42015: Fix potential crash in deallocating method objects when dynamically allocated PyMethodDef’s lifetime is managed through the self argument of a PyCFunction.

• bpo-41986: Py_FileSystemDefaultEncodeErrors and Py_UTF8Mode are available again in limited API.

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

• bpo-41497: Fix potential UnicodeDecodeError in dis module.

• bpo-41490: Update ensurepip to install pip 20.2.1 and setuptools 49.2.1.

• bpo-41467: On Windows, fix asyncio recv_into() return value when the socket/pipe is closed (BrokenPipeError): return 0 rather than an empty byte string (b'').

• bpo-41425: Make tkinter doc example runnable.

• bpo-41384: Raise TclError instead of TypeError when an unknown option is passed to tkinter.OptionMenu.

• bpo-38731: Fix NameError in command-line interface of py_compile.

• bpo-41317: Use add_done_callback() in asyncio.loop.sock_accept() to unsubscribe reader early on cancellation.

• bpo-41364: Reduce import overhead of uuid.

• bpo-41341: Recursive evaluation of typing.ForwardRef in get_type_hints.

• bpo-41182: selector: use DefaultSelector based upon implementation

• bpo-40726: Handle cases where the end_lineno is None on ast.increment_lineno().

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

• bpo-40170: Revert PyType_HasFeature() change: it reads again directly the PyTypeObject.tp_flags member when the limited C API is not used, rather than always calling PyType_GetFlags() which hides implementation details.

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

• bpo-41074: Fixed support of non-ASCII names in functions msilib.OpenDatabase() and msilib.init_database() and non-ASCII SQL in method msilib.Database.OpenView().

• bpo-40164: Updates Windows OpenSSL to 1.1.1g

• bpo-37556: Extend py.exe help to mention overrides via venv, shebang, environmental variables & ini files.

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

• bpo-17258: Skip some multiprocessing tests when MD5 hash digest is blocked.

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

• bpo-40501: uuid no longer uses ctypes to load libuuid or rpcrt4.dll at runtime.

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 Data model 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

• bpo-40385: Removed the checkpyc.py tool. Please see compileall without force mode as a potential alternative.

• bpo-40179: Fixed translation of #elif in Argument Clinic.

• bpo-40094: Fix which.py script exit code: it now uses os.waitstatus_to_exitcode() to convert os.system() exit status into an exit code.

C API

• bpo-40241: Move the PyGC_Head structure to the internal C API.

• bpo-40170: Convert PyObject_IS_GC() macro to a function to hide implementation details.

• bpo-40241: Add the functions PyObject_GC_IsTracked() and PyObject_GC_IsFinalized() to the public API to allow to query if Python objects are being currently tracked or have been already finalized by the garbage collector respectively. Patch by Pablo Galindo.

• bpo-40170: The PyObject_NEW() macro becomes an alias to the PyObject_New() macro, and the PyObject_NEW_VAR() macro becomes an alias to the PyObject_NewVar() macro, to hide implementation details. They no longer access directly the PyTypeObject.tp_basicsize member.

• bpo-40170: PyType_HasFeature() now always calls PyType_GetFlags() to hide implementation details. Previously, it accessed directly the PyTypeObject.tp_flags member when the limited C API was not used.

• bpo-40170: Convert the PyObject_GET_WEAKREFS_LISTPTR() macro to a function to hide implementation details: the macro accessed directly to the PyTypeObject.tp_weaklistoffset member.

• bpo-40170: Convert PyObject_CheckBuffer() macro to a function to hide implementation details: the macro accessed directly the PyTypeObject.tp_as_buffer member.

• bpo-40170: Always declare PyIndex_Check() as an opaque function to hide implementation details: remove PyIndex_Check() macro. The macro accessed directly the PyTypeObject.tp_as_number member.

• bpo-39947: Add PyThreadState_GetID() function: get the unique identifier of a Python thread state.

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

• bpo-40024: Add PyModule_AddType() helper function: add a type to a module. Patch by Dong-hee Na.

• bpo-39946: Remove _PyRuntime.getframe hook and remove _PyThreadState_GetFrame macro which was an alias to _PyRuntime.getframe. They were only exposed by the internal C API. Remove also PyThreadFrameGetter type.

• bpo-39947: Add PyThreadState_GetFrame() function: get the current frame of a Python thread state.

• bpo-37207: Add _PyArg_NoKwnames helper function. Patch by Dong-hee Na.

• bpo-39947: Add PyThreadState_GetInterpreter(): get the interpreter of a Python thread state.

• bpo-39947: Add PyInterpreterState_Get() function to the limited C API.

• bpo-35370: If PySys_Audit() fails in PyEval_SetProfile() or PyEval_SetTrace(), log the error as an unraisable exception.

• bpo-39947: Move the static inline function flavor of Py_EnterRecursiveCall() and Py_LeaveRecursiveCall() to the internal C API: they access PyThreadState attributes. The limited C API provides regular functions which hide implementation details.

• bpo-39947: Py_TRASHCAN_BEGIN_CONDITION and Py_TRASHCAN_END macro no longer access PyThreadState attributes, but call new private _PyTrash_begin() and _PyTrash_end() functions which hide implementation details.

• bpo-39884: PyDescr_NewMethod() and PyCFunction_NewEx() now include the method name in the SystemError “bad call flags” error message to ease debug.

• bpo-39877: Deprecated PyEval_InitThreads() and PyEval_ThreadsInitialized(). Calling PyEval_InitThreads() now does nothing.

• bpo-38249: Py_UNREACHABLE is now implemented with __builtin_unreachable() and analogs in release mode.

• bpo-38643: PyNumber_ToBase() now raises a SystemError instead of crashing when called with invalid base.

• bpo-39882: The Py_FatalError() function is replaced with a macro which logs automatically the name of the current function, unless the Py_LIMITED_API macro is defined.

• bpo-39824: Extension modules: m_traverse, m_clear and m_free functions of PyModuleDef are no longer called if the module state was requested but is not allocated yet. This is the case immediately after the module is created and before the module is executed (Py_mod_exec function). More precisely, these functions are not called if m_size is greater than 0 and the module state (as returned by PyModule_GetState()) is NULL.

  Extension modules without module state (m_size <= 0) are not affected.

• bpo-38913: Fixed segfault in Py_BuildValue() called with a format containing “#” and undefined PY_SSIZE_T_CLEAN whwn an exception is set.

• bpo-38500: Add a private API to get and set the frame evaluation function: add _PyInterpreterState_GetEvalFrameFunc() and _PyInterpreterState_SetEvalFrameFunc() C functions. The _PyFrameEvalFunction function type now takes a tstate parameter.

Python 3.9.0 alpha 4

Release date: 2020-02-25

Security

• bpo-39184: Add audit events to functions in fcntl, msvcrt, os, resource, shutil, signal and syslog.

• bpo-39401: Avoid unsafe DLL load at startup on Windows 7 and earlier.

• bpo-39184: Add audit events to command execution functions in os and pty modules.

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 TypedDict.

• 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

• bpo-38325: Skip tests on non-BMP characters of test_winconsoleio.

• bpo-39502: Skip test_zipfile.test_add_file_after_2107() if time.localtime() fails with OverflowError. It is the case on AIX 6.1 for example.

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).