Changelog

Python next

Release date: XXXX-XX-XX

Core and Builtins

• gh-92804: Fix memory leak in memoryview iterator as it was not finalized at exit. Patch by Kumar Aditya.

• gh-92236: Remove spurious “LINE” event when starting a generator or coroutine, visible tracing functions implemented in C.

• gh-92619: Make the compiler duplicate an exit block only if none of its instructions have a lineno (previously only the first instruction in the block was checked, leading to unnecessarily duplicated blocks).

• gh-92261: Fix hang when trying to iterate over a typing.Union.

Library

• gh-90473: subprocess now fails early on Emscripten and WASI platforms to work around missing os.pipe() on WASI.

• gh-92671: Fixed ast.unparse() for empty tuples in the assignment target context.

• gh-91581: utcfromtimestamp() no longer attempts to resolve fold in the pure Python implementation, since the fold is never 1 in UTC. In addition to being slightly faster in the common case, this also prevents some errors when the timestamp is close to datetime.min. Patch by Paul Ganssle.

• gh-92550: Fix pathlib.Path.rglob() for empty pattern.

• gh-92530: Fix an issue that occurred after interrupting threading.Condition.notify().

• gh-92531: The statistics.median_grouped() function now always return a float. Formerly, it did not convert the input type when for sequences of length one.

• gh-91810: ElementTree method write() and function tostring() now use the text file’s encoding (“UTF-8” if not available) instead of locale encoding in XML declaration when encoding="unicode" is specified.

• gh-90622: Worker processes for concurrent.futures.ProcessPoolExecutor are no longer spawned on demand (a feature added in 3.9) when the multiprocessing context start method is "fork" as that can lead to deadlocks in the child processes due to a fork happening while threads are running.

• gh-91581: Remove an unhandled error case in the C implementation of calls to datetime.fromtimestamp with no time zone (i.e. getting a local time from an epoch timestamp). This should have no user-facing effect other than giving a possibly more accurate error message when called with timestamps that fall on 10000-01-01 in the local time. Patch by Paul Ganssle.

• bpo-45046: Add support of context managers in unittest: methods enterContext() and enterClassContext() of class TestCase, method enterAsyncContext() of class IsolatedAsyncioTestCase and function unittest.enterModuleContext().

• bpo-42627: Fix incorrect parsing of Windows registry proxy settings

Documentation

• bpo-40838: Document that inspect.getdoc(), inspect.getmodule(), and inspect.getsourcefile() might return None.

• bpo-38056: Overhaul the Error Handlers documentation in codecs.

• bpo-13553: Document tkinter.Tk args.

Build

• gh-90473: Disable pymalloc and increase stack size on wasm32-wasi.

Windows

• gh-92841: asyncio no longer throws RuntimeError: Event loop is closed on interpreter exit after asynchronous socket activity. Patch by Oleg Iarygin.

• bpo-46907: Update Windows installer to use SQLite 3.38.4.

C API

• gh-92781: Avoid mixing declarations and code in the C API to fix the compiler warning: “ISO C90 forbids mixed declarations and code” [-Werror=declaration-after-statement]. Patch by Victor Stinner.

Python 3.11.0 beta 1

Release date: 2022-05-06

Security

• gh-57684: Add the -P command line option and the PYTHONSAFEPATH environment variable to not prepend a potentially unsafe path to sys.path. Patch by Victor Stinner.

Core and Builtins

• gh-89519: Chaining classmethod descriptors (introduced in bpo-19072) is deprecated. It can no longer be used to wrap other descriptors such as property(). The core design of this feature was flawed, and it caused a number of downstream problems.

• gh-92345: pymain_run_python() now imports readline and rlcompleter before sys.path is extended to include the current working directory of an interactive interpreter. Non-interactive interpreters are not affected.

• bpo-43857: Improve the AttributeError message when deleting a missing attribute. Patch by Géry Ogam.

• gh-92245: Make sure that PEP 523 is respected in all cases. In 3.11a7, specialization may have prevented Python-to-Python calls respecting PEP 523.

• gh-92203: Add a closure keyword-only parameter to exec(). It can only be specified when exec-ing a code object that uses free variables. When specified, it must be a tuple, with exactly the number of cell variables referenced by the code object. closure has a default value of None, and it must be None if the code object doesn’t refer to any free variables.

• gh-91173: Disable frozen modules in debug builds. Patch by Kumar Aditya.

• gh-92114: Improve error message when subscript a type with __class_getitem__ set to None.

• gh-92112: Fix crash triggered by an evil custom mro() on a metaclass.

• gh-92063: The PRECALL_METHOD_DESCRIPTOR_FAST_WITH_KEYWORDS instruction now ensures methods are called only on objects of the correct type.

• gh-92031: Deoptimize statically-allocated code objects during Py_FINALIZE() so that future _PyCode_Quicken calls always start with unquickened code.

• gh-92036: Fix a crash in subinterpreters related to the garbage collector. When a subinterpreter is deleted, untrack all objects tracked by its GC. To prevent a crash in deallocator functions expecting objects to be tracked by the GC, leak a strong reference to these objects on purpose, so they are never deleted and their deallocator functions are not called. Patch by Victor Stinner.

• gh-92032: The interpreter can now autocomplete soft keywords, as of now match, case, and _ (wildcard pattern) from PEP 634.

• gh-87999: The warning emitted by the Python parser for a numeric literal immediately followed by keyword has been changed from deprecation warning to syntax warning.

• gh-91869: Fix an issue where specialized opcodes with extended arguments could produce incorrect tracing output or lead to assertion failures.

• gh-91603: Speed up types.UnionType instantiation. Based on patch provided by Yurii Karabas.

• gh-89373: If Python is built in debug mode, Python now ensures that deallocator functions leave the current exception unchanged. Patch by Victor Stinner.

• gh-91632: Fix a minor memory leak at exit: release the memory of the generic_alias_iterator type. Patch by Dong-hee Na.

• gh-81548: Octal escapes with value larger than 0o377 now produce a DeprecationWarning. In a future Python version they will be a SyntaxWarning and eventually a SyntaxError.

• bpo-43950: Use a single compact table for line starts, ends and column offsets. Reduces memory consumption for location info by half

• gh-91102: Use Argument Clinic for EncodingMap. Patch by Oleg Iarygin.

• gh-91636: Fixed a crash in a garbage-collection edge-case, in which a PyFunction_Type.tp_clear function could leave a python function object in an inconsistent state.

• gh-91603: Speed up isinstance() and issubclass() checks for types.UnionType. Patch by Yurii Karabas.

• gh-91625: Fixed a bug in which adaptive opcodes ignored any preceding EXTENDED_ARGs on specialization failure.

• gh-78607: The LLTRACE special build now looks for the name __lltrace__ defined in module globals, rather than the name __ltrace__, which had been introduced as a typo.

• gh-91576: Speed up iteration of ascii strings by 50%. Patch by Kumar Aditya.

• gh-89279: Improve interpreter performance on Windows by inlining a few specific macros.

• gh-91502: Add a new _PyFrame_IsEntryFrame() API function, to check if a PyFrameObject is an entry frame. Patch by Pablo Galindo.

• gh-91266: Refactor the bytearray strip methods strip, lstrip and rstrip to use a common implementation.

• gh-91479: Replaced the __note__ field of BaseException (added in an earlier version of 3.11) with the final design of PEP 678. Namely, BaseException gets an add_note() method, and its __notes__ field is created when necessary.

• gh-46055: Speed up right shift of negative integers, by removing unnecessary creation of temporaries. Original patch by Xinhang Xu, reworked by Mark Dickinson.

• gh-91462: Make the interpreter’s low-level tracing (lltrace) feature output more readable by displaying opcode names (rather than just numbers), and by displaying stack contents before each opcode.

• gh-89455: Fixed an uninitialized bool value in the traceback printing code path that was introduced by the initial bpo-45292 exception groups work.

• gh-91421: Fix a potential integer overflow in _Py_DecodeUTF8Ex.

• gh-91428: Add static const char *const _PyOpcode_OpName[256] = {...}; to opcode.h for debug builds to assist in debugging the Python interpreter. It is now more convenient to make various forms of debugging output more human-readable by including opcode names rather than just the corresponding decimal digits.

• bpo-47120: Make POP_JUMP_IF_TRUE, POP_JUMP_IF_FALSE, POP_JUMP_IF_NONE and POP_JUMP_IF_NOT_NONE virtual, mapping to new relative jump opcodes.

• bpo-45317: Add internal documentation explaining design of new (for 3.11) frame stack.

• bpo-47197: ctypes used to mishandle void return types, so that for instance a function declared like ctypes.CFUNCTYPE(None, ctypes.c_int) would be called with signature int f(int) instead of void f(int). Wasm targets require function pointers to be called with the correct signatures so this led to crashes. The problem is now fixed.

• bpo-47120: Make opcodes JUMP_IF_TRUE_OR_POP and JUMP_IF_FALSE_OR_POP relative rather than absolute.

• bpo-47177: Replace the f_lasti member of the internal _PyInterpreterFrame structure with a prev_instr pointer, which reduces overhead in the main interpreter loop. The f_lasti attribute of Python-layer frame objects is preserved for backward-compatibility.

• bpo-46961: Integer mod/remainder operations, including the three-argument form of pow(), now consistently return ints from the global small integer cache when applicable.

• bpo-46962: Classes and functions that unconditionally declared their docstrings ignoring the --without-doc-strings compilation flag no longer do so.

  The classes affected are ctypes.UnionType, pickle.PickleBuffer, testcapi.RecursingInfinitelyError, and types.GenericAlias.

  The functions affected are 24 methods in ctypes.

  Patch by Oleg Iarygin.

• bpo-46942: Use Argument Clinic for the types.MethodType constructor. Patch by Oleg Iarygin.

• bpo-46764: Fix wrapping bound methods with @classmethod

• bpo-43464: Optimize set.intersection() for non-set arguments.

• bpo-46721: Optimize set.issuperset() for non-set argument.

• bpo-46509: Add type-specialized versions of the Py_DECREF(), and use them for float, int, str, bool, and None to avoid pointer-chasing at runtime where types are known at C compile time.

• bpo-46045: Do not use POSIX semaphores on NetBSD

• bpo-36819: Fix crashes in built-in encoders with error handlers that return position less or equal than the starting position of non-encodable characters.

• bpo-34093: marshal.dumps() uses FLAG_REF for all interned strings. This makes output more deterministic and helps reproducible build.

• bpo-26579: Added object.__getstate__ which provides the default implementation of the __getstate__() method.

  Copying and pickling instances of subclasses of builtin types bytearray, set, frozenset, collections.OrderedDict, collections.deque, weakref.WeakSet, and datetime.tzinfo now copies and pickles instance attributes implemented as slots.

Library

• gh-87901: Add the encoding parameter to os.popen().

• gh-90997: Fix an issue where dis utilities may interpret populated inline cache entries as valid instructions.

• gh-92332: Deprecate typing.Text (removal of the class is currently not planned). Patch by Alex Waygood.

• Deprecate nested classes in enum definitions becoming members – in 3.13 they will be normal classes; add member and nonmember functions to allow control over results now.

• gh-92356: Fixed a performance regression in ctypes function calls.

• gh-90997: Show the actual named values stored in inline caches when show_caches=True is passed to dis utilities.

• gh-92301: Prefer close_range() to iterating over procfs for file descriptor closing in subprocess for better performance.

• gh-67248: Sort the miscellaneous topics in Cmd.do_help()

• gh-92210: Port socket.__init__ to Argument Clinic. Patch by Cinder.

• gh-80010: Add support for generalized ISO 8601 parsing to datetime.datetime.fromisoformat(), datetime.date.fromisoformat() and datetime.time.fromisoformat(). Patch by Paul Ganssle.

• gh-92118: Fix a 3.11 regression in contextmanager(), which caused it to propagate exceptions with incorrect tracebacks.

• gh-90887: Adding COPYFILE_STAT, COPYFILE_ACL and COPYFILE_XATTR constants for os.fcopyfile() available in macOs.

• gh-91215: For @dataclass, add weakref_slot. Default is False. If True, and if slots=True, add a slot named “__weakref__”, which will allow instances to be weakref’d. Contributed by Eric V. Smith

• gh-85984: New function os.login_tty() for Unix.

• gh-92128: Add __class_getitem__() to logging.LoggerAdapter and logging.StreamHandler, allowing them to be parameterized at runtime. Patch by Alex Waygood.

• gh-92049: Forbid pickling constants re._constants.SUCCESS etc. Previously, pickling did not fail, but the result could not be unpickled.

• gh-92062: inspect.Parameter now raises ValueError if name is a keyword, in addition to the existing check that it is an identifier.

• gh-87390: Add an __unpacked__ attribute to types.GenericAlias. Patch by Jelle Zijlstra.

• gh-88089: Add support for generic typing.NamedTuple.

• gh-91996: New http.HTTPMethod enum to represent all the available HTTP request methods in a convenient way

• gh-91984: Modified test strings in test_argparse.py to not contain trailing spaces before end of line.

• gh-91952: Add encoding="locale" support to TextIOWrapper.reconfigure().

• gh-91954: Add encoding and errors arguments to subprocess.getoutput() and subprocess.getstatusoutput().

• bpo-47029: Always close the read end of the pipe used by multiprocessing.Queue after the last write of buffered data to the write end of the pipe to avoid BrokenPipeError at garbage collection and at multiprocessing.Queue.close() calls. Patch by Géry Ogam.

• gh-91928: Add datetime.UTC alias for datetime.timezone.utc.

  Patch by Kabir Kwatra.

• gh-68966: The mailcap module is now deprecated and will be removed in Python 3.13. See PEP 594 for the rationale and the mimetypes module for an alternative. Patch by Victor Stinner.

• gh-91401: Provide a way to disable subprocess use of vfork() just in case it is ever needed and document the existing mechanism for posix_spawn().

• gh-64783: Fix signal.NSIG value on FreeBSD to accept signal numbers greater than 32, like signal.SIGRTMIN and signal.SIGRTMAX. Patch by Victor Stinner.

• gh-91910: Add missing f prefix to f-strings in error messages from the multiprocessing and asyncio modules.

• gh-91860: Add typing.dataclass_transform(), implementing PEP 681. Patch by Jelle Zijlstra.

• gh-91832: Add required attribute to argparse.Action repr output.

• gh-91827: In the tkinter module add method info_patchlevel() which returns the exact version of the Tcl library as a named tuple similar to sys.version_info.

• gh-84461: Add --enable-wasm-pthreads to enable pthreads support for WASM builds. Emscripten/node no longer has threading enabled by default. Include additional file systems.

• gh-91821: Fix unstable test_from_tuple test in test_decimal.py.

• gh-91217: Deprecate the xdrlib module.

• gh-91217: Deprecate the uu module.

• gh-91760: More strict rules will be applied for numerical group references and group names in regular expressions. For now, a deprecation warning is emitted for group references and group names which will be errors in future Python versions.

• gh-84461: Add provisional sys._emscripten_info named tuple with build-time and run-time information about Emscripten platform.

• gh-90623: signal.raise_signal() and os.kill() now check immediately for pending signals. Patch by Victor Stinner.

• gh-91734: Fix OSS audio support on Solaris.

• gh-90633: Include the passed value in the exception thrown by typing.assert_never(). Patch by Jelle Zijlstra.

• gh-91700: Compilation of regular expression containing a conditional expression (?(group)...) now raises an appropriate re.error if the group number refers to not defined group. Previously an internal RuntimeError was raised.

• gh-91231: Add an optional keyword shutdown_timeout parameter to the multiprocessing.BaseManager constructor. Kill the process if terminate() takes longer than the timeout. Patch by Victor Stinner.

• gh-91621: Fix typing.get_type_hints() for collections.abc.Callable. Patch by Shantanu Jain.

• gh-90568: Parsing \N escapes of Unicode Named Character Sequences in a regular expression raises now re.error instead of TypeError.

• gh-91670: Remove deprecated SO config variable in sysconfig.

• gh-91217: Deprecate the telnetlib module.

• gh-91217: Deprecate the sunau module.

• gh-91217: Deprecate the spwd module.

• gh-91217: Deprecate the sndhdr module, as well as inline needed functionality for email.mime.MIMEAudio.

• gh-91616: re module, fix fullmatch() mismatch when using Atomic Grouping or Possessive Quantifiers.

• gh-91217: Deprecate the ‘pipes’ module.

• gh-91217: Deprecate the ossaudiodev module.

• bpo-47256: re module, limit the maximum capturing group to 1,073,741,823 in 64-bit build, this increases the depth of backtracking.

• gh-91217: Deprecate the nis module.

• gh-91595: Fix the comparison of character and integer inside Tools.gdb.libpython.write_repr(). Patch by Yu Liu.

• gh-74166: Add option to raise all errors from create_connection() in an ExceptionGroup when it fails to create a connection. The default remains to raise only the last error that had occurred when multiple addresses were tried.

• gh-91487: Optimize asyncio UDP speed, over 100 times faster when transferring a large file.

• gh-91575: Update case-insensitive matching in the re module to the latest Unicode version.

• gh-90622: In concurrent.futures.process.ProcessPoolExecutor disallow the “fork” multiprocessing start method when the new max_tasks_per_child feature is used as the mix of threads+fork can hang the child processes. Default to using the safe “spawn” start method in that circumstance if no mp_context was supplied.

• gh-89022: In sqlite3, SQLITE_MISUSE result codes are now mapped to InterfaceError instead of ProgrammingError. Also, more accurate exceptions are raised when binding parameters fail. Patch by Erlend E. Aasland.

• gh-91526: Stop calling os.device_encoding(file.fileno()) in TextIOWrapper. It was complex, never documented, and didn’t work for most cases. (Patch by Inada Naoki.)

• gh-88116: Change the frame-related functions in the inspect module to return a regular object (that is backwards compatible with the old tuple-like interface) that include the extended PEP 657 position information (end line number, column and end column). The affected functions are: inspect.getframeinfo(), inspect.getouterframes(), inspect.getinnerframes(), inspect.stack() and inspect.trace(). Patch by Pablo Galindo.

• gh-69093: Add indexing and slicing support to sqlite3.Blob. Patch by Aviv Palivoda and Erlend E. Aasland.

• gh-69093: Add context manager support to sqlite3.Blob. Patch by Aviv Palivoda and Erlend E. Aasland.

• gh-91217: Deprecate nntplib.

• gh-91217: Deprecate msilib.

• gh-91404: Improve the performance of re matching by using computed gotos (or “threaded code”) on supported platforms and removing expensive pointer indirections.

• gh-91217: Deprecate the imghdr module.

• gh-91217: Deprecate the crypt module.

• gh-91276: Make space for longer opcodes in dis output.

• bpo-47000: Make TextIOWrapper uses locale encoding when encoding="locale" is specified even in UTF-8 mode.

• gh-91230: warnings.catch_warnings() now accepts arguments for warnings.simplefilter(), providing a more concise way to locally ignore warnings or convert them to errors.

• gh-91217: Deprecate the chunk module.

• Add the TCP_CONNECTION_INFO option (available on macOS) to socket.

• bpo-47260: Fix os.closerange() potentially being a no-op in a Linux seccomp sandbox.

• bpo-47087: Implement typing.Required and typing.NotRequired (PEP 655). Patch by David Foster and Jelle Zijlstra.

• bpo-47061: Deprecate cgi and cgitb.

• bpo-47061: Deprecate audioop.

• bpo-47000: Add locale.getencoding() to get the current locale encoding. It is similar to locale.getpreferredencoding(False) but ignores the Python UTF-8 Mode.

• bpo-42012: Add wsgiref.types, containing WSGI-specific types for static type checking.

• bpo-47227: Suppress expression chaining for more re parsing errors.

• bpo-47211: Remove undocumented and never working function re.template() and flag re.TEMPLATE.

• bpo-47135: decimal.localcontext() now accepts context attributes via keyword arguments

• bpo-43323: Fix errors in the email module if the charset itself contains undecodable/unencodable characters.

• bpo-46841: Disassembly of quickened code.

• bpo-46681: Forward gzip.compress() compresslevel to zlib.

• bpo-45100: Add typing.get_overloads() and typing.clear_overloads(). Patch by Jelle Zijlstra.

• bpo-44807: typing.Protocol no longer silently replaces __init__() methods defined on subclasses. Patch by Adrian Garcia Badaracco.

• bpo-46787: Fix concurrent.futures.ProcessPoolExecutor exception memory leak

• bpo-46720: Add support for path-like objects to multiprocessing.set_executable() for Windows to be on a par with Unix-like systems. Patch by Géry Ogam.

• bpo-46696: Add SO_INCOMING_CPU constant to socket.

• bpo-46053: Fix OSS audio support on NetBSD.

• bpo-45639: image/avif and image/webp were added to mimetypes.

• bpo-46285: Add command-line option -p/--protocol to module http.server which specifies the HTTP version to which the server is conformant (HTTP/1.1 conformant servers can now be run from the command-line interface of module http.server). Patch by Géry Ogam.

• bpo-44791: Accept ellipsis as the last argument of typing.Concatenate.

• bpo-46547: Remove variables leaking into pydoc.Helper class namespace.

• bpo-46415: Fix ipaddress.ip_{address,interface,network} raising TypeError instead of ValueError if given invalid tuple as address parameter.

• bpo-46075: CookieJar with DefaultCookiePolicy now can process cookies from localhost with domain=localhost explicitly specified in Set-Cookie header.

• bpo-45995: Add a “z” option to the string formatting specification that coerces negative zero floating-point values to positive zero after rounding to the format precision. Contributed by John Belmonte.

• bpo-26175: Fully implement the io.BufferedIOBase or io.TextIOBase interface for tempfile.SpooledTemporaryFile objects. This lets them work correctly with higher-level layers (like compression modules). Patch by Carey Metcalfe.

• bpo-45138: Fix a regression in the sqlite3 trace callback where bound parameters were not expanded in the passed statement string. The regression was introduced in Python 3.10 by bpo-40318. Patch by Erlend E. Aasland.

• bpo-44863: Allow TypedDict subclasses to also include Generic as a base class in class based syntax. Thereby allowing the user to define a generic TypedDict, just like a user-defined generic but with TypedDict semantics.

• bpo-44587: Fix BooleanOptionalAction to not automatically add a default string. If a default string is desired, use a formatter to add it.

• bpo-43827: All positional-or-keyword parameters to ABCMeta.__new__ are now positional-only to avoid conflicts with keyword arguments to be passed to __init_subclass__().

• bpo-43218: Prevent creation of a venv whose path contains the PATH separator. This could affect the usage of the activate script. Patch by Dustin Rodrigues.

• bpo-38435: Add a process_group parameter to subprocess.Popen to help move more things off of the unsafe preexec_fn parameter.

• bpo-42066: Fix cookies getting sorted in CookieJar.__iter__() which is an extra behavior and not mentioned in RFC 2965 or Netscape cookie protocol. Now the cookies in CookieJar follows the order of the Set-Cookie header. Patch by Iman Kermani.

• bpo-40617: Add create_window_function() to sqlite3.Connection for creating aggregate window functions. Patch by Erlend E. Aasland.

• bpo-40676: Convert csv to use Argument Clinic for csv.field_size_limit(), csv.get_dialect(), csv.unregister_dialect() and csv.list_dialects().

• bpo-39716: Raise an ArgumentError when the same subparser name is added twice to an argparse.ArgumentParser. This is consistent with the (default) behavior when the same option string is added twice to an ArgumentParser.

• bpo-36073: Raise ProgrammingError instead of segfaulting on recursive usage of cursors in sqlite3 converters. Patch by Sergey Fedoseev.

• bpo-34975: Adds a start_tls() method to StreamWriter, which upgrades the connection with TLS using the given SSLContext.

• bpo-22276: Path methods glob() and rglob() return only directories if pattern ends with a pathname components separator (/ or sep). Patch by Eisuke Kawashima.

• bpo-24905: Add blobopen() to sqlite3.Connection. sqlite3.Blob allows incremental I/O operations on blobs. Patch by Aviv Palivoda and Erlend E. Aasland.

Documentation

• gh-91888: Add a new gh role to the documentation to link to GitHub issues.

• gh-91783: Document security issues concerning the use of the function shutil.unpack_archive()

• gh-91547: Remove “Undocumented modules” page.

• gh-91298: In importlib.resources.abc, refined the documentation of the Traversable Protocol, applying changes from importlib_resources 5.7.1.

• bpo-44347: Clarify the meaning of dirs_exist_ok, a kwarg of shutil.copytree().

• bpo-36329: Remove ‘make -C Doc serve’ in favour of ‘make -C Doc htmlview’

• bpo-47189: Add a What’s New in Python 3.11 entry for the Faster CPython project. Documentation by Ken Jin and Kumar Aditya.

• bpo-38668: Update the introduction to documentation for os.path to remove warnings that became irrelevant after the implementations of PEP 383 and PEP 529.

• bpo-47115: The documentation now lists which members of C structs are part of the Limited API/Stable ABI.

• bpo-46962: All docstrings in code snippets are now wrapped into PyDoc_STR() to follow the guideline of PEP 7’s Documentation Strings paragraph. Patch by Oleg Iarygin.

• bpo-26792: Improve the docstrings of runpy.run_module() and runpy.run_path(). Original patch by Andrew Brezovsky.

Tests

• gh-92169: Use warnings_helper.import_deprecated() to import deprecated modules uniformly in tests. Patch by Hugo van Kemenade.

• gh-84461: When multiprocessing is enabled, libregrtest can now use a Python executable other than sys.executable via the --python flag.

• gh-91904: Fix initialization of PYTHONREGRTEST_UNICODE_GUARD which prevented running regression tests on non-UTF-8 locale.

• gh-91752: Added @requires_zlib to test.test_tools.test_freeze.TestFreeze.

• gh-91607: Fix test_concurrent_futures to test the correct multiprocessing start method context in several cases where the test logic mixed this up.

• bpo-40280: Threading tests are now skipped on WASM targets without pthread support.

• bpo-47109: Test for ctypes.macholib.dyld, ctypes.macholib.dylib, and ctypes.macholib.framework are brought from manual pre-unittest times to ctypes.test location and structure. Patch by Oleg Iarygin.

• bpo-29890: Add tests for ipaddress.IPv4Interface and ipaddress.IPv6Interface construction with tuple arguments. Original patch and tests by louisom.

Build

• gh-89452: gdbm-compat is now preferred over ndbm if both are available on the system. This allows avoiding the problematic ndbm.h on macOS.

• gh-91731: Python is now built with -std=c11 compiler option, rather than -std=c99. Patch by Victor Stinner.

• bpo-47152: Add script and make target for generating sre_constants.h.

• bpo-47103: Windows PGInstrument builds now copy a required DLL into the output directory, making it easier to run the profile stage of a PGO build.

Windows

• bpo-46907: Update Windows installer to use SQLite 3.38.3.

• bpo-47239: Fixed –list and –list-paths output for Python Launcher for Windows when used in an active virtual environment.

• bpo-46907: Update Windows installer to use SQLite 3.38.2.

• bpo-46785: Fix race condition between os.stat() and unlinking a file on Windows, by using errors codes returned by FindFirstFileW() when appropriate in win32_xstat_impl.

• bpo-40859: Update Windows build to use xz-5.2.5

macOS

• bpo-46907: Update macOS installer to SQLite 3.38.4.

Tools/Demos

• gh-91583: Fix regression in the code generated by Argument Clinic for functions with the defining_class parameter.

• gh-91575: Add script Tools/scripts/generate_re_casefix.py and the make target regen-re for generating additional data for case-insensitive matching according to the current Unicode version.

• gh-91551: Remove the ancient Pynche color editor. It has moved to https://gitlab.com/warsaw/pynche

C API

• gh-88279: Deprecate the C functions: PySys_SetArgv(), PySys_SetArgvEx(), PySys_SetPath(). Patch by Victor Stinner.

• gh-92154: Added the PyCode_GetCode() function. This function does the equivalent of the Python code getattr(code_object, 'co_code').

• gh-92173: Fix the closure argument to PyEval_EvalCodeEx().

• gh-91320: Fix C++ compiler warnings about “old-style cast” (g++ -Wold-style-cast) in the Python C API. Use C++ reinterpret_cast<> and static_cast<> casts when the Python C API is used in C++. Patch by Victor Stinner.

• gh-80527: Mark functions as deprecated by PEP 623: PyUnicode_AS_DATA(), PyUnicode_AS_UNICODE(), PyUnicode_GET_DATA_SIZE(), PyUnicode_GET_SIZE(). Patch by Victor Stinner.

• gh-91768: Py_REFCNT(), Py_TYPE(), Py_SIZE() and Py_IS_TYPE() functions argument type is now PyObject*, rather than const PyObject*. Patch by Victor Stinner.

• gh-91020: Add PyBytes_Type.tp_alloc to initialize PyBytesObject.ob_shash for bytes subclasses.

• bpo-40421: Add PyFrame_GetLasti C-API function to access frame object’s f_lasti attribute safely from C code.

• bpo-35134: Remove the Include/code.h header file. C extensions should only include the main <Python.h> header file. Patch by Victor Stinner.

• bpo-47169: PyOS_CheckStack() is now exported in the Stable ABI on Windows.

• bpo-47169: PyThread_get_thread_native_id() is excluded from the stable ABI on platforms where it doesn’t exist (like Solaris).

• bpo-46343: Added PyErr_GetHandledException() and PyErr_SetHandledException() as simpler alternatives to PyErr_GetExcInfo() and PyErr_SetExcInfo().

  They are included in the stable ABI.

Python 3.11.0 alpha 7

Release date: 2022-04-05

Core and Builtins

• bpo-47212: Raise IndentationError instead of SyntaxError for a bare except with no following indent. Improve SyntaxError locations for an un-parenthesized generator used as arguments. Patch by Matthieu Dartiailh.

• bpo-47186: Replace JUMP_IF_NOT_EG_MATCH by CHECK_EG_MATCH + jump.

• bpo-47176: Emscripten builds cannot handle signals in the usual way due to platform limitations. Python can now handle signals. To use, set Module.Py_EmscriptenSignalBuffer to be a single byte SharedArrayBuffer and set Py_EMSCRIPTEN_SIGNAL_HANDLING to 1. Writing a number into the SharedArrayBuffer will cause the corresponding signal to be raised into the Python thread.

• bpo-47186: Replace JUMP_IF_NOT_EXC_MATCH by CHECK_EXC_MATCH + jump.

• bpo-47120: Replace the absolute jump opcode JUMP_NO_INTERRUPT by the relative JUMP_BACKWARD_NO_INTERRUPT.

• bpo-46841: Avoid unnecessary allocations when comparing code objects.

• bpo-47182: Fix a crash when using a named unicode character like "\N{digit nine}" after the main interpreter has been initialized a second time.

• bpo-47162: WebAssembly cannot deal with bad function pointer casts (different count or types of arguments). Python can now use call trampolines to mitigate the problem. Define PY_CALL_TRAMPOLINE to enable call trampolines.

• bpo-46775: Some Windows system error codes(>= 10000) are now mapped into the correct errno and may now raise a subclass of OSError. Patch by Dong-hee Na.

• bpo-47129: Improve error messages in f-string syntax errors concerning empty expressions.

• bpo-47117: Fix a crash if we fail to decode characters in interactive mode if the tokenizer buffers are uninitialized. Patch by Pablo Galindo.

• bpo-47127: Speed up calls to c functions with keyword arguments by 25% with specialization. Patch by Kumar Aditya.

• bpo-47120: Replaced JUMP_ABSOLUTE by the relative jump JUMP_BACKWARD.

• bpo-42197: PyFrame_FastToLocalsWithError() and PyFrame_LocalsToFast() are no longer called during profiling nor tracing. C code can access the f_locals attribute of PyFrameObject by calling PyFrame_GetLocals().

• bpo-47070: Improve performance of array_inplace_repeat by reducing the number of invocations of memcpy. Refactor the repeat and inplace repeat methods of array, bytes, bytearray and unicodeobject to use the common _PyBytes_Repeat.

• bpo-47053: Reduce de-optimization in the specialized BINARY_OP_INPLACE_ADD_UNICODE opcode.

• bpo-47045: Remove the f_state field from the _PyInterpreterFrame struct. Add the owner field to the _PyInterpreterFrame struct to make ownership explicit to simplify clearing and deallocing frames and generators.

• bpo-46968: Check for the existence of the “sys/auxv.h” header in faulthandler to avoid compilation problems in systems where this header doesn’t exist. Patch by Pablo Galindo

• bpo-46329: Use low bit of LOAD_GLOBAL to indicate whether to push a NULL before the global. Helps streamline the call sequence a bit.

• bpo-46841: Quicken bytecode in-place by storing it as part of the corresponding PyCodeObject.

• bpo-47012: Speed up iteration of bytes and bytearray by 30%. Patch by Kumar Aditya.

• bpo-47009: Improved the performance of list.append() and list comprehensions by optimizing for the common case, where no resize is needed. Patch by Dennis Sweeney.

• bpo-47005: Improve performance of bytearray_repeat and bytearray_irepeat by reducing the number of invocations of memcpy.

• bpo-46829: Deprecate passing a message into asyncio.Future.cancel() and asyncio.Task.cancel()

• bpo-46993: Speed up bytearray creation from list and tuple by 40%. Patch by Kumar Aditya.

• bpo-39829: Removed the __len__() call when initializing a list and moved initializing to list_extend. Patch by Jeremiah Pascual.

• bpo-46944: Speed up throwing exception in generator with METH_FASTCALL calling convention. Patch by Kumar Aditya.

• bpo-46841: Modify STORE_SUBSCR to use an inline cache entry (rather than its oparg) as an adaptive counter.

• bpo-46841: Use inline caching for PRECALL and CALL, and remove the internal machinery for managing the (now unused) non-inline caches.

• bpo-46881: Statically allocate and initialize the latin1 characters.

• bpo-46838: Improve syntax errors for incorrect function definitions. Patch by Pablo Galindo

• bpo-43721: Fix docstrings of getter, setter, and deleter to clarify that they create a new copy of the property.

• bpo-43224: Make grammar changes required for PEP 646.

Library

• bpo-47208: Allow vendors to override CTYPES_MAX_ARGCOUNT.

• bpo-23689: re module: fix memory leak when a match is terminated by a signal or memory allocation failure. Patch by Ma Lin.

• bpo-47167: Allow overriding a future compliance check in asyncio.Task.

• bpo-47151: When subprocess tries to use vfork, it now falls back to fork if vfork returns an error. This allows use in situations where vfork isn’t allowed by the OS kernel.

• bpo-47152: Convert the re module into a package. Deprecate modules sre_compile, sre_constants and sre_parse.

• bpo-4833: Add ZipFile.mkdir()

• bpo-27929: Fix asyncio.loop.sock_connect() to only resolve names for socket.AF_INET or socket.AF_INET6 families. Resolution may not make sense for other families, like socket.AF_BLUETOOTH and socket.AF_UNIX.

• bpo-14265: Adds the fully qualified test name to unittest output

• bpo-47061: Deprecate the aifc module.

• bpo-39622: Handle Ctrl+C in asyncio programs to interrupt the main task.

• bpo-47101: hashlib.algorithms_available now lists only algorithms that are provided by activated crypto providers on OpenSSL 3.0. Legacy algorithms are not listed unless the legacy provider has been loaded into the default OSSL context.

• bpo-47099: All URLError exception messages raised in urllib.request.URLopener now contain a colon between ftp error and the rest of the message. Previously, open_ftp() missed the colon. Patch by Oleg Iarygin.

• bpo-47099: Exception chaining is changed from Exception.with_traceback()/sys.exc_info() to PEP 3134. Patch by Oleg Iarygin.

• bpo-47095: hashlib’s internal _blake2 module now prefers libb2 from https://www.blake2.net/ over Python’s vendored copy of blake2.

• bpo-47098: The Keccak Code Package for hashlib’s internal _sha3 module has been replaced with tiny_sha3. The module is used as fallback when Python is built without OpenSSL.

• bpo-47088: Implement typing.LiteralString, part of PEP 675. Patch by Jelle Zijlstra.

• bpo-42885: Optimize re.search(), re.split(), re.findall(), re.finditer() and re.sub() for regular expressions starting with \A or ^.

• bpo-23691: Protect the re.finditer() iterator from re-entering.

• bpo-47067: Optimize calling GenericAlias objects by using PEP 590 vectorcall and by replacing PyObject_SetAttrString with PyObject_SetAttr.

• bpo-28080: Add the metadata_encoding parameter in the zipfile.ZipFile constructor and the --metadata-encoding option in the zipfile CLI to allow reading zipfiles using non-standard codecs to encode the filenames within the archive.

• bpo-47000: Make io.text_encoding() returns “utf-8” when UTF-8 mode is enabled.

• bpo-42369: Fix thread safety of zipfile._SharedFile.tell() to avoid a “zipfile.BadZipFile: Bad CRC-32 for file” exception when reading a ZipFile from multiple threads.

• bpo-38256: Fix binascii.crc32() when it is compiled to use zlib’c crc32 to work properly on inputs 4+GiB in length instead of returning the wrong result. The workaround prior to this was to always feed the function data in increments smaller than 4GiB or to just call the zlib module function.

  We also have binascii.crc32() release the GIL when computing on larger inputs as zlib.crc32() and hashlib do.

  This also boosts performance on Windows as it now uses the zlib crc32 implementation for binascii.crc32() for a 2-3x speedup.

  That the stdlib has a crc32 API in two modules is a known historical oddity. This moves us closer to a single implementation behind them.

• bpo-47066: Global inline flags (e.g. (?i)) can now only be used at the start of the regular expressions. Using them not at the start of expression was deprecated since Python 3.6.

• bpo-39394: A warning about inline flags not at the start of the regular expression now contains the position of the flag.

• bpo-433030: Add support of atomic grouping ((?>...)) and possessive quantifiers (*+, ++, ?+, {m,n}+) in regular expressions.

• bpo-47062: Implement asyncio.Runner context manager.

• bpo-46382: dataclass() slots=True now correctly omits slots already defined in base classes. Patch by Arie Bovenberg.

• bpo-47057: Use FASTCALL convention for FutureIter.throw()

• bpo-47061: Deprecate the various modules listed by PEP 594:

  aifc, asynchat, asyncore, audioop, cgi, cgitb, chunk, crypt, imghdr, msilib, nntplib, nis, ossaudiodev, pipes, smtpd, sndhdr, spwd, sunau, telnetlib, uu, xdrlib

• bpo-34790: Remove passing coroutine objects to asyncio.wait().

• bpo-47039: Normalize repr() of asyncio future and task objects.

• bpo-2604: Fix bug where doctests using globals would fail when run multiple times.

• bpo-45150: Add hashlib.file_digest() helper for efficient hashing of file object.

• bpo-34861: Made cumtime the default sorting key for cProfile

• bpo-45997: Fix asyncio.Semaphore re-aquiring FIFO order.

• bpo-47022: The asynchat, asyncore and smtpd modules have been deprecated since at least Python 3.6. Their documentation and deprecation warnings and have now been updated to note they will removed in Python 3.12 (PEP 594).

• bpo-43253: Fix a crash when closing transports where the underlying socket handle is already invalid on the Proactor event loop.

• bpo-40280: select.select() now passes NULL to select for each empty fdset.

• bpo-47004: Apply bugfixes from importlib_metadata 4.11.3, including bugfix for EntryPoint.extras, which was returning match objects and not the extras strings.

• bpo-46998: Allow subclassing of typing.Any. Patch by Shantanu Jain.

• bpo-46995: Deprecate missing asyncio.Task.set_name() for third-party task implementations, schedule making it mandatory in Python 3.13.

• bpo-46994: Accept explicit contextvars.Context in asyncio.create_task() and asyncio.loop.create_task().

• bpo-46981: typing.get_args(typing.Tuple[()]) now returns () instead of ((),).

• bpo-46968: Add os.sysconf_names['SC_MINSIGSTKSZ'].

• bpo-46985: Upgrade pip wheel bundled with ensurepip (pip 22.0.4)

• bpo-46968: faulthandler: On Linux 5.14 and newer, dynamically determine size of signal handler stack size CPython allocates using getauxval(AT_MINSIGSTKSZ). This changes allows for Python extension’s request to Linux kernel to use AMX_TILE instruction set on Sapphire Rapids Xeon processor to succeed, unblocking use of the ISA in frameworks.

• bpo-46917: The math.nan value is now always available. Patch by Victor Stinner.

• bpo-46955: Expose asyncio.base_events.Server as asyncio.Server. Patch by Stefan Zabka.

• bpo-23325: The signal module no longer assumes that SIG_IGN and SIG_DFL are small int singletons.

• bpo-46932: Update bundled libexpat to 2.4.7

• bpo-46933: The pwd module is now optional. os.path.expanduser() returns the path when the pwd module is not available.

• bpo-40059: PEP 680, the tomllib module. Adds support for parsing TOML.

• bpo-464471: asyncio.timeout() and asyncio.timeout_at() context managers added. Patch by Tin Tvrtković and Andrew Svetlov.

• bpo-46805: Added raw datagram socket functions for asyncio: sock_sendto(), sock_recvfrom() and sock_recvfrom_into().

• bpo-46644: No longer require valid typeforms to be callable. This allows typing.Annotated to wrap typing.ParamSpecArgs and dataclasses.InitVar. Patch by Gregory Beauregard.

• bpo-46581: Brings ParamSpec propagation for GenericAlias in line with Concatenate (and others).

• bpo-45413: Define posix_venv and nt_venv sysconfig installation schemes to be used for bootstrapping new virtual environments. Add venv sysconfig installation scheme to get the appropriate one of the above. The schemes are identical to the pre-existing posix_prefix and nt install schemes. The venv module now uses the venv scheme to create new virtual environments instead of hardcoding the paths depending only on the platform. Downstream Python distributors customizing the posix_prefix or nt install scheme in a way that is not compatible with the install scheme used in virtual environments are encouraged not to customize the venv schemes. When Python itself runs in a virtual environment, sysconfig.get_default_scheme() and sysconfig.get_preferred_scheme() with key="prefix" returns venv.

• bpo-43224: Implement support for PEP 646 in typing.py.

• bpo-43224: Allow unpacking types.GenericAlias objects, e.g. *tuple[int, str].

• bpo-46557: Warnings captured by the logging module are now logged without a format string to prevent systems that group logs by the msg argument from grouping captured warnings together.

• bpo-41370: typing.get_type_hints() now supports evaluating strings as forward references in PEP 585 generic aliases.

• bpo-46607: Add DeprecationWarning to LegacyInterpolation, deprecated in the docstring since Python 3.2. Will be removed in Python 3.13. Use BasicInterpolation or ExtendedInterpolation instead.

• bpo-26120: pydoc now excludes __future__ imports from the module’s data items.

• bpo-46480: Add typing.assert_type(). Patch by Jelle Zijlstra.

• bpo-46421: Fix a unittest issue where if the command was invoked as python -m unittest and the filename(s) began with a dot (.), a ValueError is returned.

• bpo-46245: Add optional parameter dir_fd in shutil.rmtree().

• bpo-22859: usageExit() is marked deprecated, to be removed in 3.13.

• bpo-46170: Improve the error message when you try to subclass an instance of typing.NewType.

• bpo-40296: Fix supporting generic aliases in pydoc.

• bpo-20392: Fix inconsistency with uppercase file extensions in MimeTypes.guess_type(). Patch by Kumar Aditya.

• bpo-46030: Add LOCAL_CREDS, LOCAL_CREDS_PERSISTENT and SCM_CREDS2 FreeBSD constants to the socket module.

• bpo-44439: Fix .write() method of a member file in ZipFile, when the input data is an object that supports the buffer protocol, the file length may be wrong.

• bpo-45171: Fix handling of the stacklevel argument to logging functions in the logging module so that it is consistent accross all logging functions and, as advertised, similar to the stacklevel argument used in warn().

• bpo-24959: Fix bug where unittest sometimes drops frames from tracebacks of exceptions raised in tests.

• bpo-44859: Raise more accurate and PEP 249 compatible exceptions in sqlite3.

  • Raise InterfaceError instead of ProgrammingError for SQLITE_MISUSE errors.

  • Don’t overwrite BufferError with ValueError when conversion to BLOB fails.

  • Raise ProgrammingError instead of Warning if user tries to execute() more than one SQL statement.

  • Raise ProgrammingError instead of ValueError if an SQL query contains null characters.

• bpo-44493: Add missing terminated NUL in sockaddr_un’s length

  This was potentially observable when using non-abstract AF_UNIX datagram sockets to processes written in another programming language.

• bpo-41930: Add serialize() and deserialize() support to sqlite3. Patch by Erlend E. Aasland.

• bpo-33178: Added ctypes.BigEndianUnion and ctypes.LittleEndianUnion classes, as originally documented in the library docs but not yet implemented.

• bpo-43352: Add an Barrier object in synchronization primitives of asyncio Lib in order to be consistant with Barrier from threading and multiprocessing libs*

• bpo-35859: re module, fix a few bugs about capturing group. In rare cases, capturing group gets an incorrect string. Patch by Ma Lin.

Documentation

• bpo-45099: Document internal asyncio API.

• bpo-47126: Update PEP URLs to PEP 676’s new canonical form.

• bpo-47040: Clarified the old Python versions compatiblity note of binascii.crc32() / zlib.adler32() / zlib.crc32() functions.

• bpo-46033: Clarify for statement execution in its doc.

• bpo-45790: Adjust inaccurate phrasing in Defining Extension Types: Tutorial about the ob_base field and the macros used to access its contents.

• bpo-42340: Document that in some circumstances KeyboardInterrupt may cause the code to enter an inconsistent state. Provided a sample workaround to avoid it if needed.

• bpo-41233: Link the errnos referenced in Doc/library/exceptions.rst to their respective section in Doc/library/errno.rst, and vice versa. Previously this was only done for EINTR and InterruptedError. Patch by Yan “yyyyyyyan” Orestes.

Tests

• bpo-47205: Skip test for sched_getaffinity() and sched_setaffinity() error case on FreeBSD.

• bpo-46126: Restore ‘descriptions’ when running tests internally.

• bpo-47104: Rewrite asyncio.to_thread() tests to use unittest.IsolatedAsyncioTestCase.

• bpo-40280: The test suite is now passing on the Emscripten platform. All fork, socket, and subprocess-based tests are skipped.

• bpo-47037: Skip strftime("%4Y") feature test on Windows. It can cause an assertion error in debug builds.

• bpo-46587: Skip tests if platform’s strftime does not support non-portable glibc extensions.

• bpo-47015: A test case for os.sendfile() is converted from deprecated asyncore (see PEP 594) to asyncio. Patch by Oleg Iarygin.

Build

• bpo-40280: Add configure option --enable-wasm-dynamic-linking to enable dlopen and MAIN_MODULE / SIDE_MODULE on wasm32-emscripten.

• bpo-46023: makesetup now detects and skips all duplicated module definitions. The first entry wins.

• bpo-40280: Add SOABI wasm32-emscripten for Emscripten and wasm32-wasi for WASI on 32bit WASM as well as wasm64 counter parts.

• bpo-47032: Ensure Windows install builds fail correctly with a non-zero exit code when part of the build fails.

• bpo-47024: Update OpenSSL to 1.1.1n for macOS installers and all Windows builds.

• bpo-46996: The tkinter package now requires Tcl/Tk version 8.5.12 or newer.

• bpo-46973: Add regen-configure make target to regenerate configure script with Christian’s container image quay.io/tiran/cpython_autoconf:269.

• bpo-46917: Building Python now requires support of IEEE 754 floating point numbers. Patch by Victor Stinner.

• bpo-45774: configure now verifies that all SQLite C APIs needed for the sqlite3 extension module are found.

Windows

• bpo-47194: Update zlib to v1.2.12 to resolve CVE-2018-25032.

• bpo-47171: Enables installing the py.exe launcher on Windows ARM64.

• bpo-46566: Upgraded Python Launcher for Windows to support a new -V:company/tag argument for full PEP 514 support and to detect ARM64 installs. The -64 suffix on arguments is deprecated, but still selects any non-32-bit install. Setting PYLAUNCHER_ALLOW_INSTALL and specifying a version that is not installed will attempt to install the requested version from the Microsoft Store.

• bpo-47086: The installer for Windows now includes documentation as loose HTML files rather than a single compiled .chm file.

• bpo-46907: Update Windows installer to use SQLite 3.38.1.

• bpo-44549: Update bzip2 to 1.0.8 in Windows builds to mitigate CVE-2016-3189 and CVE-2019-12900

• bpo-46948: Prevent CVE-2022-26488 by ensuring the Add to PATH option in the Windows installer uses the correct path when being repaired.

macOS

• bpo-46890: Fix a regression in the setting of sys._base_executable in framework builds, and thereby fix a regression in venv virtual environments with such builds.

• bpo-46907: Update macOS installer to SQLite 3.38.1.

Tools/Demos

• bpo-40280: Replace Emscripten’s limited shell with Katie Bell’s browser-ui REPL from python-wasm project.

C API

• bpo-40421: Add PyFrame_GetBuiltins, PyFrame_GetGenerator and PyFrame_GetGlobals C-API functions to access frame object attributes safely from C code.

• bpo-46850: Move the private _PyFrameEvalFunction type, and private _PyInterpreterState_GetEvalFrameFunc() and _PyInterpreterState_SetEvalFrameFunc() functions to the internal C API. The _PyFrameEvalFunction callback function type now uses the _PyInterpreterFrame type which is part of the internal C API. Patch by Victor Stinner.

• bpo-46850: Move the private undocumented _PyEval_EvalFrameDefault() function to the internal C API. The function now uses the _PyInterpreterFrame type which is part of the internal C API. Patch by Victor Stinner.

• bpo-46850: Remove the private undocumented function _PyEval_CallTracing() from the C API. Call the public sys.call_tracing() function instead. Patch by Victor Stinner.

• bpo-46850: Remove the private undocumented function _PyEval_GetCoroutineOriginTrackingDepth() from the C API. Call the public sys.get_coroutine_origin_tracking_depth() function instead. Patch by Victor Stinner.

• bpo-46850: Remove the following private undocumented functions from the C API:

  • _PyEval_GetAsyncGenFirstiter()

  • _PyEval_GetAsyncGenFinalizer()

  • _PyEval_SetAsyncGenFirstiter()

  • _PyEval_SetAsyncGenFinalizer()

  Call the public sys.get_asyncgen_hooks() and sys.set_asyncgen_hooks() functions instead. Patch by Victor Stinner.

• bpo-46987: Remove private functions _PySys_GetObjectId() and _PySys_SetObjectId(). Patch by Dong-hee Na.

• bpo-46906: Add new functions to pack and unpack C double (serialize and deserialize): PyFloat_Pack2(), PyFloat_Pack4(), PyFloat_Pack8(), PyFloat_Unpack2(), PyFloat_Unpack4() and PyFloat_Unpack8(). Patch by Victor Stinner.

Python 3.11.0 alpha 6

Release date: 2022-03-07

Core and Builtins

• bpo-46940: Avoid overriding AttributeError metadata information for nested attribute access calls. Patch by Pablo Galindo.

• bpo-46927: Include the type’s name in the error message for subscripting non-generic types.

• bpo-46921: Support vectorcall for super(). Patch by Ken Jin.

• bpo-46841: Fix incorrect handling of inline cache entries when specializing BINARY_OP.

• bpo-46841: Use an oparg to simplify the construction of helpful error messages in GET_AWAITABLE.

• bpo-46903: Make sure that str subclasses can be used as attribute names for instances with virtual dictionaries. Fixes regression in 3.11alpha

• bpo-46841: Add more detailed specialization failure stats for COMPARE_OP followed by EXTENDED_ARG.

• bpo-46891: Fix bug introduced during 3.11alpha where subclasses of types.ModuleType with __slots__ were not initialized correctly, resulting in an interpreter crash.

• bpo-46841: Use inline caching for LOAD_ATTR, LOAD_METHOD, and STORE_ATTR.

• bpo-46841: Use inline cache for BINARY_SUBSCR.

• bpo-46841: Use inline caching for COMPARE_OP.

• bpo-46864: Deprecate PyBytesObject.ob_shash. It will be removed in Python 3.13.

• bpo-46841: Use inline caching for UNPACK_SEQUENCE.

• bpo-46845: Reduces dict size by removing hash value from hash table when all inserted keys are Unicode. For example, sys.getsizeof(dict.fromkeys("abcdefg")) becomes 272 bytes from 352 bytes on 64bit platform.

• bpo-46841: Use inline cache for LOAD_GLOBAL.

• bpo-46852: Rename the private undocumented float.__set_format__() method to float.__setformat__() to fix a typo introduced in Python 3.7. The method is only used by test_float. Patch by Victor Stinner.

• bpo-46852: Remove the undocumented private float.__set_format__() method, previously known as float.__setformat__() in Python 3.7. Its docstring said: “You probably don’t want to use this function. It exists mainly to be used in Python’s test suite.” Patch by Victor Stinner.

• bpo-40116: Fix regression that dict.update(other) may don’t respect iterate order of other when other is key sharing dict.

• bpo-46712: Share global string identifiers in deep-frozen modules.

• bpo-46430: Fix memory leak in interned strings of deep-frozen modules.

• bpo-46841: Store BINARY_OP caches inline using a new CACHE instruction.

• bpo-45107: Specialize LOAD_METHOD for instances with a dict.

• bpo-44337: Reduce the memory usage of specialized LOAD_ATTR and STORE_ATTR instructions.

• bpo-46729: Add number of sub-exceptions to BaseException.__str__().

• bpo-45885: Don’t un-adapt COMPARE_OP when collecting specialization stats.

• bpo-46329: Fix specialization stats gathering for PRECALL instructions.

• bpo-46794: Bump up the libexpat version into 2.4.6

• bpo-46823: Implement a specialized combined opcode LOAD_FAST__LOAD_ATTR_INSTANCE_VALUE. Patch by Dennis Sweeney.

• bpo-46820: Fix parsing a numeric literal immediately (without spaces) followed by “not in” keywords, like in 1not in x. Now the parser only emits a warning, not a syntax error.

• bpo-46329: Move KW_NAMES before PRECALL instruction in call sequence. Change operand of CALL to match PRECALL for easier specialization.

• bpo-46808: Remove the NEXT_BLOCK macro from compile.c, and make the compiler automatically generate implicit blocks when they are needed.

• bpo-46329: Add PUSH_NULL instruction. This is used as a prefix when evaluating a callable, so that the stack has the same shape for methods and other calls. PRECALL_FUNCTION and PRECALL_METHOD are merged into a single PRECALL instruction.

  There is no change in semantics.

• bpo-46762: Fix an assert failure in debug builds when a ‘<’, ‘>’, or ‘=’ is the last character in an f-string that’s missing a closing right brace.

• bpo-46730: Message of AttributeError caused by getting, setting or deleting a property without the corresponding function now mentions that the attribute is in fact a property and also specifies type of the class that it belongs to.

• bpo-46724: Make sure that all backwards jumps use the JUMP_ABSOLUTE instruction, rather than JUMP_FORWARD with an argument of (2**32)+offset.

• bpo-46732: Correct the docstring for the __bool__() method. Patch by Jelle Zijlstra.

• bpo-46072: Add more detailed specialization failure statistics for BINARY_OP.

• bpo-46707: Avoid potential exponential backtracking when producing some syntax errors involving lots of brackets. Patch by Pablo Galindo.

• bpo-46323: ctypes now allocates memory on the stack instead of on the heap to pass arguments while calling a Python callback function. Patch by Dong-hee Na.

• bpo-45923: Add a quickened form of RESUME that skips quickening checks.

• bpo-46702: Specialize UNPACK_SEQUENCE for tuple and list unpackings.

• bpo-46072: Opcode pair stats are now gathered with --enable-pystats. Defining DYNAMIC_EXECUTION_PROFILE or DXPAIRS no longer has any effect.

• bpo-46675: Allow more than 16 items in a split dict before it is combined. The limit is now 254.

• bpo-40479: Add a missing call to va_end() in Modules/_hashopenssl.c.

• bpo-46323: Use PyObject_Vectorcall() while calling ctypes callback function. Patch by Dong-hee Na.

• bpo-46615: When iterating over sets internally in setobject.c, acquire strong references to the resulting items from the set. This prevents crashes in corner-cases of various set operations where the set gets mutated.

• bpo-45828: The bytecode compiler now attempts to apply runtime stack manipulations at compile-time (whenever it is feasible to do so).

• bpo-30496: Fixed a minor portability issue in the implementation of PyLong_FromLong(), and added a fast path for single-digit integers to PyLong_FromLongLong().

Library

• bpo-25707: Fixed a file leak in xml.etree.ElementTree.iterparse() when the iterator is not exhausted. Patch by Jacob Walls.

• bpo-46877: Export unittest.doModuleCleanups() in unittest. Patch by Kumar Aditya.

• bpo-46848: For performance, use the optimized string-searching implementations from find() and rfind() for find() and rfind().

• bpo-46736: SimpleHTTPRequestHandler now uses HTML5 grammar. Patch by Dong-hee Na.

• bpo-44886: Inherit asyncio proactor datagram transport from asyncio.DatagramTransport.

• bpo-46827: Support UDP sockets in asyncio.loop.sock_connect() for selector-based event loops. Patch by Thomas Grainger.

• bpo-46811: Make test suite support Expat >=2.4.5

• bpo-46252: Raise TypeError if ssl.SSLSocket is passed to transport-based APIs.

• bpo-46784: Fix libexpat symbols collisions with user dynamically loaded or statically linked libexpat in embedded Python.

• bpo-46786: The HTML serialisation in xml.etree.ElementTree now writes embed, source, track and wbr as empty tags, as defined in HTML 5.

• bpo-39327: shutil.rmtree() can now work with VirtualBox shared folders when running from the guest operating-system.

• bpo-45390: Propagate asyncio.CancelledError message from inner task to outer awaiter.

• bpo-46756: Fix a bug in urllib.request.HTTPPasswordMgr.find_user_password() and urllib.request.HTTPPasswordMgrWithPriorAuth.is_authenticated() which allowed to bypass authorization. For example, access to URI example.org/foobar was allowed if the user was authorized for URI example.org/foo.

• bpo-46737: random.gauss() and random.normalvariate() now have default arguments.

• bpo-46752: Add task groups to asyncio (structured concurrency, inspired by Trio’s nurseries). This also introduces a change to task cancellation, where a cancelled task can’t be cancelled again until it calls .uncancel().

• bpo-46724: Fix dis behavior on negative jump offsets.

• bpo-46333: The __repr__() method of typing.ForwardRef now includes the module parameter of typing.ForwardRef when it is set.

• bpo-46643: In typing.get_type_hints(), support evaluating stringified ParamSpecArgs and ParamSpecKwargs annotations. Patch by Gregory Beauregard.

• bpo-45863: When the tarfile module creates a pax format archive, it will put an integer representation of timestamps in the ustar header (if possible) for the benefit of older unarchivers, in addition to the existing full-precision timestamps in the pax extended header.

• bpo-46066: Deprecate kwargs-based syntax for typing.TypedDict definitions. It had confusing semantics when specifying totality, and was largely unused. Patch by Jingchen Ye.

• bpo-46676: Make typing.ParamSpec args and kwargs equal to themselves. Patch by Gregory Beauregard.

• bpo-46323: ctypes.CFUNCTYPE() and ctypes.WINFUNCTYPE() now fail to create the type if its _argtypes_ member contains too many arguments. Previously, the error was only raised when calling a function. Patch by Victor Stinner.

• bpo-46672: Fix NameError in asyncio.gather() when initial type check fails.

• bpo-46659: The calendar.LocaleTextCalendar and calendar.LocaleHTMLCalendar classes now use locale.getlocale(), instead of using locale.getdefaultlocale(), if no locale is specified. Patch by Victor Stinner.

• bpo-46659: The locale.getdefaultlocale() function is deprecated and will be removed in Python 3.13. Use locale.setlocale(), locale.getpreferredencoding(False) and locale.getlocale() functions instead. Patch by Victor Stinner.

• bpo-46655: In typing.get_type_hints(), support evaluating bare stringified TypeAlias annotations. Patch by Gregory Beauregard.

• bpo-45948: Fixed a discrepancy in the C implementation of the xml.etree.ElementTree module. Now, instantiating an xml.etree.ElementTree.XMLParser with a target=None keyword provides a default xml.etree.ElementTree.TreeBuilder target as the Python implementation does.

• bpo-46626: Expose Linux’s IP_BIND_ADDRESS_NO_PORT option in socket.

• bpo-46521: Fix a bug in the codeop module that was incorrectly identifying invalid code involving string quotes as valid code.

• bpo-46571: Improve typing.no_type_check().

  Now it does not modify external classes and functions. We also now correctly mark classmethods as not to be type checked.

• bpo-46400: expat: Update libexpat from 2.4.1 to 2.4.4

• bpo-46556: Deprecate undocumented support for using a pathlib.Path object as a context manager.

• bpo-46534: Implement PEP 673 typing.Self. Patch by James Hilton-Balfe.

• bpo-46522: Make various module __getattr__ AttributeErrors more closely match a typical AttributeError

• bpo-46475: Add typing.Never and typing.assert_never(). Patch by Jelle Zijlstra.

• bpo-46333: The __eq__() and __hash__() methods of typing.ForwardRef now honor the module parameter of typing.ForwardRef. Forward references from different modules are now differentiated.

• bpo-46246: Add missing __slots__ to importlib.metadata.DeprecatedList. Patch by Arie Bovenberg.

• bpo-46232: The ssl module now handles certificates with bit strings in DN correctly.

• bpo-46195: typing.get_type_hints() no longer adds Optional to parameters with None as a default. This aligns to changes to PEP 484 in https://github.com/python/peps/pull/689

• bpo-31369: Add RegexFlag to re.__all__ and documented it. Add NOFLAG to indicate no flags being set.

• bpo-45898: ctypes no longer defines ffi_type_* symbols in cfield.c. The symbols have been provided by libffi for over a decade.

• bpo-44953: Calling operator.itemgetter objects and operator.attrgetter objects is now faster due to use of the vectorcall calling convention.

• bpo-44289: Fix an issue with is_tarfile() method when using fileobj argument: position in the fileobj was advanced forward which made it unreadable with tarfile.TarFile.open().

• bpo-44011: Reimplement SSL/TLS support in asyncio, borrow the implementation from uvloop library.

• bpo-41086: Make the configparser.ConfigParser constructor raise TypeError if the interpolation parameter is not of type configparser.Interpolation

• bpo-29418: Implement inspect.ismethodwrapper() and fix inspect.isroutine() for cases where methodwrapper is given. Patch by Hakan Çelik.

• bpo-14156: argparse.FileType now supports an argument of ‘-’ in binary mode, returning the .buffer attribute of sys.stdin/sys.stdout as appropriate. Modes including ‘x’ and ‘a’ are treated equivalently to ‘w’ when argument is ‘-’. Patch contributed by Josh Rosenberg

Documentation

• bpo-42238: Doc/tools/rstlint.py has moved to its own repository and is now packaged on PyPI as sphinx-lint.

Tests

• bpo-46913: Fix test_faulthandler.test_sigfpe() if Python is built with undefined behavior sanitizer (UBSAN): disable UBSAN on the faulthandler_sigfpe() function. Patch by Victor Stinner.

• bpo-46760: Remove bytecode offsets from expected values in test.test_dis module. Reduces the obstacles to modifying the VM or compiler.

• bpo-46708: Prevent default asyncio event loop policy modification warning after test_asyncio execution.

• bpo-46678: The function make_legacy_pyc in Lib/test/support/import_helper.py no longer fails when PYTHONPYCACHEPREFIX is set to a directory on a different device from where tempfiles are stored.

• bpo-46623: Skip test_pair() and test_speech128() of test_zlib on s390x since they fail if zlib uses the s390x hardware accelerator. Patch by Victor Stinner.

Build

• bpo-46860: Respect --with-suffix when building on case-insensitive file systems.

• bpo-46656: Building Python now requires a C11 compiler without optional C11 features. Patch by Victor Stinner.

• bpo-46656: Building Python now requires support for floating point Not-a-Number (NaN): remove the Py_NO_NAN macro. Patch by by Victor Stinner.

• bpo-46640: Building Python now requires a C99 <math.h> header file providing a NAN constant, or the __builtin_nan() built-in function. Patch by Victor Stinner.

• bpo-46608: Exclude marshalled-frozen data if deep-freezing to save 300 KB disk space. This includes adding a new is_package field to _frozen. Patch by Kumar Aditya.

• bpo-40280: Fix wasm32-emscripten test failures and platform issues. - Disable syscalls that are not supported or don’t work, e.g. wait, getrusage, prlimit, mkfifo, mknod, setres[gu]id, setgroups. - Use fd_count to cound open fds. - Add more checks for subprocess and fork. - Add workarounds for missing _multiprocessing and failing socket.accept(). - Enable bzip2. - Disable large file support. - Disable signal.alarm.

• bpo-46430: Intern strings in deep-frozen modules. Patch by Kumar Aditya.

Windows

• bpo-46744: The default all users install directory for ARM64 is now under the native Program Files folder, rather than Program Files (Arm) which is intended for ARM (32-bit) files.

• bpo-46567: Adds Tcl and Tk support for Windows ARM64. This also adds IDLE to the installation.

• bpo-46638: Ensures registry virtualization is consistently disabled. For 3.10 and earlier, it remains enabled (some registry writes are protected), while for 3.11 and later it is disabled (registry modifications affect all applications).

IDLE

• bpo-46630: Make query dialogs on Windows start with a cursor in the entry box.

• bpo-45447: Apply IDLE syntax highlighting to pyi files. Patch by Alex Waygood and Terry Jan Reedy.

C API

• bpo-46748: Python’s public headers no longer import <stdbool.h>, leaving code that embedd/extends Python free to define bool, true and false.

• bpo-46836: Move the PyFrameObject type definition (struct _frame) to the internal C API pycore_frame.h header file. Patch by Victor Stinner.

• bpo-45459: Rename Include/buffer.h header file to Include/pybuffer.h to avoid conflits with projects having an existing buffer.h header file. Patch by Victor Stinner.

• bpo-45412: Remove the HAVE_PY_SET_53BIT_PRECISION macro (moved to the internal C API). Patch by Victor Stinner.

• bpo-46613: Added function PyType_GetModuleByDef(), which allows accesss to module state when a method’s defining class is not available.

Python 3.11.0 alpha 5

Release date: 2022-02-03

Core and Builtins

• bpo-45773: Remove two invalid “peephole” optimizations from the bytecode compiler.

• bpo-46564: Do not create frame objects when creating super object. Patch by Kumar Aditya.

• bpo-45885: Added more fined-grained specialization failure stats regarding the COMPARE_OP bytecode.

• bpo-44977: The delegation of int() to __trunc__() is now deprecated. Calling int(a) when type(a) implements __trunc__() but not __int__() or __index__() now raises a DeprecationWarning.

• bpo-46458: Reorder code emitted by the compiler for a try-except block so that the else block’s code immediately follows the try body (without a jump). This is more optimal for the happy path.

• bpo-46527: Allow passing iterable as a keyword argument to enumerate() again. Patch by Jelle Zijlstra.

• bpo-46528: Replace several stack manipulation instructions (DUP_TOP, DUP_TOP_TWO, ROT_TWO, ROT_THREE, ROT_FOUR, and ROT_N) with new COPY and SWAP instructions.

• bpo-46329: Use two or three bytecodes to implement most calls.

  Calls without named arguments are implemented as a sequence of two instructions: PRECALL; CALL. Calls with named arguments are implemented as a sequence of three instructions: PRECALL; KW_NAMES; CALL. There are two different PRECALL instructions: PRECALL_FUNTION and PRECALL_METHOD. The latter pairs with LOAD_METHOD.

  This partition into pre-call and call allows better specialization, and thus better performance ultimately.

  There is no change in semantics.

• bpo-46503: Fix an assert when parsing some invalid N escape sequences in f-strings.

• bpo-46431: Improve error message on invalid calls to BaseExceptionGroup.__new__().

• bpo-46476: Fix memory leak in code objects generated by deepfreeze. Patch by Kumar Aditya.

• bpo-46481: Speed up calls to weakref.ref.__call__() by using the PEP 590 vectorcall calling convention. Patch by Dong-hee Na.

• bpo-46417: Fix a race condition on setting a type __bases__ attribute: the internal function add_subclass() now gets the PyTypeObject.tp_subclasses member after calling PyWeakref_NewRef() which can trigger a garbage collection which can indirectly modify PyTypeObject.tp_subclasses. Patch by Victor Stinner.

• bpo-46417: python -X showrefcount now shows the total reference count after clearing and destroyed the main Python interpreter. Previously, it was shown before. Patch by Victor Stinner.

• bpo-43683: Add ASYNC_GEN_WRAP opcode to wrap the value to be yielded in async generators. Removes the need to special case async generators in the YIELD_VALUE instruction.

• bpo-46407: Optimize some modulo operations in Objects/longobject.c. Patch by Jeremiah Vivian.

• bpo-46409: Add new RETURN_GENERATOR bytecode to make generators. Simplifies calling Python functions in the VM, as they no longer any need to special case generator functions.

  Also add JUMP_NO_INTERRUPT bytecode that acts like JUMP_ABSOLUTE, but does not check for interrupts.

• bpo-46406: The integer division // implementation has been optimized to better let the compiler understand its constraints. It can be 20% faster on the amd64 platform when dividing an int by a value smaller than 2**30.

• bpo-46383: Fix invalid signature of _zoneinfo’s module_free function to resolve a crash on wasm32-emscripten platform.

• bpo-46361: Ensure that “small” integers created by int.from_bytes() and decimal.Decimal are properly cached.

• bpo-46161: Fix the class building error when the arguments are constants and CALL_FUNCTION_EX is used.

• bpo-46028: Fixes calculation of sys._base_executable when inside a virtual environment that uses symlinks with different binary names than the base environment provides.

• bpo-46091: Correctly calculate indentation levels for lines with whitespace character that are ended by line continuation characters. Patch by Pablo Galindo

• bpo-30512: Add CAN Socket support for NetBSD.

• bpo-46045: Do not use POSIX semaphores on NetBSD

• bpo-44024: Improve the exc:TypeError message for non-string second arguments passed to the built-in functions getattr() and hasattr(). Patch by Géry Ogam.

Library

• bpo-46624: Restore support for non-integer arguments of random.randrange() and random.randint().

• bpo-46591: Make the IDLE doc URL on the About IDLE dialog clickable.

• bpo-46565: Remove loop variables that are leaking into modules’ namespaces.

• bpo-46553: In typing.get_type_hints(), support evaluating bare stringified ClassVar annotations. Patch by Gregory Beauregard.

• bpo-46544: Don’t leak x & uspace intermediate vars in textwrap.TextWrapper.

• bpo-46487: Add the get_write_buffer_limits method to asyncio.transports.WriteTransport and to the SSL transport.

• bpo-45173: Note the configparser deprecations will be removed in Python 3.12.

• bpo-45162: The deprecated unittest APIs removed in 3.11a1 have been temporarily restored to be removed in 3.12 while cleanups in external projects go in.

• bpo-46539: In typing.get_type_hints(), support evaluating stringified ClassVar and Final annotations inside Annotated. Patch by Gregory Beauregard.

• bpo-46510: Add missing test for types.TracebackType and types.FrameType. Calculate them directly from the caught exception without calling sys.exc_info().

• bpo-46491: Allow typing.Annotated to wrap typing.Final and typing.ClassVar. Patch by Gregory Beauregard.

• bpo-46483: Remove __class_getitem__() from pathlib.PurePath as this class was not supposed to be generic.

• bpo-46436: Fix command-line option -d/--directory in module http.server which is ignored when combined with command-line option --cgi. Patch by Géry Ogam.

• bpo-41403: Make mock.patch() raise a TypeError with a relevant error message on invalid arg. Previously it allowed a cryptic AttributeError to escape.

• bpo-46474: In importlib.metadata.EntryPoint.pattern, avoid potential REDoS by limiting ambiguity in consecutive whitespace.

• bpo-46474: Removed private method from importlib.metadata.Path. Sync with importlib_metadata 4.10.0.

• bpo-46470: Remove unused branch from typing._remove_dups_flatten

• bpo-46469: asyncio generic classes now return types.GenericAlias in __class_getitem__ instead of the same class.

• bpo-41906: Support passing filter instances in the filters values of handlers and loggers in the dictionary passed to logging.config.dictConfig().

• bpo-46422: Use dis.Positions in dis.Instruction instead of a regular tuple.

• bpo-46434: pdb now gracefully handles help when __doc__ is missing, for example when run with pregenerated optimized .pyc files.

• bpo-43869: Python uses the same time Epoch on all platforms. Add an explicit unit test to ensure that it’s the case. Patch by Victor Stinner.

• bpo-46414: Add typing.reveal_type(). Patch by Jelle Zijlstra.

• bpo-40280: subprocess now imports Windows-specific imports when msvcrt module is available, and POSIX-specific imports on all other platforms. This gives a clean exception when _posixsubprocess is not available (e.g. Emscripten browser target).

• bpo-40066: IntEnum, IntFlag, and StrEnum use the mixed-in type for their str() and format() output.

• bpo-46316: Optimize pathlib.Path.iterdir() by removing an unnecessary check for special entries.

• bpo-29688: Document pathlib.Path.absolute() (which has always existed).

• bpo-43012: The pathlib module’s obsolete and internal _Accessor class has been removed to prepare the terrain for upcoming enhancements to the module.

• bpo-46258: Speed up math.isqrt() for small positive integers by replacing two division steps with a lookup table.

• bpo-46242: Improve error message when creating a new enum.Enum type subclassing an existing Enum with _member_names_ using enum.Enum.__call__().

• bpo-43118: Fix a bug in inspect.signature() that was causing it to fail on some subclasses of classes with a __text_signature__ referencing module globals. Patch by Weipeng Hong.

• bpo-26552: Fixed case where failing asyncio.ensure_future() did not close the coroutine. Patch by Kumar Aditya.

• bpo-21987: Fix an issue with tarfile.TarFile.getmember() getting a directory name with a trailing slash.

• bpo-46124: Update zoneinfo to rely on importlib.resources traversable API.

• bpo-46103: Now inspect.getmembers() only gets __bases__ attribute from class type. Patch by Weipeng Hong.

• bpo-46080: Fix exception in argparse help text generation if a argparse.BooleanOptionalAction argument’s default is argparse.SUPPRESS and it has help specified. Patch by Felix Fontein.

• bpo-44791: Fix substitution of ParamSpec in Concatenate with different parameter expressions. Substitution with a list of types returns now a tuple of types. Substitution with Concatenate returns now a Concatenate with concatenated lists of arguments.

Documentation

• bpo-46463: Fixes escape4chm.py script used when building the CHM documentation file

Tests

• bpo-43478: Mocks can no longer be provided as the specs for other Mocks. As a result, an already-mocked object cannot be passed to mock.Mock(). This can uncover bugs in tests since these Mock-derived Mocks will always pass certain tests (e.g. isinstance) and builtin assert functions (e.g. assert_called_once_with) will unconditionally pass.

• bpo-46616: Ensures test_importlib.test_windows cleans up registry keys after completion.

• bpo-44359: test_ftplib now silently ignores socket errors to prevent logging unhandled threading exceptions. Patch by Victor Stinner.

• bpo-46600: Fix test_gdb.test_pycfunction() for Python built with clang -Og. Tolerate inlined functions in the gdb traceback. Patch by Victor Stinner.

• bpo-46542: Fix a Python crash in test_lib2to3 when using Python built in debug mode: limit the recursion limit. Patch by Victor Stinner.

• bpo-46576: test_peg_generator now disables compiler optimization when testing compilation of its own C extensions to significantly speed up the testing on non-debug builds of CPython.

• bpo-46542: Fix test_json tests checking for RecursionError: modify these tests to use support.infinite_recursion(). Patch by Victor Stinner.

• bpo-13886: Skip test_builtin PTY tests on non-ASCII characters if the readline module is loaded. The readline module changes input() behavior, but test_builtin is not intented to test the readline module. Patch by Victor Stinner.

• bpo-40280: Add test.support.requires_fork() decorators to mark tests that require a working os.fork().

• bpo-40280: Add test.support.requires_subprocess() decorator to mark tests which require working subprocess module or os.spawn*. The wasm32-emscripten platform has no support for processes.

• bpo-46126: Disable ‘descriptions’ when running tests internally.

Build

• bpo-46602: Tidied up configure.ac so that conftest.c is truncated rather than appended. This assists in the case where the ‘rm’ of conftest.c fails to happen between tests. Downstream issues such as a clobbered SOABI can result.

• bpo-46600: Fix the test checking if the C compiler supports -Og option in the ./configure script to also use -Og on clang which supports it. Patch by Victor Stinner.

• bpo-38472: Fix GCC detection in setup.py when cross-compiling. The C compiler is now run with LC_ALL=C. Previously, the detection failed with a German locale.

• bpo-46513: configure no longer uses AC_C_CHAR_UNSIGNED macro and pyconfig.h no longer defines reserved symbol __CHAR_UNSIGNED__.

• bpo-46471: Use global singletons for single byte bytes objects in deepfreeze.

• bpo-46443: Deepfreeze now uses cached small integers as it saves some space for common small integers.

• bpo-46429: Merge all deep-frozen files into one for space savings. Patch by Kumar Aditya.

• bpo-45569: The build now defaults to using 30-bit digits for Python integers. Previously either 15-bit or 30-bit digits would be selected, depending on the platform. 15-bit digits may still be selected using the --enable-big-digits=15 option to the configure script, or by defining PYLONG_BITS_IN_DIGIT in pyconfig.h.

• bpo-45925: Update Windows installer to use SQLite 3.37.2.

• bpo-43112: Detect musl libc as a separate SOABI (tagged as linux-musl).

Windows

• bpo-33125: The traditional EXE/MSI based installer for Windows is now available for ARM64

• bpo-46362: os.path.abspath(“C:CON”) is now fixed to return “\.CON”, not the same path. The regression was true of all legacy DOS devices such as COM1, LPT1, or NUL.

• bpo-44934: The installer now offers a command-line only option to add the installation directory to the end of PATH instead of at the start.

macOS

• bpo-45925: Update macOS installer to SQLite 3.37.2.

IDLE

• bpo-45296: Clarify close, quit, and exit in IDLE. In the File menu, ‘Close’ and ‘Exit’ are now ‘Close Window’ (the current one) and ‘Exit’ is now ‘Exit IDLE’ (by closing all windows). In Shell, ‘quit()’ and ‘exit()’ mean ‘close Shell’. If there are no other windows, this also exits IDLE.

C API

• bpo-40170: Remove the PyHeapType_GET_MEMBERS() macro. It was exposed in the public C API by mistake, it must only be used by Python internally. Use the PyTypeObject.tp_members member instead. Patch by Victor Stinner.

• bpo-40170: Move _Py_GetAllocatedBlocks() and _PyObject_DebugMallocStats() private functions to the internal C API. Patch by Victor Stinner.

• bpo-46433: The internal function _PyType_GetModuleByDef now correctly handles inheritance patterns involving static types.

• bpo-45459: Py_buffer and various Py_buffer related functions are now part of the limited API and stable ABI.

• bpo-14916: Fixed bug in the tokenizer that prevented PyRun_InteractiveOne from parsing from the provided FD.

Python 3.11.0 alpha 4

Release date: 2022-01-13

Core and Builtins

• bpo-46070: Py_EndInterpreter() now explicitly untracks all objects currently tracked by the GC. Previously, if an object was used later by another interpreter, calling PyObject_GC_UnTrack() on the object crashed if the previous or the next object of the PyGC_Head structure became a dangling pointer. Patch by Victor Stinner.

• bpo-46347: Fix memory leak in PyEval_EvalCodeEx.

• bpo-46339: Fix a crash in the parser when retrieving the error text for multi-line f-strings expressions that do not start in the first line of the string. Patch by Pablo Galindo

• bpo-46331: Do not set line number of instruction storing doc-string. Fixes regression introduced in 3.11 alpha.

• bpo-46314: Remove spurious “call” event when creating a lambda function that was accidentally introduced in 3.11a4.

• bpo-46289: ASDL declaration of FormattedValue has changed to reflect conversion field is not optional.

• bpo-46297: Fixed an interpreter crash on bootup with multiple PythonPaths set in the Windows registry. Patch by Derzsi Dániel.

• bpo-46237: Fix the line number of tokenizer errors inside f-strings. Patch by Pablo Galindo.

• bpo-46263: We always expect the “use_frozen_modules” config to be set, now that getpath.c was rewritten in pure Python and the logic improved.

• bpo-46006: Fix a regression when a type method like __init__() is modified in a subinterpreter. Fix a regression in _PyUnicode_EqualToASCIIId() and type update_slot(). Revert the change which made the Unicode dictionary of interned strings compatible with subinterpreters: the internal interned dictionary is shared again by all interpreters. Patch by Victor Stinner.

• bpo-45923: Add RESUME opcode. This is a logical no-op. It is emitted by the compiler anywhere a Python function can be entered. It is used by the interpreter to perform tracing and optimizer checks.

• bpo-46208: Fix the regression of os.path.normpath(“A/../../B”) not returning expected “../B” but “B”.

• bpo-46240: Correct the error message for unclosed parentheses when the tokenizer doesn’t reach the end of the source when the error is reported. Patch by Pablo Galindo

• bpo-46009: Remove the GEN_START opcode.

• bpo-46235: Certain sequence multiplication operations like [0] * 1_000 are now faster due to reference-counting optimizations. Patch by Dennis Sweeney.

• bpo-46221: PREP_RERAISE_STAR no longer pushes lasti to the stack.

• bpo-46202: Remove POP_EXCEPT_AND_RERAISE and replace it by an equivalent sequence of other opcodes.

• bpo-46085: Fix iterator cache mechanism of OrderedDict.

• bpo-46055: Speed up shifting operation involving integers less than PyLong_BASE. Patch by Xinhang Xu.

• bpo-46110: Add a maximum recursion check to the PEG parser to avoid stack overflow. Patch by Pablo Galindo

• bpo-46107: Fix bug where ExceptionGroup.split() and ExceptionGroup.subgroup() did not copy the exception group’s __note__ field to the parts.

• bpo-45711: The interpreter state’s representation of handled exceptions (a.k.a exc_info, or _PyErr_StackItem) now has only the exc_value field, exc_type and exc_traceback have been removed as their values can be derived from exc_value.

• bpo-44525: Replace the four call bytecode instructions which one pre-call instruction and two call instructions.

  Removes CALL_FUNCTION, CALL_FUNCTION_KW, CALL_METHOD and CALL_METHOD_KW.

  Adds CALL_NO_KW and CALL_KW call instructions, and PRECALL_METHOD prefix for pairing with LOAD_METHOD.

• bpo-46039: Remove the YIELD_FROM instruction and replace it with the SEND instruction which performs the same operation, but without the loop.

• bpo-45635: The code called from _PyErr_Display() was refactored to improve error handling. It now exits immediately upon an unrecoverable error.

• bpo-46054: Fix parser error when parsing non-utf8 characters in source files. Patch by Pablo Galindo.

• bpo-46042: Improve the location of the caret in SyntaxError exceptions emitted by the symbol table. Patch by Pablo Galindo.

• bpo-46049: Ensure ._pth files work as intended on platforms other than Windows.

• bpo-46048: Fixes parsing of ._pth files on startup so that single-character paths are correctly read.

• bpo-37971: Fix a bug where the line numbers given in a traceback when a decorator application raised an exception were wrong.

• bpo-46031: Add POP_JUMP_IF_NOT_NONE and POP_JUMP_IF_NONE opcodes to speed up conditional jumps.

• bpo-45654: Deepfreeze runpy, patch by Kumar Aditya.

• bpo-46025: Fix a crash in the atexit module involving functions that unregister themselves before raising exceptions. Patch by Pablo Galindo.

• bpo-46000: Improve compatibility of the curses module with NetBSD curses.

• bpo-44525: Specialize the CALL_FUNCTION instruction for calls to builtin types with a single argument. Speeds up range(x), list(x), and specifically type(obj).

• bpo-42918: Fix bug where the built-in compile() function did not always raise a SyntaxError when passed multiple statements in ‘single’ mode. Patch by Weipeng Hong.

• bpo-45953: The main interpreter in _PyRuntimeState.interpreters is now statically allocated (as part of _PyRuntime). Likewise for the initial thread state of each interpreter. This means less allocation during runtime init, as well as better memory locality for these key state objects.

• bpo-45292: Complete the PEP 654 implementation: add except*.

• bpo-43413: Revert changes in set.__init__. Subclass of set needs to define a __init__() method if it defines a __new__() method with additional keyword parameters.

• bpo-43931: Added the Py_Version constant which bears the same value as PY_VERSION_HEX. Patch by Gabriele N. Tornetta.

Library

• bpo-46342: The @typing.final decorator now sets the __final__ attribute on the decorated object to allow runtime introspection. Patch by Jelle Zijlstra.

• bpo-46328: Added the sys.exception() method which returns the active exception instance.

• bpo-46307: Add string.Template.is_valid() and string.Template.get_identifiers() methods.

• bpo-46306: Assume that types.CodeType always has types.CodeType.co_firstlineno in doctest.

• bpo-40479: Fix hashlib usedforsecurity option to work correctly with OpenSSL 3.0.0 in FIPS mode.

• bpo-46070: Fix possible segfault when importing the asyncio module from different sub-interpreters in parallel. Patch by Erlend E. Aasland.

• bpo-46244: Removed __slots__ from typing.ParamSpec and typing.TypeVar. They served no purpose. Patch by Arie Bovenberg.

• bpo-46278: Reflect context argument in AbstractEventLoop.call_*() methods. Loop implementations already support it.

• bpo-46269: Remove special-casing of __new__ in enum.Enum.__dir__().

• bpo-46266: Improve day constants in calendar.

  Now all constants (MONDAY … SUNDAY) are documented, tested, and added to __all__.

• bpo-46257: Optimized the mean, variance, and stdev functions in the statistics module. If the input is an iterator, it is consumed in a single pass rather than eating memory by conversion to a list. The single pass algorithm is about twice as fast as the previous two pass code.

• bpo-41011: Added two new variables to pyvenv.cfg which is generated by venv module: executable for the executable and command for the command line used to create the environment.

• bpo-46239: Improve error message when importing asyncio.windows_events on non-Windows.

• bpo-46238: Reuse _winapi constants in asyncio.windows_events.

• bpo-46222: Adding SF_NOCACHE sendfile constant for FreeBSD for the posixmodule.

• bpo-37295: Add fast path for 0 <= k <= n <= 67 for math.comb().

• bpo-46176: Adding the MAP_STACK constant for the mmap module.

• bpo-43424: Deprecate webbrowser.MacOSXOSAScript._name and use name instead.

• bpo-45321: Added missing error codes to module xml.parsers.expat.errors.

• bpo-46125: Refactor tests to test traversable API directly. Includes changes from importlib 5.4.0.

• bpo-46118: Moved importlib.resources and its related functionality to a package.

• bpo-37578: Add include_hidden parameter to glob() and iglob() to match hidden files and directories when using special characters like *, **, ? and [].

• bpo-20369: concurrent.futures.wait() no longer blocks forever when given duplicate Futures. Patch by Kumar Aditya.

• bpo-46105: Honor spec when generating requirement specs with urls and extras (importlib_metadata 4.8.3).

• bpo-44893: EntryPoint objects are no longer tuples. Recommended means to access is by attribute (‘.name’, ‘.group’) or accessor (‘.load()’). Access by index is deprecated and will raise deprecation warning.

• bpo-22815: Print unexpected successes together with failures and errors in summary in unittest.TextTestResult.

• bpo-22047: Calling add_argument_group() on an argument group is deprecated. Calling add_argument_group() or add_mutually_exclusive_group() on a mutually exclusive group is deprecated.

  These features were never supported and do not always work correctly. The functions exist on the API by accident through inheritance and will be removed in the future.

• bpo-26952: argparse raises ValueError with clear message when trying to render usage for an empty mutually-exclusive group. Previously it raised a cryptic IndexError.

• bpo-45615: Functions in the traceback module raise TypeError rather than AttributeError when an exception argument is not of type BaseException.

• bpo-16594: Add allow allow_reuse_port flag in socketserver.

• bpo-27718: Fix help for the signal module. Some functions (e.g. signal() and getsignal()) were omitted.

• bpo-46032: The registry() method of functools.singledispatch() functions checks now the first argument or the first parameter annotation and raises a TypeError if it is not supported. Previously unsupported “types” were ignored (e.g. typing.List[int]) or caused an error at calling time (e.g. list[int]).

• bpo-46014: Add ability to use typing.Union and types.UnionType as dispatch argument to functools.singledispatch. Patch provided by Yurii Karabas.

• bpo-27062: Add __all__ to inspect, patch by Kumar Aditya.

• bpo-46018: Ensure that math.expm1() does not raise on underflow.

• bpo-46016: Adding F_DUP2FD and F_DUP2FD_CLOEXEC constants from FreeBSD into the fcntl module.

• bpo-45755: typing generic aliases now reveal the class attributes of the original generic class when passed to dir(). This was the behavior up to Python 3.6, but was changed in 3.7-3.9.

• bpo-45874: The empty query string, consisting of no query arguments, is now handled correctly in urllib.parse.parse_qsl. This caused problems before when strict parsing was enabled.

• bpo-44674: Change how dataclasses disallows mutable default values. It used to use a list of known types (list, dict, set). Now it disallows unhashable objects to be defaults. It’s using unhashability as a proxy for mutability. Patch by Eric V. Smith, idea by Raymond Hettinger.

• bpo-23882: Remove namespace package (PEP 420) support from unittest discovery. It was introduced in Python 3.4 but has been broken since Python 3.7.

• bpo-25066: Added a __repr__() method to multiprocessing.Event objects, patch by Kumar Aditya.

• bpo-45643: Added signal.SIGSTKFLT on platforms where this signal is defined.

• bpo-44092: Fetch across rollback no longer raises InterfaceError. Instead we leave it to the SQLite library to handle these cases. Patch by Erlend E. Aasland.

• bpo-42413: Replace concurrent.futures.TimeoutError and asyncio.TimeoutError with builtin TimeoutError, keep these names as deprecated aliases.

Documentation

• bpo-46196: Document method cmd.Cmd.columnize().

• bpo-46120: State that | is preferred for readability over Union in the typing docs.

• bpo-46109: Extracted importlib.resources and importlib.resources.abc documentation into separate files.

• bpo-19737: Update the documentation for the globals() function.

Tests

• bpo-46296: Add a test case for enum with _use_args_ == True and _member_type_ == object.

• bpo-46205: Fix hang in runtest_mp due to race condition

• bpo-46263: Fix test_capi on FreeBSD 14-dev: instruct jemalloc to not fill freed memory with junk byte.

• bpo-46262: Cover ValueError path in tests for enum.Flag._missing_().

• bpo-46150: Now fakename in test_pathlib.PosixPathTest.test_expanduser is checked to be non-existent.

• bpo-46129: Rewrite asyncio.locks tests with unittest.IsolatedAsyncioTestCase usage.

• bpo-23819: Fixed asyncio tests in python optimized mode. Patch by Kumar Aditya.

• bpo-46114: Fix test case for OpenSSL 3.0.1 version. OpenSSL 3.0 uses 0xMNN00PP0L.

Build

• bpo-44133: When Python is configured with --without-static-libpython, the Python static library (libpython.a) is no longer built. Patch by Victor Stinner.

• bpo-44133: When Python is built without --enable-shared, the python program is now linked to object files, rather than being linked to the Python static library (libpython.a), to make sure that all symbols are exported. Previously, the linker omitted some symbols like the Py_FrozenMain() function. Patch by Victor Stinner.

• bpo-40280: The configure script has a new option --with-emscripten-target to select browser or node as Emscripten build target.

• bpo-46315: Added and fixed #ifdef HAVE_FEATURE checks for functionality that is not available on WASI platform.

• bpo-45723: Fixed a regression in configure check for select.epoll().

• bpo-46263: configure no longer sets MULTIARCH on FreeBSD platforms.

• bpo-46106: Updated OpenSSL to 1.1.1m in Windows builds, macOS installer builds, and CI. Patch by Kumar Aditya.

• bpo-46088: Automatically detect or install bootstrap Python runtime when building from Visual Studio.

• bpo-46072: Add a –with-pystats configure option to turn on internal statistics gathering.

• bpo-40280: A new directory Tools/wasm contains WebAssembly-related helpers like config.site override for wasm32-emscripten, wasm assets generator to bundle the stdlib, and a README.

• bpo-46023: makesetup no longer builds extensions that have been marked as disabled. This allows users to disable modules in Modules/Setup.local.

• bpo-45949: Use pure Python freeze_module for all but importlib bootstrap files. --with-freeze-module configure option is no longer needed for cross builds.

Windows

• bpo-46217: Removed parameter that is unsupported on Windows 8.1 and early Windows 10 and may have caused build or runtime failures.

macOS

• bpo-40477: The Python Launcher app for macOS now properly launches scripts and, if necessary, the Terminal app when running on recent macOS releases.

C API

• bpo-46236: Fix a bug in PyFunction_GetAnnotations() that caused it to return a tuple instead of a dict.

• bpo-46140: PyBuffer_GetPointer(), PyBuffer_FromContiguous(), PyBuffer_ToContiguous() and PyMemoryView_FromBuffer() now take buffer info by const Py_buffer * instead of Py_buffer *, as they do not need mutability. PyBuffer_FromContiguous() also now takes the source buffer as const void *, and similarly PyBuffer_GetPointer() takes the strides as const Py_ssize_t *.

• bpo-45855: Document that the no_block argument to PyCapsule_Import() is a no-op now.

• bpo-45855: Replaced deprecated usage of PyImport_ImportModuleNoBlock() with PyImport_ImportModule() in stdlib modules. Patch by Kumar Aditya.

• bpo-46007: The PyUnicode_CHECK_INTERNED() macro has been excluded from the limited C API. It was never usable there, because it used internal structures which are not available in the limited C API. Patch by Victor Stinner.

Python 3.11.0 alpha 3

Release date: 2021-12-08

Core and Builtins

• bpo-46009: Restore behavior from 3.9 and earlier when sending non-None to newly started generator. In 3.9 this did not affect the state of the generator. In 3.10.0 and 3.10.1 gen_func().send(0) is equivalent to gen_func().throw(TypeError(...) which exhausts the generator. In 3.10.2 onward, the behavior has been reverted to that of 3.9.

• bpo-46004: Fix the SyntaxError location for errors involving for loops with invalid targets. Patch by Pablo Galindo

• bpo-45711: _PyErr_ChainStackItem() no longer normalizes exc_info (including setting the traceback on the exception instance) because exc_info is always normalized.

• bpo-45607: The __note__ field was added to BaseException. It is None by default but can be set to a string which is added to the exception’s traceback.

• bpo-45947: Place pointers to dict and values immediately before GC header. This reduces number of dependent memory loads to access either dict or values from 3 to 1.

• bpo-45915: is_valid_fd now uses faster fcntl(fd, F_GETFD) on Linux, macOS, and Windows.

• bpo-44530: Reverts a change to the code.__new__ audit event from an earlier prerelease.

• bpo-42268: Fail the configure step if the selected compiler doesn’t support memory sanitizer. Patch by Pablo Galindo

• bpo-45711: The three values of exc_info are now always consistent with each other. In particular, the type and traceback fields are now derived from the exception instance. This impacts the return values of sys.exc_info() and PyErr_GetExcInfo() if the exception instance is modified while the exception is handled, as well as PyErr_SetExcInfo(), which now ignores the type and traceback arguments provided to it.

• bpo-45727: Refine the custom syntax error that suggests that a comma may be missing to trigger only when the expressions are detected between parentheses or brackets. Patch by Pablo Galindo

• bpo-45885: Specialized the COMPARE_OP opcode using the PEP 659 machinery.

• bpo-45786: Allocate space for the interpreter frame in the frame object, to avoid an additional allocation when the frame object outlives the frame activation.

• bpo-45614: Fix traceback display for exceptions with invalid module name.

• bpo-45813: Fix crash when calling coro.cr_frame.clear() after coroutine has been freed.

• bpo-45811: Improve the tokenizer errors when encountering invisible control characters in the parser. Patch by Pablo Galindo

• bpo-45848: Allow the parser to obtain error lines directly from encoded files. Patch by Pablo Galindo

• bpo-45709: Restore behavior from 3.10 when tracing an exception raised within a with statement.

• bpo-44525: Adds new COPY_FREE_VARS opcode, to make copying of free variables from function to frame explicit. Helps optimization of calls to Python function.

• bpo-45829: Specialize BINARY_SUBSCR for classes with a __getitem__ method implemented in Python

• bpo-45826: Fixed a crash when calling .with_traceback(None) on NameError. This occurs internally in unittest.TestCase.assertRaises().

• bpo-45822: Fixed a bug in the parser that was causing it to not respect PEP 263 coding cookies when no flags are provided. Patch by Pablo Galindo

• bpo-45820: Fix a segfault when the parser fails without reading any input. Patch by Pablo Galindo

• bpo-45636: Simplify the implementation of BINARY_OP by indexing into an array of function pointers (rather than switching on the oparg).

• bpo-42540: Fix crash when os.fork() is called with an active non-default memory allocator.

• bpo-45738: Fix computation of error location for invalid continuation characters in the parser. Patch by Pablo Galindo.

• bpo-45636: Remove an existing “fast path” for old-style string formatting, since it no longer appears to have any measurable impact.

• bpo-45753: Make recursion checks a bit more efficient by tracking amount of calls left before overflow.

• bpo-45773: Fix a compiler hang when attempting to optimize certain jump patterns.

• bpo-45764: The parser now gives a better error message when leaving out the opening parenthesis ( after a def-statement:

  >>> def f:
    File "<stdin>", line 1
      def f:
           ^
  SyntaxError: expected '('
  

• bpo-45609: Specialized the STORE_SUBSCR opcode using the PEP 659 machinery.

• bpo-45636: Replace all numeric BINARY_* and INPLACE_* instructions with a single BINARY_OP implementation.

• bpo-45582: Path calculation (known as getpath) has been reimplemented as a frozen Python module. This should have no visible impact, but may affect calculation of all paths referenced in sys and sysconfig.

• bpo-45450: Improve the syntax error message for parenthesized arguments. Patch by Pablo Galindo.

Library

• bpo-27946: Fix possible crash when getting an attribute of class:xml.etree.ElementTree.Element simultaneously with replacing the attrib dict.

• bpo-45711: Make asyncio normalize exceptions as soon as they are captured with PyErr_Fetch(), and before they are stored as an exc_info triplet. This brings asyncio in line with the rest of the codebase, where an exc_info triplet is always normalized.

• bpo-23819: Replaced asserts with exceptions in asyncio, patch by Kumar Aditya.

• bpo-13236: unittest.TextTestResult and unittest.TextTestRunner flush now the output stream more often.

• bpo-45917: Added math.exp2():, which returns 2 raised to the power of x.

• bpo-37658: Fix issue when on certain conditions asyncio.wait_for() may allow a coroutine to complete successfully, but fail to return the result, potentially causing memory leaks or other issues.

• bpo-45876: Improve the accuracy of stdev() and pstdev() in the statistics module. When the inputs are floats or fractions, the output is a correctly rounded float

• bpo-44649: Handle dataclass(slots=True) with a field that has default a default value, but for which init=False.

• bpo-45803: Added missing kw_only parameter to dataclasses.make_dataclass().

• bpo-45837: The turtle.RawTurtle.settiltangle() is deprecated since Python 3.1, it now emits a deprecation warning and will be removed in Python 3.13.

  Use turtle.RawTurtle.tiltangle() instead.

  turtle.RawTurtle.tiltangle() was earlier incorrectly marked as deprecated, its docstring has been corrected.

  Patch by Hugo van Kemenade.

• bpo-45831: faulthandler can now write ASCII-only strings (like filenames and function names) with a single write() syscall when dumping a traceback. It reduces the risk of getting an unreadable dump when two threads or two processes dump a traceback to the same file (like stderr) at the same time. Patch by Victor Stinner.

• bpo-45828: sqlite C callbacks now use unraisable exceptions if callback tracebacks are enabled. Patch by Erlend E. Aasland.

• bpo-41735: Fix thread lock in zlib.Decompress.flush() method before PyObject_GetBuffer.

• bpo-45235: Reverted an argparse bugfix that caused regression in the handling of default arguments for subparsers. This prevented leaf level arguments from taking precedence over root level arguments.

• bpo-45754: Fix a regression in Python 3.11a1 and 3.11a2 where sqlite3 incorrectly would use SQLITE_LIMIT_LENGTH when checking SQL statement lengths. Now, SQLITE_LIMIT_SQL_LENGTH is used. Patch by Erlend E. Aasland.

• bpo-45766: Added proportional option to statistics.linear_regression().

• bpo-45765: In importlib.metadata, fix distribution discovery for an empty path.

• bpo-45757: Fix bug where dis produced an incorrect oparg when EXTENDED_ARG is followed by an opcode that does not use its argument.

• bpo-45644: In-place JSON file formatting using python3 -m json.tool infile infile now works correctly, previously it left the file empty. Patch by Chris Wesseling.

• bpo-45703: When a namespace package is imported before another module from the same namespace is created/installed in a different sys.path location while the program is running, calling the importlib.invalidate_caches() function will now also guarantee the new module is noticed.

• bpo-45535: Improve output of dir() with Enums.

• bpo-45664: Fix types.resolve_bases() and types.new_class() for types.GenericAlias instance as a base.

• bpo-45663: Fix dataclasses.is_dataclass() for dataclasses which are subclasses of types.GenericAlias.

• bpo-45662: Fix the repr of dataclasses.InitVar with a type alias to the built-in class, e.g. InitVar[list[int]].

• bpo-43137: Launch GNOME web browsers via gio tool instead of obsolete gvfs-open

• bpo-45429: On Windows, time.sleep() now uses a waitable timer which supports high-resolution timers. Patch by Dong-hee Na and Eryk Sun.

• bpo-37295: Optimize math.comb() and math.perm().

• bpo-45514: Deprecated legacy functions in importlib.resources.

• bpo-45507: Add tests for truncated/missing trailers in gzip.decompress implementation.

• bpo-45359: Implement PEP 585 for graphlib.TopologicalSorter.

• bpo-44733: Add max_tasks_per_child to concurrent.futures.ProcessPoolExecutor. This allows users to specify the maximum number of tasks a single process should execute before the process needs to be restarted.

• bpo-28806: Improve netrc library. netrc file no longer needs to contain all tokens. And if the login name is anonymous, security check is no longer need.

• bpo-43498: Avoid a possible “RuntimeError: dictionary changed size during iteration” when adjusting the process count of ProcessPoolExecutor.

• bpo-42158: Add MIME types for N-quads, N-triples, Notation3 and TriG to mimetypes.

• bpo-30533: Add inspect.getmembers_static() , it return all members without triggering dynamic lookup via the descriptor protocol. Patch by Weipeng Hong.

Documentation

• bpo-42238: make -C Doc suspicious will be removed soon in favor of make -C Doc check, mark it as deprecated.

• bpo-45840: Improve cross-references in the documentation for the data model.

• bpo-45640: Properly marked-up grammar tokens in the documentation are now clickable and take you to the definition of a given piece of grammar. Patch by Arthur Milchior.

• bpo-45788: Link doc for sys.prefix to sysconfig doc on installation paths.

• bpo-45772: socket.socket documentation is corrected to a class from a function.

• bpo-45392: Update the docstring of the type built-in to remove a redundant line and to mention keyword arguments for the constructor.

• bpo-45250: Update the documentation to note that CPython does not consistently require iterators to define __iter__.

• bpo-25381: In the extending chapter of the extending doc, update a paragraph about the global variables containing exception information.

• bpo-43905: Expanded astuple() and asdict() docs, warning about deepcopy being applied and providing a workaround.

Tests

• bpo-45695: Out-of-tree builds with a read-only source directory are now tested by CI.

• bpo-19460: Add new Test for Lib/email/mime/nonmultipart.py::MIMENonMultipart.

• bpo-45835: Fix race condition in test_queue tests with multiple “feeder” threads.

• bpo-45783: The test for the freeze tool now handles file moves and deletions.

• bpo-45745: Remove the --findleaks command line option of regrtest: use the --fail-env-changed option instead. Since Python 3.7, it was a deprecated alias to the --fail-env-changed option.

• bpo-45701: Add tests with tuple type with functools.lru_cache() to test_functools.

Build

• bpo-44035: CI now verifies that autoconf files have been regenerated with a current and unpatched autoconf package.

• bpo-45950: The build system now uses a _bootstrap_python interpreter for freezing and deepfreezing again. To speed up build process the build tools _bootstrap_python and _freeze_module are no longer build with LTO.

• bpo-45881: The configure script now accepts --with-build-python and --with-freeze-module options to make cross compiling easier.

• bpo-40280: Emscripten platform now uses .wasm suffix by default.

• bpo-40280: Disable unusable core extension modules on WASM/Emscripten targets.

• bpo-40280: configure now checks for socket shutdown function. The check makes it possible to disable SYS_shutdown with ac_cv_func_shutdown=no in CONFIG_SITE.

• bpo-40280: configure now checks for functions fork1, getegid, geteuid, getgid, getppid, getuid, opendir, pipe, system, wait, ttyname.

• bpo-33393: Update config.guess to 2021-06-03 and config.sub to 2021-08-14. Makefile now has an update-config target to make updating more convenient.

• bpo-45866: make regen-all now produces the same output when run from a directory other than the source tree: when building Python out of the source tree. pegen now strips directory of the “generated by pygen from <FILENAME>” header Patch by Victor Stinner.

• bpo-40280: configure now accepts machine wasm32 or wasm64 and OS wasi or emscripten for cross building, e.g. wasm32-unknown-emscripten, wasm32-wasi, or wasm32-unknown-wasi.

• bpo-41498: Python now compiles on platforms without sigset_t. Several functions in signal are not available when sigset_t is missing.

  Based on patch by Roman Yurchak for pyodide.

• bpo-45881: setup.py now uses CC from environment first to discover multiarch and cross compile paths.

• bpo-45886: The _freeze_module program path can now be overridden on the command line, e.g. make FREEZE_MODULE=../x86_64/Program/_freeze_module.

• bpo-45873: Get rid of the _bootstrap_python build step. The deepfreeze.py script is now run using $(PYTHON_FOR_REGEN) which can be Python 3.7 or newer (on Windows, 3.8 or newer).

• bpo-45847: Port builtin hashlib extensions to PY_STDLIB_MOD macro and addext().

• bpo-45723: Add autoconf helpers for saving and restoring environment variables:

  • SAVE_ENV: Save $CFLAGS, $LDFLAGS, $LIBS, and $CPPFLAGS.

  • RESTORE_ENV: Restore $CFLAGS, $LDFLAGS, $LIBS, and $CPPFLAGS.

  • WITH_SAVE_ENV([SCRIPT]): Run SCRIPT wrapped with SAVE_ENV and RESTORE_ENV.

  Patch by Erlend E. Aasland.

• bpo-45573: Mandatory core modules, that are required to bootstrap Python, are now in Modules/Setup.bootstrap.

• bpo-45573: configure now creates Modules/Setup.stdlib with conditionally enabled/disabled extension module lines. The file is not used, yet.

• bpo-45573: configure now uses a unified format to set state, compiler flags, and linker flags in Makefile. The new macro PY_STDLIB_MOD sets three variables that are consumed by Modules/Setup and setup.py.

• bpo-45816: Python now supports building with Visual Studio 2022 (MSVC v143, VS Version 17.0). Patch by Jeremiah Vivian.

• bpo-45800: Settings for pyexpat C extension are now detected by configure. The bundled expat library is built in Makefile.

• bpo-45798: Settings for decimal internal C extension are now detected by configure. The bundled libmpdec library is built in Makefile.

• bpo-45723: configure has a new option --with-pkg-config to disable or require pkg-config.

• bpo-45774: The build dependencies for sqlite3 are now detected by configure and pkg-config. Patch by Erlend E. Aasland.

• bpo-45763: The build dependencies for zlib, bz2, and lzma are now detected by configure.

• bpo-45747: gdbm and dbm build dependencies are now detected by configure.

• bpo-45743: On macOS, the build system no longer passes search_paths_first to the linker. The flag has been the default since Xcode 4 / macOS 10.6.

• bpo-45723: configure.ac is now compatible with autoconf 2.71. Deprecated checks STDC_HEADERS and AC_HEADER_TIME have been removed.

• bpo-45723: configure now prints a warning when pkg-config is missing.

• bpo-45731: configure --enable-loadable-sqlite-extensions is now handled by new PY_SQLITE_ENABLE_LOAD_EXTENSION macro instead of logic in setup.py.

• bpo-45723: configure.ac now uses custom helper macros and AC_CACHE_CHECK to simplify and speed up configure runs.

• bpo-45696: Skip the marshal step for frozen modules by generating C code that produces a set of ready-to-use code objects. This speeds up startup time by another 10% or more.

• bpo-45561: Run smelly.py tool from $(srcdir).

Windows

• bpo-46105: Fixed calculation of sys.path in a venv on Windows.

• bpo-45901: When installed through the Microsoft Store and set as the default app for *.py files, command line arguments will now be passed to Python when invoking a script without explicitly launching Python (that is, script.py args rather than python script.py args).

• bpo-45616: Fix Python Launcher’s ability to distinguish between versions 3.1 and 3.10 when either one is explicitly requested. Previously, 3.1 would be used if 3.10 was requested but not installed, and 3.10 would be used if 3.1 was requested but 3.10 was installed.

• bpo-45850: Implement changes to build with deep-frozen modules on Windows. Note that we now require Python 3.10 as the “bootstrap” or “host” Python.

• bpo-45732: Updates bundled Tcl/Tk to 8.6.12.

• bpo-45720: Internal reference to shlwapi.dll was dropped to help improve startup time. This DLL will no longer be loaded at the start of every Python process.

macOS

• bpo-45732: Update python.org macOS installer to use Tcl/Tk 8.6.12.

C API

• bpo-39026: Fix Python.h to build C extensions with Xcode: remove a relative include from Include/cpython/pystate.h.

Python 3.11.0 alpha 2

Release date: 2021-11-05

Core and Builtins

• bpo-45716: Improve the SyntaxError message when using True, None or False as keywords in a function call. Patch by Pablo Galindo.

• bpo-45688: sys.stdlib_module_names now contains the macOS-specific module _scproxy.

• bpo-45379: Clarify ImportError message when we try to explicitly import a frozen module but frozen modules are disabled.

• bpo-44525: Specialize simple calls to Python functions (no starargs, keyowrd dict, or closure)

• bpo-45530: Cases of sorting using tuples as keys may now be significantly faster in some cases. Patch by Tim Peters.

  The order of the result may differ from earlier releases if the tuple elements don’t define a total ordering (see Value comparisons for information on total ordering). It’s generally true that the result of sorting simply isn’t well-defined in the absence of a total ordering on list elements.

• bpo-45526: In obmalloc, set ADDRESS_BITS to not ignore any bits (ignored 16 before). That is safer in the case that the kernel gives user-space virtual addresses that span a range greater than 48 bits.

• bpo-30570: Fixed a crash in issubclass() from infinite recursion when searching pathological __bases__ tuples.

• bpo-45521: Fix a bug in the obmalloc radix tree code. On 64-bit machines, the bug causes the tree to hold 46-bits of virtual addresses, rather than the intended 48-bits.

• bpo-45494: Fix parser crash when reporting errors involving invalid continuation characters. Patch by Pablo Galindo.

• bpo-45445: Python now fails to initialize if it finds an invalid -X option in the command line. Patch by Pablo Galindo.

• bpo-45340: Object attributes are held in an array instead of a dictionary. An object’s dictionary are created lazily, only when needed. Reduces the memory consumption of a typical Python object by about 30%. Patch by Mark Shannon.

• bpo-45408: Fix a crash in the parser when reporting tokenizer errors that occur at the same time unclosed parentheses are detected. Patch by Pablo Galindo.

• bpo-29410: Add SipHash13 for string hash algorithm and use it by default.

• bpo-45385: Fix reference leak from descr_check. Patch by Dong-hee Na.

• bpo-45367: Specialized the BINARY_MULTIPLY opcode to BINARY_MULTIPLY_INT and BINARY_MULTIPLY_FLOAT using the PEP 659 machinery.

• bpo-21736: Frozen stdlib modules now have __file__ to the .py file they would otherwise be loaded from, if possible. For packages, __path__ now has the correct entry instead of being an empty list, which allows unfrozen submodules to be imported. These are set only if the stdlib directory is known when the runtime is initialized. Note that the file at __file__ is not guaranteed to exist. None of this affects non-stdlib frozen modules nor, for now, frozen modules imported using PyImport_ImportFrozenModule(). Also, at the moment co_filename is not updated for the module.

• bpo-45020: For frozen stdlib modules, record the original module name as module.__spec__.loader_state.origname. If the value is different than module.__spec__.name then the module was defined as an alias in Tools/scripts/freeze_modules.py. If it is None then the module comes from a source file outside the stdlib.

• bpo-45324: In FrozenImporter.find_spec(), we now preserve the information needed in exec_module() to load the module. This change mostly impacts internal details, rather than changing the importer’s behavior.

• bpo-45292: Implement PEP 654. Add ExceptionGroup and BaseExceptionGroup. Update traceback display code.

• bpo-40116: Change to the implementation of split dictionaries. Classes where the instances differ either in the exact set of attributes, or in the order in which those attributes are set, can still share keys. This should have no observable effect on users of Python or the C-API. Patch by Mark Shannon.

• bpo-44050: Extensions that indicate they use global state (by setting m_size to -1) can again be used in multiple interpreters. This reverts to behavior of Python 3.8.

• bpo-44525: Setup initial specialization infrastructure for the CALL_FUNCTION opcode. Implemented initial specializations for C function calls:

  • CALL_FUNCTION_BUILTIN_O for METH_O flag.

  • CALL_FUNCTION_BUILTIN_FAST for METH_FASTCALL flag without keywords.

  • CALL_FUNCTION_LEN for len(o).

  • CALL_FUNCTION_ISINSTANCE for isinstance(o, t).

• bpo-44511: Improve the generated bytecode for class and mapping patterns.

• bpo-43706: Speed up calls to enumerate() by using the PEP 590 vectorcall calling convention. Patch by Dong-hee Na.

Library

• bpo-45679: Fix caching of multi-value typing.Literal. Literal[True, 2] is no longer equal to Literal[1, 2].

• bpo-42064: Convert sqlite3 to multi-phase initialisation (PEP 489). Patches by Erlend E. Aasland.

• bpo-45438: Fix typing.Signature string representation for generic builtin types.

• bpo-45613: sqlite3 now sets sqlite3.threadsafety based on the default threading mode the underlying SQLite library has been compiled with. Patch by Erlend E. Aasland.

• bpo-45574: Fix warning about print_escape being unused.

• bpo-45581: sqlite3.connect() now correctly raises MemoryError if the underlying SQLite API signals memory error. Patch by Erlend E. Aasland.

• bpo-45557: pprint.pprint() now handles underscore_numbers correctly. Previously it was always setting it to False.

• bpo-44019: Add operator.call() to operator.__all__. Patch by Kreusada.

• bpo-42174: shutil.get_terminal_size() now falls back to sane values if the column or line count are 0.

• bpo-35673: Improve the introspectability of the __loader__ attribute for namespace packages. importlib.machinery.NamespaceLoader is now public, and implements the importlib.abc.InspectLoader interface. _NamespaceLoader is kept for backward compatibility.

• bpo-45515: Add references to zoneinfo in the datetime documentation, mostly replacing outdated references to dateutil.tz. Change by Paul Ganssle.

• bpo-45475: Reverted optimization of iterating gzip.GzipFile, bz2.BZ2File, and lzma.LZMAFile (see bpo-43787) because it caused regression when user iterate them without having reference of them. Patch by Inada Naoki.

• bpo-45489: Update ForwardRef to support | operator. Patch by Dong-hee Na.

• bpo-42222: Removed deprecated support for float arguments in randrange().

• bpo-45428: Fix a regression in py_compile when reading filenames from standard input.

• bpo-45467: Fix incremental decoder and stream reader in the “raw-unicode-escape” codec. Previously they failed if the escape sequence was split.

• bpo-45461: Fix incremental decoder and stream reader in the “unicode-escape” codec. Previously they failed if the escape sequence was split.

• bpo-45239: Fixed email.utils.parsedate_tz() crashing with UnboundLocalError on certain invalid input instead of returning None. Patch by Ben Hoyt.

• bpo-45417: Fix quadratic behaviour in the enum module: Creation of enum classes with a lot of entries was quadratic.

• bpo-45249: Fix the behaviour of traceback.print_exc() when displaying the caret when the end_offset in the exception is set to 0. Patch by Pablo Galindo

• bpo-45416: Fix use of asyncio.Condition with explicit asyncio.Lock objects, which was a regression due to removal of explicit loop arguments. Patch by Joongi Kim.

• bpo-20028: Empty escapechar/quotechar is not allowed when initializing csv.Dialect. Patch by Vajrasky Kok and Dong-hee Na.

• bpo-44904: Fix bug in the doctest module that caused it to fail if a docstring included an example with a classmethod property. Patch by Alex Waygood.

• bpo-45406: Make inspect.getmodule() catch FileNotFoundError raised by :’func:inspect.getabsfile, and return None to indicate that the module could not be determined.

• bpo-45411: Add extensions for files containing subtitles - .srt & .vtt - to the mimetypes.py module.

• bpo-10716: Migrated pydoc to HTML5 (without changing the look of it). Side effect is to update xmlrpc’s ServerHTMLDoc which now uses the CSS too. cgitb now relies less on pydoc (as it can’t use the CSS file).

• bpo-27580: Add support of null characters in csv.

• bpo-45262: Prevent use-after-free in asyncio. Make sure the cached running loop holder gets cleared on dealloc to prevent use-after-free in get_running_loop

• bpo-45386: Make xmlrpc.client more robust to C runtimes where the underlying C strftime function results in a ValueError when testing for year formatting options.

• bpo-20028: Improve error message of csv.Dialect when initializing. Patch by Vajrasky Kok and Dong-hee Na.

• bpo-45343: Update bundled pip to 21.2.4 and setuptools to 58.1.0

• bpo-45328: Fixed http.client.HTTPConnection to work properly in OSs that don’t support the TCP_NODELAY socket option.

• bpo-45243: Add setlimit() and getlimit() to sqlite3.Connection for setting and getting SQLite limits by connection basis. Patch by Erlend E. Aasland.

• bpo-45320: Removed from the inspect module:

  • the getargspec function, deprecated since Python 3.0;

    use inspect.signature() or inspect.getfullargspec() instead.

  • the formatargspec function, deprecated since Python 3.5; use the inspect.signature() function and Signature object directly.

  • the undocumented Signature.from_callable and Signature.from_function functions, deprecated since Python 3.5; use the Signature.from_callable() method instead.

  Patch by Hugo van Kemenade.

• bpo-45192: Fix the tempfile._infer_return_type function so that the dir argument of the tempfile functions accepts an object implementing the os.PathLike protocol.

  Patch by Kyungmin Lee.

• bpo-45160: When tracing a tkinter variable used by a ttk OptionMenu, callbacks are no longer made twice.

• bpo-25625: Added non parallel-safe chdir() context manager to change the current working directory and then restore it on exit. Simple wrapper around chdir().

• bpo-24139: Add support for SQLite extended result codes in sqlite3.Error. Patch by Erlend E. Aasland.

• bpo-24444: Fixed an error raised in argparse help display when help for an option is set to 1+ blank spaces or when choices arg is an empty container.

• bpo-44547: Implement Fraction.__int__, so that a fractions.Fraction instance f passes an isinstance(f, typing.SupportsInt) check.

• bpo-40321: Adds support for HTTP 308 redirects to urllib. See RFC 7538 for details. Patch by Jochem Schulenklopper.

• bpo-10572: Move sqlite3 tests to /Lib/test/test_sqlite3. Patch by Erlend E. Aasland.

• bpo-41374: Ensure that socket.TCP_* constants are exposed on Cygwin 3.1.6 and greater.

• bpo-35970: Add help flag to the base64 module’s command line interface. Patch contributed by Robert Kuska.

Documentation

• bpo-45726: Improve documentation for functools.singledispatch() and functools.singledispatchmethod.

• bpo-45680: Amend the docs on GenericAlias objects to clarify that non-container classes can also implement __class_getitem__. Patch contributed by Alex Waygood.

• bpo-45618: Update Sphinx version used to build the documentation to 4.2.0. Patch by Maciej Olko.

• bpo-45655: Add a new “relevant PEPs” section to the top of the documentation for the typing module. Patch by Alex Waygood.

• bpo-45604: Add level argument to multiprocessing.log_to_stderr function docs.

• bpo-45516: Add protocol description to the importlib.abc.TraversableResources documentation.

• bpo-45464: Mention in the documentation of Built-in Exceptions that inheriting from multiple exception types in a single subclass is not recommended due to possible memory layout incompatibility.

• bpo-45449: Add note about PEP 585 in collections.abc.

• bpo-45516: Add protocol description to the importlib.abc.Traversable documentation.

• bpo-20692: Add Programming FAQ entry explaining that int literal attribute access requires either a space after or parentheses around the literal.

Tests

• bpo-45678: Add tests for scenarios in which functools.singledispatchmethod is stacked on top of a method that has already been wrapped by two other decorators. Patch by Alex Waygood.

• bpo-45578: Add tests for dis.distb()

• bpo-45678: Add tests to ensure that functools.singledispatchmethod correctly wraps the attributes of the target function.

• bpo-45668: PGO tests now pass when Python is built without test extension modules.

• bpo-45577: Add subtests for all pickle protocols in test_zoneinfo.

• bpo-45566: Fix test_frozen_pickle in test_dataclasses to check all pickle versions.

• bpo-43592: test.libregrtest now raises the soft resource limit for the maximum number of file descriptors when the default is too low for our test suite as was often the case on macOS.

• bpo-39679: Add more test cases for @functools.singledispatchmethod when combined with @classmethod or @staticmethod.

• bpo-45410: When libregrtest spawns a worker process, stderr is now written into stdout to keep messages order. Use a single pipe for stdout and stderr, rather than two pipes. Previously, messages were out of order which made analysis of buildbot logs harder Patch by Victor Stinner.

• bpo-45402: Fix test_tools.test_sundry() when Python is built out of tree: fix how the freeze_modules.py tool locates the _freeze_module program. Patch by Victor Stinner.

• bpo-45403: Fix test_sys.test_stdlib_dir() when Python is built outside the source tree: compare normalized paths. Patch by Victor Stinner.

• bpo-45400: Fix test_name_error_suggestions_do_not_trigger_for_too_many_locals() of test_exceptions if a directory name contains “a1” (like “Python-3.11.0a1”): use a stricter regular expression. Patch by Victor Stinner.

Build

• bpo-43158: setup.py now uses values from configure script to build the _uuid extension module. Configure now detects util-linux’s libuuid, too.

• bpo-45666: Fix warning of swprintf and %s usage in _testembed.c

• bpo-45548: Modules/Setup and Modules/makesetup have been improved. The Setup file now contains working rules for all extensions. Outdated comments have been removed. Rules defined by makesetup track dependencies correctly.

• bpo-45548: The math and cmath implementation now require a C99 compatible libm and no longer ship with workarounds for missing acosh, asinh, atanh, expm1, and log1p functions.

• bpo-45595: setup.py and makesetup now track build dependencies on all Python header files and module specific header files.

• bpo-45571: Modules/Setup now use PY_CFLAGS_NODIST instead of PY_CFLAGS to compile shared modules.

• bpo-45570: pyexpat and _elementtree no longer define obsolete macros HAVE_EXPAT_CONFIG_H and USE_PYEXPAT_CAPI. XML_POOR_ENTROPY is now defined in expat_config.h.

• bpo-43974: setup.py no longer defines Py_BUILD_CORE_MODULE. Instead every module, that uses the internal API, defines the macro.

• bpo-45548: Fill in missing entries in Modules/Setup.

• bpo-45532: Update sys.version to use main as fallback information. Patch by Jeong YunWon.

• bpo-45536: The configure script now checks whether OpenSSL headers and libraries provide required APIs. Most common APIs are verified. The check detects outdated or missing OpenSSL. Failures do not stop configure.

• bpo-45221: Fixed regression in handling of LDFLAGS and CPPFLAGS options where argparse.parse_known_args() could interpret an option as one of the built-in command line argument, for example -h for help.

• bpo-45440: Building Python now requires a C99 <math.h> header file providing the following functions: copysign(), hypot(), isfinite(), isinf(), isnan(), round(). Patch by Victor Stinner.

• bpo-45405: Prevent internal configure error when running configure with recent versions of non-Apple clang. Patch by David Bohman.

• bpo-45433: Avoid linking libpython with libcrypt.

Windows

• bpo-43652: Update Tcl/Tk to 8.6.11, actually this time. The previous update incorrectly included 8.6.10.

• bpo-45337: venv now warns when the created environment may need to be accessed at a different path, due to redirections, links or junctions. It also now correctly installs or upgrades components when the alternate path is required.

• bpo-43851: Build SQLite SQLITE_OMIT_AUTOINIT on Windows. Patch by Erlend E. Aasland.

macOS

• bpo-44828: Avoid tkinter file dialog failure on macOS 12 Monterey when using the Tk 8.6.11 provided by python.org macOS installers. Patch by Marc Culler of the Tk project.

IDLE

• bpo-45495: Add context keywords ‘case’ and ‘match’ to completions list.

C API

• bpo-29103: PyType_FromSpec* now copies the class name from the spec to a buffer owned by the class, so the original can be safely deallocated. Patch by Petr Viktorin.

• bpo-45522: The internal freelists for frame, float, list, dict, async generators, and context objects can now be disabled.

• bpo-35134: Exclude PyWeakref_GET_OBJECT() from the limited C API. It never worked since the PyWeakReference structure is opaque in the limited C API.

• bpo-35081: Move the interpreteridobject.h header file from Include/ to Include/internal/. It only provides private functions. Patch by Victor Stinner.

• bpo-35134: The non-limited API files cellobject.h, classobject.h, context.h, funcobject.h, genobject.h and longintrepr.h have been moved to the Include/cpython directory. Moreover, the eval.h header file was removed. These files must not be included directly, as they are already included in Python.h: Include Files. If they have been included directly, consider including Python.h instead. Patch by Victor Stinner.

• bpo-45474: The following items are no longer available when Py_LIMITED_API is defined:

  • PyMarshal_WriteLongToFile()

  • PyMarshal_WriteObjectToFile()

  • PyMarshal_ReadObjectFromString()

  • PyMarshal_WriteObjectToString()

  • the Py_MARSHAL_VERSION macro

  These are not part of the limited API.

  Patch by Victor Stinner.

• bpo-45434: Remove the pystrhex.h header file. It only contains private functions. C extensions should only include the main <Python.h> header file. Patch by Victor Stinner.

• bpo-45440: Remove the Py_FORCE_DOUBLE() macro. It was used by the Py_IS_INFINITY() macro. Patch by Victor Stinner.

• bpo-45434: <Python.h> no longer includes the header files <stdlib.h>, <stdio.h>, <errno.h> and <string.h> when the Py_LIMITED_API macro is set to 0x030b0000 (Python 3.11) or higher. C extensions should explicitly include the header files after #include <Python.h>. Patch by Victor Stinner.

• bpo-41123: Remove Py_UNICODE_COPY() and Py_UNICODE_FILL() macros, deprecated since Python 3.3. Use PyUnicode_CopyCharacters() or memcpy() (wchar_t* string), and PyUnicode_Fill() functions instead. Patch by Victor Stinner.

• bpo-45412: Remove the following math macros using the errno variable:

  • Py_ADJUST_ERANGE1()

  • Py_ADJUST_ERANGE2()

  • Py_OVERFLOWED()

  • Py_SET_ERANGE_IF_OVERFLOW()

  • Py_SET_ERRNO_ON_MATH_ERROR()

  Patch by Victor Stinner.

• bpo-45395: Custom frozen modules (the array set to PyImport_FrozenModules) are now treated as additions, rather than replacing all the default frozen modules. Frozen stdlib modules can still be disabled by setting the “code” field of the custom array entry to NULL.

• bpo-43760: Add new PyThreadState_EnterTracing(), and PyThreadState_LeaveTracing() functions to the limited C API to suspend and resume tracing and profiling. Patch by Victor Stinner.

• bpo-44220: PyStructSequence_UnnamedField is added to the Stable ABI.

Python 3.11.0 alpha 1

Release date: 2021-10-05

Security

• bpo-42278: Replaced usage of tempfile.mktemp() with TemporaryDirectory to avoid a potential race condition.

• bpo-44600: Fix incorrect line numbers while tracing some failed patterns in match statements. Patch by Charles Burkland.

• bpo-41180: Add auditing events to the marshal module, and stop raising code.__init__ events for every unmarshalled code object. Directly instantiated code objects will continue to raise an event, and audit event handlers should inspect or collect the raw marshal data. This reduces a significant performance overhead when loading from .pyc files.

• bpo-44394: Update the vendored copy of libexpat to 2.4.1 (from 2.2.8) to get the fix for the CVE-2013-0340 “Billion Laughs” vulnerability. This copy is most used on Windows and macOS.

• bpo-43124: Made the internal putcmd function in smtplib sanitize input for presence of \r and \n characters to avoid (unlikely) command injection.

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

Core and Builtins

• bpo-43760: The number of hardware branches per instruction dispatch is reduced from two to one by adding a special instruction for tracing. Patch by Mark Shannon.

• bpo-45061: Add a deallocator to the bool type to detect refcount bugs in C extensions which call Py_DECREF(Py_True) or Py_DECREF(Py_False) by mistake. Detect also refcount bugs when the empty tuple singleton or the Unicode empty string singleton is destroyed by mistake. Patch by Victor Stinner.

• bpo-24076: sum() was further optimised for summing up single digit integers.

• bpo-45190: Update Unicode databases to Unicode 14.0.0.

• bpo-45167: Fix deepcopying of types.GenericAlias objects.

• bpo-45155: int.to_bytes() and int.from_bytes() now take a default value of "big" for the byteorder argument. int.to_bytes() also takes a default value of 1 for the length argument.

• bpo-44219: Release the GIL while performing isatty system calls on arbitrary file descriptors. In particular, this affects os.isatty(), os.device_encoding() and io.TextIOWrapper. By extension, io.open() in text mode is also affected. This change solves a deadlock in os.isatty(). Patch by Vincent Michel in bpo-44219.

• bpo-44959: Added fallback to extension modules with ‘.sl’ suffix on HP-UX

• bpo-45121: Fix issue where Protocol.__init__ raises RecursionError when it’s called directly or via super(). Patch provided by Yurii Karabas.

• bpo-44348: The deallocator function of the BaseException type now uses the trashcan mechanism to prevent stack overflow. For example, when a RecursionError instance is raised, it can be linked to another RecursionError through the __context__ attribute or the __traceback__ attribute, and then a chain of exceptions is created. When the chain is destroyed, nested deallocator function calls can crash with a stack overflow if the chain is too long compared to the available stack memory. Patch by Victor Stinner.

• bpo-45123: Fix PyAiter_Check to only check for the __anext__ presence (not for __aiter__). Rename PyAiter_Check to PyAIter_Check, PyObject_GetAiter -> PyObject_GetAIter.

• bpo-1514420: Interpreter no longer attempts to open files with names in angle brackets (like “<string>” or “<stdin>”) when formatting an exception.

• bpo-41031: Match C and Python code formatting of unprintable exceptions and exceptions in the __main__ module.

• bpo-37330: open(), io.open(), codecs.open() and fileinput.FileInput no longer accept 'U' (“universal newline”) in the file mode. This flag was deprecated since Python 3.3. Patch by Victor Stinner.

• bpo-45083: When the interpreter renders an exception, its name now has a complete qualname. Previously only the class name was concatenated to the module name, which sometimes resulted in an incorrect full name being displayed.

  (This issue impacted only the C code exception rendering, the traceback module was using qualname already).

• bpo-34561: List sorting now uses the merge-ordering strategy from Munro and Wild’s powersort(). Unlike the former strategy, this is provably near-optimal in the entropy of the distribution of run lengths. Most uses of list.sort() probably won’t see a significant time difference, but may see significant improvements in cases where the former strategy was exceptionally poor. However, as these are all fast linear-time approximations to a problem that’s inherently at best quadratic-time to solve truly optimally, it’s also possible to contrive cases where the former strategy did better.

• bpo-45056: Compiler now removes trailing unused constants from co_consts.

• bpo-45020: Add a new command line option, “-X frozen_modules=[on|off]” to opt out of (or into) using optional frozen modules. This defaults to “on” (or “off” if it’s running out of the source tree).

• bpo-45012: In posix, release GIL during stat(), lstat(), and fstatat() syscalls made by os.DirEntry.stat(). Patch by Stanisław Skonieczny.

• bpo-45018: Fixed pickling of range iterators that iterated for over 2**32 times.

• bpo-45000: A SyntaxError is now raised when trying to delete __debug__. Patch by Dong-hee Na.

• bpo-44963: Implement send() and throw() methods for anext_awaitable objects. Patch by Pablo Galindo.

• bpo-44962: Fix a race in WeakKeyDictionary, WeakValueDictionary and WeakSet when two threads attempt to commit the last pending removal. This fixes asyncio.create_task and fixes a data loss in asyncio.run where shutdown_asyncgens is not run

• bpo-24234: Implement the __bytes__() special method on the bytes type, so a bytes object b passes an isinstance(b, typing.SupportsBytes) check.

• bpo-24234: Implement the __complex__() special method on the complex type, so a complex number z passes an isinstance(z, typing.SupportsComplex) check.

• bpo-44954: Fixed a corner case bug where the result of float.fromhex('0x.8p-1074') was rounded the wrong way.

• bpo-44947: Refine the syntax error for trailing commas in import statements. Patch by Pablo Galindo.

• bpo-44945: Specialize the BINARY_ADD instruction using the PEP 659 machinery. Adds five new instructions:

  • BINARY_ADD_ADAPTIVE

  • BINARY_ADD_FLOAT

  • BINARY_ADD_INT

  • BINARY_ADD_UNICODE

  • BINARY_ADD_UNICODE_INPLACE_FAST

• bpo-44929: Fix some edge cases of enum.Flag string representation in the REPL. Patch by Pablo Galindo.

• bpo-44914: Class version tags are no longer recycled.

  This means that a version tag serves as a unique identifier for the state of a class. We rely on this for effective specialization of the LOAD_ATTR and other instructions.

• bpo-44698: Restore behaviour of complex exponentiation with integer-valued exponent of type float or complex.

• bpo-44895: A debug variable PYTHONDUMPREFSFILE is added for creating a dump file which is generated by --with-trace-refs. Patch by Dong-hee Na.

• bpo-44900: Add five superinstructions for PEP 659 quickening:

  • LOAD_FAST LOAD_FAST

  • STORE_FAST LOAD_FAST

  • LOAD_FAST LOAD_CONST

  • LOAD_CONST LOAD_FAST

  • STORE_FAST STORE_FAST

• bpo-44889: Initial implementation of adaptive specialization of LOAD_METHOD. The following specialized forms were added:

  • LOAD_METHOD_CACHED

  • LOAD_METHOD_MODULE

  • LOAD_METHOD_CLASS

• bpo-44890: Specialization stats are always collected in debug builds.

• bpo-44885: Correct the ast locations of f-strings with format specs and repeated expressions. Patch by Pablo Galindo

• bpo-44878: Remove the loop from the bytecode interpreter. All instructions end with a DISPATCH macro, so the loop is now redundant.

• bpo-44878: Remove switch statement for interpreter loop when using computed gotos. This makes sure that we only have one dispatch table in the interpreter.

• bpo-44874: Deprecate the old trashcan macros (Py_TRASHCAN_SAFE_BEGIN/Py_TRASHCAN_SAFE_END). They should be replaced by the new macros Py_TRASHCAN_BEGIN and Py_TRASHCAN_END.

• bpo-44872: Use new trashcan macros (Py_TRASHCAN_BEGIN/END) in frameobject.c instead of the old ones (Py_TRASHCAN_SAFE_BEGIN/END).

• bpo-33930: Fix segmentation fault with deep recursion when cleaning method objects. Patch by Augusto Goulart and Pablo Galindo.

• bpo-25782: Fix bug where PyErr_SetObject hangs when the current exception has a cycle in its context chain.

• bpo-44856: Fix reference leaks in the error paths of update_bases() and __build_class__. Patch by Pablo Galindo.

• bpo-44826: Initial implementation of adaptive specialization of STORE_ATTR

  Three specialized forms of STORE_ATTR are added:

  • STORE_ATTR_SLOT

  • STORE_ATTR_SPLIT_KEYS

  • STORE_ATTR_WITH_HINT

• bpo-44838: Fixed a bug that was causing the parser to raise an incorrect custom SyntaxError for invalid ‘if’ expressions. Patch by Pablo Galindo.

• bpo-44821: Create instance dictionaries (__dict__) eagerly, to improve regularity of object layout and assist specialization.

• bpo-44792: Improve syntax errors for if expressions. Patch by Miguel Brito

• bpo-34013: Generalize the invalid legacy statement custom error message (like the one generated when “print” is called without parentheses) to include more generic expressions. Patch by Pablo Galindo

• bpo-44732: Rename types.Union to types.UnionType.

• bpo-44725: Expose specialization stats in python via _opcode.get_specialization_stats().

• bpo-44717: Improve AttributeError on circular imports of submodules.

• bpo-44698: Fix undefined behaviour in complex object exponentiation.

• bpo-44653: Support typing types in parameter substitution in the union type.

• bpo-44676: Add ability to serialise types.Union objects. Patch provided by Yurii Karabas.

• bpo-44633: Parameter substitution of the union type with wrong types now raises TypeError instead of returning NotImplemented.

• bpo-44661: Update property_descr_set to use vectorcall if possible. Patch by Dong-hee Na.

• bpo-44662: Add __module__ to types.Union. This also fixes types.Union issues with typing.Annotated. Patch provided by Yurii Karabas.

• bpo-44655: Include the name of the type in unset __slots__ attribute errors. Patch by Pablo Galindo

• bpo-44655: Don’t include a missing attribute with the same name as the failing one when offering suggestions for missing attributes. Patch by Pablo Galindo

• bpo-44646: Fix the hash of the union type: it no longer depends on the order of arguments.

• bpo-44636: Collapse union of equal types. E.g. the result of int | int is now int. Fix comparison of the union type with non-hashable objects. E.g. int | str == {} no longer raises a TypeError.

• bpo-44611: On Windows, os.urandom(): uses BCryptGenRandom API instead of CryptGenRandom API which is deprecated from Microsoft Windows API. Patch by Dong-hee Na.

• bpo-44635: Convert None to type(None) in the union type constructor.

• bpo-26280: Implement adaptive specialization for BINARY_SUBSCR

  Three specialized forms of BINARY_SUBSCR are added:

  • BINARY_SUBSCR_LIST_INT

  • BINARY_SUBSCR_TUPLE_INT

  • BINARY_SUBSCR_DICT

• bpo-44589: Mapping patterns in match statements with two or more equal literal keys will now raise a SyntaxError at compile-time.

• bpo-44606: Fix __instancecheck__ and __subclasscheck__ for the union type.

• bpo-42073: The @classmethod decorator can now wrap other classmethod-like descriptors.

• bpo-41972: Tuned the string-searching algorithm of fastsearch.h to have a shorter inner loop for most cases.

• bpo-44590: All necessary data for executing a Python function (local variables, stack, etc) is now kept in a per-thread stack. Frame objects are lazily allocated on demand. This increases performance by about 7% on the standard benchmark suite. Introspection and debugging are unaffected as frame objects are always available when needed. Patch by Mark Shannon.

• bpo-44584: The threading debug (PYTHONTHREADDEBUG environment variable) is deprecated in Python 3.10 and will be removed in Python 3.12. This feature requires a debug build of Python. Patch by Victor Stinner.

• bpo-43895: An obsolete internal cache of shared object file handles added in 1995 that attempted, but did not guarantee, that a .so would not be dlopen’ed twice to work around flaws in mid-1990s posix-ish operating systems has been removed from dynload_shlib.c.

• bpo-44490: typing now searches for type parameters in types.Union objects. get_type_hints will also properly resolve annotations with nested types.Union objects. Patch provided by Yurii Karabas.

• bpo-43950: Code objects can now provide the column information for instructions when available. This is levaraged during traceback printing to show the expressions responsible for errors.

  Contributed by Pablo Galindo, Batuhan Taskaya and Ammar Askar as part of PEP 657.

• bpo-44562: Remove uses of PyObject_GC_Del() in error path when initializing types.GenericAlias.

• bpo-41486: Fix a memory consumption and copying performance regression in earlier 3.10 beta releases if someone used an output buffer larger than 4GiB with zlib.decompress on input data that expands that large.

• bpo-43908: Heap types with the Py_TPFLAGS_IMMUTABLETYPE flag can now inherit the PEP 590 vectorcall protocol. Previously, this was only possible for static types. Patch by Erlend E. Aasland.

• bpo-44553: Implement GC methods for types.Union to break reference cycles and prevent memory leaks.

• bpo-44490: Add __parameters__ attribute and __getitem__ operator to types.Union. Patch provided by Yurii Karabas.

• bpo-44523: Remove the pass-through for hash() of weakref.proxy objects to prevent unintended consequences when the original referred object dies while the proxy is part of a hashable object. Patch by Pablo Galindo.

• bpo-44483: Fix a crash in types.Union objects when creating a union of an object with bad __module__ field.

• bpo-44486: Modules will always have a dictionary, even when created by types.ModuleType.__new__()

• bpo-44472: Fix ltrace functionality when exceptions are raised. Patch by Pablo Galindo

• bpo-12022: A TypeError is now raised instead of an AttributeError in with and async with statements for objects which do not support the context manager or asynchronous context manager protocols correspondingly.

• bpo-44297: Make sure that the line number is set when entering a comprehension scope. Ensures that backtraces inclusing generator expressions show the correct line number.

• bpo-44456: Improve the syntax error when mixing positional and keyword patterns. Patch by Pablo Galindo.

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

• bpo-44396: Fix a possible crash in the tokenizer when raising syntax errors for unclosed strings. Patch by Pablo Galindo.

• bpo-44376: Exact integer exponentiation (like i**2 or pow(i, 2)) with a small exponent is much faster, due to reducing overhead in such cases.

• bpo-44313: Directly imported objects and modules (through import and from import statements) don’t generate LOAD_METHOD/CALL_METHOD for directly accessed objects on their namespace. They now use the regular LOAD_ATTR/CALL_FUNCTION.

• bpo-44338: Implement adaptive specialization for LOAD_GLOBAL

  Two specialized forms of LOAD_GLOBAL are added:

  • LOAD_GLOBAL_MODULE

  • LOAD_GLOBAL_BUILTIN

• bpo-44368: Improve syntax errors for invalid “as” targets. Patch by Pablo Galindo

• bpo-44349: Fix an edge case when displaying text from files with encoding in syntax errors. Patch by Pablo Galindo.

• bpo-44337: Initial implementation of adaptive specialization of LOAD_ATTR

  Four specialized forms of LOAD_ATTR are added:

  • LOAD_ATTR_SLOT

  • LOAD_ATTR_SPLIT_KEYS

  • LOAD_ATTR_WITH_HINT

  • LOAD_ATTR_MODULE

• bpo-44335: Fix a regression when identifying incorrect characters in syntax errors. Patch by Pablo Galindo

• bpo-43693: Computation of the offsets of cell variables is done in the compiler instead of at runtime. This reduces the overhead of handling cell and free variables, especially in the case where a variable is both an argument and cell variable.

• bpo-44317: Improve tokenizer error with improved locations. Patch by Pablo Galindo.

• bpo-44304: Fix a crash in the sqlite3 module that happened when the garbage collector clears sqlite.Statement objects. Patch by Pablo Galindo

• bpo-44305: Improve error message for try blocks without except or finally blocks. Patch by Pablo Galindo.

• bpo-43413: Constructors of subclasses of some builtin classes (e.g. tuple, list, frozenset) no longer accept arbitrary keyword arguments. [reverted in 3.11a4] Subclass of set can now define a __new__() method with additional keyword parameters without overriding also __init__().

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

• bpo-43693: A new opcode MAKE_CELL has been added that effectively moves some of the work done on function entry into the compiler and into the eval loop. In addition to creating the required cell objects, the new opcode converts relevant arguments (and other locals) to cell variables on function entry.

• bpo-44232: Fix a regression in type() when a metaclass raises an exception. The C function type_new() must properly report the exception when a metaclass constructor raises an exception and the winner class is not the metaclass. Patch by Victor Stinner.

• bpo-44201: Avoid side effects of checking for specialized syntax errors in the REPL that was causing it to ask for extra tokens after a syntax error had been detected. Patch by Pablo Galindo

• bpo-43693: PyCodeObject gained co_fastlocalnames and co_fastlocalkinds as the authoritative source of fast locals info. Marshaled code objects have changed accordingly.

• bpo-44184: Fix a crash at Python exit when a deallocator function removes the last strong reference to a heap type. Patch by Victor Stinner.

• bpo-44187: Implement quickening in the interpreter. This offers no advantages as yet, but is an enabler of future optimizations. See PEP 659 for full explanation.

• bpo-44180: The parser doesn’t report generic syntax errors that happen in a position further away that the one it reached in the first pass. Patch by Pablo Galindo

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

• bpo-44156: String caches in compile.c are now subinterpreter compatible.

• bpo-44143: Fixed a crash in the parser that manifest when raising tokenizer errors when an existing exception was present. Patch by Pablo Galindo.

• bpo-44032: Move ‘fast’ locals and other variables from the frame object to a per-thread datastack.

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

• bpo-44110: Improve str.__getitem__() error message

• bpo-26110: Add CALL_METHOD_KW opcode to speed up method calls with keyword arguments. Idea originated from PyPy. A side effect is executing CALL_METHOD is now branchless in the evaluation loop.

• bpo-28307: Compiler now optimizes simple C-style formatting with literal format containing only format codes %s, %r and %a by converting them to f-string expressions.

• bpo-43149: Correct the syntax error message regarding multiple exception types to not refer to “exception groups”. Patch by Pablo Galindo

• bpo-43822: The parser will prioritize tokenizer errors over custom syntax errors when raising exceptions. Patch by Pablo Galindo.

• bpo-40222: “Zero cost” exception handling.

  • Uses a lookup table to determine how to handle exceptions.

  • Removes SETUP_FINALLY and POP_TOP block instructions, eliminating the runtime overhead of try statements.

  • Reduces the size of the frame object by about 60%.

  Patch by Mark Shannon

• bpo-43918: Document the signature and default argument in the docstring of the new anext builtin.

• bpo-43833: Emit a deprecation warning if the numeric literal is immediately followed by one of keywords: and, else, for, if, in, is, or. Raise a syntax error with more informative message if it is immediately followed by other keyword or identifier.

• bpo-43879: Add native_thread_id to PyThreadState. Patch by Gabriele N. Tornetta.

• bpo-43693: Compute cell offsets relative to locals in compiler. Allows the interpreter to treats locals and cells a single array, which is slightly more efficient. Also make the LOAD_CLOSURE opcode an alias for LOAD_FAST. Preserving LOAD_CLOSURE helps keep bytecode a bit more readable.

• bpo-17792: More accurate error messages for access of unbound locals or free vars.

• 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.

• bpo-39091: Fix crash when using passing a non-exception to a generator’s throw() method. Patch by Noah Oxer

• bpo-33346: Asynchronous comprehensions are now allowed inside comprehensions in asynchronous functions. Outer comprehensions implicitly become asynchronous.

Library

• bpo-45371: Fix clang rpath issue in distutils. The UnixCCompiler now uses correct clang option to add a runtime library directory (rpath) to a shared library.

• bpo-45329: Fix freed memory access in pyexpat.xmlparser when building it with an installed expat library <= 2.2.0.

• bpo-41710: On Unix, if the sem_clockwait() function is available in the C library (glibc 2.30 and newer), the threading.Lock.acquire() method now uses the monotonic clock (time.CLOCK_MONOTONIC) for the timeout, rather than using the system clock (time.CLOCK_REALTIME), to not be affected by system clock changes. Patch by Victor Stinner.

• bpo-1596321: Fix the threading._shutdown() function when the threading module was imported first from a thread different than the main thread: no longer log an error at Python exit.

• bpo-45274: Fix a race condition in the Thread.join() method of the threading module. If the function is interrupted by a signal and the signal handler raises an exception, make sure that the thread remains in a consistent state to prevent a deadlock. Patch by Victor Stinner.

• bpo-21302: In Unix operating systems, time.sleep() now uses the nanosleep() function, if clock_nanosleep() is not available but nanosleep() is available. nanosleep() allows to sleep with nanosecond precision.

• bpo-21302: On Windows, time.sleep() now uses a waitable timer which has a resolution of 100 nanoseconds (10^-7 seconds). Previously, it had a resolution of 1 millisecond (10^-3 seconds). Patch by Benjamin Szőke and Victor Stinner.

• bpo-45238: Fix unittest.IsolatedAsyncioTestCase.debug(): it runs now asynchronous methods and callbacks.

• bpo-36674: unittest.TestCase.debug() raises now a unittest.SkipTest if the class or the test method are decorated with the skipping decorator.

• bpo-45235: Fix an issue where argparse would not preserve values in a provided namespace when using a subparser with defaults.

• bpo-45183: Have zipimport.zipimporter.find_spec() not raise an exception when the underlying zip file has been deleted and the internal cache has been reset via invalidate_cache().

• bpo-45234: Fixed a regression in copyfile(), copy(), copy2() raising FileNotFoundError when source is a directory, which should raise IsADirectoryError

• bpo-45228: Fix stack buffer overflow in parsing J1939 network address.

• bpo-45225: use map function instead of genexpr in capwords.

• bpo-42135: Fix typo: importlib.find_loader is really slated for removal in Python 3.12 not 3.10, like the others in PR 25169.

  Patch by Hugo van Kemenade.

• bpo-20524: Improves error messages on .format() operation for str, float, int, and complex. New format now shows the problematic pattern and the object type.

• bpo-45168: Change dis.dis() output to omit op arg values that cannot be resolved due to co_consts, co_names etc not being provided. Previously the oparg itself was repeated in the value field, which is not useful and can be confusing.

• bpo-21302: In Unix operating systems, time.sleep() now uses the clock_nanosleep() function, if available, which allows to sleep for an interval specified with nanosecond precision.

• bpo-45173: Remove from the configparser module: the SafeConfigParser class, the filename property of the ParsingError class, the readfp() method of the ConfigParser class, deprecated since Python 3.2.

  Patch by Hugo van Kemenade.

• bpo-44987: Pure ASCII strings are now normalized in constant time by unicodedata.normalize(). Patch by Dong-hee Na.

• bpo-35474: Calling mimetypes.guess_all_extensions() with strict=False no longer affects the result of the following call with strict=True. Also, mutating the returned list no longer affects the global state.

• bpo-45166: typing.get_type_hints() now works with Final wrapped in ForwardRef.

• bpo-45162: Remove many old deprecated unittest features:

  • “fail*” and “assert*” aliases of TestCase methods.

  • Broken from start TestCase method assertDictContainsSubset().

  • Ignored <unittest.TestLoader.loadTestsFromModule> TestLoader.loadTestsFromModule() parameter use_load_tests.

  • Old alias _TextTestResult of TextTestResult.

• bpo-38371: Remove the deprecated split() method of _tkinter.TkappType. Patch by Erlend E. Aasland.

• bpo-20499: Improve the speed and accuracy of statistics.pvariance().

• bpo-45132: Remove __getitem__() methods of xml.dom.pulldom.DOMEventStream, wsgiref.util.FileWrapper and fileinput.FileInput, deprecated since Python 3.9.

  Patch by Hugo van Kemenade.

• bpo-45129: Due to significant security concerns, the reuse_address parameter of asyncio.loop.create_datagram_endpoint(), disabled in Python 3.9, is now entirely removed. This is because of the behavior of the socket option SO_REUSEADDR in UDP.

  Patch by Hugo van Kemenade.

• bpo-45124: The bdist_msi command, deprecated in Python 3.9, is now removed.

  Use bdist_wheel (wheel packages) instead.

  Patch by Hugo van Kemenade.

• bpo-30856: unittest.TestResult methods addFailure(), addError(), addSkip() and addSubTest() are now called immediately after raising an exception in test or finishing a subtest. Previously they were called only after finishing the test clean up.

• bpo-45034: Changes how error is formatted for struct.pack with 'H' and 'h' modes and too large / small numbers. Now it shows the actual numeric limits, while previously it was showing arithmetic expressions.

• bpo-25894: unittest now always reports skipped and failed subtests separately: separate characters in default mode and separate lines in verbose mode. Also the test description is now output for errors in test method, class and module cleanups.

• bpo-45081: Fix issue when dataclasses that inherit from typing.Protocol subclasses have wrong __init__. Patch provided by Yurii Karabas.

• bpo-45085: The binhex module, deprecated in Python 3.9, is now removed. The following binascii functions, deprecated in Python 3.9, are now also removed:

  • a2b_hqx(), b2a_hqx();

  • rlecode_hqx(), rledecode_hqx().

  The binascii.crc_hqx() function remains available.

  Patch by Victor Stinner.

• bpo-40360: The lib2to3 package is now deprecated and may not be able to parse Python 3.10 or newer. See the PEP 617 (New PEG parser for CPython). Patch by Victor Stinner.

• bpo-45075: Rename traceback.StackSummary.format_frame() to traceback.StackSummary.format_frame_summary(). This method was added for 3.11 so it was not released yet.

  Updated code and docs to better distinguish frame and FrameSummary.

• bpo-31299: Add option to completely drop frames from a traceback by returning None from a format_frame() override.

• bpo-41620: run() now always return a TestResult instance. Previously it returned None if the test class or method was decorated with a skipping decorator.

• bpo-45021: Fix a potential deadlock at shutdown of forked children when using concurrent.futures module

• bpo-43913: Fix bugs in cleaning up classes and modules in unittest:

  • Functions registered with addModuleCleanup() were not called unless the user defines tearDownModule() in their test module.

  • Functions registered with addClassCleanup() were not called if tearDownClass is set to None.

  • Buffering in TestResult did not work with functions registered with addClassCleanup() and addModuleCleanup().

  • Errors in functions registered with addClassCleanup() and addModuleCleanup() were not handled correctly in buffered and debug modes.

  • Errors in setUpModule() and functions registered with addModuleCleanup() were reported in wrong order.

  • And several lesser bugs.

• bpo-45030: Fix integer overflow in pickling and copying the range iterator.

• bpo-45001: Made email date parsing more robust against malformed input, namely a whitespace-only Date: header. Patch by Wouter Bolsterlee.

• bpo-45010: Remove support of special method __div__ in unittest.mock. It is not used in Python 3.

• bpo-39218: Improve accuracy of variance calculations by using x*x instead of x**2.

• bpo-43613: Improve the speed of gzip.compress() and gzip.decompress() by compressing and decompressing at once in memory instead of in a streamed fashion.

• bpo-37596: Ensure that set and frozenset objects are always marshalled reproducibly.

• bpo-44019: A new function operator.call has been added, such that operator.call(obj, *args, **kwargs) == obj(*args, **kwargs).

• bpo-42255: webbrowser.MacOSX is deprecated and will be removed in Python 3.13. It is untested and undocumented and also not used by webbrowser itself. Patch by Dong-hee Na.

• bpo-44955: Method stopTestRun() is now always called in pair with method startTestRun() for TestResult objects implicitly created in run(). Previously it was not called for test methods and classes decorated with a skipping decorator.

• bpo-39039: tarfile.open raises ReadError when a zlib error occurs during file extraction.

• bpo-44935: subprocess on Solaris now also uses os.posix_spawn() for better performance.

• bpo-44911: IsolatedAsyncioTestCase will no longer throw an exception while cancelling leaked tasks. Patch by Bar Harel.

• bpo-41322: Added DeprecationWarning for tests and async tests that return a value!=None (as this may indicate an improperly written test, for example a test written as a generator function).

• bpo-44524: Make exception message more useful when subclass from typing special form alias. Patch provided by Yurii Karabas.

• bpo-38956: argparse.BooleanOptionalAction’s default value is no longer printed twice when used with argparse.ArgumentDefaultsHelpFormatter.

• bpo-44860: Fix the posix_user scheme in sysconfig to not depend on sys.platlibdir.

• bpo-44859: Improve error handling in sqlite3 and raise more accurate exceptions.

  • MemoryError is now raised instead of sqlite3.Warning when memory is not enough for encoding a statement to UTF-8 in Connection.__call__() and Cursor.execute().

  • UnicodEncodeError is now raised instead of sqlite3.Warning when the statement contains surrogate characters in Connection.__call__() and Cursor.execute().

  • TypeError is now raised instead of ValueError for non-string script argument in Cursor.executescript().

  • ValueError is now raised for script containing the null character instead of truncating it in Cursor.executescript().

  • Correctly handle exceptions raised when getting boolean value of the result of the progress handler.

  • Add many tests covering different corner cases.

• bpo-44581: Upgrade bundled pip to 21.2.3 and setuptools to 57.4.0

• bpo-44849: Fix the os.set_inheritable() function on FreeBSD 14 for file descriptor opened with the O_PATH flag: ignore the EBADF error on ioctl(), fallback on the fcntl() implementation. Patch by Victor Stinner.

• bpo-44605: The @functools.total_ordering() decorator now works with metaclasses.

• bpo-44524: Fixed an issue wherein the __name__ and __qualname__ attributes of subscribed specialforms could be None.

• bpo-44839: MemoryError raised in user-defined functions will now produce a MemoryError in sqlite3. OverflowError will now be converted to DataError. Previously OperationalError was produced in these cases.

• bpo-44822: sqlite3 user-defined functions and aggregators returning strings with embedded NUL characters are no longer truncated. Patch by Erlend E. Aasland.

• bpo-44801: Ensure that the ParamSpec variable in Callable can only be substituted with a parameters expression (a list of types, an ellipsis, ParamSpec or Concatenate).

• bpo-44806: Non-protocol subclasses of typing.Protocol ignore now the __init__ method inherited from protocol base classes.

• bpo-27275: collections.OrderedDict.popitem() and collections.OrderedDict.pop() no longer call __getitem__ and __delitem__ methods of the OrderedDict subclasses.

• bpo-44793: Fix checking the number of arguments when subscribe a generic type with ParamSpec parameter.

• bpo-44784: In importlib.metadata tests, override warnings behavior under expected DeprecationWarnings (importlib_metadata 4.6.3).

• bpo-44667: The tokenize.tokenize() doesn’t incorrectly generate a NEWLINE token if the source doesn’t end with a new line character but the last line is a comment, as the function is already generating a NL token. Patch by Pablo Galindo

• bpo-44771: Added importlib.simple module implementing adapters from a low-level resources reader interface to a TraversableResources interface. Legacy API (path, contents, …) is now supported entirely by the .files() API with a compatibility shim supplied for resource loaders without that functionality. Feature parity with importlib_resources 5.2.

• bpo-44752: rcompleter does not call getattr() on property objects to avoid the side-effect of evaluating the corresponding method.

• bpo-44747: Refactor usage of sys._getframe in typing module. Patch provided by Yurii Karabas.

• bpo-42378: Fixes the issue with log file being overwritten when logging.FileHandler is used in atexit with filemode set to 'w'. Note this will cause the message in atexit not being logged if the log stream is already closed due to shutdown of logging.

• bpo-44720: weakref.proxy objects referencing non-iterators now raise TypeError rather than dereferencing the null tp_iternext slot and crashing.

• bpo-44704: The implementation of collections.abc.Set._hash() now matches that of frozenset.__hash__().

• bpo-44666: Fixed issue in compileall.compile_file() when sys.stdout is redirected. Patch by Stefan Hölzl.

• bpo-44688: sqlite3.Connection.create_collation() now accepts non-ASCII collation names. Patch by Erlend E. Aasland.

• bpo-44690: Adopt binacii.a2b_base64’s strict mode in base64.b64decode.

• bpo-42854: Fixed a bug in the _ssl module that was throwing OverflowError when using _ssl._SSLSocket.write() and _ssl._SSLSocket.read() for a big value of the len parameter. Patch by Pablo Galindo

• bpo-44686: Replace unittest.mock._importer with pkgutil.resolve_name.

• bpo-44353: Make NewType.__call__ faster by implementing it in C. Patch provided by Yurii Karabas.

• bpo-44682: Change the pdb commands directive to disallow setting commands for an invalid breakpoint and to display an appropriate error.

• bpo-44353: Refactor typing.NewType from function into callable class. Patch provided by Yurii Karabas.

• bpo-44678: Added a separate error message for discontinuous padding in binascii.a2b_base64 strict mode.

• bpo-44524: Add missing __name__ and __qualname__ attributes to typing module classes. Patch provided by Yurii Karabas.

• bpo-40897: Give priority to using the current class constructor in inspect.signature(). Patch by Weipeng Hong.

• bpo-44638: Add a reference to the zipp project and hint as to how to use it.

• bpo-44648: Fixed wrong error being thrown by inspect.getsource() when examining a class in the interactive session. Instead of TypeError, it should be OSError with appropriate error message.

• bpo-44608: Fix memory leak in _tkinter._flatten() if it is called with a sequence or set, but not list or tuple.

• bpo-44594: Fix an edge case of ExitStack and AsyncExitStack exception chaining. They will now match with block behavior when __context__ is explicitly set to None when the exception is in flight.

• bpo-42799: In fnmatch, the cache size for compiled regex patterns (functools.lru_cache()) was bumped up from 256 to 32768, affecting functions: fnmatch.fnmatch(), fnmatch.fnmatchcase(), fnmatch.filter().

• bpo-41928: Update shutil.copyfile() to raise FileNotFoundError instead of confusing IsADirectoryError when a path ending with a os.path.sep does not exist; shutil.copy() and shutil.copy2() are also affected.

• bpo-44569: Added the StackSummary.format_frame() function in traceback. This allows users to customize the way individual lines are formatted in tracebacks without re-implementing logic to handle recursive tracebacks.

• bpo-44566: handle StopIteration subclass raised from @contextlib.contextmanager generator

• bpo-44558: Make the implementation consistency of indexOf() between C and Python versions. Patch by Dong-hee Na.

• bpo-41249: Fixes TypedDict to work with typing.get_type_hints() and postponed evaluation of annotations across modules.

• bpo-44554: Refactor argument processing in pdb.main() to simplify detection of errors in input loading and clarify behavior around module or script invocation.

• bpo-34798: Break up paragraph about pprint.PrettyPrinter construction parameters to make it easier to read.

• bpo-44539: Added support for recognizing JPEG files without JFIF or Exif markers.

• bpo-44461: Fix bug with pdb’s handling of import error due to a package which does not have a __main__ module

• bpo-43625: Fix a bug in the detection of CSV file headers by csv.Sniffer.has_header() and improve documentation of same.

• bpo-44516: Update vendored pip to 21.1.3

• bpo-42892: Fixed an exception thrown while parsing a malformed multipart email by email.message.EmailMessage.

• bpo-44468: typing.get_type_hints() now finds annotations in classes and base classes with unexpected __module__. Previously, it skipped those MRO elements.

• bpo-44491: Allow clearing the sqlite3 authorizer callback by passing None to set_authorizer(). Patch by Erlend E. Aasland.

• bpo-43977: Set the proper Py_TPFLAGS_MAPPING and Py_TPFLAGS_SEQUENCE flags for subclasses created before a parent has been registered as a collections.abc.Mapping or collections.abc.Sequence.

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

• bpo-44466: The faulthandler module now detects if a fatal error occurs during a garbage collector collection. Patch by Victor Stinner.

• bpo-44471: A TypeError is now raised instead of an AttributeError in contextlib.ExitStack.enter_context() and contextlib.AsyncExitStack.enter_async_context() for objects which do not support the context manager or asynchronous context manager protocols correspondingly.

• bpo-44404: tkinter’s after() method now supports callables without the __name__ attribute.

• bpo-41546: Make pprint (like the builtin print) not attempt to write to stdout when it is None.

• bpo-44458: BUFFER_BLOCK_SIZE is now declared static, to avoid linking collisions when bz2, lmza or zlib are statically linked.

• bpo-44464: Remove exception for flake8 in deprecated importlib.metadata interfaces. Sync with importlib_metadata 4.6.

• bpo-44446: Take into account that lineno might be None in traceback.FrameSummary.

• 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-42972: The _thread.RLock type now fully implement the GC protocol: add a traverse function and the Py_TPFLAGS_HAVE_GC flag. 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-38291: Importing typing.io or typing.re now prints a DeprecationWarning.

• bpo-37880: argparse actions store_const and append_const each receive a default value of None when the const kwarg is not provided. Previously, this raised a TypeError.

• bpo-44389: Fix deprecation of ssl.OP_NO_TLSv1_3

• bpo-27827: pathlib.PureWindowsPath.is_reserved() now identifies a greater range of reserved filenames, including those with trailing spaces or colons.

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

• bpo-34266: Handle exceptions from parsing the arg of pdb’s run/restart command.

• bpo-44362: Improve ssl module’s deprecation messages, error reporting, and documentation for deprecations.

• bpo-44342: [Enum] Change pickling from by-value to by-name.

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

• bpo-44351: Restore back parse_makefile() in distutils.sysconfig because it behaves differently than the similar implementation in sysconfig.

• bpo-35800: smtpd.MailmanProxy is now removed as it is unusable without an external module, mailman. Patch by Dong-hee Na.

• bpo-44357: Added a function that returns cube root of the given number math.cbrt()

• bpo-44339: Change math.pow(±0.0, -math.inf) to return inf instead of raising ValueError. This brings the special-case handling of math.pow into compliance with the IEEE 754 standard.

• bpo-44242: Remove missing flag check from Enum creation and move into a verify decorator.

• bpo-44246: In importlib.metadata, restore compatibility in the result from Distribution.entry_points (EntryPoints) to honor expectations in older implementations and issuing deprecation warnings for these cases: A. EntryPoints objects are once again mutable, allowing for sort() and other list-based mutation operations. Avoid deprecation warnings by casting to a mutable sequence (e.g. list(dist.entry_points).sort()). B. EntryPoints results once again allow for access by index. To avoid deprecation warnings, cast the result to a Sequence first (e.g. tuple(dist.entry_points)[0]).

• bpo-44246: In importlib.metadata.entry_points, de-duplication of distributions no longer requires loading the full metadata for PathDistribution objects, improving entry point loading performance by ~10x.

• bpo-43858: Added a function that returns a copy of a dict of logging levels: logging.getLevelNamesMapping()

• bpo-44260: The random.Random constructor no longer reads system entropy without need.

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

• bpo-44258: Support PEP 515 for Fraction’s initialization from string.

• bpo-44235: Remove deprecated functions in the gettext. Patch by Dong-hee Na.

• bpo-38693: Prefer f-strings to .format in importlib.resources.

• bpo-33693: Importlib.metadata now prefers f-strings to .format.

• bpo-44241: Incorporate minor tweaks from importlib_metadata 4.1: SimplePath protocol, support for Metadata 2.2.

• bpo-43216: Remove the @asyncio.coroutine decorator enabling legacy generator-based coroutines to be compatible with async/await code; remove asyncio.coroutines.CoroWrapper used for wrapping legacy coroutine objects in the debug mode. The decorator has been deprecated since Python 3.8 and the removal was initially scheduled for Python 3.10. Patch by Illia Volochii.

• bpo-44210: Make importlib.metadata._meta.PackageMetadata public.

• bpo-43643: Declare readers.MultiplexedPath.name as a property per the spec.

• bpo-27334: The sqlite3 context manager now performs a rollback (thus releasing the database lock) if commit failed. Patch by Luca Citi and Erlend E. Aasland.

• bpo-4928: Documented existing behavior on POSIX: NamedTemporaryFiles are not deleted when creating process is killed with SIGKILL

• bpo-44154: Optimize fractions.Fraction pickling for large components.

• bpo-33433: For IPv4 mapped IPv6 addresses (RFC 4291 Section 2.5.5.2), the ipaddress.IPv6Address.is_private check is deferred to the mapped IPv4 address. This solves a bug where public mapped IPv4 addresses were considered private by the IPv6 check.

• bpo-44150: Add optional weights argument to statistics.fmean().

• bpo-44142: ast.unparse() will now drop the redundant parentheses when tuples used as assignment targets (e.g in for loops).

• 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-44095: zipfile.Path now supports zipfile.Path.stem, zipfile.Path.suffixes, and zipfile.Path.suffix attributes.

• bpo-44077: It’s now possible to receive the type of service (ToS), a.k.a. differentiated services (DS), a.k.a. differentiated services code point (DSCP) and explicit congestion notification (ECN) IP header fields with socket.IP_RECVTOS.

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

• bpo-38908: Subclasses of typing.Protocol which only have data variables declared will now raise a TypeError when checked with isinstance unless they are decorated with runtime_checkable(). Previously, these checks passed silently. Patch provided by Yurii Karabas.

• bpo-44098: typing.ParamSpec will no longer be found in the __parameters__ of most typing generics except in valid use locations specified by PEP 612. This prevents incorrect usage like typing.List[P][int]. This change means incorrect usage which may have passed silently in 3.10 beta 1 and earlier will now error.

• bpo-44089: Allow subclassing csv.Error in 3.10 (it was allowed in 3.9 and earlier but was disallowed in early versions of 3.10).

• bpo-44081: ast.unparse() now doesn’t use redundant spaces to separate lambda and the : if there are no parameters.

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

• bpo-44059: Register the SerenityOS Browser in the webbrowser module.

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

• bpo-40465: Remove random module features deprecated in Python 3.9.

• 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-44002: urllib.parse now uses functool.lru_cache() for its internal URL splitting and quoting caches instead of rolling its own like its the ’90s.

  The undocumented internal urllib.parse Quoted class API is now deprecated, for removal in 3.14.

• 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-43853: Improved string handling for sqlite3 user-defined functions and aggregates:

  • It is now possible to pass strings with embedded null characters to UDFs

  • Conversion failures now correctly raise MemoryError

  Patch by Erlend E. Aasland.

• 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 similar 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-43612: zlib.compress() now accepts a wbits parameter which allows users to compress data as a raw deflate block without zlib headers and trailers in one go. Previously this required instantiating a zlib.compressobj. It also provides a faster alternative to gzip.compress when wbits=31 is used.

• bpo-43392: importlib._bootstrap._find_and_load() now implements a two-step check to avoid locking when modules have been already imported and are ready. This improves performance of repeated calls to importlib.import_module() and importlib.__import__().

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

• bpo-43234: Prohibit passing non-concurrent.futures.ThreadPoolExecutor executors to loop.set_default_executor() following a deprecation in Python 3.8. Patch by Illia Volochii.

• bpo-43232: Prohibit previously deprecated potentially disruptive operations on asyncio.trsock.TransportSocket. Patch by Illia Volochii.

• bpo-30077: Added support for Apple’s aifc/sowt pseudo-compression

• bpo-42971: Add definition of errno.EQFULL for platforms that define this constant (such as macOS).

• bpo-43086: Added a new optional strict_mode parameter to binascii.a2b_base64. When scrict_mode is set to True, the a2b_base64 function will accept only valid base64 content. More details about what “valid base64 content” is, can be found in the function’s documentation.

• bpo-43024: Improve the help signature of traceback.print_exception(), traceback.format_exception() and traceback.format_exception_only().

• bpo-33809: Add the traceback.TracebackException.print() method which prints the formatted exception information.

• bpo-42862: sqlite3 now utilizes functools.lru_cache() to implement the connection statement cache. As a small optimisation, the default statement cache size has been increased from 100 to 128. Patch by Erlend E. Aasland.

• bpo-41818: Soumendra Ganguly: add termios.tcgetwinsize(), termios.tcsetwinsize().

• bpo-40497: subprocess.check_output() now raises ValueError when the invalid keyword argument check is passed by user code. Previously such use would fail later with a TypeError. Patch by Rémi Lapeyre.

• bpo-37449: ensurepip now uses importlib.resources.files() traversable APIs

• bpo-40956: Use Argument Clinic in sqlite3. Patches by Erlend E. Aasland.

• bpo-41730: DeprecationWarning is now raised when importing tkinter.tix, which has been deprecated in documentation since Python 3.6.

• bpo-20684: Remove unused _signature_get_bound_param function from inspect - by Anthony Sottile.

• bpo-41402: Fix email.message.EmailMessage.set_content() when called with binary data and 7bit content transfer encoding.

• bpo-32695: The compresslevel and preset keyword arguments of tarfile.open() are now both documented and tested.

• bpo-41137: Use utf-8 encoding while reading .pdbrc files. Patch by Srinivas Reddy Thatiparthy

• bpo-24391: Improved reprs of threading synchronization objects: Semaphore, BoundedSemaphore, Event and Barrier.

• bpo-5846: Deprecated the following unittest functions, scheduled for removal in Python 3.13:

  • findTestCases()

  • makeSuite()

  • getTestCaseNames()

  Use TestLoader methods instead:

  • unittest.TestLoader.loadTestsFromModule()

  • unittest.TestLoader.loadTestsFromTestCase()

  • unittest.TestLoader.getTestCaseNames()

  Patch by Erlend E. Aasland.

• bpo-40563: Support pathlike objects on dbm/shelve. Patch by Hakan Çelik and Henry-Joseph Audéoud.

• bpo-34990: Fixed a Y2k38 bug in the compileall module where it would fail to compile files with a modification time after the year 2038.

• bpo-39549: Whereas the code for reprlib.Repr had previously used a hardcoded string value of ‘…’, this PR updates it to use of a “fillvalue” attribute, whose value defaults to ‘…’ and can be reset in either individual reprlib.Repr instances or in subclasses thereof.

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

• bpo-38840: Fix test___all__ on platforms lacking a shared memory implementation.

• bpo-39359: Add one missing check that the password is a bytes object for an encrypted zipfile.

• bpo-38741: configparser: using ‘]’ inside a section header will no longer cut the section name short at the ‘]’

• bpo-38415: Added missing behavior to contextlib.asynccontextmanager() to match contextlib.contextmanager() so decorated functions can themselves be decorators.

• bpo-30256: Pass multiprocessing BaseProxy argument manager_owned through AutoProxy.

• bpo-27513: email.utils.getaddresses() now accepts email.header.Header objects along with string values. Patch by Zackery Spytz.

• bpo-16379: Add SQLite error code and name to sqlite3 exceptions. Patch by Aviv Palivoda, Daniel Shahaf, and Erlend E. Aasland.

• bpo-26228: pty.spawn no longer hangs on FreeBSD, macOS, and Solaris.

• bpo-33349: lib2to3 now recognizes async generators everywhere.

• bpo-29298: Fix TypeError when required subparsers without dest do not receive arguments. Patch by Anthony Sottile.

Documentation

• bpo-45216: Remove extra documentation listing methods in difflib. It was rendering twice in pydoc and was outdated in some places.

• bpo-45024: collections.abc documentation has been expanded to explicitly cover how instance and subclass checks work, with additional doctest examples and an exhaustive list of ABCs which test membership purely by presence of the right special methods. Patch by Raymond Hettinger.

• bpo-44957: Promote PEP 604 union syntax by using it where possible. Also, mention X | Y more prominently in section about Union and mention X | None at all in section about Optional.

• bpo-16580: Added code equivalents for the int.to_bytes() and int.from_bytes() methods, as well as tests ensuring that these code equivalents are valid.

• bpo-44903: Removed the othergui.rst file, any references to it, and the list of GUI frameworks in the FAQ. In their place I’ve added links to the Python Wiki page on GUI frameworks.

• bpo-33479: Tkinter documentation has been greatly expanded with new “Architecture” and “Threading model” sections.

• bpo-36700: base64 RFC references were updated to point to RFC 4648; a section was added to point users to the new “security considerations” section of the RFC.

• bpo-44740: Replaced occurrences of uppercase “Web” and “Internet” with lowercase versions per the 2016 revised Associated Press Style Book.

• bpo-44693: Update the definition of __future__ in the glossary by replacing the confusing word “pseudo-module” with a more accurate description.

• bpo-35183: Add typical examples to os.path.splitext docs

• bpo-30511: Clarify that shutil.make_archive() is not thread-safe due to reliance on changing the current working directory.

• bpo-44561: Update of three expired hyperlinks in Doc/distributing/index.rst: “Project structure”, “Building and packaging the project”, and “Uploading the project to the Python Packaging Index”.

• bpo-44651: Delete entry “coercion” in Doc/glossary.rst for its outdated definition.

• bpo-42958: Updated the docstring and docs of filecmp.cmp() to be more accurate and less confusing especially in respect to shallow arg.

• bpo-44631: Refactored the repr() code of the _Environ (os module).

• bpo-44613: importlib.metadata is no longer provisional.

• bpo-44558: Match the docstring and python implementation of countOf() to the behavior of its c implementation.

• bpo-44544: List all kwargs for textwrap.wrap(), textwrap.fill(), and textwrap.shorten(). Now, there are nav links to attributes of TextWrap, which makes navigation much easier while minimizing duplication in the documentation.

• bpo-38062: Clarify that atexit uses equality comparisons internally.

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

• bpo-43066: Added a warning to zipfile docs: filename arg with a leading slash may cause archive to be un-openable on Windows systems.

• bpo-39452: Rewrote Doc/library/__main__.rst. Broadened scope of the document to explicitly discuss and differentiate between __main__.py in packages versus the __name__ == '__main__' expression (and the idioms that surround it).

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

• bpo-27752: Documentation of csv.Dialect is more descriptive.

• bpo-44453: Fix documentation for the return type of sysconfig.get_path().

• 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-42392: Document the deprecation and removal of the loop parameter for many functions and classes in asyncio.

• 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-44025: Clarify when ‘_’ in match statements is a keyword, and when not.

• bpo-41706: Fix docs about how methods like __add__ are invoked when evaluating operator expressions.

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

• bpo-41576: document BaseException in favor of bare except

• bpo-21760: The description for __file__ fixed. Patch by Furkan Onder

• bpo-39498: Add a “Security Considerations” index which links to standard library modules that have explicitly documented security considerations.

• bpo-33479: Remove the unqualified claim that tkinter is threadsafe. It has not been true for several years and likely never was. An explanation of what is true may be added later, after more discussion, and possibly after patching _tkinter.c,

Tests

• bpo-40173: Fix test.support.import_helper.import_fresh_module().

• bpo-45280: Add a test case for empty typing.NamedTuple.

• bpo-45269: Cover case when invalid markers type is supplied to c_make_encoder.

• bpo-45128: Fix test_multiprocessing_fork failure due to test_logging and sys.modules manipulation.

• bpo-45209: Fix UserWarning: resource_tracker warning in _test_multiprocessing._TestSharedMemory.test_shared_memory_cleaned_after_process_termination

• bpo-45185: Enables TestEnumerations test cases in test_ssl suite.

• bpo-45195: Fix test_readline.test_nonascii(): sometimes, the newline character is not written at the end, so don’t expect it in the output. Patch by Victor Stinner.

• bpo-45156: Fixes infinite loop on unittest.mock.seal() of mocks created by create_autospec().

• bpo-45125: Improves pickling tests and docs of SharedMemory and SharableList objects.

• bpo-44860: Update test_sysconfig.test_user_similar() for the posix_user scheme: platlib doesn’t use sys.platlibdir. Patch by Victor Stinner.

• bpo-45052: WithProcessesTestSharedMemory.test_shared_memory_basics test was ignored, because self.assertEqual(sms.size, sms2.size) line was failing. It is now removed and test is unskipped.

  The main motivation for this line to be removed from the test is that the size of SharedMemory is not ever guaranteed to be the same. It is decided by the platform.

• bpo-44895: libregrtest now clears the type cache later to reduce the risk of false alarm when checking for reference leaks. Previously, the type cache was cleared too early and libregrtest raised a false alarm about reference leaks under very specific conditions. Patch by Irit Katriel and Victor Stinner.

• bpo-45042: Fixes that test classes decorated with @hashlib_helper.requires_hashdigest were skipped all the time.

• bpo-25130: Add calls of gc.collect() in tests to support PyPy.

• bpo-45011: Made tests relying on the _asyncio C extension module optional to allow running on alternative Python implementations. Patch by Serhiy Storchaka.

• bpo-44949: Fix auto history tests of test_readline: sometimes, the newline character is not written at the end, so don’t expect it in the output.

• bpo-44891: Tests were added to clarify id() is preserved when obj * 1 is used on str and bytes objects. Patch by Nikita Sobolev.

• bpo-44852: Add ability to wholesale silence DeprecationWarnings while running the regression test suite.

• bpo-40928: Notify users running test_decimal regression tests on macOS of potential harmless “malloc can’t allocate region” messages spewed by test_decimal.

• bpo-44734: Fixed floating point precision issue in turtle tests.

• bpo-44708: Regression tests, when run with -w, are now re-running only the affected test methods instead of re-running the entire test file.

• bpo-42095: Added interop tests for Apple plists: generate plist files with Python plistlib and parse with Apple plutil; and the other way round.

• bpo-44647: Added a permanent Unicode-valued environment variable to regression tests to ensure they handle this use case in the future. If your test environment breaks because of that, report a bug to us, and temporarily set PYTHONREGRTEST_UNICODE_GUARD=0 in your test environment.

• bpo-44515: Adjust recently added contextlib tests to avoid assuming the use of a refcounted GC

• 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-44451: Reset DeprecationWarning filters in test.test_importlib.test_metadata_api.APITests.test_entry_points_by_index to avoid StopIteration error if DeprecationWarnings are ignored.

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

• bpo-44364: Add non integral tests for math.sqrt() function.

• bpo-43921: Fix test_ssl.test_wrong_cert_tls13(): use suppress_ragged_eofs=False, since read() can raise ssl.SSLEOFError on Windows. Patch by Victor Stinner.

• bpo-43921: Fix test_pha_required_nocert() of test_ssl: catch two more EOF cases (when the recv() method returns an empty string). Patch by Victor Stinner.

• bpo-44131: Add test_frozenmain to test_embed to test the Py_FrozenMain() C function. Patch by Victor Stinner.

• bpo-31904: Ignore error string case in test_file_not_exists().

• bpo-42083: Add test to check that PyStructSequence_NewType accepts a PyStructSequence_Desc with doc field set to NULL.

• bpo-35753: Fix crash in doctest when doctest parses modules that include unwrappable functions by skipping those functions.

• bpo-30256: Add test for nested queues when using multiprocessing shared objects AutoProxy[Queue] inside ListProxy and DictProxy

Build

• bpo-45220: Avoid building with the Windows 11 SDK previews automatically. This may be overridden by setting the DefaultWindowsSDKVersion environment variable before building.

• bpo-45020: Freeze stdlib modules that are imported during startup. This provides significant performance improvements to startup. If necessary, use the previously added “-X frozen_modules=off” commandline option to force importing the source modules.

• bpo-45188: Windows builds now regenerate frozen modules as the first part of the build. Previously the regeneration was later in the build, which would require it to be restarted if any modules had changed.

• bpo-45163: Fixes Haiku platform build.

• bpo-45067: The ncurses function extended_color_content was introduced in 2017

  (https://invisible-island.net/ncurses/NEWS.html#index-t20170401). The

  ncurses-devel package in CentOS 7 had a older version ncurses resulted in compilation error. For compiling ncurses with extended color support, we verify the version of the ncurses library >= 20170401.

• bpo-45019: Generate lines in relevant files for frozen modules. Up until now each of the files had to be edited manually. This change makes it easier to add to and modify the frozen modules.

• bpo-44340: Add support for building with clang thin lto via –with-lto=thin/full. Patch by Dong-hee Na and Brett Holman.

• bpo-44535: Enable building using a Visual Studio 2022 install on Windows.

• bpo-43298: Improved error message when building without a Windows SDK installed.

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

• bpo-41282: Fix broken make install that caused standard library extension modules to be unnecessarily and incorrectly rebuilt during the install phase of cpython.

Windows

• bpo-45375: Fixes an assertion failure due to searching for the standard library in unnormalised paths.

• bpo-45022: Update Windows release to include libffi 3.4.2

• bpo-45007: Update to OpenSSL 1.1.1l in Windows build

• bpo-44848: Upgrade Windows installer to use SQLite 3.36.0.

• bpo-44572: Avoid consuming standard input in the platform module

• bpo-44582: Accelerate speed of mimetypes initialization using a native implementation of the registry scan.

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

• bpo-42686: Build sqlite3 with math functions enabled. Patch by Erlend E. Aasland.

• bpo-40263: This is a follow-on bug from https://bugs.python.org/issue26903. Once that is applied we run into an off-by-one assertion problem. The assert was not correct.

macOS

• bpo-45007: Update macOS installer builds to use OpenSSL 1.1.1l.

• bpo-34602: When building CPython on macOS with ./configure --with-undefined-behavior-sanitizer --with-pydebug, the stack size is now quadrupled to allow for the entire test suite to pass.

• bpo-44848: Update macOS installer to use SQLite 3.36.0.

• bpo-44689: ctypes.util.find_library() now works correctly on macOS 11 Big Sur even if Python is built on an older version of macOS. Previously, when built on older macOS systems, find_library was not able to find macOS system libraries when running on Big Sur due to changes in how system libraries are stored.

• bpo-41972: The framework build’s user header path in sysconfig is changed to add a ‘pythonX.Y’ component to match distutils’s behavior.

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

• bpo-34932: Add socket.TCP_KEEPALIVE support for macOS. Patch by Shane Harvey.

IDLE

• bpo-45296: On Windows, change exit/quit message to suggest Ctrl-D, which works, instead of <Ctrl-Z Return>, which does not work in IDLE.

• bpo-45193: Make completion boxes appear on Ubuntu again.

• 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.

• bpo-44010: Highlight the new match statement’s soft keywords: match, case, and _. However, this highlighting is not perfect and will be incorrect in some rare cases, including some _-s in case patterns.

• bpo-44026: Include interpreter’s typo fix suggestions in message line for NameErrors and AttributeErrors. Patch by E. Paine.

Tools/Demos

• bpo-44786: Fix a warning in regular expression in the c-analyzer script.

• bpo-44967: pydoc now returns a non-zero status code when a module cannot be found.

• bpo-44978: Allow the Argument Clinic tool to handle __complex__ special methods.

• bpo-43425: Removed the ‘test2to3’ demo project that demonstrated using lib2to3 to support Python 2.x and Python 3.x from a single source in a distutils package. Patch by Dong-hee Na

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

• bpo-20291: Added support for variadic positional parameters in Argument Clinic.

C API

• bpo-41710: The PyThread_acquire_lock_timed() function now clamps the timeout if it is too large, rather than aborting the process. Patch by Victor Stinner.

• bpo-44687: BufferedReader.peek() no longer raises ValueError when the entire file has already been buffered.

• bpo-45116: Add the Py_ALWAYS_INLINE macro to ask the compiler to always inline a static inline function. The compiler can ignore it and decides to not inline the function. Patch by Victor Stinner.

• bpo-45094: Add the Py_NO_INLINE macro to disable inlining on a function. Patch by Victor Stinner.

• bpo-45061: Add a deallocator to the bool type to detect refcount bugs in C extensions which call Py_DECREF(Py_True); or Py_DECREF(Py_False); by mistake. Patch by Victor Stinner.

• bpo-42035: Add a new PyType_GetQualName() function to get type’s qualified name.

• bpo-41103: Reverts removal of the old buffer protocol because they are part of stable ABI.

• bpo-44751: Remove crypt.h include from the public Python.h header.

• bpo-42747: The Py_TPFLAGS_HAVE_VERSION_TAG type flag now does nothing. The Py_TPFLAGS_HAVE_AM_SEND flag (which was added in 3.10) is removed. Both were unnecessary because it is not possible to have type objects with the relevant fields missing.

• bpo-44530: Added the co_qualname to the PyCodeObject structure to propagate the qualified name from the compiler to code objects.

  Patch by Gabriele N. Tornetta

• 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-39947: Remove 4 private trashcan C API functions which were only kept for the backward compatibility of the stable ABI with Python 3.8 and older, since the trashcan API was not usable with the limited C API on Python 3.8 and older. The trashcan API was excluded from the limited C API in Python 3.9.

  Removed functions:

  • _PyTrash_deposit_object()

  • _PyTrash_destroy_chain()

  • _PyTrash_thread_deposit_object()

  • _PyTrash_thread_destroy_chain()

  The trashcan C API was never usable with the limited C API, since old trashcan macros accessed directly PyThreadState members like _tstate->trash_delete_nesting, whereas the PyThreadState structure is opaque in the limited C API.

  Exclude also the PyTrash_UNWIND_LEVEL constant from the C API.

  Patch by Victor Stinner.

• bpo-40939: Removed documentation for the removed PyParser_* C API.

• bpo-43795: The list in Contents of Limited API now shows the public name PyFrameObject rather than _frame. The non-existing entry _node no longer appears in the list.

• bpo-44378: Py_IS_TYPE() no longer uses Py_TYPE() to avoid a compiler warning: no longer cast const PyObject* to PyObject*. Patch by Victor Stinner.

• bpo-39573: Convert the Py_TYPE() and Py_SIZE() macros to static inline functions. The Py_SET_TYPE() and Py_SET_SIZE() functions must now be used to set an object type and size. Patch by Victor Stinner.

• bpo-44263: The PyType_Ready() function now raises an error if a type is defined with the Py_TPFLAGS_HAVE_GC flag set but has no traverse function (PyTypeObject.tp_traverse). Patch by Victor Stinner.

• bpo-43795: The undocumented function Py_FrozenMain() is removed from the Limited API.

• bpo-44113: Deprecate the following functions to configure the Python initialization:

  • PySys_AddWarnOptionUnicode()

  • PySys_AddWarnOption()

  • PySys_AddXOption()

  • PySys_HasWarnOptions()

  • Py_SetPath()

  • Py_SetProgramName()

  • Py_SetPythonHome()

  • Py_SetStandardStreamEncoding()

  • _Py_SetProgramFullPath()

  Use the new PyConfig API of the Python Initialization Configuration instead (PEP 587).

• bpo-44094: Remove PyErr_SetFromErrnoWithUnicodeFilename(), PyErr_SetFromWindowsErrWithUnicodeFilename(), and PyErr_SetExcFromWindowsErrWithUnicodeFilename(). They are not documented and have been deprecated since Python 3.3.

• bpo-43795: PyCodec_Unregister() is now properly exported as a function in the Windows Stable ABI DLL.

• bpo-44029: Remove deprecated Py_UNICODE APIs: PyUnicode_Encode, PyUnicode_EncodeUTF7, PyUnicode_EncodeUTF8, PyUnicode_EncodeUTF16, PyUnicode_EncodeUTF32, PyUnicode_EncodeLatin1, PyUnicode_EncodeMBCS, PyUnicode_EncodeDecimal, PyUnicode_EncodeRawUnicodeEscape, PyUnicode_EncodeCharmap, PyUnicode_EncodeUnicodeEscape, PyUnicode_TransformDecimalToASCII, PyUnicode_TranslateCharmap, PyUnicodeEncodeError_Create, PyUnicodeTranslateError_Create. See PEP 393 and PEP 624 for reference.

• bpo-42035: Add a new PyType_GetName() function to get type’s short name.

Python 3.10.0 beta 1

Release date: 2021-05-03

Security

• bpo-43434: Creating sqlite3.Connection objects now also produces sqlite3.connect and sqlite3.connect/handle auditing events. Previously these events were only produced by sqlite3.connect() calls. Patch by Erlend E. Aasland.

• bpo-43998: The ssl module sets more secure cipher suites defaults. Ciphers without forward secrecy and with SHA-1 MAC are disabled by default. Security level 2 prohibits weak RSA, DH, and ECC keys with less than 112 bits of security. SSLContext defaults to minimum protocol version TLS 1.2. Settings are based on Hynek Schlawack’s research.

• 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-43362: Fix invalid free in _sha3 module. The issue was introduced in 3.10.0a1. Python 3.9 and earlier are not affected.

• bpo-43762: Add audit events for sqlite3.connect/handle(), sqlite3.Connection.enable_load_extension(), and sqlite3.Connection.load_extension(). Patch by Erlend E. Aasland.

• bpo-43756: Add new audit event glob.glob/2 to incorporate the new root_dir and dir_fd arguments added to glob.glob() and glob.iglob().

• 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 notation. 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.

• bpo-37363: Add audit events to the http.client module.

Core and Builtins

• bpo-43977: Prevent classes being both a sequence and a mapping when pattern matching.

• bpo-43977: Use tp_flags on the class object to determine if the subject is a sequence or mapping when pattern matching. Avoids the need to import collections.abc when pattern matching.

• bpo-43892: Restore proper validation of complex literal value patterns when parsing match blocks.

• bpo-43933: Set frame.f_lineno to the line number of the ‘with’ kweyword when executing the call to __exit__.

• bpo-43933: If the current position in a frame has no line number then set the f_lineno attribute to None, instead of -1, to conform to PEP 626. This should not normally be possible, but might occur in some unusual circumstances.

• bpo-43963: Importing the _signal module in a subinterpreter has no longer side effects.

• bpo-42739: The internal representation of line number tables is changed to not use sentinels, and an explicit length parameter is added to the out of process API function PyLineTable_InitAddressRange. This makes the handling of line number tables more robust in some circumstances.

• bpo-43908: Make re types immutable. Patch by Erlend E. Aasland.

• bpo-43908: Make the array.array type immutable. Patch by Erlend E. Aasland.

• bpo-43901: Change class and module objects to lazy-create empty annotations dicts on demand. The annotations dicts are stored in the object’s __dict__ for backwards compatibility.

• bpo-43892: Match patterns now use new dedicated AST nodes (MatchValue, MatchSingleton, MatchSequence, MatchStar, MatchMapping, MatchClass) rather than reusing expression AST nodes. MatchAs and MatchOr are now defined as pattern nodes rather than as expression nodes. Patch by Nick Coghlan.

• bpo-42725: Usage of await/yield/yield from and named expressions within an annotation is now forbidden when PEP 563 is activated.

• bpo-43754: When performing structural pattern matching (PEP 634), captured names are now left unbound until the entire pattern has matched successfully.

• bpo-42737: Annotations for complex targets (everything beside simple names) no longer cause any runtime effects with from __future__ import annotations.

• bpo-43914: SyntaxError exceptions raised by the interpreter will highlight the full error range of the expression that consistutes the syntax error itself, instead of just where the problem is detected. Patch by Pablo Galindo.

• bpo-38605: Revert making from __future__ import annotations the default. This follows the Steering Council decision to postpone PEP 563 changes to at least Python 3.11. See the original email for more information regarding the decision: https://mail.python.org/archives/list/python-dev@python.org/thread/CLVXXPQ2T2LQ5MP2Y53VVQFCXYWQJHKZ/. Patch by Pablo Galindo.

• bpo-43475: Hashes of NaN values now depend on object identity. Formerly, they always hashed to 0 even though NaN values are not equal to one another. Having the same hash for unequal values caused pile-ups in hash tables.

• bpo-43859: Improve the error message for IndentationError exceptions. Patch by Pablo Galindo

• bpo-41323: Constant tuple folding in bytecode optimizer now reuses tuple in constant table.

• bpo-43846: Data stack usage is much reduced for large literal and call expressions.

• bpo-38530: When printing NameError raised by the interpreter, PyErr_Display() will offer suggestions of similar variable names in the function that the exception was raised from. Patch by Pablo Galindo

• bpo-43823: Improve syntax errors for invalid dictionary literals. Patch by Pablo Galindo.

• bpo-43822: Improve syntax errors in the parser for missing commas between expressions. Patch by Pablo Galindo.

• bpo-43798: ast.alias nodes now include source location metadata attributes e.g. lineno, col_offset.

• bpo-43797: Improve SyntaxError error messages for invalid comparisons. Patch by Pablo Galindo.

• bpo-43760: Move the flag for checking whether tracing is enabled to the C stack, from the heap. Should speed up dispatch in the interpreter.

• bpo-43682: Static methods (@staticmethod) and class methods (@classmethod) now inherit the method attributes (__module__, __name__, __qualname__, __doc__, __annotations__) and have a new __wrapped__ attribute. Patch by Victor Stinner.

• bpo-43751: Fixed a bug where anext(ait, default) would erroneously return None.

• bpo-42128: __match_args__ is no longer allowed to be a list.

• bpo-43683: Add GEN_START opcode. Marks start of generator, including async, or coroutine and handles sending values to a newly created generator or coroutine.

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

• bpo-43682: Static methods (@staticmethod) are now callable as regular functions. Patch by Victor Stinner.

• bpo-42609: Prevented crashes in the AST validator and optimizer when compiling some absurdly long expressions like "+0"*1000000. RecursionError is now raised instead.

• bpo-38530: When printing AttributeError, PyErr_Display() will offer suggestions of similar attribute names in the object that the exception was raised from. Patch by Pablo Galindo

Library

• bpo-44015: In @dataclass(), raise a TypeError if KW_ONLY is specified more than once.

• bpo-25478: Added a total() method to collections.Counter() to compute the sum of the counts.

• bpo-43733: Change netrc.netrc to use UTF-8 encoding before using locale encoding.

• bpo-43979: Removed an unnecessary list comprehension before looping from urllib.parse.parse_qsl(). Patch by Christoph Zwerschke and Dong-hee Na.

• bpo-43993: Update bundled pip to 21.1.1.

• bpo-43957: [Enum] Deprecate TypeError when non-member is used in a containment check; In 3.12 True or False will be returned instead, and containment will return True if the value is either a member of that enum or one of its members’ value.

• bpo-42904: For backwards compatibility with previous minor versions of Python, if typing.get_type_hints() receives no namespace dictionary arguments, typing.get_type_hints() will search through the global then local namespaces during evaluation of stringized type annotations (string forward references) inside a class.

• bpo-43945: [Enum] Deprecate non-standard mixin format() behavior: in 3.12 the enum member, not the member’s value, will be used for format() calls.

• bpo-41139: Deprecate undocumented cgi.log() API.

• 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-43907: Fix a bug in the pure-Python pickle implementation when using protocol 5, where bytearray instances that occur several time in the pickled object graph would incorrectly unpickle into repeated copies of the bytearray object.

• bpo-43926: In importlib.metadata, provide a uniform interface to Description, allow for any field to be encoded with multiline values, remove continuation lines from multiline values, and add a .json property for easy access to the PEP 566 JSON-compatible form. Sync with importlib_metadata 4.0.

• 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-43817: Add inspect.get_annotations(), which safely computes the annotations defined on an object. It works around the quirks of accessing the annotations from various types of objects, and makes very few assumptions about the object passed in. inspect.get_annotations() can also correctly un-stringize stringized annotations.

  inspect.signature(), inspect.from_callable(), and inspect.from_function() now call inspect.get_annotations() to retrieve annotations. This means inspect.signature() and inspect.from_callable() can now un-stringize stringized annotations, too.

• 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-42854: The ssl module now uses SSL_read_ex and SSL_write_ex internally. The functions support reading and writing of data larger than 2 GB. Writing zero-length data no longer fails with a protocol violation error.

• bpo-42333: Port _ssl extension module to multiphase initialization.

• bpo-43880: ssl now raises DeprecationWarning for OP_NO_SSL/TLS* options, old TLS versions, old protocols, and other features that have been deprecated since Python 3.6, 3.7, or OpenSSL 1.1.0.

• bpo-41559: PEP 612 is now implemented purely in Python; builtin types.GenericAlias objects no longer include typing.ParamSpec in __parameters__ (with the exception of collections.abc.Callable‘s GenericAlias). This means previously invalid uses of ParamSpec (such as list[P]) which worked in earlier versions of Python 3.10 alpha, will now raise TypeError during substitution.

• bpo-43867: The multiprocessing Server class now explicitly catches SystemExit and closes the client connection in this case. It happens when the Server.serve_client() method reaches the end of file (EOF).

• bpo-40443: Remove unused imports: pyclbr no longer uses copy, and typing no longer uses ast. Patch by Victor Stinner.

• bpo-43820: Remove an unneeded copy of the namespace passed to dataclasses.make_dataclass().

• bpo-43787: Add __iter__() method to bz2.BZ2File, gzip.GzipFile, and lzma.LZMAFile. It makes iterating them about 2x faster. Patch by Inada Naoki.

• bpo-43680: Deprecate io.OpenWrapper and _pyio.OpenWrapper: use io.open and _pyio.open instead. Until Python 3.9, _pyio.open was not a static method and builtins.open was set to OpenWrapper to not become a bound method when set to a class variable. _io.open is a built-in function whereas _pyio.open is a Python function. In Python 3.10, _pyio.open() is now a static method, and builtins.open() is now io.open().

• bpo-43680: The Python _pyio.open() function becomes a static method to behave as io.open() built-in function: don’t become a bound method when stored as a class variable. It becomes possible since static methods are now callable in Python 3.10. Moreover, _pyio.OpenWrapper() becomes a simple alias to _pyio.open(). Patch by Victor Stinner.

• bpo-41515: Fix KeyError raised in typing.get_type_hints() due to synthetic modules that don’t appear in sys.modules.

• 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-42248: [Enum] ensure exceptions raised in _missing__ are released

• bpo-43744: fix issue with enum member name matching the start of a private variable name

• bpo-43772: Fixed the return value of TypeVar.__ror__. Patch by Jelle Zijlstra.

• bpo-43764: Add match_args parameter to @dataclass decorator to allow suppression of __match_args__ generation.

• 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-43478: Mocks can no longer be used as the specs for other Mocks. As a result, an already-mocked object cannot have an attribute mocked using autospec=True or be the subject of a create_autospec(...) call. This can uncover bugs in tests since these Mock-derived Mocks will always pass certain tests (e.g. isinstance()) and builtin assert functions (e.g. assert_called_once_with) will unconditionally pass.

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

• bpo-43785: Improve bz2.BZ2File performance by removing the RLock from BZ2File. This makes BZ2File thread unsafe in the face of multiple simultaneous readers or writers, just like its equivalent classes in gzip and lzma have always been. Patch by Inada Naoki.

• 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-43766: Implement PEP 647 in the typing module by adding TypeGuard.

• bpo-25264: os.path.realpath() now accepts a strict keyword-only argument. When set to True, OSError is raised if a path doesn’t exist or a symlink loop is encountered.

• bpo-43780: In importlib.metadata, incorporate changes from importlib_metadata 3.10: Add mtime-based caching during distribution discovery. Flagged use of dict result from entry_points() as deprecated.

• The P.args and P.kwargs attributes of typing.ParamSpec are now instances of the new classes typing.ParamSpecArgs and typing.ParamSpecKwargs, which enables a more useful repr(). Patch by Jelle Zijlstra.

• bpo-43731: Add an encoding parameter logging.fileConfig().

• bpo-43712: Add encoding and errors parameters to fileinput.input() and fileinput.FileInput.

• bpo-38659: A simple_enum decorator is added to the enum module to convert a normal class into an Enum. test_simple_enum added to test simple enums against a corresponding normal Enum. Standard library modules updated to use simple_enum.

• bpo-43764: Fix an issue where __match_args__ generation could fail for some dataclasses.

• bpo-43752: Fix sqlite3 regression for zero-sized blobs with converters, where b"" was returned instead of None. The regression was introduced by PR 24723. Patch by Erlend E. Aasland.

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

• bpo-43723: The following threading methods are now deprecated and should be replaced:

  • currentThread => threading.current_thread()

  • activeCount => threading.active_count()

  • Condition.notifyAll => threading.Condition.notify_all()

  • Event.isSet => threading.Event.is_set()

  • Thread.setName => threading.Thread.name

  • thread.getName => threading.Thread.name

  • Thread.isDaemon => threading.Thread.daemon

  • Thread.setDaemon => threading.Thread.daemon

  Patch by Jelle Zijlstra.

• bpo-2135: Deprecate find_module() and find_loader() implementations in importlib and zipimport.

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

• bpo-43532: Add the ability to specify keyword-only fields to dataclasses. These fields will become keyword-only arguments to the generated __init__.

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

• bpo-8978: Improve error message for tarfile.open() when lzma / bz2 are unavailable. Patch by Anthony Sottile.

• 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-43296: Improve sqlite3 error handling: sqlite3_value_blob() errors that set SQLITE_NOMEM now raise MemoryError. Patch by Erlend E. Aasland.

• bpo-43312: New functions sysconfig.get_preferred_scheme() and sysconfig.get_default_scheme() are added to query a platform for its preferred “user”, “home”, and “prefix” (default) scheme names.

• bpo-43265: Improve sqlite3.Connection.backup() error handling. The error message for non-existent target database names is now unknown database <database name> instead of SQL logic error. Patch by Erlend E. Aasland.

• bpo-41282: Install schemes in distutils.command.install are now loaded from sysconfig.

• bpo-41282: distutils.sysconfig has been merged to sysconfig.

• 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-43080: pprint now has support for dataclasses.dataclass. Patch by Lewis Gaul.

• bpo-39950: Add pathlib.Path.hardlink_to() method that supersedes link_to(). The new method has the same argument order as symlink_to().

• bpo-42904: typing.get_type_hints() now checks the local namespace of a class when evaluating PEP 563 annotations inside said class.

• bpo-42269: Add slots parameter to dataclasses.dataclass decorator to automatically generate __slots__ for class. Patch provided by Yurii Karabas.

• bpo-39529: Deprecated use of asyncio.get_event_loop() without running event loop. Emit deprecation warning for asyncio functions which implicitly create a Future or Task objects if there is no running event loop and no explicit loop argument is passed: ensure_future(), wrap_future(), gather(), shield(), as_completed() and constructors of Future, Task, StreamReader, StreamReaderProtocol.

• bpo-18369: Certificate and PrivateKey classes were added to the ssl module. Certificates and keys can now be loaded from memory buffer, too.

• bpo-41486: Use a new output buffer management code for bz2 / lzma / zlib modules, and add .readall() function to _compression.DecompressReader class. These bring some performance improvements. Patch by Ma Lin.

• bpo-31870: The ssl.get_server_certificate() function now has a timeout parameter.

• 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-40849: Expose X509_V_FLAG_PARTIAL_CHAIN ssl flag

• bpo-35114: ssl.RAND_status() now returns a boolean value (as documented) instead of 1 or 0.

• bpo-39906: pathlib.Path.stat() and chmod() now accept a follow_symlinks keyword-only argument for consistency with corresponding functions in the os module.

• bpo-39899: os.path.expanduser() now refuses to guess Windows home directories if the basename of current user’s home directory does not match their username.

  pathlib.Path.expanduser() and home() now consistently raise RuntimeError exception when a home directory cannot be resolved. Previously a KeyError exception could be raised on Windows when the "USERNAME" environment variable was unset.

• bpo-36076: Added SNI support to ssl.get_server_certificate().

• bpo-38490: Covariance, Pearson’s correlation, and simple linear regression functionality was added to statistics module. Patch by Tymoteusz Wołodźko.

• bpo-33731: Provide a locale.localize() function, which converts a normalized number string into a locale format.

• 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-43987: Add “Annotations Best Practices” document as a new HOWTO.

• bpo-43977: Document the new Py_TPFLAGS_MAPPING and Py_TPFLAGS_SEQUENCE type flags.

• 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-43778: Fix the Sphinx glossary_search extension: create the _static/ sub-directory if it doesn’t exist.

• 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-43843: test.libregrtest now marks a test as ENV_CHANGED (altered the execution environment) if a thread raises an exception but does not catch it. It sets a hook on threading.excepthook(). Use --fail-env-changed option to mark the test as failed. 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.

Build

• bpo-43567: Improved generated code refresh (AST/tokens/opcodes/keywords) on Windows.

• bpo-43669: Implement PEP 644. Python now requires OpenSSL 1.1.1 or newer.

Windows

• bpo-35306: Adds additional arguments to os.startfile() function.

• bpo-43538: 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-43652: Update Tcl and Tk to 8.6.11 in Windows installer.

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

• bpo-30555: Fix WindowsConsoleIO errors in the presence of fd redirection. Patch by Segev Finer.

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-43568: Drop support for MACOSX_DEPLOYMENT_TARGET < 10.3

• 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-43851: Build SQLite with SQLITE_OMIT_AUTOINIT on macOS. Patch by Erlend E. Aasland.

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

• bpo-42235: Mac/BuildScript/build-installer.py will now use “–enable-optimizations” and --with-lto when building on macOS 10.15 or later.

IDLE

• bpo-37903: Add mouse actions to the shell sidebar. Left click and optional drag selects one or more lines, as with the editor line number sidebar. Right click after selecting raises a context menu with ‘copy with prompts’. This zips together prompts from the sidebar with lines from the selected text.

• bpo-43981: Fix reference leak in test_sidebar and test_squeezer. Patches by Terry Jan Reedy and Pablo Galindo

• bpo-37892: Indent IDLE Shell input with spaces instead of tabs

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

• bpo-37903: IDLE’s shell now shows prompts in a separate side-bar.

C API

• bpo-43916: Add a new Py_TPFLAGS_DISALLOW_INSTANTIATION type flag to disallow creating type instances. Patch by Victor Stinner.

• bpo-43774: Remove the now unused PYMALLOC_DEBUG macro. Debug hooks on memory allocators are now installed by default if Python is built in debug mode (if Py_DEBUG macro is defined). Moreover, they can now be used on Python build in release mode (ex: using PYTHONMALLOC=debug environment variable).

• bpo-43962: _PyInterpreterState_IDIncref() now calls _PyInterpreterState_IDInitref() and always increments id_refcount. Previously, calling _xxsubinterpreters.get_current() could create an id_refcount inconsistency when a _xxsubinterpreters.InterpreterID object was deallocated. Patch by Victor Stinner.

• bpo-28254: Add new C-API functions to control the state of the garbage collector: PyGC_Enable(), PyGC_Disable(), PyGC_IsEnabled(), corresponding to the functions in the gc module.

• bpo-43908: Introduce Py_TPFLAGS_IMMUTABLETYPE flag for immutable type objects, and modify PyType_Ready() to set it for static types. Patch by Erlend E. Aasland.

• bpo-43795: PyMem_Calloc() is now available in the limited C API (Py_LIMITED_API).

• bpo-43868: PyOS_ReadlineFunctionPointer() is no longer exported by limited C API headers and by python3.dll on Windows. Like any function that takes FILE*, it is not part of the stable ABI.

• bpo-43795: Stable ABI and limited API definitions are generated from a central manifest (PEP 652).

• bpo-43753: Add the Py_Is(x, y) function to test if the x object is the y object, the same as x is y in Python. Add also the Py_IsNone(), Py_IsTrue(), Py_IsFalse() functions to test if an object is, respectively, the None singleton, the True singleton or the False singleton. Patch by Victor Stinner.

Python 3.10.0 alpha 7

Release date: 2021-04-05

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-27129: Update CPython bytecode magic number.

• bpo-43672: Raise ImportWarning when calling find_loader().

• 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-27129: The bytecode interpreter uses instruction, rather byte, offsets internally. This reduces the number of EXTENDED_ARG instructions needed and streamlines instruction dispatch a bit.

• bpo-40645: Fix reference leak in the _hashopenssl extension. Patch by Pablo Galindo.

• bpo-42134: Calls to find_module() by the import system now raise ImportWarning.

• bpo-41064: Improve the syntax error for invalid usage of double starred elements (‘**’) in f-strings. Patch by Pablo Galindo.

• bpo-43575: Speed up calls to map() by using the PEP 590 vectorcall calling convention. Patch by Dong-hee Na.

• bpo-42137: The import system now prefers using __spec__ for ModuleType.__repr__ over module_repr().

• bpo-43452: Added micro-optimizations to _PyType_Lookup() to improve cache lookup performance in the common case of cache hits.

• 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-43497: Emit SyntaxWarnings for assertions with tuple constants, this is a regression introduced in python3.7

• bpo-39316: Tracing now has correct line numbers for attribute accesses when the attribute is on a different line from the object. Improves debugging and profiling for multi-line method chains.

• 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-43410: Fix a bug that was causing the parser to crash when emitting syntax errors when reading input from stdin. Patch by Pablo Galindo

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

• bpo-42128: Add __match_args__ to structsequence based classes. Patch by Pablo Galindo.

• bpo-43390: CPython now sets the SA_ONSTACK flag in PyOS_setsig for the VM’s default signal handlers. This is friendlier to other in-process code that an extension module or embedding use could pull in (such as Golang’s cgo) where tiny thread stacks are the norm and sigaltstack() has been used to provide for signal handlers. This is a no-op change for the vast majority of processes that don’t use sigaltstack.

• bpo-43287: Speed up calls to filter() by using the PEP 590 vectorcall calling convention. Patch by Dong-hee Na.

• bpo-37448: Add a radix tree based memory map to track in-use obmalloc arenas. Use to replace the old implementation of address_in_range(). The radix tree approach makes it easy to increase pool sizes beyond the OS page size. Boosting the pool and arena size allows obmalloc to handle a significantly higher percentage of requests from its ultra-fast paths.

  It also has the advantage of eliminating the memory unsanitary behavior of the previous address_in_range(). The old address_in_range() was marked with the annotations _Py_NO_SANITIZE_ADDRESS, _Py_NO_SANITIZE_THREAD, and _Py_NO_SANITIZE_MEMORY. Those annotations are no longer needed.

  To disable the radix tree map, set a preprocessor flag as follows: -DWITH_PYMALLOC_RADIX_TREE=0.

  Co-authored-by: Tim Peters <tim.peters@gmail.com>

• bpo-29988: Only handle asynchronous exceptions and requests to drop the GIL when returning from a call or on the back edges of loops. Makes sure that __exit__() is always called in with statements, even for interrupts.

Library

• bpo-43720: Document various stdlib deprecations in imp, pkgutil, and importlib.util for removal in Python 3.12.

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

• bpo-31956: The index() method of array.array now has optional start and stop parameters.

• bpo-40066: Enum: adjust repr() to show only enum and member name (not value, nor angle brackets) and str() to show only member name. Update and improve documentation to match.

• bpo-42136: Deprecate all module_repr() methods found in importlib as their use is being phased out by Python 3.12.

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

• bpo-41369: Finish updating the vendored libmpdec to version 2.5.1. Patch by Stefan Krah.

• bpo-43422: Revert the _decimal C API which was added in bpo-41324.

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

• bpo-43571: It’s now possible to create MPTCP sockets with IPPROTO_MPTCP

• bpo-43542: image/heic and image/heif were added to mimetypes.

• bpo-40645: The hmac module now uses OpenSSL’s HMAC implementation when digestmod argument is a hash name or builtin hash function.

• bpo-43510: Implement PEP 597: Add EncodingWarning warning, -X warn_default_encoding option, PYTHONWARNDEFAULTENCODING environment variable and encoding="locale" argument value.

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

• bpo-42914: pprint.pprint() gains a new boolean underscore_numbers optional argument to emit integers with thousands separated by an underscore character for improved readability (for example 1_000_000 instead of 1000000).

• bpo-41361: rotate() calls are now slightly faster due to faster argument parsing.

• 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-43445: Add frozen modules to sys.stdlib_module_names. For example, add "_frozen_importlib" and "_frozen_importlib_external" names.

• bpo-43245: Add keyword arguments support to ChainMap.new_child().

• bpo-29982: Add optional parameter ignore_cleanup_errors to tempfile.TemporaryDirectory() and allow multiple cleanup() attempts. Contributed by C.A.M. Gerlach.

• bpo-43428: Include changes from importlib_metadata 3.7:

  Performance enhancements to distribution discovery.

  entry_points only returns unique distributions.

  Introduces new EntryPoints object for containing a set of entry points with convenience methods for selecting entry points by group or name. entry_points now returns this object if selection parameters are supplied but continues to return a dict object for compatibility. Users are encouraged to rely on the selection interface. The dict object result is likely to be deprecated in the future.

  Added packages_distributions function to return a mapping of packages to the distributions that provide them.

• 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-43420: Improve performance of fractions.Fraction arithmetics for large components. Contributed by Sergey B. Kirpichev.

• bpo-43356: Allow passing a signal number to _thread.interrupt_main().

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

• bpo-43369: Improve sqlite3 error handling: If sqlite3_column_text() and sqlite3_column_blob() set SQLITE_NOMEM, MemoryError is now raised. Patch by Erlend E. Aasland.

• bpo-43368: Fix a regression introduced in PR 24562, where an empty bytestring was fetched as None instead of b'' in sqlite3. Patch by Mariusz Felisiak.

• bpo-41282: Fixed stacklevel of DeprecationWarning emitted from import distutils.

• bpo-42129: importlib.resources now honors namespace packages, merging resources from each location in the namespace as introduced in importlib_resources 3.2 and including incidental changes through 5.0.3.

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

• bpo-43125: Return empty string if base64mime.body_encode receive empty bytes

• bpo-43084: curses.window.enclose() returns now True or False (as was documented) instead of 1 or 0.

• bpo-42994: Add MIME types for opus, AAC, 3gpp and 3gpp2

• bpo-14678: Add an invalidate_caches() method to the zipimport.zipimporter class to support importlib.invalidate_caches(). Patch by Desmond Cheong.

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

• bpo-40066: Enum’s repr() and str() have changed: repr() is now EnumClass.MemberName and str() is MemberName. Additionally, stdlib Enum’s whose contents are available as module attributes, such as RegexFlag.IGNORECASE, have their repr() as module.name, e.g. re.IGNORECASE.

• 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.

• bpo-24160: Fixed bug where breakpoints did not persist across multiple debugger sessions in pdb’s interactive mode.

• bpo-40701: When the tempfile.tempdir global variable is set to a value of type bytes, it is now handled consistently. Previously exceptions could be raised from some tempfile APIs when the directory did not already exist in this situation. Also ensures that the tempfile.gettempdir() and tempfile.gettempdirb() functions always return str and bytes respectively.

• bpo-39342: Expose X509_V_FLAG_ALLOW_PROXY_CERTS as VERIFY_ALLOW_PROXY_CERTS to allow proxy certificate validation as explained in https://www.openssl.org/docs/man1.1.1/man7/proxy-certificates.html.

• bpo-31861: Add builtins.aiter and builtins.anext. Patch by Joshua Bronson (@jab), Daniel Pope (@lordmauve), and Justin Wang (@justin39).

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-43354: Fix type documentation for Fault.faultCode; the type has to be int instead of str.

• bpo-41933: Clarified wording of s * n in the Common Sequence Operations

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.

Build

• bpo-43179: Introduce and correctly use ALIGNOF_X in place of SIZEOF_X for alignment-related code in optimized string routines. Patch by Jessica Clarke.

• 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.

• bpo-43466: The configure script now supports --with-openssl-rpath option.

• bpo-43372: Use _freeze_importlib to generate code for the __hello__ module. This approach ensures the code matches the interpreter version. Previously, PYTHON_FOR_REGEN was used to generate the code, which might be wrong. The marshal format for code objects has changed with bpo-42246, commit 877df851. Update the code and the expected code sizes in ctypes test_frozentable.

Windows

• bpo-43440: Build sqlite3 with the R*Tree module enabled. Patch by Erlend E. Aasland.

IDLE

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

C API

• bpo-43688: The limited C API is now supported if Python is built in debug mode (if the Py_DEBUG macro is defined). In the limited C API, the Py_INCREF() and Py_DECREF() functions are now implemented as opaque function calls, rather than accessing directly the PyObject.ob_refcnt member, if Python is built in debug mode and the Py_LIMITED_API macro targets Python 3.10 or newer. It became possible to support the limited C API in debug mode because the PyObject structure is the same in release and debug mode since Python 3.8 (see bpo-36465).

  The limited C API is still not supported in the --with-trace-refs special build (Py_TRACE_REFS macro).

  Patch by Victor Stinner.

• bpo-43244: Remove the pyarena.h header file with functions:

  • PyArena_New()

  • PyArena_Free()

  • PyArena_Malloc()

  • PyArena_AddPyObject()

  These functions were undocumented, excluded from the limited C API, and were only used internally by the compiler. Patch by Victor Stinner.

• bpo-43244: Remove the compiler and parser functions using struct _mod type, because the public AST C API was removed:

  • PyAST_Compile()

  • PyAST_CompileEx()

  • PyAST_CompileObject()

  • PyFuture_FromAST()

  • PyFuture_FromASTObject()

  • PyParser_ASTFromFile()

  • PyParser_ASTFromFileObject()

  • PyParser_ASTFromFilename()

  • PyParser_ASTFromString()

  • PyParser_ASTFromStringObject()

  These functions were undocumented and excluded from the limited C API. Patch by Victor Stinner.

• bpo-43244: Remove ast.h, asdl.h, and Python-ast.h header files. These functions were undocumented and excluded from the limited C API. Most names defined by these header files were not prefixed by Py and so could create names conflicts. For example, Python-ast.h defined a Yield macro which was conflict with the Yield name used by the Windows <winbase.h> header. Use the Python ast module instead. Patch by Victor Stinner.

• bpo-43541: Fix a PyEval_EvalCodeEx() regression: fix reference counting on builtins. Patch by Victor Stinner.

• bpo-43244: Remove the symtable.h header file and the undocumented functions:

  • PyST_GetScope()

  • PySymtable_Build()

  • PySymtable_BuildObject()

  • PySymtable_Free()

  • Py_SymtableString()

  • Py_SymtableStringObject()

  The Py_SymtableString() function was part the stable ABI by mistake but it could not be used, because the symtable.h header file was excluded from the limited C API.

  The Python symtable module remains available and is unchanged.

  Patch by Victor Stinner.

• bpo-43244: Remove the PyAST_Validate() function. It is no longer possible to build a AST object (mod_ty type) with the public C API. The function was already excluded from the limited C API (PEP 384). Patch by Victor Stinner.

Python 3.10.0 alpha 6

Release date: 2021-03-01

Security

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

Core and Builtins

• bpo-43321: Fix SystemError raised when PyArg_Parse*() is used with # but without PY_SSIZE_T_CLEAN defined.

• bpo-36346: PyArg_Parse*() functions now emits DeprecationWarning when u or Z format is used. See PEP 623 for detail.

• bpo-43277: Add a new PySet_CheckExact() function to the C-API to check if an object is an instance of set but not an instance of a subtype. Patch by Pablo Galindo.

• bpo-42990: The types.FunctionType constructor now inherits the current builtins if the globals dictionary has no "__builtins__" key, rather than using {"None": None} as builtins: same behavior as eval() and exec() functions. Defining a function with def function(...): ... in Python is not affected, globals cannot be overridden with this syntax: it also inherits the current builtins. Patch by Victor Stinner.

• bpo-42990: Functions have a new __builtins__ attribute which is used to look for builtin symbols when a function is executed, instead of looking into __globals__['__builtins__']. Patch by Mark Shannon and Victor Stinner.

• bpo-43149: Improve the error message in the parser for exception groups without parentheses. Patch by Pablo Galindo.

• bpo-43121: Fixed an incorrect SyntaxError message for missing comma in literals. Patch by Pablo Galindo.

• 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-42808: Simple calls to type(object) are now faster due to the vectorcall calling convention. Patch by Dennis Sweeney.

• bpo-42217: Make the compiler merges same co_code and co_linetable objects in a module like already did for co_consts.

• bpo-41972: Substring search functions such as str1 in str2 and str2.find(str1) now sometimes use the “Two-Way” string comparison algorithm to avoid quadratic behavior on long strings.

• bpo-42128: Implement PEP 634 (structural pattern matching). Patch by Brandt Bucher.

• bpo-40692: In the concurrent.futures.ProcessPoolExecutor, validate that multiprocess.synchronize() is available on a given platform and rely on that check in the concurrent.futures test suite so we can run tests that are unrelated to ProcessPoolExecutor on those platforms.

• bpo-38302: If object.__ipow__() returns NotImplemented, the operator will correctly fall back to object.__pow__() and object.__rpow__() as expected.

Library

• 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-43317: Set the chunk size for the gzip module main function to io.DEFAULT_BUFFER_SIZE. This is slightly faster than the 1024 bytes constant that was used previously.

• bpo-43146: Handle None in single-arg versions of print_exception() and format_exception().

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

• bpo-43258: Prevent needless allocation of sqlite3 aggregate function context when no rows match an aggregate query. Patch by Erlend E. Aasland.

• bpo-43251: Improve sqlite3 error handling: sqlite3_column_name() failures now result in MemoryError. Patch by Erlend E. Aasland.

• bpo-40956: Fix segfault in sqlite3.Connection.backup() if no argument was provided. The regression was introduced by PR 23838. Patch by Erlend E. Aasland.

• bpo-43172: The readline module now passes its tests when built directly against libedit. Existing irreconcilable API differences remain in readline.get_begidx() and readline.get_endidx() behavior based on libreadline vs libedit use.

• bpo-43163: Fix a bug in codeop that was causing it to not ask for more input when multi-line snippets have unclosed parentheses. Patch by Pablo Galindo

• bpo-43162: deprecate unsupported ability to access enum members as attributes of other enum members

• bpo-43146: Fix recent regression in None argument handling in traceback module functions.

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

• bpo-43106: Added O_EVTONLY, O_FSYNC, O_SYMLINK and O_NOFOLLOW_ANY for macOS. Patch by Dong-hee Na.

• bpo-42960: Adds resource.RLIMIT_KQUEUES constant from FreeBSD to the resource module.

• bpo-42151: Make the pure Python implementation of xml.etree.ElementTree behave the same as the C implementation (_elementree) regarding default attribute values (by not setting specified_attributes=1).

• bpo-29753: In ctypes, now packed bitfields are calculated properly and the first item of packed bitfields is now shrank correctly.

Documentation

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

Build

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

• bpo-43103: Add a new configure --without-static-libpython option to not build the libpythonMAJOR.MINOR.a static library and not install the python.o object file.

• bpo-13501: The configure script can now use libedit instead of readline with the command line option --with-readline=editline.

• bpo-42603: Make configure script use pkg-config to detect the location of Tcl/Tk headers and libraries, used to build tkinter.

  On macOS, a Tcl/Tk configuration provided by pkg-config will be preferred over Tcl/Tk frameworks installed in /{System/,}Library/Frameworks. If both exist and the latter is preferred, the appropriate --with-tcltk-* configuration options need to be explicitly set.

• bpo-39448: Add the “regen-frozen” makefile target that regenerates the code for the frozen __hello__ module.

Windows

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

macOS

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

IDLE

• 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.

C API

• bpo-43278: Always put compiler and system information on the first line of the REPL welcome message.

• bpo-43270: Remove the private _PyErr_OCCURRED() macro: use the public PyErr_Occurred() function instead.

• bpo-35134: Move odictobject.h, parser_interface.h, picklebufobject.h, pydebug.h, and pyfpe.h into the cpython/ directory. They must not be included directly, as they are already included by Python.h: Include Files.

• bpo-35134: Move pyarena.h, pyctype.h, and pytime.h into the cpython/ directory. They must not be included directly, as they are already included by Python.h: Include Files.

• bpo-40170: PyExceptionClass_Name() is now always declared as a function, in order to hide implementation details. The macro accessed PyTypeObject.tp_name directly. Patch by Erlend E. Aasland.

• bpo-43239: The PyCFunction_New() function is now exported in the ABI when compiled with -fvisibility=hidden.

• bpo-40170: PyIter_Check() is now always declared as a function, in order to hide implementation details. The macro accessed PyTypeObject.tp_iternext directly. Patch by Erlend E. Aasland.

• bpo-40170: Convert PyDescr_IsData() macro to a function to hide implementation details: The macro accessed PyTypeObject.tp_descr_set directly. Patch by Erlend E. Aasland.

• bpo-43181: Convert PyObject_TypeCheck() macro to a static inline function. Patch by Erlend E. Aasland.

Python 3.10.0 alpha 5

Release date: 2021-02-02

Security

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

Core and Builtins

• bpo-42990: Refactor the PyEval_ family of functions.

  • An new function _PyEval_Vector is added to simplify calls to Python from C.

  • _PyEval_EvalCodeWithName is removed

  • PyEval_EvalCodeEx is retained as part of the API, but is not used internally

• bpo-38631: Replace Py_FatalError() calls in the compiler with regular SystemError exceptions. Patch by Victor Stinner.

• bpo-42997: Improve error message for missing “:” before blocks. Patch by Pablo Galindo.

• bpo-43017: Improve error message in the parser when using un-parenthesised tuples in comprehensions. Patch by Pablo Galindo.

• bpo-42986: Fix parser crash when reporting syntax errors in f-string with newlines. Patch by Pablo Galindo.

• bpo-40176: Syntax errors for unterminated string literals now point to the start of the string instead of reporting EOF/EOL.

• bpo-42927: The inline cache for LOAD_ATTR now also optimizes access to attributes defined by __slots__. This makes reading such attribute up to 30% faster.

• bpo-42864: Improve error messages in the parser when parentheses are not closed. Patch by Pablo Galindo.

• 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).

• bpo-42882: Fix the _PyUnicode_FromId() function (_Py_IDENTIFIER(var) API) when Py_Initialize() / Py_Finalize() is called multiple times: preserve _PyRuntime.unicode_ids.next_index value.

• bpo-42827: Fix a crash when working out the error line of a SyntaxError in some multi-line expressions.

• bpo-42823: frame.f_lineno is correct even if frame.f_trace is set to True

• bpo-37324: Remove deprecated aliases to Collections Abstract Base Classes from the collections module.

• bpo-41994: Fixed possible leak in import when sys.modules is not a dict.

• bpo-27772: In string formatting, preceding the width field by '0' no longer affects the default alignment for strings.

Library

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

• bpo-43077: Update the bundled pip to 21.0.1 and setuptools to 52.0.0.

• bpo-41282: Deprecate distutils in documentation and add warning on import.

• bpo-43014: Improve performance of tokenize by 20-30%. Patch by Anthony Sottile.

• bpo-42323: Fix math.nextafter() for NaN on AIX.

• bpo-42955: Add sys.stdlib_module_names, containing the list of the standard library module names. Patch by Victor Stinner.

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

• bpo-42934: Use TracebackException’s new compact param in TestResult to reduce time and memory consumed by traceback formatting.

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

• bpo-38250: [Enum] Flags consisting of a single bit are now considered canonical, and will be the only flags returned from listing and iterating over a Flag class or a Flag member. Multi-bit flags are considered aliases; they will be returned from lookups and operations that result in their value. Iteration for both Flag and Flag members is in definition order.

• bpo-42877: Added the compact parameter to the constructor of traceback.TracebackException to reduce time and memory for use cases that only need to call TracebackException.format() and TracebackException.format_exception_only().

• bpo-42923: The Py_FatalError() function and the faulthandler module now dump the list of extension modules on a fatal error.

• bpo-42848: Removed recursion from TracebackException to allow it to handle long exception chains.

• bpo-42901: [Enum] move member creation from EnumMeta.__new__ to _proto_member.__set_name__, allowing members to be created and visible in __init_subclass__.

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

• bpo-42866: Fix a reference leak in the getcodec() function of CJK codecs. Patch by Victor Stinner.

• bpo-42846: Convert the 6 CJK codec extension modules (_codecs_cn, _codecs_hk, _codecs_iso2022, _codecs_jp, _codecs_kr and _codecs_tw) to the multiphase initialization API (PEP 489). Patch by Victor Stinner.

• bpo-42851: remove __init_subclass__ support for Enum members

• bpo-42834: Make internal caches of the _json module compatible with subinterpreters.

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

• bpo-40810: Require SQLite 3.7.15 or newer. Patch by Erlend E. Aasland.

• bpo-1635741: Convert the _multibytecodec extension module (CJK codecs) to multi-phase initialization (PEP 489). Patch by Erlend E. Aasland.

• bpo-42802: The distutils bdist_wininst command deprecated in Python 3.8 has been removed. The distutils bdist_wheel command is now recommended to distribute binary packages on Windows.

• bpo-24464: The undocumented built-in function sqlite3.enable_shared_cache is now deprecated, scheduled for removal in Python 3.12. Its use is strongly discouraged by the SQLite3 documentation. Patch by Erlend E. Aasland.

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

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

• bpo-41149: Allow executing callables that have a boolean value of False when passed to Threading.thread as the target. Patch contributed by Barney Stratford.

• bpo-38307: Add an ‘end_lineno’ attribute to the Class and Function objects that appear in the tree returned by pyclbr functions. This and the existing ‘lineno’ attribute define the extent of class and def statements. Patch by Aviral Srivastava.

• bpo-39273: The BUTTON5_* constants are now exposed in the curses module if available.

• 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.)

Tests

• bpo-40823: Use unittest.TestLoader().loadTestsFromTestCase() instead of unittest.makeSuite() in sqlite3 tests. Patch by Erlend E. Aasland.

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

Build

• bpo-43031: Pass --timeout=$(TESTTIMEOUT) option to the default profile task ./python -m test --pgo command.

• bpo-36143: make regen-all now also runs regen-keyword. Patch by Victor Stinner.

• bpo-42874: Removed the grep -q and -E flags in the tzpath validation section of the configure script to better accommodate users of some platforms (specifically Solaris 10).

• bpo-31904: Add library search path by wr-cc in add_cross_compiling_paths() for VxWorks.

• bpo-42856: Add --with-wheel-pkg-dir=PATH option to the ./configure script. If specified, the ensurepip module looks for setuptools and pip wheel packages in this directory: if both are present, these wheel packages are used instead of ensurepip bundled wheel packages.

  Some Linux distribution packaging policies recommend against bundling dependencies. For example, Fedora installs wheel packages in the /usr/share/python-wheels/ directory and don’t install the ensurepip._bundled package.

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.

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.

C API

• bpo-42979: When Python is built in debug mode (with C assertions), calling a type slot like sq_length (__len__() in Python) now fails with a fatal error if the slot succeeded with an exception set, or failed with no exception set. The error message contains the slot, the type name, and the current exception (if an exception is set). Patch by Victor Stinner.

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

Python 3.10.0 alpha 4

Release date: 2021-01-04

Core and Builtins

• bpo-42814: Fix undefined behavior in Objects/genericaliasobject.c.

• 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-27794: Improve the error message for failed writes/deletes to property objects. When possible, the attribute name is now shown. Patch provided by Yurii Karabas.

• bpo-42745: Make the type attribute lookup cache per-interpreter. Patch by Victor Stinner.

• bpo-42246: Jumps to jumps are not eliminated when it would break PEP 626.

• bpo-42246: Make sure that the f_lasti and f_lineno attributes of a frame are set correctly when an exception is raised or re-raised. Required for PEP 626.

• bpo-32381: The coding cookie (ex: # coding: latin1) is now ignored in the command passed to the -c command line option. Patch by Victor Stinner.

• bpo-30858: Improve error location in expressions that contain assignments. Patch by Pablo Galindo and Lysandros Nikolaou.

• bpo-42615: Remove jump commands made redundant by the deletion of unreachable bytecode blocks

• bpo-42639: Make the atexit module state per-interpreter. It is now safe have more than one atexit module instance. Patch by Dong-hee Na and Victor Stinner.

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

• 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 Callables no longer validate their argtypes, in Callable[[argtypes], resulttype] to prepare for PEP 612. Patch by Ken Jin.

• bpo-40137: Convert functools module to use PyType_FromModuleAndSpec().

• bpo-40077: Convert array to use heap types, and establish module state for these.

• bpo-42008: Fix _random.Random() seeding.

• bpo-1635741: Port the pyexpat extension module to multi-phase initialization (PEP 489).

• bpo-40521: Make the Unicode dictionary of interned strings compatible with subinterpreters. Patch by Victor Stinner.

• bpo-39465: Make _PyUnicode_FromId() function compatible with subinterpreters. Each interpreter now has an array of identifier objects (interned strings decoded from UTF-8). Patch by Victor Stinner.

Library

• bpo-42257: Handle empty string in variable executable in platform.libc_ver()

• bpo-42772: randrange() now raises a TypeError when step is specified without a stop argument. Formerly, it silently ignored the step argument.

• 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-42740: typing.get_args() and typing.get_origin() now support PEP 604 union types and PEP 612 additions to Callable.

• 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-38308: Add optional weights to statistics.harmonic_mean().

• bpo-42721: When simple query dialogs (tkinter.simpledialog), message boxes (tkinter.messagebox) or color choose dialog (tkinter.colorchooser) are created without arguments master and parent, and the default root window is not yet created, and NoDefaultRoot() was not called, a new temporal hidden root window will be created automatically. It will not be set as the default root window and will be destroyed right after closing the dialog window. It will help to use these simple dialog windows in programs which do not need other GUI.

• bpo-25246: Optimized collections.deque.remove().

• bpo-35728: Added a root parameter to tkinter.font.nametofont().

• bpo-15303: tkinter supports now widgets with boolean value False.

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

• bpo-42685: Improved placing of simple query windows in Tkinter (such as tkinter.simpledialog.askinteger()). They are now centered at the center of the parent window if it is specified and shown, otherwise at the center of the screen.

• bpo-9694: Argparse help no longer uses the confusing phrase, “optional arguments”. It uses “options” instead.

• bpo-1635741: Port the _thread extension module to the multiphase initialization API (PEP 489) and convert its static types to heap types.

• 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-42639: atexit._run_exitfuncs() now logs callback exceptions using sys.unraisablehook, rather than logging them directly into sys.stderr and raise the last exception.

• 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-42639: At Python exit, if a callback registered with atexit.register() fails, its exception is now logged. Previously, only some exceptions were logged, and the last exception was always silently ignored.

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

• bpo-42382: In importlib.metadata: - EntryPoint objects now expose a .dist object referencing the Distribution when constructed from a Distribution. - Add support for package discovery under package normalization rules. - The object returned by metadata() now has a formally-defined protocol called PackageMetadata with declared support for the .get_all() method. - Synced with importlib_metadata 3.3.

• bpo-41877: A check is added against misspellings of autospect, auto_spec and set_spec being passed as arguments to patch, patch.object and create_autospec.

• bpo-39717: [tarfile] update nested exception raising to use from None or from e

• bpo-41877: AttributeError for suspected misspellings of assertions on mocks are now pointing out that the cause are misspelled assertions and also what to do if the misspelling is actually an intended attribute name. The unittest.mock document is also updated to reflect the current set of recognised misspellings.

• bpo-41559: Implemented PEP 612: added ParamSpec and Concatenate to typing. Patch by Ken Jin.

• bpo-42385: StrEnum: fix _generate_next_value_ to return a str

• bpo-31904: Define THREAD_STACK_SIZE for VxWorks.

• bpo-34750: [Enum] _EnumDict.update() is now supported

• bpo-42517: Enum: private names do not become members / do not generate errors – they remain normal attributes

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

• bpo-28964: ast.literal_eval() adds line number information (if available) in error message for malformed nodes.

• bpo-42470: random.sample() no longer warns on a sequence which is also a set.

• bpo-31904: posixpath.expanduser() returns the input path unchanged if user home directory is None on VxWorks.

• 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-42393: Raise OverflowError instead of silent truncation in socket.ntohs() and socket.htons(). Silent truncation was deprecated in Python 3.7. Patch by Erlend E. Aasland

• bpo-42222: Harmonized random.randrange() argument handling to match range().

  • The integer test and conversion in randrange() now uses operator.index().

  • Non-integer arguments to randrange() are deprecated.

  • The ValueError is deprecated in favor of a TypeError.

  • It now runs a little faster than before.

  (Contributed by Raymond Hettinger and Serhiy Storchaka.)

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

• bpo-42090: zipfile.Path.joinpath now accepts arbitrary arguments, same as pathlib.Path.joinpath.

• bpo-1635741: Port the _csv module to the multi-phase initialization API (PEP 489).

• 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-41960: Add globalns and localns parameters to the inspect.signature() and inspect.Signature.from_callable().

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

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

• bpo-24792: Fixed bug where zipimporter sometimes reports an incorrect cause of import errors.

• bpo-31904: Fix site and sysconfig modules for VxWorks RTOS which has no home directories.

• bpo-41462: Add os.set_blocking() support for VxWorks RTOS.

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

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

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

Documentation

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

• bpo-34398: Prominently feature listings from the glossary in documentation search results. Patch by Ammar Askar.

Tests

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

• bpo-31904: Skip some asyncio tests on VxWorks.

• bpo-42641: Enhance test_select.test_select(): it now takes 500 milliseconds rather than 10 seconds. Use Python rather than a shell to make the test more portable.

• bpo-31904: Skip some tests in _test_all_chown_common() on VxWorks.

• bpo-42199: Fix bytecode helper assertNotInBytecode.

• bpo-41443: Add more attribute checking in test_posix.py

• bpo-31904: Disable os.popen and impacted tests on VxWorks

• bpo-41439: Port test_ssl and test_uuid to VxWorks RTOS.

Build

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

• bpo-27640: Added --disable-test-modules option to the configure script: don’t build nor install test modules. Patch by Xavier de Gaye, Thomas Petazzoni and Peixing Xin.

• 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”). Previously 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-31904: Enable libpython3.so for VxWorks.

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

macOS

• 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.

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-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-32381: Remove the private _Py_fopen() function which is no longer needed. Use _Py_wfopen() or _Py_fopen_obj() instead. Patch by Victor Stinner.

• bpo-1635741: Port resource extension module to module state

• bpo-42111: Update the xxlimited module to be a better example of how to use the limited C API.

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

Python 3.10.0 alpha 3

Release date: 2020-12-07

Security

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

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.

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

• bpo-42246: PEP 626: After a return, the f_lineno attribute of a frame is always the last line executed.

• bpo-42435: Speed up comparison of bytes objects with non-bytes objects when option -b is specified. Speed up comparison of bytarray objects with non-buffer object.

• bpo-1635741: Port the _warnings extension module to the multi-phase initialization API (PEP 489). Patch by Victor Stinner.

• 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-42202: Change function parameters annotations internal representation to tuple of strings. Patch provided by Yurii Karabas.

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

• bpo-42316: Allow an unparenthesized walrus in subscript indexes.

• bpo-42349: Make sure that the compiler front-end produces a well-formed control flow graph. Be be more aggressive in the compiler back-end, as it is now safe to do so.

• 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-42282: Optimise constant subexpressions that appear as part of named expressions (previously the AST optimiser did not descend into named expressions). Patch by Nick Coghlan.

• bpo-42266: Fixed a bug with the LOAD_ATTR opcode cache that was not respecting monkey-patching a class-level attribute to make it a descriptor. Patch by Pablo Galindo.

• bpo-40077: Convert queue to use heap types.

• bpo-42246: Improved accuracy of line tracing events and f_lineno attribute of Frame objects. See PEP 626 for details.

• bpo-40077: Convert mmap to use heap types.

• bpo-42233: Allow GenericAlias objects to use union type expressions. This allows expressions like list[int] | dict[float, str] where previously a TypeError would have been thrown. This also fixes union type expressions not de-duplicating GenericAlias objects. (Contributed by Ken Jin in bpo-42233.)

• bpo-26131: The import system triggers a ImportWarning when it falls back to using load_module().

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-42562: Fix issue when dis failed to parse function that has no line numbers. Patch provided by Yurii Karabas.

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

• bpo-38200: Added itertools.pairwise()

• bpo-41818: Fix test_master_read() so that it succeeds on all platforms that either raise OSError or return b”” upon reading from master.

• 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-41818: Make test_openpty() avoid unexpected success due to number of rows and/or number of columns being == 0.

• bpo-42392: Remove loop parameter from asyncio.subprocess and asyncio.tasks functions. Patch provided by Yurii Karabas.

• bpo-42392: Remove loop parameter from asyncio.open_connection and asyncio.start_server functions. Patch provided by Yurii Karabas.

• bpo-28468: Add platform.freedesktop_os_release() function to parse freedesktop.org os-release files.

• bpo-42299: Removed the formatter module, which was deprecated in Python 3.4. It is somewhat obsolete, little used, and not tested. It was originally scheduled to be removed in Python 3.6, but such removals were delayed until after Python 2.7 EOL. Existing users should copy whatever classes they use into their code. Patch by Dong-hee Na and and Terry J. Reedy.

• bpo-26131: Deprecate zipimport.zipimporter.load_module() in favour of exec_module().

• bpo-41818: Updated tests for the pty library. test_basic() has been changed to test_openpty(); this additionally checks if slave termios and slave winsize are being set properly by pty.openpty(). In order to add support for FreeBSD, NetBSD, OpenBSD, and Darwin, this also adds test_master_read(), which demonstrates that pty.spawn() should not depend on an OSError to exit from its copy loop.

• bpo-42392: Remove loop parameter from __init__ in all asyncio.locks and asyncio.Queue classes. Patch provided by Yurii Karabas.

• bpo-15450: Make filecmp.dircmp respect subclassing. Now the filecmp.dircmp.subdirs behaves as expected when subclassing dircmp.

• bpo-42413: The exception socket.timeout is now an alias of TimeoutError.

• bpo-31904: Support signal module on VxWorks.

• 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-42403: Simplify the importlib external bootstrap code: importlib._bootstrap_external now uses regular imports to import builtin modules. When it is imported, the builtin __import__() function is already fully working and so can be used to import builtin modules like sys. Patch by Victor Stinner.

• bpo-1635741: Convert _sre module types to heap types (PEP 384). Patch by Erlend E. Aasland.

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

• bpo-41713: Port the _signal extension module to the multi-phase initialization API (PEP 489). Patch by Victor Stinner and Mohamed Koubaa.

• bpo-37205: time.time(), time.perf_counter() and time.monotonic() functions can no longer fail with a Python fatal error, instead raise a regular Python exception on failure.

• 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-37205: time.perf_counter() on Windows and time.monotonic() on macOS are now system-wide. Previously, they used an offset computed at startup to reduce the precision loss caused by the float type. Use time.perf_counter_ns() and time.monotonic_ns() added in Python 3.7 to avoid this precision loss.

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

• 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-42333: Port _ssl extension module to heap types.

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

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

• bpo-42308: Add threading.__excepthook__ to allow retrieving the original value of threading.excepthook() in case it is set to a broken or a different value. Patch by Mario Corchero.

• bpo-42131: Implement PEP 451/spec methods on zipimport.zipimporter: find_spec(), create_module(), and exec_module().

  This also allows for the documented deprecation of find_loader(), find_module(), and load_module().

• bpo-41877: Mock objects which are not unsafe will now raise an AttributeError if an attribute with the prefix asert, aseert, or assrt is accessed, in addition to this already happening for the prefixes assert or assret.

• bpo-42264: sqlite3.OptimizedUnicode has been undocumented and obsolete since Python 3.3, when it was made an alias to str. It is now deprecated, scheduled for removal in Python 3.12.

• bpo-42251: Added threading.gettrace() and threading.getprofile() to retrieve the functions set by threading.settrace() and threading.setprofile() respectively. Patch by Mario Corchero.

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

• bpo-42236: On Unix, the os.device_encoding() function now returns 'UTF-8' rather than the device encoding if the Python UTF-8 Mode is enabled.

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

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

• bpo-42133: Update various modules in the stdlib to fall back on __spec__.loader when __loader__ isn’t defined on a module.

• bpo-26131: The load_module() methods found in importlib now trigger a DeprecationWarning.

• 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-26389: The traceback.format_exception(), traceback.format_exception_only(), and traceback.print_exception() functions can now take an exception object as a positional-only argument.

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

• bpo-41861: Convert sqlite3 to use heap types (PEP 384). Patch by Erlend E. Aasland.

• bpo-40624: Added support for the XPath != operator in xml.etree

• bpo-28850: Fix pprint.PrettyPrinter.format() overrides being ignored for contents of small containers. The pprint._safe_repr() function was removed.

• bpo-41625: Expose the splice() as os.splice() in the os module. Patch by Pablo Galindo

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

• bpo-41543: Add async context manager support for contextlib.nullcontext.

• bpo-21041: pathlib.PurePath.parents now supports negative indexing. Patch contributed by Yaroslav Pankovych.

• bpo-41332: Added missing connect_accepted_socket() method to asyncio.AbstractEventLoop.

• 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.

• bpo-40968: urllib.request and http.client now send http/1.1 ALPN extension during TLS handshake when no custom context is supplied.

• bpo-41001: Add func:os.eventfd to provide a low level interface for Linux’s event notification file descriptor.

• bpo-40816: Add AsyncContextDecorator to contextlib to support async context manager as a decorator.

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

• bpo-39411: Add an is_async identifier to pyclbr’s Function objects. Patch by Batuhan Taskaya

• bpo-35498: Add slice support to pathlib.PurePath.parents.

Documentation

• bpo-42238: Tentative to deprecate make suspicious by first removing it from the CI and documentation builds, but keeping it around for manual uses.

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

• bpo-41028: Language and version switchers, previously maintained in every cpython branches, are now handled by docsbuild-script.

Tests

• bpo-41473: Re-enable 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.

• bpo-31904: Fix test_netrc on VxWorks: create temporary directories using temp_cwd().

• bpo-31904: skip test_getaddrinfo_ipv6_scopeid_symbolic and test_getnameinfo_ipv6_scopeid_symbolic on VxWorks

• bpo-31904: skip test_test of test_mailcap on VxWorks

• bpo-31904: add shell requirement for test_pipes

• bpo-31904: skip some tests related to fifo on VxWorks

• bpo-31904: Fix test_doctest.py failures for VxWorks.

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

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

• bpo-31904: Fix os module failures for VxWorks RTOS.

• bpo-31904: Fix fifo test cases for VxWorks RTOS.

Build

• bpo-31904: remove libnet dependency from detect_socket() for VxWorks

• 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-38823: It is no longer possible to build the _ctypes extension module without wchar_t type: remove CTYPES_UNICODE macro. Anyway, the wchar_t type is required to build Python. Patch by Victor Stinner.

• bpo-42087: Support was removed for AIX 5.3 and below. See bpo-40680.