Changelog

Python next

Release date: XXXX-XX-XX

macOS

• gh-127592: Usage of the unified Apple System Log APIs was disabled when the minimum macOS version is earlier than 10.12.

Tools/Demos

• gh-128152: Fix a bug where Argument Clinic’s C pre-processor parser tried to parse pre-processor directives inside C comments. Patch by Erlend Aasland.

Tests

• gh-128690: Temporarily do not use test_embed in PGO profile builds until the problem with test_init_pyvenv_cfg failing in some configurations is resolved.

Library

• gh-128731: Fix ResourceWarning in urllib.robotparser.RobotFileParser.read().

• gh-71339: Add new assertion methods for unittest: assertHasAttr(), assertNotHasAttr(), assertIsSubclass(), assertNotIsSubclass() assertStartsWith(), assertNotStartsWith(), assertEndsWith() and assertNotEndsWith().

• gh-128661: Fixes typing.evaluate_forward_ref() not showing deprecation when type_params arg is not passed.

• gh-128562: Fix possible conflicts in generated tkinter widget names if the widget class name ends with a digit.

• gh-128559: Improved import time of asyncio.

• gh-128552: Fix cyclic garbage introduced by asyncio.loop.create_task() and asyncio.TaskGroup.create_task() holding a reference to the created task if it is eager.

• gh-128340: Add internal thread safe handle to be used in asyncio.loop.call_soon_threadsafe() for thread safe cancellation.

• gh-128182: Fix crash when using ctypes pointers concurrently on the free threaded build.

• gh-128400: Only show the current thread in faulthandler on the free threaded build to prevent races.

• gh-128400: Fix crash when using faulthandler.dump_traceback() while other threads are active on the free threaded build.

• gh-128388: Fix PyREPL on Windows to support more keybindings, like the Control-← and Control-→ word-skipping keybindings and those with meta (i.e. Alt), e.g. Alt-d to kill-word or Alt-Backspace backward-kill-word.

• gh-88834: Unify the instance check for typing.Union and types.UnionType: Union now uses the instance checks against its parameters instead of the subclass checks.

• gh-128302: Fix xml.dom.xmlbuilder.DOMEntityResolver.resolveEntity(), which was broken by the Python 3.0 transition.

• gh-128317: Highlight today in colour in calendar’s CLI output. Patch by Hugo van Kemenade.

• gh-128302: Allow xml.dom.xmlbuilder.DOMParser.parse() to correctly handle xml.dom.xmlbuilder.DOMInputSource instances that only have a systemId attribute set.

• gh-128151: Improve generation of UUID objects version 3, 4, 5, and 8 via their dedicated functions by 30%. Patch by Bénédikt Tran.

• gh-128118: Improve performance of copy.copy() by 30% via a fast path for atomic types and container types.

• gh-127946: Fix crash when modifying ctypes._CFuncPtr objects concurrently on the free threaded build.

• gh-128062: Revert the font of turtledemo’s menu bar to its default value and display the shortcut keys in the correct position.

• gh-128014: Fix resetting the default window icon by passing default='' to the tkinter method wm_iconbitmap().

• gh-41872: Fix quick extraction of module docstrings from a file in pydoc. It now supports docstrings with single quotes, escape sequences, raw string literals, and other Python syntax.

• gh-127060: Set TERM environment variable to “dumb” to disable traceback colors in IDLE, since IDLE doesn’t understand ANSI escape sequences. Patch by Victor Stinner.

• gh-126742: Fix support of localized error messages reported by dlerror(3) and gdbm_strerror in ctypes and dbm.gnu functions respectively. Patch by Bénédikt Tran.

• gh-122548: Adds two new local events to sys.monitoring, BRANCH_LEFT and BRANCH_RIGHT. This allows the two arms of the branch to be disabled independently, which should hugely improve performance of branch-level coverage tools. The old branch event, BRANCH is now deprecated.

• gh-127847: Fix the position when doing interleaved seeks and reads in uncompressed, unencrypted zip files returned by zipfile.ZipFile.open().

• gh-127688: Add the SCHED_DEADLINE and SCHED_NORMAL constants to the os module.

• gh-83662: Add missing __class_getitem__ method to the Python implementation of functools.partial(), to make it compatible with the C version. This is mainly relevant for alternative Python implementations like PyPy and GraalPy, because CPython will usually use the C-implementation of that function.

• gh-127586: multiprocessing.pool.Pool now properly restores blocked signal handlers of the parent thread when creating processes via either spawn or forkserver.

• gh-98188: Fix an issue in email.message.Message.get_payload() where data cannot be decoded if the Content Transfer Encoding mechanism contains trailing whitespaces or additional junk text. Patch by Hui Liu.

• gh-127529: Correct behavior of asyncio.selector_events.BaseSelectorEventLoop._accept_connection() in handling ConnectionAbortedError in a loop. This improves performance on OpenBSD.

• gh-127360: When a descriptive error message cannot be provided for an ssl.SSLError, the “unknown error” message now shows the internal error code (as retrieved by ERR_get_error and similar OpenSSL functions).

• gh-127196: Fix crash when dict with keys in invalid encoding were passed to several functions in _interpreters module.

• gh-124130: Fix a bug in matching regular expression \B in empty input string. Now it is always the opposite of \b. To get an old behavior, use (?!\A\Z)\B. To get a new behavior in old Python versions, use (?!\b).

• gh-126639: tempfile.NamedTemporaryFile will now issue a ResourceWarning when it is finalized by the garbage collector without being explicitly closed.

• gh-126624: Expose error code XML_ERROR_NOT_STARTED of Expat >=2.6.4 in xml.parsers.expat.errors.

• gh-126225: getopt and optparse are no longer marked as deprecated. There are legitimate reasons to use one of these modules in preference to argparse, and none of these modules are at risk of being removed from the standard library. Of the three, argparse remains the recommended default choice, unless one of the concerns noted at the top of the optparse module documentation applies.

• gh-124761: Add SO_REUSEPORT_LB constant to socket for FreeBSD.

• gh-121720: enum.EnumDict can now be used without resorting to private API.

• gh-123424: Add zipfile.ZipInfo._for_archive() setting default properties on ZipInfo objects. Patch by Bénédikt Tran and Jason R. Coombs.

• gh-121676: Deprecate calling the Python implementation of functools.reduce() with a function or sequence as a keyword argument. This will be forbidden in Python 3.16 in order to match the C implementation.

• gh-112015: ctypes.memoryview_at() now exists to create a memoryview object that refers to the supplied pointer and length. This works like ctypes.string_at() except it avoids a buffer copy, and is typically useful when implementing pure Python callback functions that are passed dynamically-sized buffers.

• gh-95371: Added support for other image formats (PNG, PGM, and PPM) to the turtle module. Patch by Shin-myoung-serp.

Core and Builtins

• gh-128078: Fix a SystemError when using anext() with a default tuple value. Patch by Bénédikt Tran.

• gh-128717: Fix a crash when setting the recursion limit while other threads are active on the free threaded build.

• gh-124483: Treat Py_DECREF and variants as escaping when generating opcode and uop metadata. This prevents the possibility of a __del__ method causing the JIT to behave incorrectly.

• gh-126703: Improve performance of class methods by using a freelist.

• gh-128137: Update PyASCIIObject layout to handle interned field with the atomic operation. Patch by Donghee Na.

• gh-128192: Upgrade HTTP digest authentication algorithm for urllib.request by supporting SHA-256 digest authentication as specified in RFC 7616.

• gh-126868: Increase usage of freelist for int allocation.

• gh-114203: Optimize Py_BEGIN_CRITICAL_SECTION for simple recursive calls.

• gh-127705: Adds stackref debugging when Py_STACKREF_DEBUG is set. Finds all double-closes and leaks, logging the origin and last borrow.

  Inspired by HPy’s debug mode. https://docs.hpyproject.org/en/latest/debug-mode.html

• gh-128079: Fix a bug where except* does not properly check the return value of an ExceptionGroup’s split() function, leading to a crash in some cases. Now when split() returns an invalid object, except* raises a TypeError with the original raised ExceptionGroup object chained to it.

• gh-128030: Avoid error from calling PyModule_GetFilenameObject on a non-module object when importing a non-existent symbol from a non-module object.

• gh-128035: Indicate through ssl.HAS_PHA whether the ssl module supports TLSv1.3 post-handshake client authentication (PHA). Patch by Will Childs-Klein.

• gh-127274: Add a new flag, CO_METHOD, to co_flags that indicates whether the code object belongs to a function defined in class scope.

• gh-66409: During the path initialization, we now check if base_exec_prefix is the same as base_prefix before falling back to searching the Python interpreter directory.

• gh-127970: We now use the location of the libpython runtime library used in the current proccess to determine sys.base_prefix on all platforms implementing the dladdr function defined by the UNIX standard — this includes Linux, Android, macOS, iOS, FreeBSD, etc. This was already the case on Windows and macOS Framework builds.

• gh-127773: Do not use the type attribute cache for types with incompatible MRO.

• gh-127903: Objects/unicodeobject.c: fix a crash on DEBUG builds in _copy_characters when there is nothing to copy.

• gh-127809: Fix an issue where the experimental JIT may infer an incorrect result type for exponentiation (** and **=), leading to bugs or crashes.

• gh-126862: Fix a possible overflow when a class inherits from an absurd number of super-classes. Reported by Valery Fedorenko. Patch by Bénédikt Tran.

C API

• gh-128400: Py_FatalError() no longer shows all threads on the free threaded build to prevent crashes.

• gh-128629: Add macros Py_PACK_VERSION() and Py_PACK_FULL_VERSION() for bit-packing Python version numbers.

• gh-128008: Add PyWeakref_IsDead() function, which tests if a weak reference is dead.

• gh-127350: Add Py_fopen() function to open a file. Similar to the fopen() function, but the path parameter is a Python object and an exception is set on error. Add also Py_fclose() function to close a file, function needed for Windows support. Patch by Victor Stinner.

Build

• gh-128627: For Emscripten builds the function pointer cast call trampoline now uses the wasm-gc ref.test instruction if it’s available instead of Wasm JS type reflection.

• gh-128472: Skip BOLT optimization of functions using computed gotos, fixing errors on build with LLVM 19.

• gh-115765: GNU Autoconf 2.72 is now required to generate !configure. Patch by Erlend Aasland.

• gh-123925: Fix building the curses module on platforms with libncurses but without libncursesw.

• gh-90905: Add support for cross-compiling to x86_64 on aarch64/arm64 macOS.

• gh-128321: Set LIBS instead of LDFLAGS when checking if sqlite3 library functions are available. This fixes the ordering of linked libraries during checks, which was incorrect when using a statically linked libsqlite3.

• gh-100384: Error on unguarded-availability in macOS builds, preventing invalid use of symbols that are not available in older versions of the OS.

• gh-128104: Remove Py_STRFTIME_C99_SUPPORT conditions in favor of requiring C99 strftime(3) specifier support at build time. When cross-compiling, there is no build time check and support is assumed.

• gh-127951: Add option --pystats to the Windows build to enable performance statistics collection.

Python 3.14.0 alpha 3

Release date: 2024-12-17

Windows

• gh-127353: Allow to force color output on Windows using environment variables. Patch by Andrey Efremov.

• gh-125729: Makes the presence of the turtle module dependent on the Tcl/Tk installer option. Previously, the module was always installed but would be unusable without Tcl/Tk.

Tools/Demos

• gh-126700: Add support for multi-argument gettext functions in pygettext.py.

Tests

• gh-127906: Test the limited C API in test_cppext. Patch by Victor Stinner.

• gh-127637: Add tests for the dis command-line interface. Patch by Bénédikt Tran.

• gh-126925: iOS test results are now streamed during test execution, and the deprecated xcresulttool is no longer used.

• gh-127076: Disable strace based system call tests when LD_PRELOAD is set.

• gh-127076: Filter out memory-related mmap, munmap, and mprotect calls from file-related ones when testing io behavior using strace.

Security

• gh-127655: Fixed the asyncio.selector_events._SelectorSocketTransport transport not pausing writes for the protocol when the buffer reaches the high water mark when using asyncio.WriteTransport.writelines().

Library

• gh-126907: Fix crash when using atexit concurrently on the free-threaded build.

• gh-127870: Detect recursive calls in ctypes _as_parameter_ handling. Patch by Victor Stinner.

• gh-127732: The platform module now correctly detects Windows Server 2025.

• gh-126789: Fixed sysconfig.get_config_vars(), sysconfig.get_paths(), and siblings, returning outdated cached data if the value of sys.prefix or sys.exec_prefix changes. Overwriting sys.prefix or sys.exec_prefix still is discouraged, as that might break other parts of the code.

• gh-127718: Add colour to test.regrtest output. Patch by Hugo van Kemenade.

• gh-127610: Added validation for more than one var-positional or var-keyword parameters in inspect.Signature. Patch by Maxim Ageev.

• gh-127627: Added posix._emscripten_debugger() to help with debugging the test suite on the Emscripten target.

• gh-126821: macOS and iOS apps can now choose to redirect stdout and stderr to the system log during interpreter configuration.

• gh-93312: Include <sys/pidfd.h> to get os.PIDFD_NONBLOCK constant. Patch by Victor Stinner.

• gh-127481: Add the EPOLLWAKEUP constant to the select module.

• gh-127065: Make operator.methodcaller() thread-safe and re-entrant safe.

• gh-127321: pdb.set_trace() will not stop at an opcode that does not have an associated line number anymore.

• gh-127429: Fixed bug where, on cross-builds, the sysconfig POSIX data was being generated with the host Python’s Makefile. The data is now generated from current build’s Makefile.

• gh-127413: Add the dis --specialized command-line option to show specialized bytecode. Patch by Bénédikt Tran.

• gh-125413: Revert addition of pathlib.Path.scandir(). This method was added in 3.14.0a2. The optimizations remain for file system paths, but other subclasses should only have to implement pathlib.Path.iterdir().

• gh-127257: In ssl, system call failures that OpenSSL reports using ERR_LIB_SYS are now raised as OSError.

• gh-59705: On Linux, threading.Thread now sets the thread name to the operating system. Patch by Victor Stinner.

• gh-127303: Publicly expose EXACT_TOKEN_TYPES in token.__all__.

• gh-127331: ssl can show descriptions for errors added in OpenSSL 3.4.

• gh-123967: Fix faulthandler for trampoline frames. If the top-most frame is a trampoline frame, skip it. Patch by Victor Stinner.

• gh-127178: A _sysconfig_vars_(...).json file is now shipped in the standard library directory. It contains the output of sysconfig.get_config_vars() on the default environment encoded as JSON data. This is an implementation detail, and may change at any time.

• gh-127072: Remove outdated socket.NETLINK_* constants not present in Linux kernels beyond 2.6.17.

• gh-127255: The CopyComPointer() function is now public. Previously, this was private and only available in _ctypes.

• gh-127182: Fix io.StringIO.__setstate__() crash, when None was passed as the first value.

• gh-127217: Fix urllib.request.pathname2url() for paths starting with multiple slashes on Posix.

• gh-125866: urllib.request.pathname2url() now adds an empty authority when generating a URL for a path that begins with exactly one slash. For example, the path /etc/hosts is converted to the scheme-less URL ///etc/hosts. As a result of this change, URLs without authorities are only generated for relative paths.

• gh-127221: Add colour to unittest output. Patch by Hugo van Kemenade.

• gh-127035: Fix shutil.which on Windows. Now it looks at direct match if and only if the command ends with a PATHEXT extension or X_OK is not in mode. Support extensionless files if “.” is in PATHEXT. Support PATHEXT extensions that end with a dot.

• gh-122273: Support PyREPL history on Windows. Patch by devdanzin and Victor Stinner.

• gh-125866: urllib.request.pathname2url() and url2pathname() no longer convert Windows drive letters to uppercase.

• gh-127078: Fix issue where urllib.request.url2pathname() failed to discard an extra slash before a UNC drive in the URL path on Windows.

• gh-126766: Fix issue where urllib.request.url2pathname() failed to discard any ‘localhost’ authority present in the URL.

• gh-127065: Fix crash when calling a operator.methodcaller() instance from multiple threads in the free threading build.

• gh-127090: Fix value of urllib.response.addinfourl.url for file: URLs that express relative paths and absolute Windows paths. The canonical URL generated by urllib.request.pathname2url() is now used.

• gh-126992: Fix LONG and INT opcodes to only use base 10 for string to integer conversion in pickle.

• gh-126997: Fix support of STRING and GLOBAL opcodes with non-ASCII arguments in pickletools. pickletools.dis() now outputs non-ASCII bytes in STRING, BINSTRING and SHORT_BINSTRING arguments as escaped (\xXX).

• gh-126316: grp: Make grp.getgrall() thread-safe by adding a mutex. Patch by Victor Stinner.

• gh-126618: Fix the representation of itertools.count objects when the count value is sys.maxsize.

• gh-126615: The COMError exception is now public. Previously, this was private and only available in _ctypes.

• gh-126985: When running under a virtual environment with the site disabled (see -S), sys.prefix and sys.base_prefix will now point to the virtual environment, instead of the base installation.

• gh-112192: In the trace module, increase the coverage precision (cov%) to one decimal.

• gh-118761: Improve import time of mimetypes by around 11-16 times. Patch by Hugo van Kemenade.

• gh-126947: Raise TypeError in _pydatetime.timedelta.__new__() if the passed arguments are not int or float, so that the Python implementation is in line with the C implementation.

• gh-126946: Improve the GetoptError error message when a long option prefix matches multiple accepted options in getopt.getopt() and getopt.gnu_getopt().

• gh-126899: Make tkinter widget methods after() and after_idle() accept arguments passed by keyword.

• gh-85168: Fix issue where urllib.request.url2pathname() and pathname2url() always used UTF-8 when quoting and unquoting file URIs. They now use the filesystem encoding and error handler.

• gh-126780: Fix os.path.normpath() for drive-relative paths on Windows.

• gh-126775: Make linecache.checkcache() thread safe and GC re-entrancy safe.

• gh-126601: Fix issue where urllib.request.pathname2url() raised OSError when given a Windows path containing a colon character not following a drive letter, such as before an NTFS alternate data stream.

• gh-126727: locale.nl_langinfo(locale.ERA) now returns multiple era description segments separated by semicolons. Previously it only returned the first segment on platforms with Glibc.

• gh-85046: Add EHWPOISON error code to errno.

• gh-118201: Fixed intermittent failures of os.confstr, os.pathconf and os.sysconf on iOS and Android.

• gh-86463: The usage parameter of argparse.ArgumentParser no longer affects the default value of the prog parameter in subparsers.

• gh-124008: Fix possible crash (in debug build), incorrect output or returning incorrect value from raw binary write() when writing to console on Windows.

• gh-123401: The http.cookies module now supports parsing obsolete RFC 850 date formats, in accordance with RFC 9110 requirements. Patch by Nano Zheng.

• gh-122431: readline.append_history_file() now raises a ValueError when given a negative value.

• gh-122356: Guarantee that the position of a file-like object passed to zipfile.is_zipfile() is left untouched after the call. Patch by Bénédikt Tran.

• gh-122288: Improve the performances of fnmatch.translate() by a factor 1.7. Patch by Bénédikt Tran.

• gh-88110: Fixed multiprocessing.Process reporting a .exitcode of 1 even on success when using the "fork" start method while using a concurrent.futures.ThreadPoolExecutor.

• gh-97514: Authentication was added to the multiprocessing forkserver start method control socket so that only processes with the authentication key generated by the process that spawned the forkserver can control it. This is an enhancement over the other gh-97514 fixes so that access is no longer limited only by filesystem permissions.

  The file descriptor exchange of control pipes with the forked worker process now requires an explicit acknowledgement byte to be sent over the socket after the exchange on all forkserver supporting platforms. That makes testing the above much easier.

Documentation

• gh-127347: Publicly expose traceback.print_list() in traceback.__all__.

Core and Builtins

• gh-127740: Fix error message in bytes.fromhex() when given an odd number of digits to properly indicate that an even number of hexadecimal digits is required.

• gh-127058: PySequence_Tuple now creates the resulting tuple atomically, preventing partially created tuples being visible to the garbage collector or through gc.get_referrers()

• gh-127599: Fix statistics for increments of object reference counts (in particular, when a reference count was increased by more than 1 in a single operation).

• gh-127651: When raising ImportError for missing symbols in from imports, use __file__ in the error message if __spec__.origin is not a location

• gh-127582: Fix non-thread-safe object resurrection when calling finalizers and watcher callbacks in the free threading build.

• gh-127434: The iOS compiler shims can now accept arguments with spaces.

• gh-127536: Add missing locks around some list assignment operations in the free threading build.

• gh-127085: Fix race when exporting a buffer from a memoryview object on the free-threaded build.

• gh-127238: Correct error message for sys.set_int_max_str_digits().

• gh-113841: Fix possible undefined behavior division by zero in complex’s _Py_c_pow().

• gh-127133: Calling argparse.ArgumentParser.add_argument_group() on an argument group, and calling argparse.ArgumentParser.add_argument_group() or argparse.ArgumentParser.add_mutually_exclusive_group() on a mutually exclusive group now raise exceptions. This nesting was never supported, often failed to work correctly, and was unintentionally exposed through inheritance. This functionality has been deprecated since Python 3.11.

• gh-126491: Add a marking phase to the GC. All objects that can be transitively reached from builtin modules or the stacks are marked as reachable before cycle detection. This reduces the amount of work done by the GC by approximately half.

• gh-127020: Fix a crash in the free threading build when PyCode_GetCode(), PyCode_GetVarnames(), PyCode_GetCellvars(), or PyCode_GetFreevars() were called from multiple threads at the same time.

• gh-127010: Simplify GC tracking of dictionaries. All dictionaries are tracked when created, rather than being lazily tracked when a trackable object was added to them. This simplifies the code considerably and results in a slight speedup.

• gh-126980: Fix __buffer__() of bytearray crashing when READ or WRITE are passed as flags.

• gh-126937: Fix TypeError when a ctypes.Structure has a field size that doesn’t fit into an unsigned 16-bit integer. Instead, the maximum number of bits is sys.maxsize.

• gh-126868: Increase performance of int by adding a freelist for compact ints.

• gh-126881: Fix crash in finalization of dtoa state. Patch by Kumar Aditya.

• gh-126892: Require cold or invalidated code to “warm up” before being JIT compiled again.

• gh-126091: Ensure stack traces are complete when throwing into a generator chain that ends in a custom generator.

• gh-126024: Optimize decoding of short UTF-8 sequences containing non-ASCII characters by approximately 15%.

• gh-125420: Add memoryview.index() to memoryview objects. Patch by Bénédikt Tran.

• gh-125420: Add memoryview.count() to memoryview objects. Patch by Bénédikt Tran.

• gh-124470: Fix crash in free-threaded builds when replacing object dictionary while reading attribute on another thread

• gh-69639: Implement mixed-mode arithmetic rules combining real and complex numbers as specified by C standards since C99. Patch by Sergey B Kirpichev.

• gh-120010: Correct invalid corner cases which resulted in (nan+nanj) output in complex multiplication, e.g., (1e300+1j)*(nan+infj). Patch by Sergey B Kirpichev.

• gh-109746: If _thread.start_new_thread() fails to start a new thread, it deletes its state from interpreter and thus avoids its repeated cleanup on finalization.

C API

• gh-127896: The previously undocumented function PySequence_In() is soft deprecated. Use PySequence_Contains() instead.

• gh-127791: Fix loss of callbacks after more than one call to PyUnstable_AtExit().

• gh-127691: The Unicode Exception Objects C API now raises a TypeError if its exception argument is not a UnicodeError object. Patch by Bénédikt Tran.

• gh-123378: Ensure that the value of UnicodeEncodeError.end retrieved by PyUnicodeEncodeError_GetEnd() lies in [min(1, objlen), max(min(1, objlen), objlen)] where objlen is the length of UnicodeEncodeError.object. Similar arguments apply to UnicodeDecodeError and UnicodeTranslateError and their corresponding C interface. Patch by Bénédikt Tran.

• gh-127314: Improve error message when calling the C API without an active thread state on the free-threaded build.

• gh-123378: Ensure that the value of UnicodeEncodeError.start retrieved by PyUnicodeEncodeError_GetStart() lies in [0, max(0, objlen - 1)] where objlen is the length of UnicodeEncodeError.object. Similar arguments apply to UnicodeDecodeError and UnicodeTranslateError and their corresponding C interface. Patch by Bénédikt Tran.

• gh-109523: Reading text from a non-blocking stream with read may now raise a BlockingIOError if the operation cannot immediately return bytes.

• gh-102471: Add a new import and export API for Python int objects (PEP 757):

  • PyLong_GetNativeLayout();

  • PyLong_Export();

  • PyLong_FreeExport();

  • PyLongWriter_Create();

  • PyLongWriter_Finish();

  • PyLongWriter_Discard().

  Patch by Victor Stinner.

• gh-121058: PyThreadState_Clear() now warns (and calls sys.excepthook) if the thread state still has an active exception.

Build

• gh-127865: Fix build failure on systems without thread-locals support.

• gh-127629: Emscripten builds now include ctypes support.

• gh-127111: Updated the Emscripten web example to use ES6 modules and be built into a distinct web_example subfolder.

• gh-115869: Make jit_stencils.h (which is produced during JIT builds) reproducible.

• gh-126898: The Emscripten build of Python is now based on ES6 modules.

Python 3.14.0 alpha 2

Release date: 2024-11-19

Windows

• gh-126911: Update credits command output.

• gh-118973: Ensures the experimental free-threaded install includes the _tkinter module. The optional Tcl/Tk component must also be installed in order for the module to work.

• gh-126497: Fixes venv failure due to missing redirector executables in experimental free-threaded installs.

• gh-126074: Removed unnecessary DLLs from Windows embeddable package

• gh-125315: Avoid crashing in platform due to slow WMI calls on some Windows machines.

• gh-126084: Fix venvwlauncher to launch pythonw instead of python so no extra console window is created.

• gh-125842: Fix a SystemError when sys.exit() is called with 0xffffffff on Windows.

• gh-125550: Enable the Python Launcher for Windows to detect Python 3.14 installs from the Windows Store.

• gh-123803: All Windows code pages are now supported as “cpXXX” codecs on Windows.

Tools/Demos

• gh-126807: Fix extraction warnings in pygettext.py caused by mistaking function definitions for function calls.

• gh-126167: The iOS testbed was modified so that it can be used by third-party projects for testing purposes.

Tests

• gh-126909: Fix test_os extended attribute tests to work on filesystems with 1 KiB xattr size limit.

• gh-125730: Change make test to not run GUI tests by default. Use make ci to run tests with GUI tests instead.

• gh-124295: Add translation tests to the argparse module.

Security

• gh-126623: Upgrade libexpat to 2.6.4

Library

• gh-85957: Add missing MIME types for images with RFCs: emf, fits, g3fax, jp2, jpm, jpx, t38, tiff-fx and wmf. Patch by Hugo van Kemenade.

• gh-126920: Fix the prefix and exec_prefix keys from sysconfig.get_config_vars() incorrectly having the same value as sys.base_prefix and sys.base_exec_prefix, respectively, inside virtual environments. They now accurately reflect sys.prefix and sys.exec_prefix.

• gh-67877: Fix memory leaks when regular expression matching terminates abruptly, either because of a signal or because memory allocation fails.

• gh-125063: marshal now supports slice objects. The marshal format version was increased to 5.

• gh-126789: Fixed the values of sysconfig.get_config_vars(), sysconfig.get_paths(), and their siblings when the site initialization happens after sysconfig has built a cache for sysconfig.get_config_vars().

• gh-126188: Update bundled pip to 24.3.1

• gh-126766: Fix issue where urllib.request.url2pathname() failed to discard two leading slashes introducing an empty authority section.

• gh-126705: Allow os.PathLike to be a base for Protocols.

• gh-126699: Allow collections.abc.AsyncIterator to be a base for Protocols.

• gh-126654: Fix crash when non-dict was passed to several functions in _interpreters module.

• gh-104745: Limit starting a patcher (from unittest.mock.patch() or unittest.mock.patch.object()) more than once without stopping it

• gh-126595: Fix a crash when instantiating itertools.count with an initial count of sys.maxsize on debug builds. Patch by Bénédikt Tran.

• gh-120423: Fix issue where urllib.request.pathname2url() mishandled Windows paths with embedded forward slashes.

• gh-126565: Improve performances of zipfile.Path.open() for non-reading modes.

• gh-126505: Fix bugs in compiling case-insensitive regular expressions with character classes containing non-BMP characters: upper-case non-BMP character did was ignored and the ASCII flag was ignored when matching a character range whose upper bound is beyond the BMP region.

• gh-117378: Fixed the multiprocessing "forkserver" start method forkserver process to correctly inherit the parent’s sys.path during the importing of multiprocessing.set_forkserver_preload() modules in the same manner as sys.path is configured in workers before executing work items.

  This bug caused some forkserver module preloading to silently fail to preload. This manifested as a performance degration in child processes when the sys.path was required due to additional repeated work in every worker.

  It could also have a side effect of "" remaining in sys.path during forkserver preload imports instead of the absolute path from os.getcwd() at multiprocessing import time used in the worker sys.path.

  The sys.path differences between phases in the child process could potentially have caused preload to import incorrect things from the wrong location. We are unaware of that actually having happened in practice.

• gh-125679: The multiprocessing.Lock and multiprocessing.RLock repr values no longer say “unknown” on macOS.

• gh-126476: Raise calendar.IllegalMonthError (now a subclass of IndexError) for calendar.month() when the input month is not correct.

• gh-126489: The Python implementation of pickle no longer calls pickle.Pickler.persistent_id() for the result of persistent_id().

• gh-126451: Register the contextvars.Context type to collections.abc.Mapping.

• gh-126175: Add msg, doc, pos, lineno and colno attributes to tomllib.TOMLDecodeError. Deprecate instantiating with free-form arguments.

• gh-89416: Add RFC 9559 MIME types for Matroska audiovisual container formats. Patch by Hugo van Kemenade.

• gh-126417: Register the multiprocessing.managers.DictProxy and multiprocessing.managers.ListProxy types in multiprocessing.managers to collections.abc.MutableMapping and collections.abc.MutableSequence, respectively.

• gh-126390: Add support for returning intermixed options and non-option arguments in order in getopt.gnu_getopt().

• gh-126374: Add support for options with optional arguments in the getopt module.

• gh-126363: Speed up pattern parsing in pathlib.Path.glob() by skipping creation of a pathlib.Path object for the pattern.

• gh-126353: asyncio.get_event_loop() now does not implicitly creates an event loop. It now raises a RuntimeError if there is no set event loop. Patch by Kumar Aditya.

• gh-126313: Fix an issue in curses.napms() when curses.initscr() has not yet been called. Patch by Bénédikt Tran.

• gh-126303: Fix pickling and copying of os.sched_param objects.

• gh-126138: Fix a use-after-free crash on asyncio.Task objects whose underlying coroutine yields an object that implements an evil __getattribute__(). Patch by Nico Posada.

• gh-120057: Replace the os.environ.refresh() method with a new os.reload_environ() function. Patch by Victor Stinner.

• gh-126220: Fix crash in cProfile.Profile and _lsprof.Profiler when their callbacks were directly called with 0 arguments.

• gh-126212: Fix issue where urllib.request.pathname2url() and url2pathname() removed slashes from Windows DOS drive paths and URLs.

• gh-126223: Raise a UnicodeEncodeError instead of a SystemError upon calling _interpreters.create() with an invalid Unicode character.

• gh-126205: Fix issue where urllib.request.pathname2url() generated URLs beginning with four slashes (rather than two) when given a Windows UNC path.

• gh-126156: Improved performances of creating Morsel objects by a factor of 3.8x.

• gh-126105: Fix a crash in ast when the ast.AST._fields attribute is deleted.

• gh-126106: Fixes a possible NULL pointer dereference in ssl.

• gh-126080: Fix a use-after-free crash on asyncio.Task objects for which the underlying event loop implements an evil __getattribute__(). Reported by Nico-Posada. Patch by Bénédikt Tran.

• gh-125322: Correct detection of complex numbers support in libffi.

• gh-126083: Fixed a reference leak in asyncio.Task objects when reinitializing the same object with a non-None context. Patch by Nico Posada.

• gh-126068: Fix exceptions in the argparse module so that only error messages for ArgumentError and ArgumentTypeError are now translated. ArgumentError is now only used for command line errors, not for logical errors in the program. TypeError is now raised instead of ValueError for some logical errors.

• gh-125413: Add pathlib.Path.scandir() method to efficiently fetch directory children and their file attributes. This is a trivial wrapper of os.scandir().

• gh-125984: Fix use-after-free crashes on asyncio.Future objects for which the underlying event loop implements an evil __getattribute__(). Reported by Nico-Posada. Patch by Bénédikt Tran.

• gh-125926: Fix urllib.parse.urljoin() for base URI with undefined authority. Although RFC 3986 only specify reference resolution for absolute base URI, urljoin() should continue to return sensible result for relative base URI.

• gh-125969: Fix an out-of-bounds crash when an evil asyncio.loop.call_soon() mutates the length of the internal callbacks list. Patch by Bénédikt Tran.

• gh-125966: Fix a use-after-free crash in asyncio.Future.remove_done_callback(). Patch by Bénédikt Tran.

• gh-125789: Fix possible crash when mutating list of callbacks returned by asyncio.Future._callbacks. It now always returns a new copy in C implementation _asyncio. Patch by Kumar Aditya.

• gh-126916: Allow the initial parameter of functools.reduce() to be passed as a keyword argument. Patch by Sayandip Dutta.

• gh-124452: Fix an issue in email.policy.EmailPolicy.header_source_parse() and email.policy.Compat32.header_source_parse() that introduced spurious leading whitespaces into header values when the header includes a newline character after the header name delimiter (:) and before the value.

• gh-117941: argparse.BooleanOptionalAction now rejects option names starting with --no-.

• gh-125884: Fixed the bug for pdb where it can’t set breakpoints on functions with certain annotations.

• gh-125355: Fix several bugs in argparse.ArgumentParser.parse_intermixed_args().

  • The parser no longer changes temporarily during parsing.

  • Default values are not processed twice.

  • Required mutually exclusive groups containing positional arguments are now supported.

  • The missing arguments report now includes the names of all required optional and positional arguments.

  • Unknown options can be intermixed with positional arguments in parse_known_intermixed_args().

• gh-125767: super objects are now pickleable and copyable.

• gh-124969: locale.nl_langinfo(locale.ALT_DIGITS) now returns a string again. The returned value consists of up to 100 semicolon-separated symbols.

• gh-84850: Remove URLopener and FancyURLopener classes from urllib.request. They had previously raised DeprecationWarning since Python 3.3.

• gh-125666: Avoid the exiting the interpreter if a null byte is given as input in the new REPL.

• gh-125710: [Enum] fix hashable<->nonhashable comparisons for member values

• gh-125631: Restore ability to set persistent_id and persistent_load attributes of instances of the Pickler and Unpickler classes in the pickle module.

• gh-125378: Fixed the bug in pdb where after a multi-line command, an empty line repeats the first line of the multi-line command, instead of the full command.

• gh-125682: Reject non-ASCII digits in the Python implementation of json.loads() conforming to the JSON specification.

• gh-125660: Reject invalid unicode escapes for Python implementation of json.loads().

• gh-52551: Use wcsftime() to implement time.strftime() on Windows.

• gh-125259: Fix the notes removal logic for errors thrown in enum initialization.

• gh-125633: Add function inspect.ispackage() to determine whether an object is a package or not.

• gh-125614: In the FORWARDREF format of annotationlib, fix bug where nested expressions were not returned as annotationlib.ForwardRef format.

• gh-125590: Allow FrameLocalsProxy to delete and pop if the key is not a fast variable.

• gh-125600: Only show stale code warning in pdb when we display source code.

• gh-125542: Deprecate passing keyword-only prefix_chars argument to argparse.ArgumentParser.add_argument_group().

• gh-125541: Pressing Ctrl-C while blocked in threading.Lock.acquire(), threading.RLock.acquire(), and threading.Thread.join() now interrupts the function call and raises a KeyboardInterrupt exception on Windows, similar to how those functions behave on macOS and Linux.

• gh-125519: Improve traceback if importlib.reload() is called with an object that is not a module. Patch by Alex Waygood.

• gh-125451: Fix deadlock when concurrent.futures.ProcessPoolExecutor shuts down concurrently with an error when feeding a job to a worker process.

• gh-125115: Fixed a bug in pdb where arguments starting with - can’t be passed to the debugged script.

• gh-125398: Fix the conversion of the VIRTUAL_ENV path in the activate script in venv when running in Git Bash for Windows.

• gh-125245: Fix race condition when importing collections.abc, which could incorrectly return an empty module.

• gh-52551: Fix encoding issues in time.strftime(), the strftime() method of the datetime classes datetime, date and time and formatting of these classes. Characters not encodable in the current locale are now acceptable in the format string. Surrogate pairs and sequence of surrogatescape-encoded bytes are no longer recombinated. Embedded null character no longer terminates the format string.

• gh-124984: Fixed thread safety in ssl in the free-threaded build. OpenSSL operations are now protected by a per-object lock.

• gh-124651: Properly quote template strings in venv activation scripts.

• gh-124694: We’ve added concurrent.futures.InterpreterPoolExecutor, which allows you to run code in multiple isolated interpreters. This allows you to circumvent the limitations of CPU-bound threads (due to the GIL). Patch by Eric Snow.

  This addition is unrelated to PEP 734.

• gh-58032: Deprecate the argparse.FileType type converter.

• gh-99749: Adds a feature to optionally enable suggestions for argument choices and subparser names if mistyped by the user.

• gh-58956: Fixed a bug in pdb where sometimes the breakpoint won’t trigger if it was set on a function which is already in the call stack.

• gh-124111: The tkinter module can now be built to use either the new version 9.0.0 of Tcl/Tk or the latest release 8.6.15 of Tcl/Tk 8. Tcl/Tk 9 includes many improvements, both to the Tcl language and to the appearance and utility of the graphical user interface provided by Tk.

• gh-80958: unittest discovery supports PEP 420 namespace packages as start directory again.

• gh-123370: Fix the canvas not clearing after running turtledemo clock.

• gh-89083: Add uuid.uuid8() for generating UUIDv8 objects as specified in RFC 9562. Patch by Bénédikt Tran

• gh-122549: Add platform.invalidate_caches() to invalidate cached results.

• gh-120754: Update unbounded read calls in zipfile to specify an explicit size putting a limit on how much data they may read. This also updates handling around ZIP max comment size to match the standard instead of reading comments that are one byte too long.

• gh-121267: Improve the performance of tarfile when writing files, by caching user names and group names.

• gh-70764: Fixed an issue where inspect.getclosurevars() would incorrectly classify an attribute name as a global variable when the name exists both as an attribute name and a global variable.

• gh-118289: posixpath.realpath() now raises NotADirectoryError when strict mode is enabled and a non-directory path with a trailing slash is supplied.

• gh-119826: Always return an absolute path for os.path.abspath() on Windows.

• gh-97850: Remove deprecated pkgutil.get_loader() and pkgutil.find_loader().

• gh-118986: Add socket.IPV6_RECVERR constant (available since Linux 2.2).

• gh-116897: Accepting objects with false values (like 0 and []) except empty strings, byte-like objects and None in urllib.parse functions parse_qsl() and parse_qs() is now deprecated.

• gh-101955: Fix SystemError when match regular expression pattern containing some combination of possessive quantifier, alternative and capture group.

• gh-71936: Fix a race condition in multiprocessing.pool.Pool.

• bpo-46128: Strip unittest.IsolatedAsyncioTestCase stack frames from reported stacktraces.

• gh-84852: Add MIME types for MS Embedded OpenType, OpenType Layout, TrueType, WOFF 1.0 and 2.0 fonts. Patch by Sahil Prajapati and Hugo van Kemenade.

Documentation

• gh-126622: Added stub pages for removed modules explaining their removal, where to find replacements, and linking to the last Python version that supported them. Contributed by Ned Batchelder.

• gh-125277: Require Sphinx 7.2.6 or later to build the Python documentation. Patch by Adam Turner.

• gh-60712: Include the object type in the lists of documented types. Change by Furkan Onder and Martin Panter.

Core and Builtins

• gh-126795: Increase the threshold for JIT code warmup. Depending on platform and workload, this can result in performance gains of 1-9% and memory savings of 3-5%.

• gh-126341: Now ValueError is raised instead of SystemError when trying to iterate over a released memoryview object.

• gh-126688: Fix a crash when calling os.fork() on some operating systems, including SerenityOS.

• gh-126066: Fix importlib to not write an incomplete .pyc files when a ulimit or some other operating system mechanism is preventing the write to go through fully.

• gh-126222: Do not include count of “peek” items in _PyUop_num_popped. This ensures that the correct number of items are popped from the stack when a micro-op exits with an error.

• gh-126366: Fix crash when using yield from on an object that raises an exception in its __iter__.

• gh-126209: Fix an issue with skip_file_prefixes parameter which resulted in an inconsistent behaviour between the C and Python implementations of warnings.warn(). Patch by Daehee Kim.

• gh-126312: Fix crash during garbage collection on an object frozen by gc.freeze() on the free-threaded build.

• gh-103951: Relax optimization requirements to allow fast attribute access to module subclasses.

• gh-126072: Following gh-126101, for Code Objects like lambda, annotation and type alias, we no longer add None to its co_consts.

• gh-126195: Improve JIT performance by 1.4% on macOS Apple Silicon by using platform-specific memory protection APIs. Patch by Diego Russo.

• gh-126139: Provide better error location when attempting to use a future statement with an unknown future feature.

• gh-126072: Add a new attribute in co_flags to indicate whether the first item in co_consts is the docstring. If a code object has no docstring, None will NOT be inserted.

• gh-126076: Relocated objects such as tuple, bytes and str objects are properly tracked by tracemalloc and its associated hooks. Patch by Pablo Galindo.

• gh-90370: Avoid temporary tuple creation for vararg in argument passing with Argument Clinic generated code (if arguments either vararg or positional-only).

• gh-126018: Fix a crash in sys.audit() when passing a non-string as first argument and Python was compiled in debug mode.

• gh-126012: The memoryview type now supports subscription, making it a generic type.

• gh-125837: Adds LOAD_SMALL_INT and LOAD_CONST_IMMORTAL instructions. LOAD_SMALL_INT pushes a small integer equal to the oparg to the stack. LOAD_CONST_IMMORTAL does the same as LOAD_CONST but is more efficient for immortal objects. Removes RETURN_CONST instruction.

• gh-125942: On Android, the errors setting of sys.stdout was changed from surrogateescape to backslashreplace.

• gh-125859: Fix a crash in the free threading build when gc.get_objects() or gc.get_referrers() is called during an in-progress garbage collection.

• gh-125868: It was possible in 3.14.0a1 only for attribute lookup to give the wrong value. This was due to an incorrect specialization in very specific circumstances. This is fixed in 3.14.0a2.

• gh-125498: The JIT has been updated to leverage Clang 19’s new preserve_none attribute, which supports more platforms and is more useful than LLVM’s existing ghccc calling convention. This also removes the need to manually patch the calling convention in LLVM IR, simplifying the JIT compilation process.

• gh-125703: Correctly honour tracemalloc hooks in specialized Py_DECREF paths. Patch by Pablo Galindo

• gh-125593: Use color to highlight error locations in traceback from exception group

• gh-125017: Fix crash on certain accesses to the __annotations__ of staticmethod and classmethod objects.

• gh-125588: The Python PEG generator can now use f-strings in the grammar actions. Patch by Pablo Galindo

• gh-125444: Fix illegal instruction for older Arm architectures. Patch by Diego Russo, testing by Ross Burton.

• gh-118423: Add a new INSTRUCTION_SIZE macro to the cases generator which returns the current instruction size.

• gh-125038: Fix crash when iterating over a generator expression after direct changes on gi_frame.f_locals. Patch by Mikhail Efimov.

• gh-124855: Don’t allow the JIT and perf support to be active at the same time. Patch by Pablo Galindo

• gh-123714: Update JIT compilation to use LLVM 19

• gh-123930: Improve the error message when a script shadowing a module from the standard library causes ImportError to be raised during a “from” import. Similarly, improve the error message when a script shadowing a third party module attempts to “from” import an attribute from that third party module while still initialising.

• gh-119793: The map() built-in now has an optional keyword-only strict flag like zip() to check that all the iterables are of equal length. Patch by Wannes Boeykens.

• gh-118950: Fix bug where SSLProtocol.connection_lost wasn’t getting called when OSError was thrown on writing to socket.

• gh-113570: Fixed a bug in reprlib.repr where it incorrectly called the repr method on shadowed Python built-in types.

C API

• gh-126554: Fix error handling in ctypes.CDLL objects which could result in a crash in rare situations.

• gh-126061: Add PyLong_IsPositive(), PyLong_IsNegative() and PyLong_IsZero() for checking if a PyLongObject is positive, negative, or zero, respectively.

• gh-125608: Fix a bug where dictionary watchers (e.g., PyDict_Watch()) on an object’s attribute dictionary (__dict__) were not triggered when the object’s attributes were modified.

• gh-123619: Added the PyUnstable_Object_EnableDeferredRefcount() function for enabling PEP 703 deferred reference counting.

• gh-121654: Add PyType_Freeze() function to make a type immutable. Patch by Victor Stinner.

• gh-120026: The Py_HUGE_VAL macro is soft deprecated.

Build

• gh-126691: Removed the --with-emscripten-target configure flag. We unified the node and browser options and the same build can now be used, independent of target runtime.

• gh-123877: Use wasm32-wasip1 as the target triple for WASI instead of wasm32-wasi. The latter will eventually be reclaimed for WASI 1.0 while CPython currently only supports WASI preview1.

• gh-126458: Disable SIMD support for HACL under WASI.

• gh-89640: Hard-code float word ordering as little endian on WASM.

• gh-126206: make clinic now runs Argument Clinic using the --force option, thus forcefully regenerating generated code.

• gh-126187: Introduced Tools/wasm/emscripten.py to simplify doing Emscripten builds.

• gh-124932: For cross builds, there is now support for having a different install prefix than the host_prefix used by getpath.py. This is set to / by default for Emscripten, on other platforms the default behavior is the same as before.

• gh-125946: The minimum supported Android version is now 7.0 (API level 24).

• gh-125940: The Android build now supports 16 KB page sizes.

• gh-89640: Improve detection of float word ordering on Linux when link-time optimizations are enabled.

• gh-124928: Emscripten builds now require node >= 18.

• gh-115382: Fix cross compile failures when the host and target SOABIs match.

Python 3.14.0 alpha 1

Release date: 2024-10-15

macOS

• gh-124448: Update bundled Tcl/Tk in macOS installer to 8.6.15.

• gh-123797: Check for runtime availability of ptsname_r function on macos.

• gh-123418: Updated macOS installer build to use OpenSSL 3.0.15.

Windows

• gh-124487: Increases Windows required OS and API level to Windows 10.

• gh-124609: Fix _Py_ThreadId for Windows builds using MinGW. Patch by Tony Roberts.

• gh-124448: Updated bundled Tcl/Tk to 8.6.15.

• gh-124254: Ensures experimental free-threaded binaries remain installed when updating.

• gh-123915: Ensure that Tools\msi\buildrelease.bat uses different directories for AMD64 and ARM64 builds.

• gh-123418: Updated Windows build to use OpenSSL 3.0.15.

• gh-123476: Add support for socket.TCP_QUICKACK on Windows platforms.

• gh-122573: The Windows build of CPython now requires 3.10 or newer.

• gh-100256: mimetypes no longer fails when it encounters an inaccessible registry key.

• gh-119679: Ensures correct import libraries are included in Windows installs.

• gh-119690: Adds Unicode support and fixes audit events for _winapi.CreateNamedPipe.

• gh-111201: Add support for new pyrepl on Windows

• gh-119070: Fixes py.exe handling of shebangs like /usr/bin/env python3.12, which were previously interpreted as python3.exe instead of python3.12.exe.

• gh-117505: Fixes an issue with the Windows installer not running ensurepip in a fully isolated environment. This could cause unexpected interactions with the user site-packages.

• gh-118209: Avoid crashing in mmap on Windows when the mapped memory is inaccessible due to file system errors or access violations.

• gh-79846: Makes ssl.create_default_context() ignore invalid certificates in the Windows certificate store

Tools/Demos

• gh-123418: Update GitHub CI workflows to use OpenSSL 3.0.15 and multissltests to use 3.0.15, 3.1.7, and 3.2.3.

Tests

• gh-125041: Re-enable skipped tests for zlib on the s390x architecture: only skip checks of the compressed bytes, which can be different between zlib’s software implementation and the hardware-accelerated implementation.

• gh-124378: Updated test_ttk to pass with Tcl/Tk 8.6.15.

• gh-124213: Detect whether the test suite is running inside a systemd-nspawn container with --suppress-sync=true option, and skip the test_os and test_mmap tests that are failing in this scenario.

• gh-124190: Add capability to ignore entire files or directories in check warning CI tool

• gh-121921: Update Lib/test/crashers/bogus_code_obj.py so that it crashes properly again.

• gh-112301: Add tooling to check for changes in compiler warnings. Patch by Nate Ohlson.

• gh-59022: Add tests for pkgutil.extend_path(). Patch by Andreas Stocker.

• gh-99242: os.getloadavg() may throw OSError when running regression tests under certain conditions (e.g. chroot). This error is now caught and ignored, since reporting load average is optional.

• gh-121084: Fix test_typing random leaks. Clear typing ABC caches when running tests for refleaks (-R option): call _abc_caches_clear() on typing abstract classes and their subclasses. Patch by Victor Stinner.

• gh-121160: Add a test for readline.set_history_length(). Note that this test may fail on readline libraries.

• gh-121200: Fix test_expanduser_pwd2() of test_posixpath. Call getpwnam() to get pw_dir, since it can be different than getpwall() pw_dir. Patch by Victor Stinner.

• gh-121188: When creating the JUnit XML file, regrtest now escapes characters which are invalid in XML, such as the chr(27) control character used in ANSI escape sequences. Patch by Victor Stinner.

• gh-120801: Cleaned up fixtures for importlib.metadata tests and consolidated behavior with ‘test.support.os_helper’.

• gh-119727: Add --single-process command line option to Python test runner (regrtest). Patch by Victor Stinner.

• gh-119273: Python test runner no longer runs tests using TTY (ex: test_ioctl) in a process group (using setsid()). Previously, tests using TTY were skipped. Patch by Victor Stinner.

• gh-119050: regrtest test runner: Add XML support to the refleak checker (-R option). Patch by Victor Stinner.

• gh-101525: Skip test_gdb if the binary is relocated by BOLT. Patch by Donghee Na.

• gh-107562: Test certificates have been updated to expire far in the future. This allows testing Y2038 with system time set to after that, so that actual Y2038 issues can be exposed, and not masked by expired certificate errors.

Security

• gh-125140: Remove the current directory from sys.path when using PyREPL.

• gh-123678: Upgrade libexpat to 2.6.3

• gh-112301: Enable compiler options that warn of potential security vulnerabilities.

• gh-122792: Changed IPv4-mapped ipaddress.IPv6Address to consistently use the mapped IPv4 address value for deciding properties. Properties which have their behavior fixed are is_multicast, is_reserved, is_link_local, is_global, and is_unspecified.

• gh-112301: Add ability to ignore warnings per file with warning count in warning checking tooling. Patch by Nate Ohlson.

• gh-112301: Add macOS warning tracking to warning check tooling. Patch by Nate Ohlson.

• gh-122133: Authenticate the socket connection for the socket.socketpair() fallback on platforms where AF_UNIX is not available like Windows.

  Patch by Gregory P. Smith <greg@krypto.org> and Seth Larson <seth@python.org>. Reported by Ellie <el@horse64.org>

• gh-121957: Fixed missing audit events around interactive use of Python, now also properly firing for python -i, as well as for python -m asyncio. The events in question are cpython.run_stdin and cpython.run_startup.

• gh-112301: Enable runtime protections for glibc to abort execution when unsafe behavior is encountered, for all platforms except Windows.

• gh-121285: Remove backtracking from tarfile header parsing for hdrcharset, PAX, and GNU sparse headers.

• gh-112301: Add default compiler options to improve security. Enable -Wimplicit-fallthrough, -fstack-protector-strong, -Wtrampolines.

• gh-118773: Fixes creation of ACLs in os.mkdir() on Windows to work correctly on non-English machines.

• gh-118486: os.mkdir() on Windows now accepts mode of 0o700 to restrict the new directory to the current user. This fixes CVE 2024-4030 affecting tempfile.mkdtemp() in scenarios where the base temporary directory is more permissive than the default.

Library

• gh-125422: Fixed the bug where pdb and bdb can step into the bottom caller frame.

• gh-100141: Fixed the bug where pdb will be stuck in an infinite loop when debugging an empty file.

• gh-53203: Fix time.strptime() for %c, %x and %X formats in many locales that use non-ASCII digits, like Persian, Burmese, Odia and Shan.

• gh-125206: Workaround for old libffi versions is added. Module ctypes supports double complex only with libffi >= 3.3.0. Patch by Mikhail Efimov.

• gh-89967: Make WeakKeyDictionary and WeakValueDictionary safe against concurrent mutations from other threads. Patch by Kumar Aditya.

• gh-125260: The gzip.compress() mtime parameter now defaults to 0 for reproducible output. Patch by Bernhard M. Wiedemann and Adam Turner.

• gh-125243: Fix data race when creating zoneinfo.ZoneInfo objects in the free threading build.

• gh-125254: Fix a bug where ArgumentError includes the incorrect ambiguous option in argparse.

• gh-125235: Keep tkinter TCL paths in venv pointing to base installation on Windows.

• gh-61011: Fix inheritance of nested mutually exclusive groups from parent parser in argparse.ArgumentParser. Previously, all nested mutually exclusive groups lost their connection to the group containing them and were displayed as belonging directly to the parser.

• gh-125118: Don’t copy arbitrary values to _Bool in the struct module.

• gh-125069: Fix an issue where providing a pathlib.PurePath object as an initializer argument to a second PurePath object with a different parser resulted in arguments to the former object’s initializer being joined by the latter object’s parser.

• gh-125096: If the PYTHON_BASIC_REPL environment variable is set, the site module no longer imports the _pyrepl module. Moreover, the site module now respects -E and -I command line options: ignore PYTHON_BASIC_REPL in this case. Patch by Victor Stinner.

• gh-124969: Fix locale.nl_langinfo(locale.ALT_DIGITS). Now it returns a tuple of up to 100 strings (an empty tuple on most locales). Previously it returned the first item of that tuple or an empty string.

• gh-124960: Fix support for the barry_as_FLUFL future flag in the new REPL.

• gh-69998: Fix locale.nl_langinfo() in case when different categories have different locales. The function now sets temporarily the LC_CTYPE locale in some cases. This temporary change affects other threads.

• gh-124958: Fix refcycles in exceptions raised from asyncio.TaskGroup and the python implementation of asyncio.Future

• gh-53203: Fix time.strptime() for %c and %x formats in many locales: Arabic, Bislama, Breton, Bodo, Kashubian, Chuvash, Estonian, French, Irish, Ge’ez, Gurajati, Manx Gaelic, Hebrew, Hindi, Chhattisgarhi, Haitian Kreyol, Japanese, Kannada, Korean, Marathi, Malay, Norwegian, Nynorsk, Punjabi, Rajasthani, Tok Pisin, Yoruba, Yue Chinese, Yau/Nungon and Chinese.

• gh-123961: Convert curses to multi-phase initialization (PEP 489), thereby fixing reference leaks at interpreter shutdown. Patch by Bénédikt Tran.

• gh-124944: Add SO_ORIGINAL_DST to the socket module.

• gh-117151: The default buffer size used by shutil.copyfileobj() has been increased from 64k to 256k on non-Windows platforms. It was already larger on Windows.

• gh-90102: Skip the isatty system call during open() when the file is known to not be a character device. This provides a slight performance improvement when reading whole files.

• gh-124917: Allow calling os.path.exists() and os.path.lexists() with keyword arguments on Windows. Fixes a regression in 3.13.0.

• gh-65865: argparse now raises early error for invalid help arguments to add_argument(), add_subparsers() and add_parser().

• gh-124653: Fix detection of the minimal Queue API needed by the logging module. Patch by Bénédikt Tran.

• gh-91818: The CLI of many modules (ast, ensurepip, json, pdb, sqlite3, tokenize, venv) now uses the actual executable name instead of simply “python” to display in the usage message.

• gh-124858: Fix reference cycles left in tracebacks in asyncio.open_connection() when used with happy_eyeballs_delay

• gh-124390: Fixed AssertionError when using asyncio.staggered.staggered_race() with asyncio.eager_task_factory.

• gh-85935: argparse.ArgumentParser.add_argument() now raises an exception if an action that does not consume arguments (like ‘store_const’ or ‘store_true’) or explicit nargs=0 are specified for positional arguments.

• gh-124835: Make tomllib.loads() raise TypeError not AttributeError on bad input types that do not have the replace attribute. Improve error message when bytes is received.

• gh-124693: Fix a bug where argparse doesn’t recognize negative complex numbers or negative numbers using scientific notation.

• gh-124787: Fix typing.TypeAliasType with incorrect type_params argument. Now it raises a TypeError when a type parameter without a default follows one with a default, and when an entry in the type_params tuple is not a type parameter object.

• gh-66436: Improved prog default value for argparse.ArgumentParser. It will now include the name of the Python executable along with the module or package name, or the path to a directory, ZIP file, or directory within a ZIP file if the code was run that way.

• gh-116850: Fix argparse for namespaces with not directly writable dict (e.g. classes).

• gh-101552: Add an annoation_format parameter to inspect.signature(). Add an quote_annotation_strings parameter to inspect.Signature.format(). Use the new functionality to improve the display of annotations in signatures in pydoc. Patch by Jelle Zijlstra.

• gh-58573: Fix conflicts between abbreviated long options in the parent parser and subparsers in argparse.

• gh-124594: All asyncio REPL prompts run in the same context. Contributed by Bartosz Sławecki.

• gh-61181: Fix support of choices with string value in argparse. Substrings of the specified string no longer considered valid values.

• gh-116750: Provide sys.monitoring.clear_tool_id() to unregister all events and callbacks set by the tool.

• gh-124552: Improve the accuracy of bdb’s check for the possibility of breakpoint in a frame. This makes it possible to disable unnecessary events in functions.

• gh-124538: Fixed crash when using gc.get_referents() on a capsule object.

• gh-80259: Fix argparse support of positional arguments with nargs='?', default=argparse.SUPPRESS and specified type.

• gh-120378: Fix a crash related to an integer overflow in curses.resizeterm() and curses.resize_term().

• gh-124498: Fix typing.TypeAliasType not to be generic, when type_params is an empty tuple.

• gh-53834: Fix support of arguments with choices in argparse. Positional arguments with nargs equal to '?' or '*' no longer check default against choices. Optional arguments with nargs equal to '?' no longer check const against choices.

• gh-123884: Fixed bug in itertools.tee() handling of other tee inputs (a tee in a tee). The output now has the promised n independent new iterators. Formerly, the first iterator was identical (not independent) to the input iterator. This would sometimes give surprising results.

• gh-123017: Due to unreliable results on some devices, time.strftime() no longer accepts negative years on Android.

• gh-123014: os.pidfd_open() and signal.pidfd_send_signal() are now unavailable when building against Android API levels older than 31, since the underlying system calls may cause a crash.

• gh-124176: Add support for dataclasses.dataclass() in unittest.mock.create_autospec(). Now create_autospec will check for potential dataclasses and use dataclasses.fields() function to retrieve the spec information.

• gh-124345: argparse vim supports abbreviated single-dash long options separated by = from its value.

• gh-124400: Fixed a pdb bug where until has no effect when it appears in a commands sequence. Also avoid printing the frame information at a breakpoint that has a command list containing a command that resumes execution.

• gh-90562: Modify dataclasses to support zero-argument super() when slots=True is specified. This works by modifying all references to __class__ to point to the newly created class.

• gh-104860: Fix disallowing abbreviation of single-dash long options in argparse with allow_abbrev=False.

• gh-63143: Fix parsing mutually exclusive arguments in argparse. Arguments with the value identical to the default value (e.g. booleans, small integers, empty or 1-character strings) are no longer considered “not present”.

• gh-72795: Positional arguments with nargs equal to '*' or argparse.REMAINDER are no longer required. This allows to use positional argument with nargs='*' and without default in mutually exclusive group and improves error message about required arguments.

• gh-59317: Fix parsing positional argument with nargs equal to '?' or '*' if it is preceded by an option and another positional argument.

• gh-100980: The _fields_ attribute of ctypes.Structure and Union is no longer set if the setattr operation raises an error.

• gh-53780: argparse now ignores the first "--" (double dash) between an option and command.

• gh-124217: Add RFC 9637 reserved IPv6 block 3fff::/20 in ipaddress module.

• gh-111513: Improve the error message that may be raised by datetime.date.fromtimestamp().

• gh-124248: Fixed potential crash when using struct to process zero-width ‘Pascal string’ fields (0p).

• gh-81691: Fix handling of multiple "--" (double dashes) in argparse. Only the first one has now been removed, all subsequent ones are now taken literally.

• gh-87041: Fix a bug in argparse where lengthy subparser argument help is incorrectly indented.

• gh-84559: The default multiprocessing start method on Linux and other POSIX systems has been changed away from often unsafe "fork" to "forkserver" (when the platform supports sending file handles over pipes as most do) or "spawn". Mac and Windows are unchanged as they already default to "spawn".

• gh-124212: Fix invalid variable in venv handling of failed symlink on Windows

• gh-124171: Add workaround for broken fmod() implementations on Windows, that loose zero sign (e.g. fmod(-10, 1) returns 0.0). Patch by Sergey B Kirpichev.

• gh-123978: Remove broken time.thread_time() and time.thread_time_ns() on NetBSD.

• gh-123934: Fix unittest.mock.MagicMock resetting magic methods return values after .reset_mock(return_value=True) was called.

• gh-124016: Update unicodedata database to Unicode 16.0.0.

• gh-123968: Fix the command-line interface for the random module to select floats between 0 and N, not 1 and N.

• gh-123945: Fix a bug where argparse doesn’t recognize negative numbers with underscores

• gh-123935: Fix parent slots detection for dataclasses that inherit from classes with __dictoffset__.

• gh-123892: Add "_wmi" to sys.stdlib_module_names. Patch by Victor Stinner.

• gh-84808: Fix error handling in socket method connect_ex() on platforms where errno can be negative.

• gh-123756: Added a new argument mode to pdb.Pdb. Only allow pdb from command line to use restart command.

• gh-122765: Fix unbalanced quote errors occurring when activate.csh in venv was sourced with a custom prompt containing unpaired quotes or newlines.

• gh-123657: Fix crash and memory leak in decimal.getcontext(). It crashed when using a thread-local context by --with-decimal-contextvar=no.

• gh-123339: Fix inspect.getsource() for classes in collections.abc and decimal (for pure Python implementation) modules. inspect.getcomments() now raises OSError instead of IndexError if the __firstlineno__ value for a class is out of bound.

• gh-123374: Remove check for redefined memo entry in pickletools.dis().

• gh-123504: Fixed reference leak in the finalization of tkinter.

• gh-123430: Pages generated by the http.server module allow the browser to apply its default dark mode.

• gh-123446: Fix empty function name in TypeError when csv.reader(), csv.writer(), or csv.register_dialect() are used without the required args.

• gh-123448: Fixed memory leak of typing.NoDefault by moving it to the static types array.

• gh-123409: Fix ipaddress.IPv6Address.reverse_pointer output according to RFC 3596, §2.5. Patch by Bénédikt Tran.

• gh-123089: Make weakref.WeakSet safe against concurrent mutations while it is being iterated. Patch by Kumar Aditya.

• gh-123363: Show string value of CONTAINS_OP oparg in dis output. Patch by Alexandr153.

• gh-123341: Add __class_getitem__() to tkinter.Event for type subscript support at runtime. Patch by Adonis Rakateli.

• gh-123340: Show string value of IS_OP oparg in dis output.

• gh-119518: Speed up normalization of pathlib.PurePath and Path objects by not interning string parts.

• gh-123270: Applied a more surgical fix for malformed payloads in zipfile.Path causing infinite loops (gh-122905) without breaking contents using legitimate characters.

• gh-73991: Add pathlib.Path.copy_into() and move_into(), which copy and move files and directories into existing directories.

• gh-123228: Fix return type for _pyrepl.readline._ReadlineWrapper.get_line_buffer() to be str(). Patch by Sergey B Kirpichev.

• gh-123240: Raise audit events for the input() in the new REPL.

• gh-76960: Fix urllib.parse.urljoin() and urllib.parse.urldefrag() for URIs containing empty components. For example, urljoin() with relative reference “?” now sets empty query and removes fragment. Preserve empty components (authority, params, query, fragment) in urljoin(). Preserve empty components (authority, params, query) in urldefrag().

• gh-116810: Resolve a memory leak introduced in CPython 3.10’s ssl when the ssl.SSLSocket.session property was accessed. Speeds up read and write access to said property by no longer unnecessarily cloning session objects via serialization.

• gh-123243: Fix memory leak in _decimal.

• gh-122546: Consistently use same file name for different exceptions in the new repl. Patch by Sergey B Kirpichev.

• gh-123213: xml.etree.ElementTree.Element.extend() and Element assignment no longer hide the internal exception if an erroneous generator is passed. Patch by Bar Harel.

• gh-85110: Preserve relative path in URL without netloc in urllib.parse.urlunsplit() and urllib.parse.urlunparse().

• gh-123165: Add support for rendering Positions in dis.

• gh-122909: In urllib.request when URLError is raised opening an ftp URL, the exception argument is now consistently a string. Earlier versions passed either a string or an ftplib exception instance as the argument to URLError.

• gh-123084: Deprecate shutil.ExecError, which hasn’t been raised by any shutil function since Python 3.4. It’s now an alias for RuntimeError.

• gh-123085: In a bare call to importlib.resources.files(), ensure the caller’s frame is properly detected when importlib.resources is itself available as a compiled module only (no source).

• gh-123067: Fix quadratic complexity in parsing "-quoted cookie values with backslashes by http.cookies.

• gh-123049: Add support for UNNAMED_SECTION in configparser.ConfigParser.add_section().

• gh-121735: When working with zip archives, importlib.resources now properly honors module-adjacent references (e.g. files(pkg.mod) and not just files(pkg)).

• gh-122981: Fix inspect.getsource() for generated classes with Python base classes (e.g. enums).

• gh-122903: zipfile.Path.glob now correctly matches directories instead of silently omitting them.

• gh-122905: zipfile.Path objects now sanitize names from the zipfile.

• gh-122873: Enable json module to work as a script using the -m switch: python -m json. See the JSON command-line interface documentation. Patch by Trey Hunner.

• gh-122858: Deprecate asyncio.iscoroutinefunction() in favor of inspect.iscoroutinefunction().

• gh-116263: logging.handlers.RotatingFileHandler no longer rolls over empty log files.

• gh-105376: Restore the deprecated logging warn() method. It was removed in Python 3.13 alpha 1. Keep the deprecated warn() method in Python 3.13. Patch by Victor Stinner.

• gh-122311: Improve errors in the pickle module. PicklingError is now raised more often instead of UnicodeEncodeError, ValueError and AttributeError, and the original exception is chained to it. Improve and unify error messages in Python and C implementations.

• gh-122744: Bump the version of pip bundled in ensurepip to version 24.2.

• gh-118761: Improve import time of pprint by around seven times. Patch by Hugo van Kemenade.

• gh-118974: Add decorator parameter to dataclasses.make_dataclass() to customize the functional creation of dataclasses.

• gh-118814: Fix the typing.TypeVar constructor when name is passed by keyword.

• gh-122637: Adjust cmath.tanh(nanj) and cmath.tanh(infj) for recent C standards.

• gh-122478: Remove internal frames from tracebacks shown in code.InteractiveInterpreter with non-default sys.excepthook(). Save correct tracebacks in sys.last_traceback and update __traceback__ attribute of sys.last_value and sys.last_exc.

• gh-116622: On Android, the FICLONE and FICLONERANGE constants are no longer exposed by fcntl, as these ioctls are blocked by SELinux.

• gh-82378: Make sure that the new REPL interprets sys.tracebacklimit in the same way that the classic REPL did.

• gh-122334: Fix crash when importing ssl after the main interpreter restarts.

• gh-122459: Optimize pickling by name objects without the __module__ attribute.

• gh-87320: In code.InteractiveInterpreter, handle exceptions caused by calling a non-default sys.excepthook(). Before, the exception bubbled up to the caller, ending the REPL.

• gh-122272: On some platforms such as Linux, year with century was not 0-padded when formatted by strftime() with C99-specific specifiers '%C' or '%F'. The 0-padding behavior is now guaranteed when the format specifiers '%C' and '%F' are supported by the C library. Patch by Ben Hsing

• gh-122400: Handle ValueErrors raised by os.stat() in filecmp.dircmp and filecmp.cmpfiles(). Patch by Bénédikt Tran.

• gh-122311: Fix some error messages in pickle.

• gh-121650: email headers with embedded newlines are now quoted on output. The generator will now refuse to serialize (write) headers that are unsafely folded or delimited; see verify_generated_headers. (Contributed by Bas Bloemsaat and Petr Viktorin in gh-121650.)

• gh-122332: Fixed segfault with asyncio.Task.get_coro() when using an eager task factory.

• gh-105733: ctypes.ARRAY() is now soft deprecated: it no longer emits deprecation warnings and is not scheduled for removal.

• gh-122213: Add notes for pickle serialization errors that allow to identify the source of the error.

• gh-119180: As part of PEP 749, add the following attributes for customizing evaluation of annotation scopes:

  • evaluate_value on typing.TypeAliasType

  • evaluate_bound, evaluate_constraints, and evaluate_default on typing.TypeVar

  • evaluate_default on typing.ParamSpec

  • evaluate_default on typing.TypeVarTuple

• gh-119180: Fix handling of classes with custom metaclasses in annotationlib.get_annotations.

• gh-122170: Handle ValueErrors raised by os.stat() in linecache. Patch by Bénédikt Tran.

• gh-122163: Add notes for JSON serialization errors that allow to identify the source of the error.

• gh-122129: Improve support of method descriptors and wrappers in the help title.

• gh-122145: Fix an issue when reporting tracebacks corresponding to Python code emitting an empty AST body. Patch by Nikita Sobolev and Bénédikt Tran.

• gh-121723: Make logging.config.dictConfig() accept any object implementing the Queue public API. See the queue configuration section for details. Patch by Bénédikt Tran.

• gh-82951: Serializing objects with complex __qualname__ (such as unbound methods and nested classes) by name no longer involves serializing parent objects by value in pickle protocols < 4.

• gh-120754: Pathlib.read_bytes no longer opens the file in Python’s buffered I/O mode. This reduces overheads as the code reads a file in whole leading to a modest speedup.

• gh-113785: csv now correctly parses numeric fields (when used with csv.QUOTE_NONNUMERIC or csv.QUOTE_STRINGS) which start with an escape character.

• gh-122088: @warnings.deprecated now copies the coroutine status of functions and methods so that inspect.iscoroutinefunction() returns the correct result.

• gh-122081: Fix a crash in the decimal.IEEEContext() optional function available via the EXTRA_FUNCTIONALITY configuration flag.

• gh-73991: Add pathlib.Path.move(), which moves a file or directory tree.

• gh-121268: Remove workarounds for non-IEEE 754 systems in cmath.

• gh-119698: Due to the lack of interest for symtable.Class.get_methods(), the method is marked as deprecated and will be removed in Python 3.16. Patch by Bénédikt Tran.

• gh-121889: Adjusts cmath.acosh(complex('0+nanj')) for recent C standards.

• gh-121804: Correctly show error locations, when SyntaxError raised in new repl. Patch by Sergey B Kirpichev.

• gh-121797: Add alternative Fraction constructor Fraction.from_number().

• gh-121798: Add alternative Decimal constructor Decimal.from_number().

• gh-120930: Fixed a bug introduced by gh-92081 that added an incorrect extra blank to encoded words occurring in wrapped headers.

• gh-57141: The shallow argument to filecmp.dircmp (new in Python 3.13) is now keyword-only.

• gh-121245: Simplify handling of the history file in site.register_readline() helper. The CAN_USE_PYREPL variable now will be initialized, when imported. Patch by Sergey B Kirpichev.

• gh-121249: Support the float complex and double complex C types in the struct module if the compiler has C11 complex arithmetic. Patch by Sergey B Kirpichev.

• gh-121486: math functions isqrt(), log(), log2() and log10() now support integers larger than 2**2**32 on 32-bit platforms.

• gh-121474: Fix missing sanity check for parties arg in threading.Barrier constructor. Patch by Clinton Christian (pygeek).

• gh-121450: Hard-coded breakpoints (breakpoint() and pdb.set_trace()) now reuse the most recent Pdb instance that calls Pdb.set_trace(), instead of creating a new one each time. As a result, all the instance specific data like display and commands are preserved across Hard-coded breakpoints.

• gh-119169: Slightly speed up os.walk() by simplifying exception handling.

• gh-121423: Improve import time of socket by lazy importing modules and writing socket.errorTab as a constant.

• gh-59110: zipimport supports now namespace packages when no directory entry exists.

• gh-119004: Fix a crash in OrderedDict.__eq__ when operands are mutated during the check. Patch by Bénédikt Tran.

• gh-121313: Limit the reading size in the multiprocessing.connection.Connection class to 64 KiB to prevent memory overallocation and unnecessary memory management system calls.

• gh-121332: Fix constructor of ast nodes with custom _attributes. Previously, passing custom attributes would raise a DeprecationWarning. Passing arguments to the constructor that are not in _fields or _attributes remains deprecated. Patch by Jelle Zijlstra.

• gh-121245: Fix a bug in the handling of the command history of the new REPL that caused the history file to be wiped at REPL exit.

• gh-121210: Handle AST nodes with missing runtime fields or attributes in ast.compare(). Patch by Bénédikt Tran.

• gh-121163: Add support for all as an valid action for warnings.simplefilter() and warnings.filterwarnings().

• gh-121151: Fix wrapping of long usage text of arguments inside a mutually exclusive group in argparse.

• gh-121141: Add support for copy.replace() to AST nodes. Patch by Bénédikt Tran.

• gh-87744: Fix waitpid race while calling send_signal() in asyncio. Patch by Kumar Aditya.

• gh-121027: Add a future warning in functools.partial.__get__(). In future Python versions functools.partial will be a method descriptor.

• gh-121027: Make the functools.partial object a method descriptor.

• gh-117784: CPython now detects whether its linked TLS library supports TLSv1.3 post-handshake authentication and disables that feature if support is lacking.

• gh-121025: Improve the __repr__() of functools.partialmethod. Patch by Bénédikt Tran.

• gh-121018: Fixed issues where argparse.ArgumentParser.parse_args() did not honor exit_on_error=False. Based on patch by Ben Hsing.

• gh-119614: Fix truncation of strings with embedded null characters in some internal operations in tkinter.

• gh-120910: When reading installed files from an egg, use relative_to(walk_up=True) to honor files installed outside of the installation root.

• gh-61103: Support float complex, double complex and long double complex C types in ctypes as c_float_complex, c_double_complex and c_longdouble_complex if the compiler has C11 complex arithmetic. Patch by Sergey B Kirpichev.

• gh-120888: Upgrade pip wheel bundled with ensurepip (pip 24.1.1)

• gh-101830: Accessing the tkinter object’s string representation no longer converts the underlying Tcl object to a string on Windows.

• gh-120678: Fix regression in the new REPL that meant that globals from files passed using the -i argument would not be included in the REPL’s global namespace. Patch by Alex Waygood.

• gh-120811: Fix possible memory leak in contextvars.Context.run().

• gh-120782: Fix wrong references of the datetime types after reloading the module.

• gh-120713: datetime.datetime.strftime() now 0-pads years with less than four digits for the format specifiers %Y and %G on Linux. Patch by Ben Hsing

• gh-120769: Make empty line in pdb repeats the last command even when the command is from cmdqueue.

• gh-120780: Show string value of LOAD_SPECIAL oparg in dis output.

• gh-41431: Add datetime.time.strptime() and datetime.date.strptime(). Contributed by Wannes Boeykens.

• gh-120743: Soft deprecate os.popen() and os.spawn* functions. They should no longer be used to write new code. The subprocess module is recommended instead. Patch by Victor Stinner.

• gh-120732: Fix name passing to unittest.mock.Mock object when using unittest.mock.create_autospec().

• gh-111259: re now handles patterns like "[\s\S]" or "\s|\S" which match any character as effectively as a dot with the DOTALL modifier ("(?s:.)").

• gh-120683: Fix an error in logging.LogRecord, when the integer part of the timestamp is rounded up, while the millisecond calculation truncates, causing the log timestamp to be wrong by up to 999 ms (affected roughly 1 in 8 million timestamps).

• gh-118710: ipaddress.IPv4Address and ipaddress.IPv6Address attributes version and max_prefixlen are now available on the class.

• gh-120633: Move scrollbar and remove tear-off menus in turtledemo.

• gh-120606: Allow users to use EOF to exit commands definition in pdb

• gh-120284: Allow asyncio.Runner.run() to accept awaitable objects instead of simply coroutines.

• gh-120541: Improve the prompt in the “less” pager when help() is called with non-string argument.

• gh-120495: Fix incorrect exception handling in Tab Nanny. Patch by Wulian233.

• gh-120388: Improve a warning message when a test method in unittest returns something other than None. Now we show the returned object type and optional asyncio-related tip.

• gh-120381: Correct inspect.ismethoddescriptor() to check also for the lack of __delete__(). Patch by Jan Kaliszewski.

• gh-90425: The OS byte in gzip headers is now always set to 255 when using gzip.compress().

• gh-120343: Fix column offset reporting for tokens that come after multiline f-strings in the tokenize module.

• gh-119180: As part of implementing PEP 649 and PEP 749, add a new module annotationlib. Add support for unresolved forward references in annotations to dataclasses, typing.TypedDict, and typing.NamedTuple.

• gh-119600: Fix unittest.mock.patch() to not read attributes of the target when new_callable is set. Patch by Robert Collins.

• gh-120289: Fixed the use-after-free issue in cProfile by disallowing disable() and clear() in external timers.

• gh-82017: Added support for converting any objects that have the as_integer_ratio() method to a Fraction.

• gh-114053: Fix edge-case bug where typing.get_type_hints() would produce incorrect results if type parameters in a class scope were overridden by assignments in a class scope and from __future__ import annotations semantics were enabled. Patch by Alex Waygood.

• gh-114053: Fix erroneous NameError when calling inspect.get_annotations() with eval_str=True` on a class that made use of PEP 695 type parameters in a module that had from __future__ import annotations at the top of the file. Patch by Alex Waygood.

• gh-120268: Prohibit passing None to pure-Python datetime.date.fromtimestamp() to achieve consistency with C-extension implementation.

• gh-120244: Fix memory leak in re.sub() when the replacement string contains backreferences.

• gh-120254: Added commands argument to pdb.set_trace() which allows users to send debugger commands from the source file.

• gh-120211: Fix tkinter.ttk with Tcl/Tk 9.0.

• gh-71587: Fix crash in C version of datetime.datetime.strptime() when called again on the restarted interpreter.

• gh-117983: Defer the threading import in importlib.util until lazy loading is used.

• gh-120157: Remove unused constant concurrent.futures._base._FUTURE_STATES in concurrent.futures. Patch by Clinton Christian (pygeek).

• gh-120161: datetime no longer crashes in certain complex reference cycle situations.

• gh-119698: Fix symtable.Class.get_methods() and document its behaviour. Patch by Bénédikt Tran.

• gh-120121: Add concurrent.futures.InvalidStateError to module’s __all__.

• gh-119933: Add the symtable.SymbolTableType enumeration to represent the possible outputs of the symtable.SymbolTable.get_type method. Patch by Bénédikt Tran.

• gh-120029: Expose symtable.Symbol methods is_free_class(), is_comp_iter() and is_comp_cell(). Patch by Bénédikt Tran.

• gh-120108: Fix calling copy.deepcopy() on ast trees that have been modified to have references to parent nodes. Patch by Jelle Zijlstra.

• gh-120056: Add socket.IP_RECVERR and socket.IP_RECVTTL constants (both available since Linux 2.2). And socket.IP_RECVORIGDSTADDR constant (available since Linux 2.6.29).

• gh-112672: Support building tkinter with Tcl 9.0.

• gh-120057: Added the os.environ.refresh() method to update os.environ with changes to the environment made by os.putenv(), by os.unsetenv(), or made outside Python in the same process. Patch by Victor Stinner.

• gh-120029: Expose symtable.Symbol.is_type_parameter() in the symtable module. Patch by Bénédikt Tran.

• gh-119819: Fix regression to allow logging configuration with multiprocessing queue types.

• gh-65454: unittest.mock.Mock.attach_mock() no longer triggers a call to a PropertyMock being attached.

• gh-117142: The ctypes module may now be imported in all subinterpreters, including those that have their own GIL.

• gh-118835: Fix _pyrepl crash when using custom prompt with ANSI escape codes.

• gh-81936: help() and showtopic() methods now respect a configured output argument to pydoc.Helper and not use the pager in such cases. Patch by Enrico Tröger.

• gh-117398: The _datetime module (C implementation for datetime) now supports being imported in multiple interpreters.

• gh-119824: Print stack entry in pdb when and only when user input is needed.

• gh-119838: In mixed arithmetic operations with Fraction and complex, the fraction is now converted to float instead of complex.

• gh-119770: Make termios ioctl() constants positive. Patch by Victor Stinner.

• gh-89727: Fix issue with shutil.rmtree() where a RecursionError is raised on deep directory trees.

• gh-119577: The DeprecationWarning emitted when testing the truth value of an xml.etree.ElementTree.Element now describes unconditionally returning True in a future version rather than raising an exception in Python 3.14.

• gh-89727: Partially fix issue with shutil.rmtree() where a RecursionError is raised on deep directory trees. A recursion error is no longer raised when rmtree.avoids_symlink_attacks is false.

• gh-93963: Remove deprecated names from importlib.abc as found in importlib.resources.abc.

• gh-119118: Fix performance regression in the tokenize module by caching the line token attribute and calculating the column offset more efficiently.

• gh-89727: Fix issue with os.fwalk() where a RecursionError was raised on deep directory trees by adjusting the implementation to be iterative instead of recursive.

• gh-119594: If one calls pow(fractions.Fraction, x, module) with modulo not None, the error message now says that the types are incompatible rather than saying pow only takes 2 arguments. Patch by Wim Jeantine-Glenn and Mark Dickinson.

• gh-119588: zipfile.Path.is_symlink now assesses if the given path is a symlink.

• gh-119562: Remove ast.Num, ast.Str, ast.Bytes, ast.NameConstant and ast.Ellipsis. They had all emitted deprecation warnings since Python 3.12. Patch by Alex Waygood.

• gh-119555: Catch SyntaxError from compile() in the runsource() method of the InteractiveColoredConsole. Patch by Sergey B Kirpichev.

• gh-118908: Limit exposed globals from internal imports and definitions on new REPL startup. Patch by Eugene Triguba and Pablo Galindo.

• gh-117865: Improve the import time of the ast module by deferring the import of re. Patch by Jelle Zijlstra.

• gh-119127: Positional arguments of functools.partial() objects now support placeholders via functools.Placeholder.

• gh-113892: Now, the method sock_connect of asyncio.ProactorEventLoop raises a ValueError if given socket is not in non-blocking mode, as well as in other loop implementations.

• gh-119506: Fix io.TextIOWrapper.write() method breaks internal buffer when the method is called again during flushing internal buffer.

• gh-69214: Fix fcntl.ioctl() request parameter: use an unsigned long instead of an unsigned int for the request parameter of fcntl.ioctl() to support requests larger than UINT_MAX. Patch by Victor Stinner.

• gh-119105: difflib’s DIffer.compare() (and so also ndiff) can no longer be provoked into cubic-time behavior, or into unbounded recursion, and should generally be faster in ordinary cases too. Results may change in some cases, although that should be rare. Correctness of diffs is not affected. Some similar lines far apart may be reported as deleting one and adding the other, where before they were displayed on adjacent output lines with markup showing the intraline differences.

• gh-119443: The interactive REPL no longer runs with from __future__ import annotations enabled. Patch by Jelle Zijlstra.

• gh-119461: Add socket.VMADDR_CID_LOCAL constant. Patch by Victor Stinner.

• gh-117398: Objects in the datetime C-API are now all statically allocated, which means better memory safety, especially when the module is reloaded. This should be transparent to users.

• gh-118894: asyncio REPL now has the same capabilities as PyREPL.

• gh-118830: Bump pickle default protocol to 5.

• gh-118911: In PyREPL, updated maybe-accept’s logic so that if the user hits Enter twice, they are able to terminate the block even if there’s trailing whitespace. Also, now when the user hits arrow up, the cursor is on the last functional line. This matches IPython’s behavior. Patch by Aya Elsayed.

• gh-115225: Raise error on certain technically valid but pathological ISO 8601 strings passed to datetime.time.fromisoformat() that were previously parsed incorrectly.

• gh-111201: Remove dependency to readline from the new Python REPL.

• gh-119189: When using the ** operator or pow() with Fraction as the base and an exponent that is not rational, a float, or a complex, the fraction is no longer converted to a float.

• gh-119174: Fix high DPI causes turtledemo(turtle-graphics examples) windows blurry Patch by Wulian233 and Terry Jan Reedy

• gh-119121: Fix a NameError happening in asyncio.staggered.staggered_race. This function is now tested.

• gh-119105: difflib.Differ is much faster for some cases of diffs where many pairs of lines are equally similar.

• gh-119113: Fix issue where pathlib.PurePath.with_suffix() didn’t raise TypeError when given None as a suffix.

• gh-118643: Fix an AttributeError in the email module when re-fold a long address list. Also fix more cases of incorrect encoding of the address separator in the address list.

• gh-73991: Add pathlib.Path.copy(), which copies a file or directory to another.

• gh-58933: Make pdb return to caller frame correctly when f_trace of the caller frame is not set

• gh-82805: Support single-dot file extensions in pathlib.PurePath.suffix and related attributes and methods. For example, the suffixes of PurePath('foo.bar.') are now ['.bar', '.'] rather than []. This brings file extension splitting in line with os.path.splitext().

• gh-118924: Remove version and version_info from sqlite3. Patch by Hugo van Kemenade.

• gh-118928: Disallow using a sequence of parameters with named placeholders in sqlite3 queries. Patch by Erlend E. Aasland.

• gh-118895: Setting attributes on typing.NoDefault now raises AttributeError instead of TypeError.

• gh-118868: Fixed issue where kwargs were no longer passed to the logging handler QueueHandler

• gh-118827: Remove deprecated Quoter class from urllib.parse. It had previously raised a DeprecationWarning since Python 3.11. Patch by Nikita Sobolev.

• gh-118824: Remove deprecated pty.master_open() and pty.slave_open(). Use pty.openpty() instead. Patch by Nikita Sobolev.

• gh-118851: ctx arguments to the constructors of ast node classes now default to ast.Load(). Patch by Jelle Zijlstra.

• gh-101588: Remove copy, deepcopy, and pickle from itertools. These had previously raised a DeprecationWarning since Python 3.12.

• gh-118805: Remove type, choices, and metavar parameters of argparse.BooleanOptionalAction. They were deprecated since Python 3.12.

• gh-118803: typing.ByteString and collections.abc.ByteString are removed. They had previously raised a DeprecationWarning since Python 3.12.

• gh-118798: The isdst parameter has been removed from email.utils.localtime(). Patch by Hugo van Kemenade.

• gh-118760: Restore the default value of tkiter.wantobjects to 1.

• gh-118760: Fix errors in calling Tkinter bindings on Windows.

• gh-74033: Drop support for passing keyword arguments to pathlib.Path.

• gh-101357: Suppress all OSError exceptions from pathlib.Path.exists() and is_*() methods, rather than a selection of more common errors. The new behaviour is consistent with os.path.exists(), os.path.isdir(), etc. Use pathlib.Path.stat() to retrieve the file status without suppressing exceptions.

• gh-78707: Drop support for passing additional positional arguments to pathlib.PurePath.relative_to() and is_relative_to().

• gh-118507: Fix os.path.isfile() on Windows for pipes. Speedup os.path.isjunction() and os.path.lexists() on Windows with a native implementation.

• gh-118772: Allow typing.TypeVar instances without a default to follow instances without a default in some cases. Patch by Jelle Zijlstra.

• gh-118714: Allow restart in post-mortem debugging of pdb. Removed restart message when the user quits pdb from post-mortem mode.

• gh-118673: Removed executable bits and shebang from stdlib modules.

• gh-110863: os.path.realpath() now suppresses any OSError from os.readlink() when strict mode is disabled (the default).

• gh-118263: Speed up os.path.splitroot() & os.path.normpath() with a direct C call.

• gh-110190: Fix ctypes structs with array on SPARC by setting MAX_STRUCT_SIZE to 32 in stgdict. Patch by Jakub Kulik

• gh-118033: Fix dataclasses.dataclass() not creating a __weakref__ slot when subclassing typing.Generic.

• gh-117766: Always use str() to print choices in argparse.

• gh-106531: In importlib.resources, sync with importlib_resources 6.3.2, including: MultiplexedPath now expects Traversable paths, deprecating string arguments to MultiplexedPath; Enabled support for resources in namespace packages in zip files; Fixed NotADirectoryError when calling files on a subdirectory of a namespace package.

• gh-115937: Removed extra preprocessing for the __signature__ attribute: the code just check if it’s a inspect.Signature instance. Patch by Sergey B Kirpichev.

• gh-115808: Add operator.is_none() and operator.is_not_none() functions.

• gh-114264: Improve performance of copy.deepcopy() by adding a fast path for atomic types.

• gh-113878: Add doc parameter to dataclasses.field(), so it can be stored and shown as a documentation / metadata. If @dataclass(slots=True) is used, then the supplied string is availabl in the __slots__ dict. Otherwise, the supplied string is only available in the corresponding dataclasses.Field object.

  In order to support this feature we are changing the __slots__ format in dataclasses from tuple to dict when documentation / metadata is present.

• gh-113978: Ignore warnings on text completion inside REPL.

• gh-113008: Correct argparse usage output for required, mutually exclusive groups containing a positional argument

• gh-108172: webbrowser honors OS preferred browser on Linux when its desktop entry name contains the text of a known browser name.

• gh-109109: You can now get the raw TLS certificate chains from TLS connections via ssl.SSLSocket.get_verified_chain() and ssl.SSLSocket.get_unverified_chain() methods.

  Contributed by Mateusz Nowak.

• gh-105623: Fix performance degradation in logging.handlers.RotatingFileHandler. Patch by Craig Robson.

• gh-102450: Add missing ISO-8601 24:00 alternative to midnight of next day to datetime.datetime.fromisoformat() and datetime.time.fromisoformat(). Patch by Izan “TizzySaurus” Robinson (tizzysaurus@gmail.com)

• gh-103956: Fix lack of newline characters in trace module output when line tracing is enabled but source code line for current frame is not available.

• gh-92081: Fix missing spaces in email headers when the spaces are mixed with encoded 8-bit characters.

• gh-103194: Prepare Tkinter for C API changes in Tcl 8.7/9.0 to avoid _tkinter.Tcl_Obj being unexpectedly returned instead of bool, str, bytearray, or int.

• gh-87106: Fixed handling in inspect.Signature.bind() of keyword arguments having the same name as positional-only arguments when a variadic keyword argument (e.g. **kwargs) is present.

• gh-103134: Add additional methods to proxy objects in the multiprocessing module:

  • clear() and copy() for proxies of list

  • fromkeys(), reversed(d), d | {}, {} | d, d |= {'b': 2} for proxies of dict

• bpo-45767: Fix integer conversion in os.major(), os.minor(), and os.makedev(). Support device numbers larger than 2**63-1. Support non-existent device number (NODEV).

• bpo-44864: Do not translate user-provided strings in argparse.ArgumentParser.

• bpo-41843: Solaris now uses os.sendfile() fast-copy syscall for more efficient shutil file copy related functions.

• bpo-15987: Implemented ast.compare() for comparing two ASTs. Patch by Batuhan Taskaya with some help from Jeremy Hylton.

• gh-67693: Fix urllib.parse.urlunparse() and urllib.parse.urlunsplit() for URIs with path starting with multiple slashes and no authority. Based on patch by Ashwin Ramaswami.

• bpo-14074: Fix argparse metavar processing to allow positional arguments to have a tuple metavar.

IDLE

• gh-122392: Increase currently inadequate vertical spacing for the IDLE browsers (path, module, and stack) on high-resolution monitors.

• gh-112938: Fix uninteruptable hang when Shell gets rapid continuous output.

• gh-122482: Change About IDLE to direct users to discuss.python.org instead of the now unused idle-dev email and mailing list.

• gh-78889: Stop Shell freezes by blocking user access to non-method sys.stdout.shell attributes, which are all private.

• gh-120083: Add explicit black IDLE Hovertip foreground color needed for recent macOS. Fixes Sonoma showing unreadable white on pale yellow. Patch by John Riggles.

• gh-120104: Fix padding in config and search dialog windows in IDLE.

Documentation

• gh-124872: Added definitions for context, current context, and context management protocol, updated related definitions to be consistent, and expanded the documentation for contextvars.Context.

• gh-125018: The importlib.metadata documentation now includes semantic cross-reference targets for the significant documented APIs. This means intersphinx references like importlib.metadata.version() will now work as expected.

• gh-124720: Update “Using Python on a Mac” section of the “Python Setup and Usage” document and include information on installing free-threading support.

• gh-124457: Remove coverity scan from the CPython repo. It has not been used since 2020 and is currently unmaintained.

• gh-116622: Add an Android platform guide, and flag modules not available on Android.

• gh-123976: Refresh docs around custom providers.

• gh-70870: Clarified the dual usage of the term “free variable” (both the formal meaning of any reference to names defined outside the local scope, and the narrower pragmatic meaning of nonlocal variables named in co_freevars).

• gh-121277: Writers of CPython’s documentation can now use next as the version for the versionchanged, versionadded, deprecated directives.

• gh-117765: Improved documentation for unittest.mock.patch.dict()

• gh-121749: Fix documentation for PyModule_AddObjectRef().

• gh-120012: Clarify the behaviours of multiprocessing.Queue.empty() and multiprocessing.SimpleQueue.empty() on closed queues. Patch by Bénédikt Tran.

• gh-119574: Added some missing environment variables to the output of --help-env.

• bpo-34008: The Py_Main() documentation moved from the “Very High Level API” section to the “Initialization and Finalization” section.

  Also make it explicit that we expect Py_Main to typically be called instead of Py_Initialize rather than after it (since Py_Main makes its own call to Py_Initialize). Document that calling both is supported but is version dependent on which settings will be applied correctly.

Core and Builtins

• gh-124375: Fix a crash in the free threading build when the GC runs concurrently with a new thread starting.

• gh-125221: Fix possible race condition when calling __reduce_ex__() for the first time in the free threading build.

• gh-125174: Make the handling of reference counts of immortal objects more robust. Immortal objects with reference counts that deviate from their original reference count by up to a billion (half a billion on 32 bit builds) are still counted as immortal.

• gh-125039: Make this_instr and prev_instr const in cases generator.

• gh-125008: Fix tokenize.untokenize() producing invalid syntax for double braces preceded by certain escape characters.

• gh-124871: Fix compiler bug (in some versions of 3.13) where an assertion fails during reachability analysis.

• gh-123378: Fix a crash in the __str__() method of UnicodeError objects when the UnicodeError.start and UnicodeError.end values are invalid or out-of-range. Patch by Bénédikt Tran.

• gh-118093: Improve the experimental JIT compiler’s ability to stay “on trace” when encountering highly-biased branches.

• gh-124642: Fixed scalability issue in free-threaded builds for lock-free reads from dictionaries in multi-threaded scenarios

• gh-116510: Fix a crash caused by immortal interned strings being shared between sub-interpreters that use basic single-phase init. In that case, the string can be used by an interpreter that outlives the interpreter that created and interned it. For interpreters that share obmalloc state, also share the interned dict with the main interpreter.

• gh-116510: Fix a bug that can cause a crash when sub-interpreters use “basic” single-phase extension modules. Shared objects could refer to PyGC_Head nodes that had been freed as part of interpreter cleanup.

• gh-119180: The __main__ module no longer always contains an __annotations__ dictionary in its global namespace.

• gh-124547: When deallocating an object with inline values whose __dict__ is still live: if memory allocation for the inline values fails, clear the dictionary. Prevents an interpreter crash.

• gh-124513: Fix a crash in FrameLocalsProxy constructor: check the number of arguments. Patch by Victor Stinner.

• gh-124442: Fix nondeterminism in compilation by sorting the value of __static_attributes__. Patch by kp2pml30.

• gh-124285: Fix bug where bool(a) can be invoked more than once during the evaluation of a compound boolean expression.

• gh-123856: Fix PyREPL failure when a keyboard interrupt is triggered after using a history search

• gh-65961: Deprecate the setting and using __package__ and __cached__.

• gh-119726: The JIT now generates more efficient code for calls to C functions resulting in up to 0.8% memory savings and 1.5% speed improvement on AArch64. Patch by Diego Russo.

• gh-122878: Use the pager binary, if available (e.g. on Debian and derivatives), to display REPL help().

• gh-124188: Fix reading and decoding a line from the source file witn non-UTF-8 encoding for syntax errors raised in the compiler.

• gh-124027: Support <page up>, <page down>, and <delete> keys in the Python REPL when $TERM is set to vt100.

• gh-124022: Fix bug where docstring is removed from classes in interactive mode.

• gh-123958: docstrings are now removed from the optimized AST in optimization level 2.

• gh-123923: The f_executable field in the internal _PyInterpreterFrame struct now uses a tagged pointer. Profilers and debuggers that uses this field should clear the least significant bit to recover the PyObject* pointer.

• gh-77894: Fix possible crash in the garbage collector when it tries to break a reference loop containing a memoryview object. Now a memoryview object can only be cleared if there are no buffers that refer it.

• gh-120221: asyncio REPL is now again properly recognizing KeyboardInterrupts. Display of exceptions raised in secondary threads is fixed.

• gh-119310: Allow the new interactive shell to read history files written with the editline library that use unicode-escaped entries. Patch by aorcajo and Łukasz Langa.

• gh-123572: Fix key mappings for various F-keys in Windows for the new REPL. Patch by devdanzin

• gh-123614: Add turtle.save() to easily save Turtle drawings as PostScript files. Patch by Marie Roald and Yngve Mardal Moe.

• gh-123339: Setting the __module__ attribute for a class now removes the __firstlineno__ item from the type’s dict, so they will no longer be inconsistent.

• gh-119034: Change <page up> and <page down> keys of the Python REPL to history search forward/backward. Patch by Victor Stinner.

• gh-123562: Improve SyntaxError message for using case ... as ... with not a name.

• gh-123545: Fix a double decref in rare cases on experimental JIT builds.

• gh-123484: Fix _Py_DebugOffsets for long objects to be relative to the start of the object rather than the start of a subobject.

• gh-123446: Fix empty function name in TypeError when builtin magic methods are used without the required args.

• gh-123440: Improve SyntaxError message for using except as with not a name.

• gh-116017: Improved JIT memory consumption by periodically freeing memory used by infrequently-executed code. This change is especially likely to improve the memory footprint of long-running programs.

• gh-123344: Add AST optimizations for type parameter defaults.

• gh-123321: Prevent Parser/myreadline race condition from segfaulting on multi-threaded use. Patch by Bar Harel and Amit Wienner.

• gh-123177: Fix a bug causing stray prompts to appear in the middle of wrapped lines in the new REPL.

• gh-122982: Extend the deprecation period for bool inversion (~) by two years.

• gh-123271: Make concurrent iterations over the same zip() iterator safe under free-threading.

• gh-123275: Support -X gil=1 and PYTHON_GIL=1 on non-free-threaded builds.

• gh-123177: Deactivate line wrap in the Apple Terminal via a ANSI escape code. Patch by Pablo Galindo

• gh-123229: Fix valgrind warning by initializing the f-string buffers to 0 in the tokenizer. Patch by Pablo Galindo

• gh-122298: Restore printout of GC stats when gc.set_debug(gc.DEBUG_STATS) is called. This feature was accidentally removed when implementing incremental GC.

• gh-121804: Correctly show error locations when a SyntaxError is raised in the basic REPL. Patch by Sergey B Kirpichev.

• gh-115776: Enables inline values (Python’s equivalent of hidden classes) on any class who’s instances are of a fixed size.

• gh-123142: Fix too-wide source location in exception tracebacks coming from broken iterables in comprehensions.

• gh-123048: Fix a bug where pattern matching code could emit a JUMP_FORWARD with no source location.

• gh-118093: Break up CALL_ALLOC_AND_ENTER_INIT into micro-ops and relax requirement for exact args, in order to increase the amount of code supported by tier 2.

• gh-123123: Fix displaying SyntaxError exceptions covering multiple lines. Patch by Pablo Galindo

• gh-123083: Fix a potential use-after-free in STORE_ATTR_WITH_HINT.

• gh-123022: Fix crash in free-threaded build when calling Py_Initialize() from a non-main thread.

• gh-118093: Add three specializations for CALL_KW:

  • CALL_KW_PY for calls to Python functions

  • CALL_KW_BOUND_METHOD for calls to bound methods

  • CALL_KW_NON_PY for all other calls

• gh-122821: Make sure that branches in while statements have consistent offsets for sys.monitoring. while statements are now compiled with a simple jump at the end of the body, instead of duplicating the test.

• gh-122907: Building with HAVE_DYNAMIC_LOADING now works as well as it did in 3.12. Existing deficiences will be addressed separately. (See https://github.com/python/cpython/issues/122950.)

• gh-122888: Fix crash on certain calls to str() with positional arguments of the wrong type. Patch by Jelle Zijlstra.

• gh-118093: Improve the experimental JIT’s handling of polymorphic code.

• gh-122697: Fixed memory leaks at interpreter shutdown in the free-threaded build, and also reporting of leaked memory blocks via -X showrefcount.

• gh-116622: Fix Android stdout and stderr messages being truncated or lost.

• gh-122527: Fix a crash that occurred when a PyStructSequence was deallocated after its type’s dictionary was cleared by the GC. The type’s tp_basicsize now accounts for non-sequence fields that aren’t included in the Py_SIZE of the sequence.

• gh-122445: Add only fields which are modified via self.* to __static_attributes__.

• gh-122417: In the free-threaded build, the reference counts for heap type objects are now partially stored in a distributed manner in per-thread arrays. This reduces contention on the heap type’s reference count fields when creating or destroying instances of the same type from multiple threads concurrently.

• gh-116090: Fix an issue in JIT builds that prevented some for loops from correctly firing RAISE monitoring events.

• gh-122300: Preserve AST nodes for f-string with single-element format specifiers. Patch by Pablo Galindo

• gh-120906: frame.f_locals now supports arbitrary hashable objects as keys.

• gh-122239: When a list, tuple or dict with too many elements is unpacked, show the actual length in the error message.

• gh-122245: Detection of writes to __debug__ is moved from the compiler’s codegen stage to the symtable. This means that these errors are now detected even in code that is optimized away before codegen (such as assertions with the -O command line option).

• gh-122234: Specializations for sums with float and complex inputs in sum() now always use compensated summation. Also, for integer items in above specializations: PyLong_AsDouble() is used, instead of PyLong_AsLongAndOverflow(). Patch by Sergey B Kirpichev.

• gh-122208: Dictionary watchers now only deliver the PyDict_EVENT_ADDED event when the insertion is in a known good state to succeed.

• gh-122160: Remove the BUILD_CONST_KEY_MAP opcode. Use BUILD_MAP instead.

• gh-122029: Emit c_call events in sys.setprofile() when a PyMethodObject pointing to a PyCFunction is called.

• gh-122026: Fix a bug that caused the tokenizer to not correctly identify mismatched parentheses inside f-strings in some situations. Patch by Pablo Galindo

• gh-99108: Python’s hashlib now unconditionally uses the vendored HACL* library for Blake2. Python no longer accepts libb2 as an optional dependency for Blake2.

  We refreshed HACL* to the latest version, and now vendor HACL*’s 128-bit and 256-bit wide vector implementations for Blake2, which are used on x86/x64 toolchains when the required CPU features are available at runtime.

  HACL*’s 128-bit wide vector implementation of Blake2 can also run on ARM NEON and Power8, but lacking evidence of a performance gain, these are not enabled (yet).

• gh-121999: The default extraction filter for the tarfile module is now set to 'data'.

• gh-121860: Fix crash when rematerializing a managed dictionary after it was deleted.

• gh-121795: Improve performance of set membership testing, set.remove() and set.discard() when the argument is a set.

• gh-121814: Fixed the SegFault when PyEval_SetTrace() is used with no Python frame on stack.

• gh-121295: Fix PyREPL console getting into a blocked state after interrupting a long paste

• gh-121794: Fix bug in free-threaded Python where a resurrected object could lead to a negative ref count assertion failure.

• gh-121657: Improve the SyntaxError message if the user tries to use yield from outside a function.

• gh-121609: Fix pasting of characters containing unicode character joiners in the new REPL. Patch by Marta Gomez Macias

• gh-121297: Previously, incorrect usage of await or asynchronous comprehensions in code removed by the -O option was not flagged by the Python compiler. Now, such code raises SyntaxError. Patch by Jelle Zijlstra.

• gh-117482: Unexpected slot wrappers are no longer created for builtin static types in subinterpreters.

• gh-121562: Optimized performance of hex_from_char by replacing switch-case with a lookup table

• gh-121499: Fix a bug affecting how multi-line history was being rendered in the new REPL after interacting with the new screen cache. Patch by Pablo Galindo

• gh-121497: Fix a bug that was preventing the REPL to correctly respect the history when an input hook was set. Patch by Pablo Galindo

• gh-121012: Tier 2 execution now ensures that list iterators remain exhausted, once they become exhausted.

• gh-121439: Allow tuples of length 20 in the freelist to be reused.

• gh-121288: ValueError messages for list.index(), range.index(), deque.index(), deque.remove() and ShareableList.index() no longer contain the repr of the searched value (which can be arbitrary large) and are consistent with error messages for other index() and remove() methods.

• gh-121368: Fix race condition in _PyType_Lookup in the free-threaded build due to a missing memory fence. This could lead to _PyType_Lookup returning incorrect results on arm64.

• gh-121149: Added specialization for summation of complexes, this also improves accuracy of builtin sum() for such inputs. Patch by Sergey B Kirpichev.

• gh-121130: Fix f-strings with debug expressions in format specifiers. Patch by Pablo Galindo

• gh-121381: Remove subprocess._USE_VFORK escape hatch code and documentation. It was added just in case, and doesn’t have any known cases that require it.

• gh-119726: Optimize code layout for calls to C functions from the JIT on AArch64. Patch by Diego Russo.

• gh-121115: PyLong_AsNativeBytes() no longer uses __index__() methods by default. The Py_ASNATIVEBYTES_ALLOW_INDEX flag has been added to allow it.

• gh-120838: Py_Finalize() and Py_FinalizeEx() now always run with the main interpreter active.

• gh-113433: Subinterpreters now get cleaned up automatically during runtime finalization.

• gh-119726: Improve the speed and memory use of C function calls from JIT code on AArch64. Patch by Diego Russo

• gh-116017: Simplify the warmup mechanism used for “side exits” in JIT code, resulting in slightly better performance and slightly lower memory usage for most platforms.

• gh-98442: Fix too wide source locations of the cleanup instructions of a with statement.

• gh-120754: Reduce the number of system calls invoked when reading a whole file (ex. open('a.txt').read()). For a sample program that reads the contents of the 400+ .rst files in the cpython repository Doc folder, there is an over 10% reduction in system call count.

• gh-119462: Make sure that invariants of type versioning are maintained: * Superclasses always have their version number assigned before subclasses * The version tag is always zero if the tag is not valid. * The version tag is always non-if the tag is valid.

• gh-120437: Fix _CHECK_STACK_SPACE optimization problems introduced in gh-118322.

• gh-120722: Correctly set the bytecode position on return instructions within lambdas. Patch by Jelle Zijlstra.

• gh-120367: Fix bug where compiler creates a redundant jump during pseudo-op replacement. Can only happen with a synthetic AST that has a try on the same line as the instruction following the exception handler.

• gh-120507: Remove the BEFORE_WITH and BEFORE_ASYNC_WITH instructions. Add the new LOAD_SPECIAL instruction. Generate code for with and async with statements using the new instruction.

• gh-113993: Strings interned with sys.intern() are again garbage-collected when no longer used, as per the documentation. Strings interned with the C function PyUnicode_InternInPlace() are still immortal. Internals of the string interning mechanism have been changed. This may affect performance and identities of str objects.

• gh-120485: Add an override of allow_reuse_port on classes subclassing socketserver.TCPServer where allow_reuse_address is also overridden.

• gh-120384: Fix an array out of bounds crash in list_ass_subscript, which could be invoked via some specifically tailored input: including concurrent modification of a list object, where one thread assigns a slice and another clears it.

• gh-120367: Fix crash in compiler on code with redundant NOPs and JUMPs which show up after exception handlers are moved to the end of the code.

• gh-120380: Fix Python implementation of pickle.Pickler for bytes and bytearray objects when using protocol version 5. Patch by Bénédikt Tran.

• gh-120397: Improve the throughput by up to two times for the str.count(), bytes.count() and bytearray.count() methods for counting single characters.

• gh-120221: Deliver real signals on Ctrl-C and Ctrl-Z in the new REPL. Patch by Pablo Galindo

• gh-120346: Respect PYTHON_BASIC_REPL when running in interactive inspect mode (python -i). Patch by Pablo Galindo

• gh-93691: Fix source locations of instructions generated for the iterator of a for statement.

• gh-120198: Fix a crash when multiple threads read and write to the same __class__ of an object concurrently.

• gh-120298: Fix use-after free in list_richcompare_impl which can be invoked via some specifically tailored evil input.

• gh-119666: Fix a compiler crash in the case where two comprehensions in class scope both reference __class__.

• gh-119726: JIT: Re-use trampolines on AArch64 when creating stencils. Patch by Diego Russo

• gh-120225: Fix crash in compiler on empty block at end of exception handler.

• gh-93691: Fix source locations of instructions generated for with statements.

• gh-120097: FrameLocalsProxy now subclasses collections.abc.Mapping and can be matched as a mapping in match statements

• gh-120080: Direct call to the int.__round__() now accepts None as a valid argument.

• gh-119933: Improve SyntaxError messages for invalid expressions in a type parameters bound, a type parameter constraint tuple or a default type parameter. Patch by Bénédikt Tran.

• gh-119724: Reverted improvements to error messages for elif/else statements not matching any valid statements, which made in hard to locate the syntax errors inside those elif/else blocks.

• gh-119879: String search is now slightly faster for certain cases. It now utilizes last character gap (good suffix rule) for two-way periodic needles.

• gh-119842: Honor PyOS_InputHook() in the new REPL. Patch by Pablo Galindo

• gh-119180: classmethod() and staticmethod() now wrap the __annotations__ and __annotate__ attributes of their underlying callable lazily. See PEP 649. Patch by Jelle Zijlstra.

• gh-119821: Fix execution of annotation scopes within classes when globals is set to a non-dict. Patch by Jelle Zijlstra.

• gh-118934: Make PyEval_GetLocals return borrowed reference

• gh-119740: Remove the previously-deprecated delegation of int() to __trunc__().

• gh-119689: Generate stack effect metadata for pseudo instructions from bytecodes.c.

• gh-109218: complex() accepts now a string only as a positional argument. Passing a complex number as the “real” or “imag” argument is deprecated; it should only be passed as a single positional argument.

• gh-119548: Add a clear command to the REPL. Patch by Pablo Galindo

• gh-111999: Fix the signature of str.format_map().

• gh-119560: An invalid assert in beta 1 has been removed. The assert would fail if PyState_FindModule() was used in an extension module’s init function before the module def had been initialized.

• gh-119369: Fix deadlock during thread deletion in free-threaded build, which could occur when the GIL was enabled at runtime.

• gh-119525: Fix deadlock involving _PyType_Lookup() cache in the free-threaded build when the GIL is dynamically enabled at runtime.

• gh-119258: Eliminate type version guards in the tier two interpreter.

  Note that setting the tp_version_tag manually (which has never been supported) may result in crashes.

• gh-119311: Fix bug where names are unexpectedly mangled in the bases of generic classes.

• gh-119395: Fix bug where names appearing after a generic class are mangled as if they are in the generic class.

• gh-119372: Correct invalid corner cases in complex division (resulted in (nan+nanj) output), e.g. 1/complex('(inf+infj)'). Patch by Sergey B Kirpichev.

• gh-119180: Evaluation of annotations is now deferred. See PEP 649 for details.

• gh-119180: Replace LOAD_ASSERTION_ERROR opcode with LOAD_COMMON_CONSTANT and add support for NotImplementedError.

• gh-119213: Non-builtin modules built with argument clinic were crashing if used in a subinterpreter before the main interpreter. The objects that were causing the problem by leaking between interpreters carelessly have been fixed.

• gh-119011: Fixes type.__type_params__ to return an empty tuple instead of a descriptor.

• gh-118692: Avoid creating unnecessary StopIteration instances for monitoring.

• gh-119180: Add an __annotate__ attribute to functions, classes, and modules as part of PEP 649. Patch by Jelle Zijlstra.

• gh-119049: Fix displaying the source line for warnings created by the C API if the warnings module had not yet been imported.

• gh-119057: Improve ZeroDivisionError error message. Now, all error messages are harmonized: all /, //, and % operations just use “division by zero” message. And 0 ** -1 operation uses “zero to a negative power”.

• gh-118844: Fix build failures when configuring with both --disable-gil and --enable-experimental-jit.

• gh-118921: Add copy() method for FrameLocalsProxy which returns a snapshot dict for local variables.

• gh-117657: Fix data races on the field that stores a pointer to the interpreter’s main thread that occur in free-threaded builds.

• gh-118750: If the C version of the decimal module is available, int(str) now uses it to supply an asymptotically much faster conversion. However, this only applies if the string contains over about 2 million digits.

• gh-118767: Using NotImplemented in a boolean context now raises TypeError. Contributed by Jelle Zijlstra.

• gh-118561: Fix race condition in free-threaded build where list.extend() could expose uninitialised memory to concurrent readers.

• gh-117139: Convert the Python evaluation stack to use internal stack references. The purpose is to support tagged pointers. In PEP 703, this will allow for its form of deferred reference counting. For both the default and free-threaded builds, this sets up the infrastructure for unboxed integers in the future.

• gh-115801: Raise TypeError when passing a string to difflib.unified_diff() and difflib.context_diff().

• gh-117558: Improve error messages when a string, bytes or bytearray object of length 1 is expected.

• gh-117195: Avoid assertion failure for debug builds when calling object.__sizeof__(1)

• gh-116022: Improve the __repr__() output of AST nodes.

• gh-114091: Changed the error message for awaiting something that can’t be awaited from “object <type> can’t be used in an await expression” to “’<type>’ object can’t be awaited”.

• gh-113190: Py_Finalize() now deletes all interned strings.

• gh-84978: Add class methods float.from_number() and complex.from_number().

• gh-95144: Improve the error message from a in b when b is not a container to mention the term “container”.

• bpo-24766: Fix handling of doc argument to subclasses of property.

C API

• gh-123961: Convert the curses.window static type exposed by the PyCursesWindow_Type macro in Include/py_curses.h to a heap type. Patch by Bénédikt Tran.

• gh-124502: Add PyUnicode_Equal() function to the limited C API: test if two strings are equal. Patch by Victor Stinner.

• gh-124296: PyDictObject no longer maintains a private version tag field ma_version_tag per PEP 699. This field was originally added in Python 3.6 (PEP 509) and deprecated in Python 3.12.

• gh-124160: Fix crash when importing modules containing state and single-phase initialization in a subinterpreter.

• gh-124153: Add PyType_GetBaseByToken() and Py_tp_token slot for easier type checking, related to PEP 489 and PEP 630.

• gh-124127: In the limited C API 3.14 and newer, Py_REFCNT() is now implemented as an opaque function call to hide implementation details. Patch by Victor Stinner.

• gh-123880: Fixed a bug that prevented circular imports of extension modules that use single-phase initialization.

• gh-123909: PyType_FromSpec(), PyType_FromSpecWithBases() and PyType_FromModuleAndSpec() will now fail if the metaclass of the new type has custom tp_new.

• gh-107954: Add functions to configure the Python initialization (PEP 741):

  • PyInitConfig_Create()

  • PyInitConfig_Free()

  • PyInitConfig_GetError()

  • PyInitConfig_GetExitCode()

  • PyInitConfig_HasOption()

  • PyInitConfig_GetInt()

  • PyInitConfig_GetStr()

  • PyInitConfig_GetStrList()

  • PyInitConfig_FreeStrList()

  • PyInitConfig_SetInt()

  • PyInitConfig_SetStr()

  • PyInitConfig_SetStrList()

  • PyInitConfig_AddModule()

  • Py_InitializeFromInitConfig()

  Patch by Victor Stinner.

• gh-107954: Add functions to get and set the current runtime Python configuration:

  • PyConfig_Get()

  • PyConfig_GetInt()

  • PyConfig_Set()

  • PyConfig_Names()

  Patch by Victor Stinner.

• gh-123465: Py_RELATIVE_OFFSET is now allowed in PyMemberDef for the special offset member "__vectorcalloffset__", as well as the discouraged special offset members "__dictoffset__" and "__weaklistoffset__"

• gh-100554: Added a slot Py_tp_vectorcall to set tp_vectorcall via the PyType_FromSpec() function family. Limited API extensions can use this feature to provide more efficient vector call-based implementation of __new__ and __init__.

• gh-122854: Add Py_HashBuffer() to compute and return the hash value of a buffer. Patch by Antoine Pitrou and Victor Stinner.

• gh-122728: Fix PyEval_GetLocals() to avoid SystemError (“bad argument to internal function”). Patch by Victor Stinner.

• gh-116622: Make PyObject_Print work around a bug in Android and OpenBSD which prevented it from throwing an exception when trying to write to a read-only stream.

• gh-105201: Add PyIter_NextItem() to replace PyIter_Next(), which has an ambiguous return value. Patch by Irit Katriel and Erlend Aasland.

• gh-121489: Export private _PyBytes_Join() again.

• gh-121645: Add PyBytes_Join(sep, iterable) function, similar to sep.join(iterable) in Python. Patch by Victor Stinner.

• gh-89364: Export the PySignal_SetWakeupFd() function. Previously, the function was documented but it couldn’t be used in 3rd party code. Patch by Victor Stinner.

• gh-113993: PyUnicode_InternInPlace() no longer prevents its argument from being garbage collected.

  Several functions that take char * are now documented as possibly preventing string objects from being garbage collected; refer to their documentation for details: PyUnicode_InternFromString(), PyDict_SetItemString(), PyObject_SetAttrString(), PyObject_DelAttrString(), PyUnicode_InternFromString(), and PyModule_Add* convenience functions.

• gh-113601: Removed debug build assertions related to interning strings, which were falsely triggered by stable ABI extensions.

• gh-112136: Restore the private _PyArg_Parser structure and the private _PyArg_ParseTupleAndKeywordsFast() function, previously removed in Python 3.13 alpha 1. Patch by Victor Stinner.

• gh-120642: Remove the private _Py_CODEUNIT type from the public C API. The internal pycore_code.h header should now be used to get this internal type. Patch by Victor Stinner.

• gh-120858: PyDict_Next() no longer locks the dictionary in the free-threaded build. The locking needs to be done by the caller around the entire iteration loop.

• gh-120642: Remove the following unstable functions:

  • PyUnstable_Replace_Executor()

  • PyUnstable_SetOptimizer()

  • PyUnstable_GetOptimizer()

  • PyUnstable_GetExecutor()

  • PyUnstable_Optimizer_NewCounter()

  • PyUnstable_Optimizer_NewUOpOptimizer()

  Patch by Victor Stinner.

• gh-120389: Add new functions to convert C <stdint.h> numbers from/to Python int:

  • PyLong_FromInt32()

  • PyLong_FromUInt32()

  • PyLong_FromInt64()

  • PyLong_FromUInt64()

  • PyLong_AsInt32()

  • PyLong_AsUInt32()

  • PyLong_AsInt64()

  • PyLong_AsUInt64()

  Patch by Victor Stinner.

• gh-120600: In the limited C API 3.14 and newer, Py_TYPE() is now implemented as an opaque function call to hide implementation details. Patch by Victor Stinner.

• gh-70278: PyUnicode_FromFormat() no longer produces the ending \ufffd character for truncated C string when use precision with %s and %V. It now truncates the string before the start of truncated multibyte sequences.

• gh-119771: Set errno in _Py_c_pow() on overflows. Patch by Sergey B Kirpichev.

• gh-119182: Add a new PyUnicodeWriter API to create a Python str object:

  • PyUnicodeWriter_Create().

  • PyUnicodeWriter_Discard().

  • PyUnicodeWriter_Finish().

  • PyUnicodeWriter_WriteChar().

  • PyUnicodeWriter_WriteUTF8().

  • PyUnicodeWriter_WriteUCS4().

  • PyUnicodeWriter_WriteWideChar().

  • PyUnicodeWriter_WriteStr().

  • PyUnicodeWriter_WriteRepr().

  • PyUnicodeWriter_WriteSubstring().

  • PyUnicodeWriter_Format().

  • PyUnicodeWriter_DecodeUTF8Stateful().

  Patch by Victor Stinner.

• gh-119613: Soft deprecate the Py_MEMCPY macro: use directly memcpy() instead. Patch by Victor Stinner.

• gh-119775: Creating immutable types with mutable bases was deprecated since 3.12 and now raises a TypeError.

• gh-119585: Fix crash when a thread state that was created by PyGILState_Ensure() calls a destructor that during PyThreadState_Clear() that calls back into PyGILState_Ensure() and PyGILState_Release(). This might occur when in the free-threaded build or when using thread-local variables whose destructors call PyGILState_Ensure().

• gh-119613: Macros Py_IS_NAN, Py_IS_INFINITY and Py_IS_FINITE are soft deprecated.

• gh-119336: Restore the removed _PyLong_NumBits() function. It is used by the pywin32 project. Patch by Ethan Smith

• gh-119344: The critical section API is now public as part of the non-limited C API.

• gh-119333: Add PyContext_AddWatcher() and PyContext_ClearWatcher() APIs to register callbacks to receive notification on enter and exit of context objects.

• gh-119247: Added Py_BEGIN_CRITICAL_SECTION_SEQUENCE_FAST and Py_END_CRITICAL_SECTION_SEQUENCE_FAST macros to make it possible to use PySequence_Fast APIs safely when free-threaded, and update str.join to work without the GIL using them.

• gh-111389: Add PyHASH_MULTIPLIER constant: prime multiplier used in string and various other hashes. Patch by Victor Stinner.

• gh-118771: Several C declarations with names that didn’t start with the Py or _Py prefixes, which were added by mistake in 3.13 alpha and beta releases, were moved to internal headers.

• gh-116984: Make mimalloc includes relative to the current file to avoid embedders or extensions needing to include Internal/mimalloc if they are already including internal CPython headers.

• gh-118789: Add PyUnstable_Object_ClearWeakRefsNoCallbacks(), which clears weakrefs without calling their callbacks.

• gh-118789: Restore _PyWeakref_ClearRef that was previously removed in Python 3.13 alpha 1.

• gh-117511: Make the PyMutex public in the non-limited C API.

• gh-116560: Add PyLong_GetSign() function. Patch by Sergey B Kirpichev.

• gh-97588: Fix creating bitfields in ctypes structures and unions. Fields no longer overlap.

• gh-87135: Attempting to acquire the GIL after runtime finalization has begun in a different thread now causes the thread to hang rather than terminate, which avoids potential crashes or memory corruption caused by attempting to terminate a thread that is running code not specifically designed to support termination. In most cases this hanging is harmless since the process will soon exit anyway.

  The PyThread_exit_thread function is now deprecated. Its behavior is inconsistent across platforms, and it can only be used safely in the unlikely case that every function in the entire call stack has been designed to support the platform-dependent termination mechanism. It is recommended that users of this function change their design to not require thread termination. In the unlikely case that thread termination is needed and can be done safely, users may migrate to calling platform-specific APIs such as pthread_exit (POSIX) or _endthreadex (Windows) directly.

• bpo-34008: Added Py_IsInitialized to the list of APIs that are safe to call before the interpreter is initialized, and updated the embedding tests to cover it.

Build

• gh-125269: Fix detection of whether -latomic is needed when cross-compiling CPython using the configure script.

• gh-123990: Remove WITH_FREELISTS macro and --without-freelists build configuration

• gh-124102: Update internal documentation under PCbuild, so it now correctly states that Windows requires VS2017 or later and Python 3.10 or later

• gh-124043: Building using --with-trace-refs is (temporarily) disallowed when the GIL is disabled.

• gh-123418: Updated Android build to use OpenSSL 3.0.15.

• gh-123297: Propagate the value of LDFLAGS to LDCXXSHARED in sysconfig. Patch by Pablo Galindo

• gh-121634: Allow for specifying the target compile triple for WASI.

• gh-122578: Use WASI SDK 24 for testing.

• gh-116622: Rename build variable MODULE_LDFLAGS back to LIBPYTHON, as it’s used by package build systems (e.g. Meson).

• gh-118943: Fix an issue where the experimental JIT could be built several times by the make regen-all target, leading to possible race conditions on heavily parallelized builds.

• gh-121996: Introduce ./configure –disable-safety and –enable-slower-safety options. Patch by Donghee Na.

• gh-120522: Added a --with-app-store-compliance option to patch out known issues with macOS/iOS App Store review processes.

• gh-120371: Support WASI SDK 22 by explicitly skipping functions that are just stubs in wasi-libc.

• gh-121731: Fix mimalloc compile error on GNU/Hurd

• gh-121487: Fix deprecation warning for ATOMIC_VAR_INIT in mimalloc.

• gh-121467: Fix a Makefile bug that prevented mimalloc header files from being installed.

• gh-121103: On POSIX systems, excluding macOS framework installs, the lib directory for the free-threaded build now includes a “t” suffix to avoid conflicts with a co-located default build installation.

• gh-120831: The default minimum iOS version was increased to 13.0.

• gh-121082: Fix build failure when the developer use --enable-pystats arguments in configuration command after #118450.

• gh-120671: Fix failing configure tests due to a missing space when appending to CFLAGS.

• gh-120602: Correctly handle LLVM installs with LLVM_VERSION_SUFFIX when building with --enable-experimental-jit.

• gh-120688: On WASI in debug mode, Python is now built with compiler flag -O3 instead of -Og, to support more recursive calls. Patch by Victor Stinner.

• gh-118943: Fix a possible race condition affecting parallel builds configured with --enable-experimental-jit, in which FileNotFoundError could be caused by another process already moving jit_stencils.h.new to jit_stencils.h.

• gh-120326: On Windows, fix build error when --disable-gil and --experimental-jit options are combined.

• gh-120291: Make the python-config shell script compatible with non-bash shells.

• gh-113565: Improve curses and curses.panel dependency checks in configure.

• gh-119729: On POSIX systems, the pkg-config (.pc) filenames now include the ABI flags, which may include debug (“d”) and free-threaded (“t”). For example: * python-3.14.pc (default, non-debug build) * python-3.14d.pc (default, debug build) * python-3.14t.pc (free-threaded build)

• gh-119400: make_ssl_certs, the script that prepares certificate data for the test suite, now allows specifying expiration dates.

• gh-115119: Fall back to the bundled libmpdec if a system version cannot be found.

• gh-119132: Update sys.version to identify whether the build is default build or free-threading build. Patch By Donghee Na.

• gh-118836: Fix an AssertionError when building with --enable-experimental-jit and the compiler emits a SHT_NOTE section.

• gh-118943: Fix a possible race condition affecting parallel builds configured with --enable-experimental-jit, in which compilation errors could be caused by an incompletely-generated header file.

Python 3.13.0 beta 1

Release date: 2024-05-08

Security

• gh-116741: Update bundled libexpat to 2.6.2

• gh-117233: Detect BLAKE2, SHA3, Shake, & truncated SHA512 support in the OpenSSL-ish libcrypto library at build time. This allows hashlib to be used with libraries that do not to support every algorithm that upstream OpenSSL does.

Core and Builtins

• gh-118414: Add instrumented opcodes to YIELD_VALUE assertion for tracing cases.

• gh-117953: When a builtin or extension module is imported for the first time, while a subinterpreter is active, the module’s init function is now run by the main interpreter first before import continues in the subinterpreter. Consequently, single-phase init modules now fail in an isolated subinterpreter without the init function running under that interpreter, whereas before it would run under the subinterpreter before failing, potentially leaving behind global state and callbacks and otherwise leaving the module in an inconsistent state.

• gh-117549: Don’t use designated initializer syntax in inline functions in internal headers. They cause problems for C++ or MSVC users who aren’t yet using the latest C++ standard (C++20). While internal, pycore_backoff.h, is included (indirectly, via pycore_code.h) by some key 3rd party software that does so for speed.

• gh-95382: Improve performance of json.dumps() and json.dump() when using the argument indent. Depending on the data the encoding using json.dumps() with indent can be up to 2 to 3 times faster.

• gh-116322: In --disable-gil builds, the GIL will be enabled while loading C extension modules. If the module indicates that it supports running without the GIL, the GIL will be disabled once loading is complete. Otherwise, the GIL will remain enabled for the remainder of the interpreter’s lifetime. This behavior does not apply if the GIL has been explicitly enabled or disabled with PYTHON_GIL or -Xgil.

• gh-118513: Fix incorrect UnboundLocalError when two comprehensions in the same function both reference the same name, and in one comprehension the name is bound while in the other it’s an implicit global.

• gh-118518: Allow the Linux perf support to work without frame pointers using perf’s advanced JIT support. The feature is activated when using the PYTHON_PERF_JIT_SUPPORT environment variable or when running Python with -Xperf_jit. Patch by Pablo Galindo.

• gh-117514: Add sys._is_gil_enabled() function that returns whether the GIL is currently enabled. In the default build it always returns True because the GIL is always enabled. In the free-threaded build, it may return True or False.

• gh-118164: Break a loop between the Python implementation of the decimal module and the Python code for integer to string conversion. Also optimize integer to string conversion for values in the range from 9_000 to 135_000 decimal digits.

• gh-118473: Fix sys.set_asyncgen_hooks() not to be partially set when raising TypeError.

• gh-118465: Compiler populates the new __firstlineno__ field on a class with the line number of the first line of the class definition.

• gh-118492: Fix an issue where the type cache can expose a previously accessed attribute when a finalizer is run.

• gh-117714: update async_generator.athrow().close() and async_generator.asend().close() to close their section of the underlying async generator

• gh-111201: The interactive interpreter is now implemented in Python, which allows for a number of new features like colors, multiline input, history viewing, and paste mode. Contributed by Pablo Galindo, Łukasz Langa and Lysandros Nikolaou based on code from the PyPy project.

• gh-74929: Implement PEP 667: converted FrameType.f_locals and PyFrame_GetLocals() to return a write-through proxy object when the frame refers to a function or comprehension.

• gh-116767: Fix crash in compiler on ‘async with’ that has many context managers.

• gh-118335: Change how to use the tier 2 interpreter. Instead of running Python with -X uops or setting the environment variable PYTHON_UOPS=1, this choice is now made at build time by configuring with --enable-experimental-jit=interpreter.

  Beware! This changes the environment variable to enable or disable micro-ops to PYTHON_JIT. The old PYTHON_UOPS is no longer used.

• gh-118306: Update JIT compilation to use LLVM 18

• gh-118160: Annotation scopes within classes can now contain comprehensions. However, such comprehensions are not inlined into their parent scope at runtime. Patch by Jelle Zijlstra.

• gh-118272: Fix bug where generator.close does not free the generator frame’s locals.

• gh-118216: Don’t consider __future__ imports with dots before the module name.

• gh-118074: Make sure that the Executor objects in the COLD_EXITS array aren’t assumed to be GC-able (which would access bytes outside the object).

• gh-107674: Lazy load frame line number to improve performance of tracing

• gh-118082: Improve SyntaxError message for imports without names, like in from x import and import cases. It now points out to users that import expects at least one name after it.

• gh-118090: Improve SyntaxError message for empty type param brackets.

• gh-117958: Added a get_jit_code() method to access JIT compiled machine code from the UOp Executor when the experimental JIT is enabled. Patch by Anthony Shaw.

• gh-117901: Add option for compiler’s codegen to save nested instruction sequences for introspection.

• gh-116622: Redirect stdout and stderr to system log when embedded in an Android app.

• gh-109118: annotation scope within class scopes can now contain lambdas.

• gh-117894: Prevent agen.aclose() objects being re-used after .throw().

• gh-117881: prevent concurrent access to an async generator via athrow().throw() or asend().throw()

• gh-117536: Fix a RuntimeWarning when calling agen.aclose().throw(Exception).

• gh-117755: Fix mimalloc allocator for huge memory allocation (around 8,589,934,592 GiB) on s390x. Patch by Victor Stinner.

• gh-117750: Fix issue where an object’s dict would get out of sync with the object’s internal values when being cleared. obj.__dict__.clear() now clears the internal values, but leaves the dict attached to the object.

• gh-117431: Improve the performance of the following bytes and bytearray methods by adapting them to the METH_FASTCALL calling convention:

  • count()

  • find()

  • index()

  • rfind()

  • rindex()

• gh-117709: Speed up calls to str() with positional-only argument, by using the PEP 590 vectorcall calling convention. Patch by Erlend Aasland.

• gh-117680: Give _PyInstructionSequence a Python interface and use it in tests.

• gh-115776: Statically allocated objects are, by definition, immortal so must be marked as such regardless of whether they are in extension modules or not.

• gh-117385: Remove unhandled PY_MONITORING_EVENT_BRANCH and PY_MONITORING_EVENT_EXCEPTION_HANDLED events from sys.settrace().

• gh-116322: Extension modules may indicate to the runtime that they can run without the GIL. Multi-phase init modules do so by calling providing Py_MOD_GIL_NOT_USED for the Py_mod_gil slot, while single-phase init modules call PyUnstable_Module_SetGIL(mod, Py_MOD_GIL_NOT_USED) from their init function.

• gh-116129: Implement PEP 696, adding support for defaults on type parameters. Patch by Jelle Zijlstra.

• gh-93502: Add two new functions to the C-API, PyRefTracer_SetTracer() and PyRefTracer_GetTracer(), that allows to track object creation and destruction the same way the tracemalloc module does. Patch by Pablo Galindo

• gh-107674: Improved the performance of sys.settrace() significantly

• gh-95754: Improve the error message when a script shadowing a module from the standard library causes AttributeError to be raised. Similarly, improve the error message when a script shadowing a third party module attempts to access an attribute from that third party module while still initialising.

• gh-99180: Elide uninformative traceback indicators in return and simple assignment statements. Patch by Pablo Galindo.

• gh-105879: Allow the globals and locals arguments to exec() and eval() to be passed as keywords.

Library

• gh-118418: A DeprecationWarning is now emitted if you fail to pass a value to the new type_params parameter of typing._eval_type() or typing.ForwardRef._evaluate(). (Using either of these private and undocumented functions is discouraged to begin with, but failing to pass a value to the type_params parameter may lead to incorrect behaviour on Python 3.12 or newer.)

• gh-118660: Add an optional second type parameter to typing.ContextManager and typing.AsyncContextManager, representing the return types of __exit__() and __aexit__() respectively. This parameter defaults to bool | None.

• gh-118650: The enum module allows method named _repr_* to be defined on Enum types.

• gh-118648: Add type parameter defaults to typing.Generator and typing.AsyncGenerator.

• gh-101137: Mime type text/x-rst is now supported by mimetypes.

• gh-118164: The Python implementation of the decimal module could appear to hang in relatively small power cases (like 2**117) if context precision was set to a very high value. A different method to check for exactly representable results is used now that doesn’t rely on computing 10**precision (which could be effectively too large to compute).

• gh-111744: breakpoint() and pdb.set_trace() now enter the debugger immediately after the call rather than before the next line is executed.

• gh-118500: Add pdb support for zipapps

• gh-118406: Add signature for sqlite3.Connection objects.

• gh-101732: Use a Y2038 compatible openssl time function when available.

• gh-118404: Fix inspect.signature() for non-comparable callables.

• gh-118402: Fix inspect.signature() for the result of the functools.cmp_to_key() call.

• gh-116622: On Android, sysconfig.get_platform now returns the format specified by PEP 738.

• gh-118285: Allow to specify the signature of custom callable instances of extension type by the __text_signature__ attribute. Specify signatures of operator.attrgetter, operator.itemgetter, and operator.methodcaller instances.

• gh-118314: Fix an edge case in binascii.a2b_base64() strict mode, where excessive padding is not detected when no padding is necessary.

• gh-118271: Add the PhotoImage methods read() to read an image from a file and data() to get the image data. Add background and grayscale parameters to PhotoImage method write().

• gh-118225: Add the PhotoImage method copy_replace() to copy a region from one image to other image, possibly with pixel zooming and/or subsampling. Add from_coords parameter to PhotoImage methods copy(), zoom() and subsample(). Add zoom and subsample parameters to PhotoImage method copy().

• gh-118221: Fix a bug where sqlite3.Connection.iterdump() could fail if a custom row factory was used. Patch by Erlend Aasland.

• gh-118013: Fix regression introduced in gh-103193 that meant that calling inspect.getattr_static() on an instance would cause a strong reference to that instance’s class to persist in an internal cache in the inspect module. This caused unexpected memory consumption if the class was dynamically created, the class held strong references to other objects which took up a significant amount of memory, and the cache contained the sole strong reference to the class. The fix for the regression leads to a slowdown in getattr_static(), but the function should still be significantly faster than it was in Python 3.11. Patch by Alex Waygood.

• gh-118218: Speed up itertools.pairwise() in the common case by up to 1.8x.

• gh-117486: Improve the behavior of user-defined subclasses of ast.AST. Such classes will now require no changes in the usual case to conform with the behavior changes of the ast module in Python 3.13. Patch by Jelle Zijlstra.

• gh-90848: Fixed unittest.mock.create_autospec() to configure parent mock with keyword arguments.

• gh-118168: Fix incorrect argument substitution when typing.Unpack is used with the builtin tuple. typing.Unpack now raises TypeError when used with certain invalid types. Patch by Jelle Zijlstra.

• gh-118131: Add command-line interface for the random module. Patch by Hugo van Kemenade.

• gh-118107: Fix zipimport reading of ZIP64 files with file entries that are too big or offset too far.

• gh-102511: Fix os.path.normpath() for UNC paths on Windows. Speed up os.path.splitroot() with a native implementation.

• gh-117535: Change the unknown filename of warnings from sys to <sys> to clarify that it’s not a real filename.

• gh-114053: Fix erroneous NameError when calling typing.get_type_hints() on a class that made use of PEP 695 type parameters in a module that had from __future__ import annotations at the top of the file. Patch by Alex Waygood.

• gh-116931: Add parameter fileobj check for tarfile.TarFile.addfile()

• gh-117995: Don’t raise DeprecationWarning when a sequence of parameters is used to bind indexed, nameless placeholders. See also gh-100668.

• gh-80361: Fix TypeError in email.message.Message.get_payload() when the charset is RFC 2231 encoded.

• gh-86650: Fix IndexError when parse some emails with invalid Message-ID (including one-off addresses generated by Microsoft Outlook).

• gh-117691: Improve the error messages emitted by tarfile deprecation warnings relating to PEP 706. If a filter argument is not provided to extract() or extractall, the deprecation warning now points to the line in the user’s code where the relevant function was called. Patch by Alex Waygood.

• gh-115874: Fixed a possible segfault during garbage collection of _asyncio.FutureIter objects. Patch by Savannah Ostrowski.

• gh-115060: Speed up pathlib.Path.glob() by omitting an initial is_dir() call. As a result of this change, glob() can no longer raise OSError.

• gh-77102: site module now parses .pth file with UTF-8 first, and locale encoding if UnicodeDecodeError happened. It supported only locale encoding before.

• gh-76785: We’ve exposed the low-level _interpreters module for the sake of the PyPI implementation of PEP 734. It was sometimes available as the _xxsubinterpreters module and was formerly used only for testing. For the most part, it should be considered an internal module, like _thread and _imp. See https://discuss.python.org/t/pep-734-multiple-interpreters-in-the-stdlib/41147/26.

• gh-115060: Speed up pathlib.Path.glob() by not scanning directories for non-wildcard pattern segments.

• gh-117727: Speed up pathlib.Path.iterdir() by using os.scandir() internally.

• gh-117586: Speed up pathlib.Path.walk() by working with strings internally.

• gh-117722: Change the new multi-separator support in asyncio.StreamReader.readuntil() to only accept tuples of separators rather than arbitrary iterables.

• gh-117692: Fixes a bug when doctest.DocTestFinder was failing on wrapped builtin_function_or_method.

• gh-117348: Largely restored import time performance of configparser by avoiding dataclasses.

• gh-117641: Speedup os.path.commonpath() on Unix.

• gh-117663: Fix _simple_enum to detect aliases when multiple arguments are present but only one is the member value.

• gh-117636: Speedup os.path.join().

• gh-117618: Support package.module as filename for break command of pdb

• gh-102247: the status codes enum with constants in http.HTTPStatus are updated to include the names from RFC9110. This RFC includes some HTTP statuses previously only used for WEBDAV and assigns more generic names to them.

  The old constants are preserved for backwards compatibility.

• gh-117607: Speedup os.path.relpath().

• gh-117586: Speed up pathlib.Path.glob() by working with strings internally.

• gh-117225: Add colour to doctest output. Patch by Hugo van Kemenade.

• gh-117566: ipaddress.IPv6Address.is_loopback() will now return True for IPv4-mapped loopback addresses, i.e. addresses in the ::ffff:127.0.0.0/104 address space.

• gh-117546: Fix issue where os.path.realpath() stopped resolving symlinks after encountering a symlink loop on POSIX.

• gh-116720: Improved behavior of asyncio.TaskGroup when an external cancellation collides with an internal cancellation. For example, when two task groups are nested and both experience an exception in a child task simultaneously, it was possible that the outer task group would misbehave, because its internal cancellation was swallowed by the inner task group.

  In the case where a task group is cancelled externally and also must raise an ExceptionGroup, it will now call the parent task’s cancel() method. This ensures that a asyncio.CancelledError will be raised at the next await, so the cancellation is not lost.

  An added benefit of these changes is that task groups now preserve the cancellation count (asyncio.Task.cancelling()).

  In order to handle some corner cases, asyncio.Task.uncancel() may now reset the undocumented _must_cancel flag when the cancellation count reaches zero.

• gh-117516: Add typing.TypeIs, implementing PEP 742. Patch by Jelle Zijlstra.

• gh-117503: Fix support of non-ASCII user names in bytes paths in os.path.expanduser() on Posix.

• gh-117394: os.path.ismount() is now 2-3 times faster if the user has permissions.

• gh-117313: Only treat '\n', '\r' and '\r\n' as line separators in re-folding the email messages. Preserve control characters '\v', '\f', '\x1c', '\x1d' and '\x1e' and Unicode line separators '\x85', '\u2028' and '\u2029' as is.

• gh-117142: Convert _ctypes to multi-phase initialisation (PEP 489).

• gh-66543: Add the mimetypes.guess_file_type() function which works with file path. Passing file path instead of URL in guess_type() is soft deprecated.

• gh-68583: webbrowser CLI: replace getopt with argparse, add long options. Patch by Hugo van Kemenade.

• gh-116871: Name suggestions for AttributeError and ImportError now only include underscored names if the original name was underscored.

• gh-116023: Don’t show empty fields (value None or []) in ast.dump() by default. Add show_empty=False parameter to optionally show them.

• gh-115961: Added name and mode attributes for compressed and archived file-like objects in modules bz2, lzma, tarfile and zipfile. The value of the mode attribute of gzip.GzipFile was changed from integer (1 or 2) to string ('rb' or 'wb'). The value of the mode attribute of the readable file-like object returned by zipfile.ZipFile.open() was changed from 'r' to 'rb'.

• gh-82062: Fix inspect.signature() to correctly handle parameter defaults on methods in extension modules that use names defined in the module namespace.

• gh-83856: Honor atexit for all multiprocessing start methods

• gh-113081: Print colorized exception just like built-in traceback in pdb

• gh-112855: Speed up pickling of pathlib.PurePath objects. Patch by Barney Gale.

• gh-111744: Support opcode events in bdb

• gh-109617: ncurses: fixed a crash that could occur on macOS 13 or earlier when Python was built with Apple Xcode 15’s SDK.

• gh-83151: Enabled arbitrary statements and evaluations in pdb shell to access the local variables of the current frame, which made it possible for multi-scope code like generators or nested function to work.

• gh-110209: Add __class_getitem__() to types.GeneratorType and types.CoroutineType for type hinting purposes. Patch by James Hilton-Balfe.

• gh-108191: The types.SimpleNamespace now accepts an optional positional argument which specifies initial values of attributes as a dict or an iterable of key-value pairs.

• gh-62090: Fix assertion errors caused by whitespace in metavars or SUPPRESS-ed groups in argparse by simplifying usage formatting. Patch by Ali Hamdan.

• gh-102402: Adjust logging.LogRecord to use time.time_ns() and fix minor bug related to floating-point math.

• gh-100242: Bring pure Python implementation functools.partial.__new__ more in line with the C-implementation by not just always checking for the presence of the attribute 'func' on the first argument of partial. Instead, both the Python version and the C version perform an isinstance(func, partial) check on the first argument of partial.

• gh-99730: HEAD requests are no longer upgraded to GET request during redirects in urllib.

• gh-66410: Setting the tkinter module global wantobjects to 2 before creating the Tk object or call the wantobjects() method of the Tk object with argument 2 makes now arguments to callbacks registered in the tkinter module to be passed as various Python objects (int, float, bytes, tuple), depending on their internal representation in Tcl, instead of always str. tkinter.wantobjects is now set to 2 by default.

• bpo-40943: Fix several IndexError when parse emails with truncated Message-ID, address, routes, etc, e.g. example@.

• bpo-39324: Add mime type mapping for .md <-> text/markdown

• bpo-18108: shutil.chown() now supports dir_fd and follow_symlinks keyword arguments.

• bpo-30988: Fix parsing of emails with invalid address headers having a leading or trailing dot. Patch by tsufeki.

• bpo-32839: Add the after_info() method for Tkinter widgets.

Documentation

• gh-117928: The minimum Sphinx version required for the documentation is now 6.2.1.

Build

• gh-118734: Fixes Windows build when invoked directly (not through the build.bat script) without specifying a value for UseTIER2.

• gh-115119: The configure option --with-system-libmpdec now defaults to yes. The bundled copy of libmpdecimal will be removed in Python 3.15.

• gh-117845: Fix building against recent libedit versions by detecting readline hook signatures in configure.

• gh-116622: A testbed project was added to run the test suite on Android.

• gh-117645: Increase WASI stack size from 512 KiB to 8 MiB and the initial memory from 10 MiB to 20 MiB. Patch by Victor Stinner.

• gh-115119: configure now uses pkg-config to detect decimal dependencies if the --with-system-libmpdec option is given.

Windows

• gh-115119: Update Windows installer to use libmpdecimal 4.0.0.

• gh-118486: os.mkdir() now accepts mode of 0o700 to restrict the new directory to the current user.

• gh-118347: Fixes launcher updates not being installed.

• gh-118293: The multiprocessing module now passes the STARTF_FORCEOFFFEEDBACK flag when spawning processes to tell Windows not to change the mouse cursor.

• gh-115009: Update Windows installer to use SQLite 3.45.3.

• gh-90329: Suppress the warning displayed on virtual environment creation when the requested and created paths differ only by a short (8.3 style) name. Warnings will continue to be shown if a junction or symlink in the path caused the venv to be created in a different location than originally requested.

• gh-117786: Fixes virtual environments not correctly launching when created from a Store install.

macOS

• gh-115119: Update macOS installer to use libmpdecimal 4.0.0.

• gh-114099: iOS preprocessor symbol usage was made compatible with older macOS SDKs.

• gh-115009: Update macOS installer to use SQLite 3.45.3.

• gh-91629: Use ~/.config/fish/conf.d configs and fish_add_path to set PATH when installing for the Fish shell.

IDLE

• bpo-34774: Use user-selected color theme for Help => IDLE Doc.

C API

• gh-118124: Fix Py_BUILD_ASSERT and Py_BUILD_ASSERT_EXPR for non-constant expressions: use static_assert() on C11 and newer. Patch by Victor Stinner.

• gh-110850: Add “Raw” variant of PyTime functions

  • PyTime_MonotonicRaw()

  • PyTime_PerfCounterRaw()

  • PyTime_TimeRaw()

  Patch by Victor Stinner.

• gh-117987: Restore functions removed in Python 3.13 alpha 1:

  • Py_SetPythonHome()

  • Py_SetProgramName()

  • PySys_SetArgvEx()

  • PySys_SetArgv()

  Patch by Victor Stinner.

• gh-117929: Restore removed PyEval_InitThreads() function. Patch by Victor Stinner.

• gh-117534: Improve validation logic in the C implementation of datetime.datetime.fromisoformat() to better handle invalid years. Patch by Vlad Efanov.

• gh-68114: Fixed skipitem()’s handling of the old ‘w’ and ‘w#’ formatters. These are no longer supported and now raise an exception if used.

• gh-111997: Add a C-API for firing monitoring events.

Python 3.13.0 alpha 6

Release date: 2024-04-09

Core and Builtins

• gh-117494: Refactored the instruction sequence data structure out of compile.c into instruction_sequence.c.

• gh-116968: Introduce a unified 16-bit backoff counter type (_Py_BackoffCounter), shared between the Tier 1 adaptive specializer and the Tier 2 optimizer. The API used for adaptive specialization counters is changed but the behavior is (supposed to be) identical.

  The behavior of the Tier 2 counters is changed:

  • There are no longer dynamic thresholds (we never varied these).

  • All counters now use the same exponential backoff.

  • The counter for JUMP_BACKWARD starts counting down from 16.

  • The temperature in side exits starts counting down from 64.

• gh-117431: Improve the performance of the following bytes and bytearray methods by adapting them to the METH_FASTCALL calling convention:

  • endswith()

  • startswith()

• gh-117431: Improve the performance of the following str methods by adapting them to the METH_FASTCALL calling convention:

  • count()

  • endswith()

  • find()

  • index()

  • rfind()

  • rindex()

  • startswith()

• gh-117411: Move PyFutureFeatures to an internal header and make it private.

• gh-109120: Added handle of incorrect star expressions, e.g f(3, *). Patch by Grigoryev Semyon

• gh-117266: Fix crashes for certain user-created subclasses of ast.AST. Such classes are now expected to set the _field_types attribute.

• gh-99108: Updated the hashlib built-in HACL* project C code from upstream that we use for many implementations when they are not present via OpenSSL in a given build. This also avoids the rare potential for a C symbol name one definition rule linking issue.

• gh-117108: Change the old space bit of objects in the young generation from 0 to gcstate->visited, so that any objects created during GC will have the old bit set correctly if they get moved into the old generation.

• gh-117108: The cycle GC now chooses the size of increments based on the total heap size, instead of the rate of object creation. This ensures that it can keep up with growing heaps.

• gh-116735: For INSTRUMENTED_CALL_FUNCTION_EX, set arg0 to sys.monitoring.MISSING instead of None for CALL event.

• gh-113964: Starting new threads and process creation through os.fork() are now only prevented once all non-daemon threads exit.

• gh-116626: Ensure INSTRUMENTED_CALL_FUNCTION_EX always emits CALL

• gh-116554: list.sort() now exploits more cases of partial ordering, particularly those with long descending runs with sub-runs of equal values. Those are recognized as single runs now (previously, each block of repeated values caused a new run to be created).

• gh-114099: Added a Loader that can discover extension modules in an iOS-style Frameworks folder.

• gh-115775: Compiler populates the new __static_attributes__ field on a class with the names of attributes of this class which are accessed through self.X from any function in its body.

• gh-115776: The array of values, the PyDictValues struct is now embedded in the object during allocation. This provides better performance in the common case, and does not degrade as much when the object’s __dict__ is materialized.

• gh-108362: Implement an incremental cyclic garbage collector. By collecting the old generation in increments, there is no need for a full heap scan. This can hugely reduce maximum pause time for programs with large heaps.

  Reduce the number of generations from three to two. The old generation is split into two spaces, “visited” and “pending”.

  Collection happens in two steps:: * An increment is formed from the young generation and a small part of the pending space. * This increment is scanned and the survivors moved to the end of the visited space.

  When the collecting space becomes empty, the two spaces are swapped.

• gh-109870: Dataclasses now calls exec() once per dataclass, instead of once per method being added. This can speed up dataclass creation by up to 20%.

• gh-97901: Mime type text/rtf is now supported by mimetypes.

• bpo-24612: Improve the SyntaxError that happens when ‘not’ appears after an operator. Patch by Pablo Galindo

Library

• gh-117648: Improve performance of os.path.join() and os.path.expanduser().

• gh-117584: Raise TypeError for non-paths in posixpath.relpath().

• gh-117467: Preserve mailbox ownership when rewriting in mailbox.mbox.flush(). Patch by Tony Mountifield.

• gh-114848: Raise FileNotFoundError when getcwd() returns ‘(unreachable)’, which can happen on Linux >= 2.6.36 with glibc < 2.27.

• gh-117459: asyncio.asyncio.run_coroutine_threadsafe() now keeps the traceback of CancelledError, TimeoutError and InvalidStateError which are raised in the coroutine.

• gh-117381: Fix error message for ntpath.commonpath().

• gh-117337: Deprecate undocumented glob.glob0() and glob.glob1() functions. Use glob.glob() and pass a directory to its root_dir argument instead.

• gh-117349: Optimise several functions in os.path.

• gh-117348: Refactored configparser.RawConfigParser._read() to reduce cyclometric complexity and improve comprehensibility.

• gh-117335: Raise TypeError for non-sequences for ntpath.commonpath().

• gh-66449: configparser.ConfigParser now accepts unnamed sections before named ones, if configured to do so.

• gh-88014: In documentation of gzip.GzipFile in module gzip, explain data type of optional constructor argument mtime, and recommend mtime = 0 for generating deterministic streams.

• gh-117310: Fixed an unlikely early & extra Py_DECREF triggered crash in ssl when creating a new _ssl._SSLContext if CPython was built implausibly such that the default cipher list is empty or the SSL library it was linked against reports a failure from its C SSL_CTX_set_cipher_list() API.

• gh-117294: A DocTestCase now reports as skipped if all examples in the doctest are skipped.

• gh-98966: In subprocess, raise a more informative message when stdout=STDOUT.

• gh-117225: doctest: only print “and X failed” when non-zero, don’t pluralise “1 items”. Patch by Hugo van Kemenade.

• gh-117205: Speed up compileall.compile_dir() by 20% when using multiprocessing by increasing chunksize.

• gh-117178: Fix regression in lazy loading of self-referential modules, introduced in gh-114781.

• gh-112383: Fix dis module’s handling of ENTER_EXECUTOR instructions.

• gh-117182: Lazy-loading of modules that modify their own __class__ no longer reverts the __class__ to types.ModuleType.

• gh-117084: Fix zipfile extraction for directory entries with the name containing backslashes on Windows.

• gh-117114: Make os.path.isdevdrive() available on all platforms. For those that do not offer Dev Drives, it will always return False.

• gh-117110: Fix a bug that prevents subclasses of typing.Any to be instantiated with arguments. Patch by Chris Fu.

• gh-109653: Deferred select imports in importlib.metadata and importlib.resources for a 14% speedup.

• gh-70647: Start the deprecation period for the current behavior of datetime.datetime.strptime() and time.strptime() which always fails to parse a date string with a ValueError involving a day of month such as strptime("02-29", "%m-%d") when a year is not specified and the date happen to be February 29th. This should help avoid users finding new bugs every four years due to a natural mistaken assumption about the API when parsing partial date values.

• gh-116987: Fixed inspect.findsource() for class code objects.

• gh-114099: Modify standard library to allow for iOS platform differences.

• gh-90872: On Windows, subprocess.Popen.wait() no longer calls WaitForSingleObject() with a negative timeout: pass 0 ms if the timeout is negative. Patch by Victor Stinner.

• gh-116957: configparser: Don’t leave ConfigParser values in an invalid state (stored as a list instead of a str) after an earlier read raised DuplicateSectionError or DuplicateOptionError.

• gh-115538: _io.WindowsConsoleIO now emit a warning if a boolean value is passed as a filedescriptor argument.

• gh-90095: Ignore empty lines and comments in .pdbrc

• gh-106531: Refreshed zipfile._path from zipp 3.18, providing better compatibility for PyPy, better glob performance for deeply nested zipfiles, and providing internal access to CompleteDirs.inject for use in other tests (like importlib.resources).

• gh-63207: On Windows, time.time() now uses the GetSystemTimePreciseAsFileTime() clock to have a resolution better than 1 us, instead of the GetSystemTimeAsFileTime() clock which has a resolution of 15.6 ms. Patch by Victor Stinner.

• gh-116764: Restore support of None and other false values in urllib.parse functions parse_qs() and parse_qsl(). Also, they now raise a TypeError for non-zero integers and non-empty sequences.

• gh-116811: In PathFinder.invalidate_caches, delegate to MetadataPathFinder.invalidate_caches.

• gh-116647: Fix recursive child in dataclasses

• gh-113171: Fixed various false positives and false negatives in

  • ipaddress.IPv4Address.is_private (see these docs for details)

  • ipaddress.IPv4Address.is_global

  • ipaddress.IPv6Address.is_private

  • ipaddress.IPv6Address.is_global

  Also in the corresponding ipaddress.IPv4Network and ipaddress.IPv6Network attributes.

• gh-63283: In encodings.idna, any capitalization of the ACE prefix (xn--) is now acceptable. Patch by Pepijn de Vos and Zackery Spytz.

• gh-71042: Add platform.android_ver(), which provides device and OS information on Android.

• gh-73468: Added new math.fma() function, wrapping C99’s fma() operation: fused multiply-add function. Patch by Mark Dickinson and Victor Stinner.

• gh-116608: The importlib.resources functions is_resource(), open_binary(), open_text(), path(), read_binary(), and read_text() are un-deprecated, and support subdirectories via multiple positional arguments. The contents() function also allows subdirectories, but remains deprecated.

• gh-116484: Change automatically generated tkinter.Checkbutton widget names to avoid collisions with automatically generated tkinter.ttk.Checkbutton widget names within the same parent widget.

• gh-114314: In ctypes, ctype data is now stored in type objects directly rather than in a dict subclass. This is an internal change that should not affect usage.

• gh-116401: Fix blocking os.fwalk() and shutil.rmtree() on opening named pipe.

• gh-71052: Implement ctypes.util.find_library() on Android.

• gh-90535: Fix support of interval values > 1 in logging.TimedRotatingFileHandler for when='MIDNIGHT' and when='Wx'.

• gh-113308: Remove some internal protected parts from uuid: _has_uuid_generate_time_safe, _netbios_getnode, _ipconfig_getnode, and _load_system_functions. They were unused.

• gh-115627: Fix the ssl module error handling of connection terminate by peer. It now throws an OSError with the appropriate error code instead of an EOFError.

• gh-114847: Speed up os.path.realpath() on non-Windows platforms.

• gh-114271: Fix a race in threading.Thread.join().

  threading._MainThread now always represents the main thread of the main interpreter.

  PyThreadState.on_delete and PyThreadState.on_delete_data have been removed.

• gh-113538: Add asyncio.Server.close_clients() and asyncio.Server.abort_clients() methods which allow to more forcefully close an asyncio server.

• gh-85287: Changes Unicode codecs to return UnicodeEncodeError or UnicodeDecodeError, rather than just UnicodeError.

• gh-113548: pdb now allows CLI arguments to pdb -m.

• gh-112948: Make completion of pdb similar to Python REPL

• gh-105866: Fixed _get_slots bug which caused error when defining dataclasses with slots and a weakref_slot.

• gh-96471: Add asyncio.Queue termination with shutdown() method.

• gh-89739: The zipimport module can now read ZIP64 files.

• bpo-33533: asyncio.as_completed() now returns an object that is both an asynchronous iterator and plain iterator. The new asynchronous iteration pattern allows for easier correlation between prior tasks and their completed results. This is a closer match to concurrent.futures.as_completed()’s iteration pattern. Patch by Justin Arthur.

• bpo-27578: inspect.getsource() (and related functions) work with empty module files, returning '\n' (or reasonable equivalent) instead of raising OSError. Patch by Kernc.

• bpo-37141: Accept an iterable of separators in asyncio.StreamReader.readuntil(), stopping when one of them is encountered.

• gh-66543: Make mimetypes.guess_type() properly parsing of URLs with only a host name, URLs containing fragment or query, and filenames with only a UNC sharepoint on Windows. Based on patch by Dong-hee Na.

• bpo-15010: unittest.TestLoader.discover() now saves the original value of unittest.TestLoader._top_level_dir and restores it at the end of the call.

Documentation

• gh-115977: Remove compatibility references to Emscripten.

• gh-114099: Add an iOS platform guide, and flag modules not available on iOS.

• gh-91565: Changes to documentation files and config outputs to reflect the new location for reporting bugs - i.e. GitHub rather than bugs.python.org.

Tests

• gh-83434: Disable JUnit XML output (--junit-xml=FILE command line option) in regrtest when hunting for reference leaks (-R option). Patch by Victor Stinner.

• gh-117187: Fix XML tests for vanilla Expat <2.6.0.

• gh-116333: Tests of TLS related things (error codes, etc) were updated to be more lenient about specific error message strings and behaviors as seen in the BoringSSL and AWS-LC forks of OpenSSL.

• gh-117089: Consolidated tests for importlib.metadata in their own metadata package.

• gh-115979: Update test_importlib so that it passes under WASI SDK 21.

• gh-112536: Add –tsan to test.regrtest for running TSAN tests in reasonable execution times. Patch by Donghee Na.

• gh-116307: Added import helper isolated_modules as CleanImport does not remove modules imported during the context. Use it in importlib.resources tests to avoid leaving mod around to impede importlib.metadata tests.

Build

• gh-114736: Have WASI builds use WASI SDK 21.

• gh-115983: Skip building test modules that must be built as shared under WASI.

• gh-71052: Add Android build script and instructions.

Windows

• gh-117267: Ensure DirEntry.stat().st_ctime behaves consistently with os.stat() during the deprecation period of st_ctime by containing the same value as st_birthtime. After the deprecation period, st_ctime will be the metadata change time (or unavailable through DirEntry), and only st_birthtime will contain the creation time.

• gh-116195: Improves performance of os.getppid() by using an alternate system API when available. Contributed by vxiiduu.

• gh-88494: On Windows, time.monotonic() now uses the QueryPerformanceCounter() clock to have a resolution better than 1 us, instead of the GetTickCount64() clock which has a resolution of 15.6 ms. Patch by Victor Stinner.

• gh-116773: Fix instances of <_overlapped.Overlapped object at 0xXXX> still has pending operation at deallocation, the process may crash.

• gh-91227: Fix the asyncio ProactorEventLoop implementation so that sending a datagram to an address that is not listening does not prevent receiving any more datagrams.

• gh-115119: Switched from vendored libmpdecimal code to a separately-hosted external package in the cpython-source-deps repository when building the _decimal module.

C API

• gh-117642: Fix PEP 737 implementation for %#T and %#N.

• gh-87193: _PyBytes_Resize() can now be called for bytes objects with reference count > 1, including 1-byte bytes objects. It creates a new bytes object and destroys the old one if it has reference count > 1.

• gh-117021: Fix integer overflow in PyLong_AsPid() on non-Windows 64-bit platforms.

• gh-115756: PyCode_GetFirstFree() is an ustable API now and has been renamed to PyUnstable_Code_GetFirstFree(). (Contributed by Bogdan Romanyuk in gh-115781)

• gh-116869: Add test_cext test: build a C extension to check if the Python C API emits C compiler warnings. Patch by Victor Stinner.

• gh-116869: Make the C API compatible with -Werror=declaration-after-statement compiler flag again. Patch by Victor Stinner.

• gh-116936: Add PyType_GetModuleByDef() to the limited C API. Patch by Victor Stinner.

• gh-116809: Restore removed private _PyErr_ChainExceptions1() function. Patch by Victor Stinner.

• gh-115754: In the limited C API version 3.13, getting Py_None, Py_False, Py_True, Py_Ellipsis and Py_NotImplemented singletons is now implemented as function calls at the stable ABI level to hide implementation details. Getting these constants still return borrowed references. Patch by Victor Stinner.

• gh-115754: Add Py_GetConstant() and Py_GetConstantBorrowed() functions to get constants. For example, Py_GetConstant(Py_CONSTANT_ZERO) returns a strong reference to the constant zero. Patch by Victor Stinner.

• gh-111696: Add support for %T, %T#, %N and %N# formats to PyUnicode_FromFormat(): format the fully qualified name of an object type and of a type: call PyType_GetModuleName(). See PEP 737 for more information. Patch by Victor Stinner.

• gh-111696: Add PyType_GetModuleName() function to get the type’s module name. Equivalent to getting the type.__module__ attribute. Patch by Eric Snow and Victor Stinner.

• gh-111696: Add PyType_GetFullyQualifiedName() function to get the type’s fully qualified name. Equivalent to f"{type.__module__}.{type.__qualname__}", or type.__qualname__ if type.__module__ is not a string or is equal to "builtins". Patch by Victor Stinner.

• gh-85283: The fcntl, grp, pwd, termios, _statistics and _testconsole C extensions are now built with the limited C API. Patch by Victor Stinner.

• gh-111140: Add additional flags to PyLong_AsNativeBytes() and PyLong_FromNativeBytes() to allow the caller to determine how to handle edge cases around values that fill the entire buffer.

• gh-113024: Add PyObject_GenericHash() function.

Python 3.13.0 alpha 5

Release date: 2024-03-12

Security

• gh-115398: Allow controlling Expat >=2.6.0 reparse deferral (CVE 2023-52425) by adding five new methods:

  • xml.etree.ElementTree.XMLParser.flush()

  • xml.etree.ElementTree.XMLPullParser.flush()

  • xml.parsers.expat.xmlparser.GetReparseDeferralEnabled()

  • xml.parsers.expat.xmlparser.SetReparseDeferralEnabled()

  • xml.sax.expatreader.ExpatParser.flush()

• gh-114572: ssl.SSLContext.cert_store_stats() and ssl.SSLContext.get_ca_certs() now correctly lock access to the certificate store, when the ssl.SSLContext is shared across multiple threads.

Core and Builtins

• gh-116604: Respect the status of the garbage collector when indirect calls are made via PyErr_CheckSignals() and the evaluation breaker. Patch by Pablo Galindo

• gh-112087: list is now compatible with the implementation of PEP 703.

• gh-116381: Add specialization for CONTAINS_OP.

• gh-116296: Fix possible refleak in object.__reduce__() internal error handling.

• gh-115823: Properly calculate error ranges in the parser when raising SyntaxError exceptions caused by invalid byte sequences. Patch by Pablo Galindo

• gh-115778: Add tierN annotation for instruction definition in interpreter DSL.

• gh-115733: Fix crash when calling next() on exhausted list iterators.

• gh-115700: The regen-cases build stage now works on Windows.

• gh-115347: Fix bug where docstring was replaced by a redundant NOP when Python is run with -OO.

• gh-115323: Make error message more meaningful for when bytearray.extend() is called with a str object.

• gh-112175: Every PyThreadState now has its own eval_breaker, allowing specific threads to be interrupted.

• gh-115154: Fix a bug that was causing the tokenize.untokenize() function to handle unicode named literals incorrectly. Patch by Pablo Galindo

• gh-112433: Add ability to force alignment of ctypes.Structure by way of the new _align_ attribute on the class.

• gh-104090: The multiprocessing resource tracker now exits with non-zero status code if a resource leak was detected. It still exits with status code 0 otherwise.

• gh-105858: Improve the constructors for ast nodes. Arguments of list types now default to an empty list if omitted, and optional fields default to None. AST nodes now have an __annotations__ attribute with the expected types of their attributes. Passing unrecognized extra arguments to AST nodes is deprecated and will become an error in Python 3.15. Omitting a required argument to an AST node is deprecated and will become an error in Python 3.15. Patch by Jelle Zijlstra.

• gh-101860: Expose __name__ attribute on property.

• gh-96497: Fix incorrect resolution of mangled class variables used in assignment expressions in comprehensions.

Library

• gh-116600: Fix repr() for global Flag members.

• gh-116349: platform.java_ver() is deprecated and will be removed in 3.15. It was largely untested, had a confusing API, and was only useful for Jython support.

• gh-116143: Fix a race in pydoc _start_server, eliminating a window in which _start_server can return a thread that is “serving” but without a docserver set.

• gh-116127: typing: implement PEP 705 which adds typing.ReadOnly support to typing.TypedDict.

• gh-116325: typing: raise SyntaxError instead of AttributeError on forward references as empty strings.

• gh-115957: When asyncio.TaskGroup.create_task is called on an inactive asyncio.TaskGroup, the given coroutine will be closed (which prevents a RuntimeWarning).

• gh-115978: Disable preadv(), readv(), pwritev(), and writev() on WASI.

  Under wasmtime for WASI 0.2, these functions don’t pass test_posix (https://github.com/bytecodealliance/wasmtime/issues/7830).

• gh-88352: Fix the computation of the next rollover time in the logging.TimedRotatingFileHandler handler. computeRollover() now always returns a timestamp larger than the specified time and works correctly during the DST change. doRollover() no longer overwrite the already rolled over file, saving from data loss when run at midnight or during repeated time at the DST change.

• gh-87115: Set __main__.__spec__ to None when running a script with pdb

• gh-76511: Fix UnicodeEncodeError in email.Message.as_string() that results when a message that claims to be in the ascii character set actually has non-ascii characters. Non-ascii characters are now replaced with the U+FFFD replacement character, like in the replace error handler.

• gh-89547: Add support for nested typing special forms like Final[ClassVar[int]].

• gh-65824: Improve the less prompt in pydoc.

• gh-116040: [Enum] fix by-value calls when second value is falsey; e.g. Cardinal(1, 0)

• gh-115821: [Enum] Improve error message when calling super().__new__() in custom __new__.

• gh-85644: Use the XDG_CURRENT_DESKTOP environment variable in webbrowser to check desktop. Prefer it to the deprecated GNOME_DESKTOP_SESSION_ID for GNOME detection.

• gh-75988: Fixed unittest.mock.create_autospec() to pass the call through to the wrapped object to return the real result.

• gh-115881: Fix issue where ast.parse() would incorrectly flag conditional context managers (such as with (x() if y else z()): ...) as invalid syntax if feature_version=(3, 8) was passed. This reverts changes to the grammar made as part of gh-94949.

• gh-115886: Fix silent truncation of the name with an embedded null character in multiprocessing.shared_memory.SharedMemory.

• gh-115532: Add kernel density estimation to the statistics module.

• gh-115714: On WASI, the time module no longer get process time using times() or CLOCK_PROCESS_CPUTIME_ID, system API is that is unreliable and is likely to be removed from WASI. The affected clock functions fall back to calling clock().

• gh-115809: Improve algorithm for computing which rolled-over log files to delete in logging.TimedRotatingFileHandler. It is now reliable for handlers without namer and with arbitrary deterministic namer that leaves the datetime part in the file name unmodified.

• gh-74668: urllib.parse functions parse_qs() and parse_qsl() now support bytes arguments containing raw and percent-encoded non-ASCII data.

• gh-67044: csv.writer() now always quotes or escapes '\r' and '\n', regardless of lineterminator value.

• gh-115712: Restore support of space delimiter with skipinitialspace=True in csv. csv.writer() now quotes empty fields if delimiter is a space and skipinitialspace is true and raises exception if quoting is not possible.

• gh-112364: Fixed ast.unparse() to handle format_spec with ", ' or \\. Patched by Frank Hoffmann.

• gh-112997: Stop logging potentially sensitive callback arguments in asyncio unless debug mode is active.

• gh-114914: Fix an issue where an abandoned StreamWriter would not be garbage collected.

• gh-111358: Fix a bug in asyncio.BaseEventLoop.shutdown_default_executor() to ensure the timeout passed to the coroutine behaves as expected.

• gh-115618: Fix improper decreasing the reference count for None argument in property methods getter(), setter() and deleter().

• gh-112720: Refactor dis.ArgResolver to make it possible to subclass and change the way jump args are interpreted.

• gh-112006: Fix inspect.unwrap() for types with the __wrapper__ data descriptor. Fix inspect.Signature.from_callable() for builtins classmethod() and staticmethod().

• gh-101293: Support callables with the __call__() method and types with __new__() and __init__() methods set to class methods, static methods, bound methods, partial functions, and other types of methods and descriptors in inspect.Signature.from_callable().

• gh-103092: Isolate _lsprof (apply PEP 687).

• gh-113942: pydoc no longer skips global functions implemented as builtin methods, such as MethodDescriptorType and WrapperDescriptorType.

• gh-115256: Added DeprecationWarning when accessing the tarfile attribute of TarInfo objects. The attribute is never used internally and is only attached to TarInfos when the tarfile is opened in write-mode, not read-mode. The attribute creates an unnecessary reference cycle which may cause corruption when not closing the handle after writing a tarfile.

• gh-115197: urllib.request no longer resolves the hostname before checking it against the system’s proxy bypass list on macOS and Windows.

• gh-113812: DatagramTransport.sendto() will now send zero-length datagrams if called with an empty bytes object. The transport flow control also now accounts for the datagram header when calculating the buffer size.

• gh-114763: Protect modules loaded with importlib.util.LazyLoader from race conditions when multiple threads try to access attributes before the loading is complete.

• gh-114709: posixpath.commonpath() now raises a ValueError exception when passed an empty iterable. Previously, IndexError was raised.

  posixpath.commonpath() now raises a TypeError exception when passed None. Previously, ValueError was raised.

• gh-114610: Fix bug where pathlib.PurePath.with_stem() converted a non-empty path suffix to a stem when given an empty stem argument. It now raises ValueError, just like pathlib.PurePath.with_suffix() does when called on a path with an empty stem, given a non-empty suffix argument.

• gh-107361: Add ssl.VERIFY_X509_PARTIAL_CHAIN and VERIFY_X509_STRICT to the default SSL context created with ssl.create_default_context().

• gh-112281: Allow creating union of types for typing.Annotated with unhashable metadata.

• gh-111775: Fix importlib.resources.simple.ResourceHandle.open() for text mode, added missed stream argument.

• gh-90095: Make .pdbrc and -c work with any valid pdb commands.

• gh-107625: Raise configparser.ParsingError from read() and read_file() methods of configparser.ConfigParser if a key without a corresponding value is continued (that is, followed by an indented line).

• gh-107155: Fix incorrect output of help(x) where x is a lambda function, which has an __annotations__ dictionary attribute with a "return" key.

• gh-57141: Add option for non-shallow comparisons to filecmp.dircmp like filecmp.cmp(). Original patch by Steven Ward. Enhanced by Tobias Rautenkranz

• gh-69990: Profile.print_stats() has been improved to accept multiple sort arguments. Patched by Chiu-Hsiang Hsu and Furkan Onder.

• gh-104061: Add socket.SO_BINDTOIFINDEX constant.

• gh-60346: Fix ArgumentParser inconsistent with parse_known_args.

• gh-102389: Add windows_31j to aliases for cp932 codec

• gh-72249: functools.partial`s of :func:`repr() has been improved to include the module name. Patched by Furkan Onder and Anilyka Barry.

• gh-100985: Update HTTPSConnection to consistently wrap IPv6 Addresses when using a proxy.

• gh-100884: email: fix misfolding of comma in address-lists over multiple lines in combination with unicode encoding.

• gh-95782: Fix io.BufferedReader.tell(), io.BufferedReader.seek(), _pyio.BufferedReader.tell(), io.BufferedRandom.tell(), io.BufferedRandom.seek() and _pyio.BufferedRandom.tell() being able to return negative offsets.

• gh-96310: Fix a traceback in argparse when all options in a mutually exclusive group are suppressed.

• gh-93205: Fixed a bug in logging.handlers.TimedRotatingFileHandler where multiple rotating handler instances pointing to files with the same name but different extensions would conflict and not delete the correct files.

• bpo-31116: Add Z85 encoding to base64.

• bpo-44865: Add missing call to localization function in argparse.

• bpo-43952: Fix multiprocessing.connection.Listener.accept() to accept empty bytes as authkey. Not accepting empty bytes as key causes it to hang indefinitely.

• bpo-42125: linecache: get module name from __spec__ if available. This allows getting source code for the __main__ module when a custom loader is used.

• bpo-41122: Failing to pass arguments properly to functools.singledispatchmethod() now throws a TypeError instead of hitting an index out of bounds internally.

• bpo-40818: The asyncio REPL now runs sys.__interactivehook__ on startup. The default implementation of sys.__interactivehook__ provides auto-completion to the asyncio REPL. Patch contributed by Rémi Lapeyre.

• bpo-33775: Add ‘default’ and ‘version’ help text for localization in argparse.

Documentation

• gh-115399: Document CVE 2023-52425 of Expat <2.6.0 under “XML vulnerabilities”.

• gh-109653: Improve import time of uuid on Linux.

Tests

• gh-71052: Add test exclusions to support running the test suite on Android.

• gh-71052: Enable test_concurrent_futures on platforms that support threading but not multiprocessing.

• gh-115796: Make ‘_testinternalcapi.assemble_code_object’ construct the exception table for the code object.

• gh-115720: Leak tests (-R, --huntrleaks) now show a summary of the number of leaks found in each iteration.

• gh-115122: Add --bisect option to regrtest test runner: run failed tests with test.bisect_cmd to identify failing tests. Patch by Victor Stinner.

• gh-115596: Fix ProgramPriorityTests in test_os permanently changing the process priority.

• gh-115556: On Windows, commas passed in arguments to Tools\buildbot\test.bat and PCbuild\\rt.bat are now properly handled.

• gh-115420: Fix translation of exception handler targets by _testinternalcapi.optimize_cfg.

• gh-115376: Fix segfault in _testinternalcapi.compiler_codegen on bad input.

Build

• gh-116313: Get WASI builds to work under wasmtime 18 w/ WASI 0.2/preview2 primitives.

• gh-71052: Change Android’s sys.platform from "linux" to "android".

• gh-116117: Backport libb2’s PR #42 to fix compiling CPython on 32-bit Windows with clang-cl.

• gh-71052: Fix several Android build issues

• gh-114099: A testbed project was added to run the test suite on iOS.

• gh-115350: Fix building ctypes module with -DWIN32_LEAN_AND_MEAN defined

• gh-111225: Link extension modules against libpython on Android.

• gh-115737: The install name for libPython is now correctly set for non-framework macOS builds.

• gh-114099: Makefile targets were added to support compiling an iOS-compatible framework build.

Windows

• gh-116012: Ensure the value of GetLastError() is preserved across GIL operations.

• gh-115582: Building extensions intended for free-threaded builds of CPython now require compiling with /DPy_GIL_DISABLED manually when using a regular install. This is expected to change in future releases.

• gh-115554: The installer now has more strict rules about updating the Python Launcher for Windows. In general, most users only have a single launcher installed and will see no difference. When multiple launchers have been installed, the option to install the launcher is disabled until all but one have been removed. Downgrading the launcher (which was never allowed) is now more obviously blocked.

• gh-115543: Python Launcher for Windows can now detect Python 3.13 when installed from the Microsoft Store, and will install Python 3.12 by default when PYLAUNCHER_ALLOW_INSTALL is set.

macOS

• gh-116145: Update macOS installer to Tcl/Tk 8.6.14.

IDLE

• gh-88516: On macOS show a proxy icon in the title bar of editor windows to match platform behaviour.

Tools/Demos

• gh-100176: Remove outdated Tools/{io,cc,string}bench

• bpo-45101: Add consistency in usage message IO between 2 versions of python-config.

C API

• gh-114626: Add again _PyCFunctionFastWithKeywords name, removed in Python 3.13 alpha 4 by mistake. Keep the old private _PyCFunctionFastWithKeywords name (Python 3.7) as an alias to the new public name PyCFunctionFastWithKeywords (Python 3.13a4). Patch by Victor Stinner.

• gh-111418: Add PyHASH_MODULUS, PyHASH_BITS, PyHASH_INF and PyHASH_IMAG C macros. Patch by Sergey B Kirpichev.

Python 3.13.0 alpha 4

Release date: 2024-02-15

Security

• gh-115399: Update bundled libexpat to 2.6.0

• gh-115243: Fix possible crashes in collections.deque.index() when the deque is concurrently modified.

Core and Builtins

• gh-112087: For an empty reverse iterator for list will be reduced to reversed(). Patch by Donghee Na

• gh-114570: Add PythonFinalizationError exception. This exception derived from RuntimeError is raised when an operation is blocked during the Python finalization. Patch by Victor Stinner.

• gh-114695: Add sys._clear_internal_caches(), which clears all internal performance-related caches (and deprecate the less-general sys._clear_type_cache() function).

• gh-114828: Fix compilation crashes in uncommon code examples using super() inside a comprehension in a class body.

• gh-112069: Adapt set and frozenset methods to Argument Clinic.

• gh-115011: Setters for members with an unsigned integer type now support the same range of valid values for objects that has a __index__() method as for int.

• gh-114887: Changed socket type validation in create_datagram_endpoint() to accept all non-stream sockets. This fixes a regression in compatibility with raw sockets.

• gh-114944: Fixes a race between PyParkingLot_Park and _PyParkingLot_UnparkAll.

• gh-113462: Limit the number of versions that a single class can use. Prevents a few wayward classes using up all the version numbers.

• gh-76763: The chr() builtin function now always raises ValueError for values outside the valid range. Previously it raised OverflowError for very large or small values.

• gh-114806: No longer specialize calls to classes, if those classes have metaclasses. Fixes bug where the __call__ method of the metaclass was not being called.

• gh-107944: Improve error message for function calls with bad keyword arguments via getargs

• gh-112529: The free-threaded build no longer allocates space for the PyGC_Head structure in objects that support cyclic garbage collection. A number of other fields and data structures are used as replacements, including ob_gc_bits, ob_tid, and mimalloc internal data structures.

• gh-114456: Lower the recursion limit under a debug build of WASI.

• gh-114083: Compiler applies folding of LOAD_CONST with following instruction in a separate pass before other optimisations. This enables jump threading in certain circumstances.

• gh-114388: Fix a RuntimeWarning emitted when assign an integer-like value that is not an instance of int to an attribute that corresponds to a C struct member of type T_UINT and T_ULONG. Fix a double RuntimeWarning emitted when assign a negative integer value to an attribute that corresponds to a C struct member of type T_UINT.

• gh-114265: Compiler propagates line numbers before optimization, leading to more optimization opportunities and removing the need for the guarantee_lineno_for_exits hack.

• gh-112529: The free-threaded build now has its own thread-safe GC implementation that uses mimalloc to find GC tracked objects. It is non-generational, unlike the existing GC implementation.

• gh-114050: Fix segmentation fault caused by an incorrect format string in TypeError exception when more than two arguments are passed to int.

• gh-112354: The END_FOR instruction now pops only one value. This is to better support side exits in loops.

• gh-113884: Make queue.SimpleQueue thread safe when the GIL is disabled.

• gh-114058: Implement the foundations of the Tier 2 redundancy eliminator.

• gh-113939: frame.clear(): Clear frame.f_locals as well, and not only the fast locals. This is relevant once frame.f_locals was accessed, which would contain also references to all the locals.

• gh-112050: Convert collections.deque to use Argument Clinic.

• gh-112050: Make methods on collections.deque thread-safe when the GIL is disabled.

• gh-113464: Add an option (--enable-experimental-jit for configure-based builds or --experimental-jit for PCbuild-based ones) to build an experimental just-in-time compiler, based on copy-and-patch

• gh-113055: Make interp->obmalloc a pointer. For interpreters that share state with the main interpreter, this points to the same static memory structure. For interpreters with their own obmalloc state, it is heap allocated. Add free_obmalloc_arenas() which will free the obmalloc arenas and radix tree structures for interpreters with their own obmalloc state.

• gh-55664: Add warning when creating type using a namespace dictionary with non-string keys. Patched by Daniel Urban and Furkan Onder.

• gh-104530: Use native Win32 condition variables.

Library

• gh-115392: Fix a bug in doctest where incorrect line numbers would be reported for decorated functions.

• gh-114563: Fix several format() bugs when using the C implementation of Decimal: * memory leak in some rare cases when using the z format option (coerce negative 0) * incorrect output when applying the z format option to type F (fixed-point with capital NAN / INF) * incorrect output when applying the # format option (alternate form)

• gh-102840: Fix confused traceback when floordiv, mod, or divmod operations happens between instances of fractions.Fraction and complex.

• gh-115165: Most exceptions are now ignored when attempting to set the __orig_class__ attribute on objects returned when calling typing generic aliases (including generic aliases created using typing.Annotated). Previously only AttributeError was ignored. Patch by Dave Shawley.

• gh-112903: Fix “issubclass() arg 1 must be a class” errors in certain cases of multiple inheritance with generic aliases (regression in early 3.13 alpha releases).

• gh-115133: Fix tests for XMLPullParser with Expat 2.6.0.

• gh-115059: io.BufferedRandom.read1() now flushes the underlying write buffer.

• gh-79382: Trailing ** no longer allows to match files and non-existing paths in recursive glob().

• gh-67837: Avoid race conditions in the creation of directories during concurrent extraction in tarfile and zipfile.

• gh-115060: Speed up pathlib.Path.glob() by removing redundant regex matching.

• gh-97928: Partially revert the behavior of tkinter.Text.count(). By default it preserves the behavior of older Python versions, except that setting wantobjects to 0 no longer has effect. Add a new parameter return_ints: specifying return_ints=True makes Text.count() always returning the single count as an integer instead of a 1-tuple or None.

• gh-114628: When csv.Error is raised when handling TypeError, do not print the TypeError traceback.

• gh-85984: Added _POSIX_VDISABLE from C’s <unistd.h> to termios.

• gh-114965: Update bundled pip to 24.0

• gh-114959: tarfile no longer ignores errors when trying to extract a directory on top of a file.

• gh-114894: Add array.array.clear().

• gh-114071: Support tuple subclasses using auto() for enum member value.

• gh-109475: Fix support of explicit option value “–” in argparse (e.g. --option=--).

• gh-49766: Fix date-datetime comparison. Now the special comparison methods like __eq__ and __lt__ return NotImplemented if one of comparands is date and other is datetime instead of ignoring the time part and the time zone or forcefully return “not equal” or raise TypeError. It makes comparison of date and datetime subclasses more symmetric and allows to change the default behavior by overriding the special comparison methods in subclasses.

• gh-110190: Fix ctypes structs with array on Windows ARM64 platform by setting MAX_STRUCT_SIZE to 32 in stgdict. Patch by Diego Russo

• gh-114678: Ensure that deprecation warning for ‘N’ specifier in Decimal format is not raised for cases where ‘N’ appears in other places in the format specifier. Based on patch by Stefan Krah.

• gh-70303: Return both files and directories from pathlib.Path.glob() if a pattern ends with “**”. Previously only directories were returned.

• gh-109653: Improve import time of importlib.metadata and email.utils.

• gh-113280: Fix a leak of open socket in rare cases when error occurred in ssl.SSLSocket creation.

• gh-77749: email.policy.EmailPolicy.fold() now always encodes non-ASCII characters in headers if utf8 is false.

• gh-83383: Synchronization of the dbm.dumb database is now no-op if there was no modification since opening or last synchronization. The directory file for a newly created empty dbm.dumb database is now created immediately after opening instead of deferring this until synchronizing or closing.

• gh-91602: Add filter keyword-only parameter to sqlite3.Connection.iterdump() for filtering database objects to dump. Patch by Mariusz Felisiak.

• gh-112451: Prohibit subclassing pure-Python datetime.timezone. This is consistent with C-extension implementation. Patch by Mariusz Felisiak.

• gh-69893: Add the close() method for the iterator returned by xml.etree.ElementTree.iterparse().

• gh-109653: Reduce the import time of threading module by ~50%. Patch by Daniel Hollas.

• gh-114492: Make the result of termios.tcgetattr() reproducible on Alpine Linux. Previously it could leave a random garbage in some fields.

• gh-114315: Make threading.Lock a real class, not a factory function. Add __new__ to _thread.lock type.

• gh-100414: Add dbm.sqlite3 as a backend to dbm, and make it the new default dbm backend. Patch by Raymond Hettinger and Erlend E. Aasland.

• gh-113267: Revert changes in gh-106584 which made calls of TestResult methods startTest() and stopTest() unbalanced.

• gh-75128: Ignore an OSError in asyncio.BaseEventLoop.create_server() when IPv6 is available but the interface cannot actually support it.

• gh-114423: _DummyThread entries in threading._active are now automatically removed when the related thread dies.

• gh-114257: Dismiss the FileNotFound error in ctypes.util.find_library() and just return None on Linux.

• gh-114321: Expose more platform specific constants in the fcntl module on Linux, macOS, FreeBSD and NetBSD.

• gh-114328: The tty.setcbreak() and new tty.cfmakecbreak() no longer clears the terminal input ICRLF flag. This fixes a regression introduced in 3.12 that no longer matched how OSes define cbreak mode in their stty(1) manual pages.

• gh-114281: Remove type hints from Lib/asyncio/staggered.py. The annotations in the typeshed project should be used instead.

• gh-101438: Avoid reference cycle in ElementTree.iterparse. The iterator returned by ElementTree.iterparse may hold on to a file descriptor. The reference cycle prevented prompt clean-up of the file descriptor if the returned iterator was not exhausted.

• gh-114198: The signature for the __replace__ method on dataclasses now has the first argument named self, rather than obj.

• gh-104522: OSError raised when run a subprocess now only has filename attribute set to cwd if the error was caused by a failed attempt to change the current directory.

• gh-114149: Enum: correctly handle tuple subclasses in custom __new__.

• gh-83648: Support deprecation of options, positional arguments and subcommands in argparse.

• gh-114087: Speed up dataclasses.asdict up to 1.35x.

• gh-109534: Fix a reference leak in asyncio.selector_events.BaseSelectorEventLoop when SSL handshakes fail. Patch contributed by Jamie Phan.

• gh-79634: Accept path-like objects as patterns in pathlib.Path.glob() and rglob().

• gh-112202: Ensure that a asyncio.Condition.notify() call does not get lost if the awakened Task is simultaneously cancelled or encounters any other error.

• gh-113951: Fix the behavior of tag_unbind() methods of tkinter.Text and tkinter.Canvas classes with three arguments. Previously, widget.tag_unbind(tag, sequence, funcid) destroyed the current binding for sequence, leaving sequence unbound, and deleted the funcid command. Now it removes only funcid from the binding for sequence, keeping other commands, and deletes the funcid command. It leaves sequence unbound only if funcid was the last bound command.

• gh-97959: Fix rendering class methods, bound methods, method and function aliases in pydoc. Class methods no longer have “method of builtins.type instance” note. Corresponding notes are now added for class and unbound methods. Method and function aliases now have references to the module or the class where the origin was defined if it differs from the current. Bound methods are now listed in the static methods section. Methods of builtin classes are now supported as well as methods of Python classes.

• gh-113796: Add more validation checks in the csv.Dialect constructor. ValueError is now raised if the same character is used in different roles.

• gh-113732: Fix support of QUOTE_NOTNULL and QUOTE_STRINGS in csv.reader().

• gh-113225: Speed up pathlib.Path.walk() by using os.DirEntry.path where possible.

• gh-89039: When replace() method is called on a subclass of datetime, date or time, properly call derived constructor. Previously, only the base class’s constructor was called.

  Also, make sure to pass non-zero fold values when creating subclasses in various methods. Previously, fold was silently ignored.

• gh-112919: Speed-up datetime.datetime.replace(), datetime.date.replace() and datetime.time.replace().

• gh-59013: Set breakpoint on the first executable line of the function, instead of the line of function definition when the user do break func using pdb

• gh-112343: Improve handling of pdb convenience variables to avoid replacing string contents.

• gh-112240: Add option to calendar module CLI to specify the weekday to start each week. Patch by Steven Ward.

• gh-111741: Recognise image/webp as a standard format in the mimetypes module.

• gh-43457: Fix the tkinter widget method wm_attributes(). It now accepts the attribute name without the minus prefix to get window attributes and allows to specify attributes and values to set as keyword arguments. Add new optional keyword argument return_python_dict: calling w.wm_attributes(return_python_dict=True) returns the attributes as a dict instead of a tuple. Calling w.wm_attributes() now returns a tuple instead of string if wantobjects was set to 0.

• gh-82626: Many functions now emit a warning if a boolean value is passed as a file descriptor argument.

• gh-111051: Added check for file modification during debugging with pdb

• gh-110345: Show the Tcl/Tk patchlevel (rather than version) in tkinter._test().

• gh-38807: Fix race condition in trace. Instead of checking if a directory exists and creating it, directly call os.makedirs() with the kwarg exist_ok=True.

• gh-75705: Set unixfrom envelope in mailbox.mbox and mailbox.MMDF.

• gh-106233: Fix stacklevel in InvalidTZPathWarning during zoneinfo module import.

• gh-105102: Allow ctypes.Union to be nested in ctypes.Structure when the system endianness is the opposite of the classes.

• gh-104282: Fix null pointer dereference in lzma._decode_filter_properties() due to improper handling of BCJ filters with properties of zero length. Patch by Radislav Chugunov.

• gh-96471: Add queue.Queue termination with shutdown().

• gh-101599: Changed argparse flag options formatting to remove redundancy.

• gh-85984: Add POSIX pseudo-terminal functions os.posix_openpt(), os.grantpt(), os.unlockpt(), and os.ptsname().

• gh-102512: When os.fork() is called from a foreign thread (aka _DummyThread), the type of the thread in a child process is changed to _MainThread. Also changed its name and daemonic status, it can be now joined.

• gh-88569: Add os.path.isreserved(), which identifies reserved pathnames such as “NUL”, “AUX” and “CON”. This function is only available on Windows.

  Deprecate pathlib.PurePath.is_reserved().

• bpo-38364: The inspect functions isgeneratorfunction, iscoroutinefunction, isasyncgenfunction now support functools.partialmethod wrapped functions the same way they support functools.partial.

Documentation

• gh-115233: Fix an example for LoggerAdapter in the Logging Cookbook.

• gh-114123: Move the csv module docstring to the csv module instead of reexporting it from the internal _csv module, and remove __doc__ from csv.__all__.

  Move csv.__version__ to the csv module instead of reexporting it from the internal _csv module, and remove __version__ from csv.__all__.

Tests

• gh-114099: Added test exclusions required to run the test suite on iOS.

• gh-105089: Fix test.test_zipfile.test_core.TestWithDirectory.test_create_directory_with_write test in AIX by doing a bitwise AND of 0xFFFF on mode , so that it will be in sync with zinfo.external_attr

Build

• gh-115167: Avoid vendoring vcruntime140_threads.dll when building with Visual Studio 2022 version 17.8.

• gh-113632: Promote WASI to a tier 2 platform and drop Emscripten from tier 3 in configure.ac.

• gh-114099: configure and Makefile were refactored to accommodate framework builds on Apple platforms other than macOS.

• gh-114875: Add getgrent() as a prerequisite for building the grp module.

Windows

• gh-115049: Fixes py.exe launcher failing when run as users without user profiles.

• gh-115009: Update Windows installer to use SQLite 3.45.1.

• gh-109991: Update Windows build to use OpenSSL 3.0.13.

• gh-111239: Update Windows builds to use zlib v1.3.1.

• gh-100107: The py.exe launcher will no longer attempt to run the Microsoft Store redirector when launching a script containing a /usr/bin/env shebang

• gh-112984: Adds free-threaded binaries to Windows installer as an optional component.

• gh-89240: Allows multiprocessing to create pools of greater than 62 processes.

macOS

• gh-115009: Update macOS installer to use SQLite 3.45.1.

• gh-109991: Update macOS installer to use OpenSSL 3.0.13.

• gh-114490: Add Mach-O linkage support for platform.architecture().

• gh-87804: On macOS the result of os.statvfs and os.fstatvfs now correctly report the size of very large disks, in previous versions the reported number of blocks was wrong for disks with at least 2**32 blocks.

IDLE

• gh-96905: In idlelib code, stop redefining built-ins ‘dict’ and ‘object’.

• gh-103820: Revise IDLE bindings so that events from mouse button 4/5 on non-X11 windowing systems (i.e. Win32 and Aqua) are not mistaken for scrolling.

Tools/Demos

• gh-113516: Don’t set LDSHARED when building for WASI.

• gh-109991: Update GitHub CI workflows to use OpenSSL 3.0.13 and multissltests to use 1.1.1w, 3.0.13, 3.1.5, and 3.2.1.

• gh-115015: Fix a bug in Argument Clinic that generated incorrect code for methods with no parameters that use the METH_METHOD | METH_FASTCALL | METH_KEYWORDS calling convention. Only the positional parameter count was checked; any keyword argument passed would be silently accepted.

C API

• gh-111140: Adds PyLong_AsNativeBytes(), PyLong_FromNativeBytes() and PyLong_FromUnsignedNativeBytes() functions.

• gh-114685: PyBuffer_FillInfo() now raises a SystemError if called with PyBUF_READ or PyBUF_WRITE as flags. These flags should only be used with the PyMemoryView_* C API.

• gh-114685: PyObject_GetBuffer() now raises a SystemError if called with PyBUF_READ or PyBUF_WRITE as flags. These flags should only be used with the PyMemoryView_* C API.

• gh-114626: Add PyCFunctionFast and PyCFunctionFastWithKeywords typedefs (identical to the existing _PyCFunctionFast and _PyCFunctionFastWithKeywords typedefs, just without a leading _ prefix).

• gh-114329: Add PyList_GetItemRef(), which is similar to PyList_GetItem() but returns a strong reference instead of a borrowed reference.

• gh-110850: Add PyTime C API:

  • PyTime_t type.

  • PyTime_MIN and PyTime_MAX constants.

  • PyTime_AsSecondsDouble(), PyTime_Monotonic(), PyTime_PerfCounter(), and PyTime_Time() functions.

  Patch by Victor Stinner.

• gh-112066: Add PyDict_SetDefaultRef(): insert a key and value into a dictionary if the key is not already present. This is similar to dict.setdefault(), but returns an integer value indicating if the key was already present. It is also similar to PyDict_SetDefault(), but returns a strong reference instead of a borrowed reference.

Python 3.13.0 alpha 3

Release date: 2024-01-17

Security

• gh-113659: Skip .pth files with names starting with a dot or hidden file attribute.

• gh-112302: Created a Software Bill-of-Materials document and tooling for tracking dependencies.

Core and Builtins

• gh-107901: Compiler duplicates basic blocks that have an eval breaker check, no line number, and multiple predecessors.

• gh-107901: A jump leaving an exception handler back to normal code no longer checks the eval breaker.

• gh-113655: Set the C recursion limit to 4000 on Windows, and 10000 on Linux/OSX. This seems to be near the sweet spot to maintain safety, but not compromise backwards compatibility.

• gh-113710: Add typed stack effects to the interpreter DSL, along with various instruction annotations.

• gh-77046: On Windows, file descriptors wrapping Windows handles are now created non inheritable by default (PEP 446). Patch by Zackery Spytz and Victor Stinner.

• gh-113853: Guarantee that all executors make progress. This then guarantees that tier 2 execution always makes progress.

• gh-113753: Fix an issue where the finalizer of PyAsyncGenASend objects might not be called if they were allocated from a free list.

• gh-107901: Compiler changed so that synthetic jumps which are not at loop end no longer check the eval breaker.

• gh-113703: Fix a regression in the codeop module that was causing it to incorrectly identify incomplete f-strings. Patch by Pablo Galindo

• gh-89811: Check for a valid tp_version_tag before performing bytecode specializations that rely on this value being usable.

• gh-111488: Changed error message in case of no ‘in’ keyword after ‘for’ in list comprehensions

• gh-113657: Fix an issue that caused important instruction pointer updates to be optimized out of tier two traces.

• gh-113603: Fixed bug where a redundant NOP is not removed, causing an assertion to fail in the compiler in debug mode.

• gh-113602: Fix an error that was causing the parser to try to overwrite existing errors and crashing in the process. Patch by Pablo Galindo

• gh-113486: No longer issue spurious PY_UNWIND events for optimized calls to classes.

• gh-113297: Fix segfault in the compiler on with statement with 19 context managers.

• gh-113212: Improve super error messages.

• gh-111375: Only use NULL in the exception stack to indicate an exception was handled. Patch by Carey Metcalfe.

• gh-112215: Increase the C recursion limit by a factor of 3 for non-debug builds, except for webassembly and s390 platforms which are unchanged. This mitigates some regressions in 3.12 with deep recursion mixing builtin (C) and Python code.

• gh-113054: Fixed bug where a redundant NOP is not removed, causing an assertion to fail in the compiler in debug mode.

• gh-106905: Use per AST-parser state rather than global state to track recursion depth within the AST parser to prevent potential race condition due to simultaneous parsing.

  The issue primarily showed up in 3.11 by multithreaded users of ast.parse(). In 3.12 a change to when garbage collection can be triggered prevented the race condition from occurring.

• gh-108866: Change the API and contract of _PyExecutorObject to return the next_instr pointer, instead of the frame, and to always execute at least one instruction.

• gh-90350: Optimize builtin functions min() and max().

• gh-112943: Correctly compute end column offsets for multiline tokens in the tokenize module. Patch by Pablo Galindo

• gh-112125: Fix None.__ne__(None) returning NotImplemented instead of False.

• gh-74616: input() now raises a ValueError when output on the terminal if the prompt contains embedded null characters instead of silently truncating it.

• gh-112716: Fix SystemError in the import statement and in __reduce__() methods of builtin types when __builtins__ is not a dict.

• gh-112730: Use color to highlight error locations in tracebacks. Patch by Pablo Galindo

• gh-112625: Fixes a bug where a bytearray object could be cleared while iterating over an argument in the bytearray.join() method that could result in reading memory after it was freed.

• gh-112660: Do not clear unexpected errors during formatting error messages for ImportError and AttributeError for modules.

• gh-105967: Workaround a bug in Apple’s macOS platform zlib library where zlib.crc32() and binascii.crc32() could produce incorrect results on multi-gigabyte inputs. Including when using zipfile on zips containing large data.

• gh-95754: Provide a better error message when accessing invalid attributes on partially initialized modules. The origin of the module being accessed is now included in the message to help with the common issue of shadowing other modules.

• gh-112217: Add check for the type of __cause__ returned from calling the type T in raise from T.

• gh-111058: Change coro.cr_frame/gen.gi_frame to return None after the coroutine/generator has been closed. This fixes a bug where getcoroutinestate() and getgeneratorstate() return the wrong state for a closed coroutine/generator.

• gh-112388: Fix an error that was causing the parser to try to overwrite tokenizer errors. Patch by pablo Galindo

• gh-112387: Fix error positions for decoded strings with backwards tokenize errors. Patch by Pablo Galindo

• gh-99606: Make code generated for an empty f-string identical to the code of an empty normal string.

• gh-112367: Avoid undefined behaviour when using the perf trampolines by not freeing the code arenas until shutdown. Patch by Pablo Galindo

• gh-112320: The Tier 2 translator now tracks the confidence level for staying “on trace” (i.e. not exiting back to the Tier 1 interpreter) for branch instructions based on the number of bits set in the branch “counter”. Trace translation ends when the confidence drops below 1/3rd.

• gh-109598: PyComplex_RealAsDouble()/PyComplex_ImagAsDouble() now tries to convert an object to a complex instance using its __complex__() method before falling back to the __float__() method. Patch by Sergey B Kirpichev.

• gh-94606: Fix UnicodeEncodeError when email.message.get_payload() reads a message with a Unicode surrogate character and the message content is not well-formed for surrogateescape encoding. Patch by Sidney Markowitz.

• bpo-21861: Use the object’s actual class name in _io.FileIO.__repr__(), _io._WindowsConsoleIO() and _io.TextIOWrapper.__repr__(), to make these methods subclass friendly.

• bpo-45369: Remove LibreSSL workarounds as per PEP 644.

• bpo-34392: Added sys._is_interned().

Library

• gh-114077: Fix possible OverflowError in socket.socket.sendfile() when pass count larger than 2 GiB on 32-bit platform.

• gh-111803: plistlib now supports loading more deeply nested lists in binary format.

• gh-114014: Fixed a bug in fractions.Fraction where an invalid string using d in the decimals part creates a different error compared to other invalid letters/characters. Patch by Jeremiah Gabriel Pascual.

• gh-108364: sqlite3.Connection.iterdump() now ensures that foreign key support is disabled before dumping the database schema, if there is any foreign key violation. Patch by Erlend E. Aasland and Mariusz Felisiak.

• gh-113971: The zipfile.ZipInfo previously protected ._compresslevel attribute has been made public as .compress_level with the old _compresslevel name remaining available as a property to retain compatibility.

• gh-113877: Fix tkinter method winfo_pathname() on 64-bit Windows.

• gh-113868: Added mmap.MAP_NORESERVE, mmap.MAP_NOEXTEND, mmap.MAP_HASSEMAPHORE, mmap.MAP_NOCACHE, mmap.MAP_JIT, mmap.MAP_RESILIENT_CODESIGN, mmap.MAP_RESILIENT_MEDIA, mmap.MAP_32BIT, mmap.MAP_TRANSLATED_ALLOW_EXECUTE, mmap.MAP_UNIX03 and mmap.MAP_TPRO. All of them are mmap(2) flags on macOS.

• gh-113848: asyncio.TaskGroup() and asyncio.timeout() context managers now handle CancelledError subclasses as well as exact CancelledError.

• gh-113661: unittest runner: Don’t exit 5 if tests were skipped. The intention of exiting 5 was to detect issues where the test suite wasn’t discovered at all. If we skipped tests, it was correctly discovered.

• gh-96037: Insert TimeoutError in the context of the exception that was raised during exiting an expired asyncio.timeout() block.

• gh-113781: Silence unraisable AttributeError when warnings are emitted during Python finalization.

• gh-113238: Add Anchor to importlib.resources (in order for the code to comply with the documentation)

• gh-111693: asyncio.Condition.wait() now re-raises the same CancelledError instance that may have caused it to be interrupted. Fixed race condition in asyncio.Semaphore.acquire() when interrupted with a CancelledError.

• gh-113791: Add CLOCK_MONOTONIC_RAW_APPROX and CLOCK_UPTIME_RAW_APPROX to time on macOS. These are clocks available on macOS 10.12 or later.

• gh-112932: Restore the ability for zipfile to extractall from zip files with a “/” directory entry in them as is commonly added to zips by some wiki or bug tracker data exporters.

• gh-113568: Raise deprecation warnings from pathlib.PurePath and not its private base class PurePathBase.

• gh-113594: Fix UnicodeEncodeError in email when re-fold lines that contain unknown-8bit encoded part followed by non-unknown-8bit encoded part.

• gh-113538: In asyncio.StreamReaderProtocol.connection_made(), there is callback that logs an error if the task wrapping the “connected callback” fails. This callback would itself fail if the task was cancelled. Prevent this by checking whether the task was cancelled first. If so, close the transport but don’t log an error.

• gh-113626: Add support for the allow_code argument in the marshal module. Passing allow_code=False prevents serialization and de-serialization of code objects which is incompatible between Python versions.

• gh-85567: Fix resource warnings for unclosed files in pickle and pickletools command line interfaces.

• gh-113537: Support loads str in plistlib.loads().

• gh-89850: Add default implementations of pickle.Pickler.persistent_id() and pickle.Unpickler.persistent_load() methods in the C implementation. Calling super().persistent_id() and super().persistent_load() in subclasses of the C implementation of pickle.Pickler and pickle.Unpickler classes no longer causes infinite recursion.

• gh-113569: Indicate if there were no actual calls in unittest assert_has_calls() failure.

• gh-101225: Increase the backlog for multiprocessing.connection.Listener objects created by multiprocessing.manager and multiprocessing.resource_sharer to significantly reduce the risk of getting a connection refused error when creating a multiprocessing.connection.Connection to them.

• gh-113568: Raise audit events from pathlib.Path and not its private base class PathBase.

• gh-113543: Make sure that webbrowser.MacOSXOSAScript sends webbrowser.open audit event.

• gh-113028: When a second reference to a string appears in the input to pickle, and the Python implementation is in use, we are guaranteed that a single copy gets pickled and a single object is shared when reloaded. Previously, in protocol 0, when a string contained certain characters (e.g. newline) it resulted in duplicate objects.

• gh-113421: Fix multiprocessing logger for %(filename)s.

• gh-111784: Fix segfaults in the _elementtree module. Fix first segfault during deallocation of _elementtree.XMLParser instances by keeping strong reference to pyexpat module in module state for capsule lifetime. Fix second segfault which happens in the same deallocation process by keeping strong reference to _elementtree module in XMLParser structure for _elementtree module lifetime.

• gh-113407: Fix import of unittest.mock when CPython is built without docstrings.

• gh-113320: Fix regression in Python 3.12 where Protocol classes that were not marked as runtime-checkable would be unnecessarily introspected, potentially causing exceptions to be raised if the protocol had problematic members. Patch by Alex Waygood.

• gh-53502: Add a new option aware_datetime in plistlib to loads or dumps aware datetime.

• gh-113358: Fix rendering tracebacks with exceptions with a broken __getattr__

• gh-113214: Fix an AttributeError during asyncio SSL protocol aborts in SSL-over-SSL scenarios.

• gh-113246: Update bundled pip to 23.3.2.

• gh-87264: Fixed tarfile list() method to show file type.

• gh-112182: asyncio.futures.Future.set_exception() now transforms StopIteration into RuntimeError instead of hanging or other misbehavior. Patch contributed by Jamie Phan.

• gh-113225: Speed up pathlib.Path.glob() by using os.DirEntry.path where possible.

• gh-113149: Improve error message when a JSON array or object contains a trailing comma. Patch by Carson Radtke.

• gh-113117: The subprocess module can now use the os.posix_spawn() function with close_fds=True on platforms where posix_spawn_file_actions_addclosefrom_np is available. Patch by Jakub Kulik.

• gh-113199: Make http.client.HTTPResponse.read1 and http.client.HTTPResponse.readline close IO after reading all data when content length is known. Patch by Illia Volochii.

• gh-113191: Add support of os.fchmod() and a file descriptor in os.chmod() on Windows.

• gh-113188: Fix shutil.copymode() and shutil.copystat() on Windows. Previously they worked differently if dst is a symbolic link: they modified the permission bits of dst itself rather than the file it points to if follow_symlinks is true or src is not a symbolic link, and did not modify the permission bits if follow_symlinks is false and src is a symbolic link.

• gh-113119: os.posix_spawn() now accepts env=None, which makes the newly spawned process use the current process environment. Patch by Jakub Kulik.

• gh-113202: Add a strict option to batched() in the itertools module.

• gh-61648: Detect line numbers of properties in doctests.

• gh-113175: Sync with importlib_metadata 7.0, including improved type annotations, fixed issue with symlinked packages in package_distributions, added EntryPoints.__repr__, introduced the diagnose script, added Distribution.origin property, and removed deprecated EntryPoint access by numeric index (tuple behavior).

• gh-59616: Add support of os.lchmod() and the follow_symlinks argument in os.chmod() on Windows. Note that the default value of follow_symlinks in os.lchmod() is False on Windows.

• gh-112559: signal.signal() and signal.getsignal() no longer call repr on callable handlers. asyncio.run() and asyncio.Runner.run() no longer call repr on the task results. Patch by Yilei Yang.

• gh-112962: dis module functions add cache information to the Instruction instance rather than creating fake Instruction instances to represent the cache entries.

• gh-112989: Reduce overhead to connect sockets with asyncio SelectorEventLoop.

• gh-112970: Use closefrom() on Linux where available (e.g. glibc-2.34), rather than only FreeBSD.

• gh-110190: Fix ctypes structs with array on PPC64LE platform by setting MAX_STRUCT_SIZE to 64 in stgdict. Patch by Diego Russo.

• gh-112540: The statistics.geometric_mean() function now returns zero for datasets containing a zero. Formerly, it would raise an exception.

• gh-87286: Added LOG_FTP, LOG_NETINFO, LOG_REMOTEAUTH, LOG_INSTALL, LOG_RAS, and LOG_LAUNCHD tot the syslog module, all of them constants on used on macOS.

• gh-112800: Fix asyncio SubprocessTransport.close() not to throw PermissionError when used with setuid executables.

• gh-51944: Add the following constants to the termios module. These values are present in macOS system headers: ALTWERASE, B14400, B28800, B7200, B76800, CCAR_OFLOW, CCTS_OFLOW, CDSR_OFLOW, CDTR_IFLOW, CIGNORE, CRTS_IFLOW, EXTPROC, IUTF8, MDMBUF, NL2, NL3, NOKERNINFO, ONOEOT, OXTABS, VDSUSP, VSTATUS.

• gh-79325: Fix an infinite recursion error in tempfile.TemporaryDirectory() cleanup on Windows.

• gh-94692: shutil.rmtree() now only catches OSError exceptions. Previously a symlink attack resistant version of shutil.rmtree() could ignore or pass to the error handler arbitrary exception when invalid arguments were provided.

• gh-112736: The use of del-safe symbols in subprocess was refactored to allow for use in cross-platform build environments.

• gh-112727: Speed up pathlib.Path.absolute(). Patch by Barney Gale.

• gh-74690: Speedup issubclass() checks against simple runtime-checkable protocols by around 6%. Patch by Alex Waygood.

• gh-74690: Speedup isinstance() checks by roughly 20% for runtime-checkable protocols that only have one callable member. Speedup issubclass() checks for these protocols by roughly 10%. Patch by Alex Waygood.

• gh-112645: Remove deprecation error on passing onerror to shutil.rmtree().

• gh-112640: Add kwdefaults parameter to types.FunctionType to set default keyword argument values.

• gh-112622: Ensure name parameter is passed to event loop in asyncio.create_task().

• gh-112618: Fix a caching bug relating to typing.Annotated. Annotated[str, True] is no longer identical to Annotated[str, 1].

• gh-112334: Fixed a performance regression in 3.12’s subprocess on Linux where it would no longer use the fast-path vfork() system call when it could have due to a logic bug, instead falling back to the safe but slower fork().

  Also fixed a second 3.12.0 potential security bug. If a value of extra_groups=[] was passed to subprocess.Popen or related APIs, the underlying setgroups(0, NULL) system call to clear the groups list would not be made in the child process prior to exec().

  This was identified via code inspection in the process of fixing the first bug.

• gh-110190: Fix ctypes structs with array on Arm platform by setting MAX_STRUCT_SIZE to 32 in stgdict. Patch by Diego Russo.

• gh-81194: Fix a crash in socket.if_indextoname() with specific value (UINT_MAX). Fix an integer overflow in socket.if_indextoname() on 64-bit non-Windows platforms.

• gh-112578: Fix a spurious RuntimeWarning when executing the zipfile module.

• gh-112516: Update the bundled copy of pip to version 23.3.1.

• gh-112510: Add readline.backend for the backend readline uses (editline or readline)

• gh-112328: [Enum] Make EnumDict, EnumDict.member_names, EnumType._add_alias_ and EnumType._add_value_alias_ public.

• gh-112509: Fix edge cases that could cause a key to be present in both the __required_keys__ and __optional_keys__ attributes of a typing.TypedDict. Patch by Jelle Zijlstra.

• gh-101336: Add keep_alive keyword parameter for AbstractEventLoop.create_server() and BaseEventLoop.create_server().

• gh-63284: Added support for TLS-PSK (pre-shared key) mode to the ssl module.

• gh-112414: Fix regression in Python 3.12 where calling repr() on a module that had been imported using a custom loader could fail with AttributeError. Patch by Alex Waygood.

• gh-112358: Revert change to struct.Struct initialization that broke some cases of subclassing.

• gh-112405: Optimize pathlib.PurePath.relative_to(). Patch by Alex Waygood.

• gh-94722: Fix bug where comparison between instances of DocTest fails if one of them has None as its lineno.

• gh-112361: Speed up a small handful of pathlib methods by removing some temporary objects.

• gh-112345: Improve error message when trying to call issubclass() against a typing.Protocol that has non-method members. Patch by Randolf Scholz.

• gh-112137: Change dis output to display no-lineno as “–” instead of “None”.

• gh-112332: Deprecate the exc_type field of traceback.TracebackException. Add exc_type_str to replace it.

• gh-81620: Add extra tests for random.binomialvariate()

• gh-112292: Fix a crash in readline when imported from a sub interpreter. Patch by Anthony Shaw

• gh-77621: Slightly improve the import time of the pathlib module by deferring some imports. Patch by Barney Gale.

• gh-112137: Change dis output to display logical labels for jump targets instead of offsets.

• gh-112139: Add Signature.format() to format signatures to string with extra options. And use it in pydoc to render more readable signatures that have new lines between parameters.

• gh-112105: Make readline.set_completer_delims() work with libedit

• gh-106922: Display multiple lines with traceback when errors span multiple lines.

• gh-111874: When creating a typing.NamedTuple class, ensure __set_name__() is called on all objects that define __set_name__ and exist in the values of the NamedTuple class’s class dictionary. Patch by Alex Waygood.

• gh-68166: Add support of the “vsapi” element type in tkinter.ttk.Style.element_create().

• gh-110275: Named tuple’s methods _replace() and __replace__() now raise TypeError instead of ValueError for invalid keyword arguments.

• gh-99367: Do not mangle sys.path[0] in pdb if safe_path is set

• gh-111615: Fix a regression caused by a fix to gh-93162 whereby you couldn’t configure a QueueHandler without specifying handlers.

• gh-75666: Fix the behavior of tkinter widget’s unbind() method with two arguments. Previously, widget.unbind(sequence, funcid) destroyed the current binding for sequence, leaving sequence unbound, and deleted the funcid command. Now it removes only funcid from the binding for sequence, keeping other commands, and deletes the funcid command. It leaves sequence unbound only if funcid was the last bound command.

• gh-67790: Implement basic formatting support (minimum width, alignment, fill) for fractions.Fraction.

• gh-111049: Fix crash during garbage collection of the io.BytesIO buffer object.

• gh-102980: Redirect the output of interact command of pdb to the same channel as the debugger. Add tests and improve docs.

• gh-102988: email.utils.getaddresses() and email.utils.parseaddr() now return ('', '') 2-tuples in more situations where invalid email addresses are encountered instead of potentially inaccurate values. Add optional strict parameter to these two functions: use strict=False to get the old behavior, accept malformed inputs. getattr(email.utils, 'supports_strict_parsing', False) can be use to check if the strict parameter is available. Patch by Thomas Dwyer and Victor Stinner to improve the CVE 2023-27043 fix.

• gh-52161: cmd.Cmd.do_help() now cleans docstrings with inspect.cleandoc() before writing them. Patch by Filip Łapkiewicz.

• gh-82300: Add track parameter to multiprocessing.shared_memory.SharedMemory that allows using shared memory blocks without having to register with the POSIX resource tracker that automatically releases them upon process exit.

• gh-110109: Add private pathlib._PurePathBase class: a base class for pathlib.PurePath that omits certain magic methods. It may be made public (along with _PathBase) in future.

• gh-109858: Protect zipfile from “quoted-overlap” zipbomb. It now raises BadZipFile when try to read an entry that overlaps with other entry or central directory.

• gh-109786: Fix possible reference leaks and crash when re-enter the __next__() method of itertools.pairwise.

• gh-91539: Small (10 - 20%) and trivial performance improvement of urllib.request.getproxies_environment(), typically useful when there are many environment variables to go over.

• gh-103363: Add follow_symlinks keyword-only argument to pathlib.Path.owner() and group(), defaulting to True.

• gh-102130: Support tab completion in cmd for editline.

• gh-99437: runpy.run_path() now decodes path-like objects, making sure __file__ and sys.argv[0] of the module being run are always strings.

• gh-104003: Add warnings.deprecated(), a decorator to mark deprecated functions to static type checkers and to warn on usage of deprecated classes and functions. See PEP 702. Patch by Jelle Zijlstra.

• gh-103708: Make hardcoded python name, a configurable parameter so that different implementations of python can override it instead of making huge diffs in sysconfig.py

• gh-66515: mailbox.MH now supports folders that do not contain a .mh_sequences file (e.g. Claws Mail IMAP-cache folders). Patch by Serhiy Storchaka.

• gh-83162: Renamed re.error to PatternError for clarity, and kept re.error for backward compatibility. Patch by Matthias Bussonnier and Adam Chhina.

• gh-91133: Fix a bug in tempfile.TemporaryDirectory cleanup, which now no longer dereferences symlinks when working around file system permission errors.

• bpo-43153: On Windows, tempfile.TemporaryDirectory previously masked a PermissionError with NotADirectoryError during directory cleanup. It now correctly raises PermissionError if errors are not ignored. Patch by Andrei Kulakov and Ken Jin.

• bpo-32731: getpass.getuser() now raises OSError for all failures rather than ImportError on systems lacking the pwd module or KeyError if the password database is empty.

• bpo-34321: mmap.mmap now has a trackfd parameter on Unix; if it is False, the file descriptor specified by fileno will not be duplicated.

• bpo-35332: The shutil.rmtree() function now ignores errors when calling os.close() when ignore_errors is True, and os.close() no longer retried after error.

• bpo-35928: io.TextIOWrapper now correctly handles the decoding buffer after read() and write().

• bpo-26791: shutil.move() now moves a symlink into a directory when that directory is the target of the symlink. This provides the same behavior as the mv shell command. The previous behavior raised an exception. Patch by Jeffrey Kintscher.

• bpo-41422: Fixed memory leaks of pickle.Pickler and pickle.Unpickler involving cyclic references via the internal memo mapping.

• bpo-19821: The pydoc.ispackage() function has been deprecated.

• bpo-40262: The ssl.SSLSocket.recv_into() method no longer requires the buffer argument to implement __len__ and supports buffers with arbitrary item size.

• bpo-39912: warnings.filterwarnings() and warnings.simplefilter() now raise appropriate exceptions instead of AssertionError. Patch contributed by Rémi Lapeyre.

• bpo-37260: Fixed a race condition in shutil.rmtree() in which directory entries removed by another process or thread while shutil.rmtree() is running can cause it to raise FileNotFoundError. Patch by Jeffrey Kintscher.

• bpo-36959: Fix some error messages for invalid ISO format string combinations in strptime() that referred to directives not contained in the format string. Patch by Gordon P. Hemsley.

• bpo-18060: Fixed a class inheritance issue that can cause segfaults when deriving two or more levels of subclasses from a base class of Structure or Union.

• bpo-29779: Add a new PYTHON_HISTORY environment variable to set the location of a .python_history file.

• bpo-21360: mailbox.Maildir now ignores files with a leading dot.

Documentation

• gh-111699: Relocate smtpd deprecation notice to its own section rather than under locale in What’s New in Python 3.12 document

• gh-110746: Improved markup for valid options/values for methods ttk.treeview.column and ttk.treeview.heading, and for Layouts.

• gh-95649: Document that the asyncio module contains code taken from v0.16.0 of the uvloop project, as well as the required MIT licensing information.

Tests

• gh-111798: Disable test_super_deep() from test_call under pydebug builds on WASI; the stack depth is too small to make the test useful.

• gh-111801: Lower the recursion limit in test_isinstance for test_infinitely_many_bases(). This prevents a stack overflow on a pydebug build of WASI.

• gh-111802: Specify a low recursion depth for test_bad_getattr() in test.pickletester to avoid exhausting the stack under a pydebug build for WASI.

• gh-44626: Fix os.path.isabs() incorrectly returning True when given a path that starts with exactly one (back)slash on Windows.

  Fix pathlib.PureWindowsPath.is_absolute() incorrectly returning False for some paths beginning with two (back)slashes.

• gh-113633: Use module state for the _testcapi extension module.

• gh-109980: Fix test_tarfile_vs_tar in test_shutil for macOS, where system tar can include more information in the archive than shutil.make_archive.

• gh-112769: The tests now correctly compare zlib version when zlib.ZLIB_RUNTIME_VERSION contains non-integer suffixes. For example zlib-ng defines the version as 1.3.0.zlib-ng.

• gh-112334: Adds a regression test to verify that vfork() is used when expected by subprocess on vfork enabled POSIX systems (Linux).

• gh-108927: Fixed order dependence in running tests in the same process when a test that has submodules (e.g. test_importlib) follows a test that imports its submodule (e.g. test_importlib.util) and precedes a test (e.g. test_unittest or test_compileall) that uses that submodule.

• bpo-40648: Test modes that file can get with chmod() on Windows.

Build

• gh-114013: Fix Tools/wasm/wasi.py to not include the path to python.wasm as part of HOSTRUNNER. The environment variable is meant to specify how to run the WASI host only, having python.wasm and relevant flags appended to the HOSTRUNNER. This fixes make test work.

• gh-113258: Changed the Windows build to write out generated frozen modules into the build tree instead of the source tree.

• gh-112305: Fixed the check-clean-src step performed on out of tree builds to detect errant $(srcdir)/Python/frozen_modules/*.h files and recommend appropriate source tree cleanup steps to get a working build again.

• gh-112536: Add support for thread sanitizer (TSAN)

• gh-112867: Fix the build for the case that WITH_PYMALLOC_RADIX_TREE=0 set.

• gh-103065: Introduce Tools/wasm/wasi.py to simplify doing a WASI build.

• bpo-11102: The os.major(), os.makedev(), and os.minor() functions are now available on HP-UX v3.

• bpo-36351: Do not set ipv6type when cross-compiling.

Windows

• gh-114096: Process privileges that are activated for creating directory junctions are now restored afterwards, avoiding behaviour changes in other parts of the program.

• gh-111877: os.stat() calls were returning incorrect time values for files that could not be accessed directly.

• gh-111973: Update Windows installer to use SQLite 3.44.2.

• gh-113009: multiprocessing: On Windows, fix a race condition in Process.terminate(): no longer set the returncode attribute to always call WaitForSingleObject() in Process.wait(). Previously, sometimes the process was still running after TerminateProcess() even if GetExitCodeProcess() is not STILL_ACTIVE. Patch by Victor Stinner.

• gh-86179: Fixes path calculations when launching Python on Windows through a symlink.

• gh-71383: Update Tcl/Tk in Windows installer to 8.6.13 with a patch to suppress incorrect ThemeChanged warnings.

• gh-111650: Ensures the Py_GIL_DISABLED preprocessor variable is defined in pyconfig.h so that extension modules written in C are able to use it.

• gh-112278: Reduce the time cost for some functions in platform on Windows if current user has no permission to the WMI.

• gh-73427: Deprecate sys._enablelegacywindowsfsencoding(). Use PYTHONLEGACYWINDOWSFSENCODING instead. Patch by Inada Naoki.

• gh-87868: Correctly sort and remove duplicate environment variables in _winapi.CreateProcess().

• bpo-37308: Fix mojibake in mmap.mmap when using a non-ASCII tagname argument on Windows.

macOS

• gh-113666: Add the following constants to module stat: UF_SETTABLE, UF_TRACKED, UF_DATAVAULT, SF_SUPPORTED, SF_SETTABLE, SF_SYNTHETIC, SF_RESTRICTED, SF_FIRMLINK and SF_DATALESS. The values UF_SETTABLE, SF_SUPPORTED, SF_SETTABLE and SF_SYNTHETIC are only available on macOS.

• gh-113536: os.waitid() is now available on macOS

• gh-110459: Running configure ... --with-openssl-rpath=X/Y/Z no longer fails to detect OpenSSL on macOS.

• gh-74573: Document that dbm.ndbm can silently corrupt DBM files on updates when exceeding undocumented platform limits, and can crash (segmentation fault) when reading such a corrupted file. (FB8919203)

• gh-65701: The freeze tool doesn’t work with framework builds of Python. Document this and bail out early when running the tool with such a build.

• gh-87277: webbrowser: Don’t look for X11 browsers on macOS. Those are generally not used and probing for them can result in starting XQuartz even if it isn’t used otherwise.

• gh-111973: Update macOS installer to use SQLite 3.44.2.

• gh-108269: Set CFBundleAllowMixedLocalizations to true in the Info.plist for the framework, embedded Python.app and IDLE.app with framework installs on macOS. This allows applications to pick up the user’s preferred locale when that’s different from english.

• gh-102362: Make sure the result of sysconfig.get_plaform() includes at least a major and minor versions, even if MACOSX_DEPLOYMENT_TARGET is set to only a major version during build to match the format expected by pip.

• gh-110017: Disable a signal handling stress test on macOS due to a bug in macOS (FB13453490).

• gh-110820: Make sure the preprocessor definitions for ALIGNOF_MAX_ALIGN_T, SIZEOF_LONG_DOUBLE and HAVE_GCC_ASM_FOR_X64 are correct for Universal 2 builds on macOS.

• gh-109981: Use /dev/fd on macOS to determine the number of open files in test.support.os_helper.fd_count to avoid a crash with “guarded” file descriptors when probing for open files.

IDLE

• gh-72284: Improve the lists of features, editor key bindings, and shell key bingings in the IDLE doc.

• gh-113903: Fix rare failure of test.test_idle, in test_configdialog.

• gh-113729: Fix the “Help -> IDLE Doc” menu bug in 3.11.7 and 3.12.1.

• gh-113269: Fix test_editor hang on macOS Catalina.

• gh-112898: Fix processing unsaved files when quitting IDLE on macOS.

• bpo-13586: Enter the selected text when opening the “Replace” dialog.

C API

• gh-106560: Fix redundant declarations in the public C API. Declare PyBool_Type, PyLong_Type and PySys_Audit() only once. Patch by Victor Stinner.

• gh-112438: Fix support of format units “es”, “et”, “es#”, and “et#” in nested tuples in PyArg_ParseTuple()-like functions.

• gh-111545: Add Py_HashPointer() function to hash a pointer. Patch by Victor Stinner.

• gh-65210: Change the declaration of the keywords parameter of PyArg_ParseTupleAndKeywords() and PyArg_VaParseTupleAndKeywords() for better compatibility with C++.

Python 3.13.0 alpha 2

Release date: 2023-11-22

Core and Builtins

• gh-112243: Don’t include comments in f-string debug expressions. Patch by Pablo Galindo

• gh-112287: Slightly optimize the Tier 2 (uop) interpreter by only loading oparg and operand when needed. Also double the trace size limit again, to 512 this time.

• gh-112266: Change docstrings of __dict__ and __weakref__.

• gh-111807: Lower the max parser stack depth to 1000 under WASI debug builds.

• gh-111798: When Python is built in debug mode, set the C recursion limit to 500 instead of 1500. A debug build is likely built with low optimization level which implies higher stack memory usage than a release build. Patch by Victor Stinner.

• gh-106529: Enable translating unspecialized FOR_ITER to Tier 2.

• gh-111916: Make hashlib related modules thread-safe without the GIL

• gh-81137: Deprecate assignment to a function’s __code__ field when the new code object is of a mismatched type (e.g., from a generator to a plain function).

• gh-79932: Raise exception if frame.clear() is called on a suspended frame.

• gh-81925: Implement native thread ids for GNU KFreeBSD.

• gh-111843: Use exponential backoff to reduce the number of failed tier 2 optimization attempts by over 99%.

• gh-110829: Joining a thread now ensures the underlying OS thread has exited. This is required for safer fork() in multi-threaded processes.

• gh-109369: Make sure that tier 2 traces are de-optimized if the code is instrumented

• gh-111772: Specialize slot loads and stores for _Py_T_OBJECT as well as Py_T_OBJECT_EX

• gh-111666: Speed up BaseExceptionGroup.derive(), BaseExceptionGroup.subgroup(), and BaseExceptionGroup.split() by changing how they parse passed arguments.

• gh-111654: Fix runtime crash when some error happens in opcode LOAD_FROM_DICT_OR_DEREF.

• gh-111623: Add support for sharing tuples between interpreters using the cross-interpreter API. Patch by Anthony Shaw.

• gh-111354: The oparg of YIELD_VALUE is now 1 if the instruction is part of a yield-from or await, and 0 otherwise.

  The SUSPENDED frame state is now split into SUSPENDED and SUSPENDED_YIELD_FROM. This simplifies the code in _PyGen_yf.

• gh-111520: Merge the Tier 1 (bytecode) and Tier 2 (micro-ops) interpreters together, moving the Tier 2 interpreter loop and switch into _PyEval_EvalFrameDefault() in Python/ceval.c. The Python/executor.c file is gone. Also the TIER_ONE and TIER_TWO macros are now handled by the code generator.

  Beware! This changes the environment variables to enable micro-ops and their debugging to PYTHON_UOPS and PYTHON_LLTRACE.

• gh-109181: Speed up Traceback object creation by lazily compute the line number. Patch by Pablo Galindo

• gh-111420: Allow type comments in parenthesized with statements

• gh-111438: Add support for sharing floats between interpreters using the cross-interpreter API. Patch by Anthony Shaw.

• gh-111435: Add support for sharing of True and False between interpreters using the cross-interpreter API. Patch by Anthony Shaw.

• gh-102388: Fix a bug where iso2022_jp_3 and iso2022_jp_2004 codecs read out of bounds

• gh-111366: Fix an issue in the codeop that was causing SyntaxError exceptions raised in the presence of invalid syntax to not contain precise error messages. Patch by Pablo Galindo

• gh-111380: Fix a bug that was causing SyntaxWarning to appear twice when parsing if invalid syntax is encountered later. Patch by Pablo galindo

• gh-111374: Added a new environment variable PYTHON_FROZEN_MODULES. It determines whether or not frozen modules are ignored by the import machinery, equivalent of the -X frozen_modules command-line option.

• gh-111354: Remove oparg from YIELD_VALUE. Change oparg of RESUME to include information about the except-depth. These changes make it possible to simplify the code in generator close.

• gh-94438: Fix a regression that prevented jumping across is None and is not None when debugging. Patch by Savannah Ostrowski.

• gh-67224: Show source lines in tracebacks when using the -c option when running Python. Patch by Pablo Galindo

• gh-111123: Fix a bug where a global declaration in an except block is rejected when the global is used in the else block.

• gh-110938: Fix error messages for indented blocks with functions and classes with generic type parameters. Patch by Pablo Galindo

• gh-109214: Remove unnecessary instruction pointer updates before returning from frames.

• gh-110912: Correctly display the traceback for MemoryError exceptions using the traceback module. Patch by Pablo Galindo

• gh-109894: Fixed crash due to improperly initialized static MemoryError in subinterpreter.

• gh-110892: Return NULL for PyTrace_RETURN events caused by an exception

• gh-110864: Fix argument parsing by _PyArg_UnpackKeywordsWithVararg for functions defining pos-or-keyword, vararg, and kw-only parameters.

• gh-109094: Replace prev_instr on the interpreter frame by instr_ptr which points to the beginning of the instruction that is currently executing (or will execute once the frame resumes).

• gh-110805: Allow the repl to show source code and complete tracebacks. Patch by Pablo Galindo

• gh-110722: Add PYTHON_PRESITE=package.module to import a module early in the interpreter lifecycle before site.py is executed. Python needs to be built in debug mode for this option to exist.

• gh-110481: Implement biased reference counting in --disable-gil builds.

• gh-110543: Fix regression in Python 3.12 where types.CodeType.replace() would produce a broken code object if called on a module or class code object that contains a comprehension. Patch by Jelle Zijlstra.

• gh-89519: Removed chained classmethod descriptors (introduced in bpo-19072). This can no longer be used to wrap other descriptors such as property. The core design of this feature was flawed and caused a number of downstream problems. To “pass-through” a classmethod, consider using the __wrapped__ attribute that was added in Python 3.10.

• gh-103615: Use local events for opcode tracing

• bpo-46657: Add mimalloc memory allocator support.

• gh-106718: When PyConfig.stdlib_dir is explicitly set, it’s now respected and won’t be overridden by PyConfig.home.

• gh-106905: Fix incorrect SystemError about AST constructor recursion depth mismatch.

• gh-100445: Improve error message for unterminated strings with escapes.

• bpo-45759: Improved error messages for elif/else statements not matching any valid statements. Patch by Jeremiah Vivian.

Library

• gh-111942: Fix SystemError in the TextIOWrapper constructor with non-encodable “errors” argument in non-debug mode.

• gh-111995: Added the NI_IDN constant to the socket module when present in C at build time for use with socket.getnameinfo().

• gh-109538: Issue warning message instead of having RuntimeError be displayed when event loop has already been closed at StreamWriter.__del__().

• gh-111942: Fix crashes in io.TextIOWrapper.reconfigure() when pass invalid arguments, e.g. non-string encoding.

• gh-111460: curses: restore wide character support (including curses.unget_wch() and get_wch()) on macOS, which was unavailable due to a regression in Python 3.12.

• gh-103791: contextlib.suppress now supports suppressing exceptions raised as part of a BaseExceptionGroup, in addition to the recent support for ExceptionGroup.

• gh-111835: The mmap.mmap class now has an seekable() method that can be used when a seekable file-like object is required. The seek() method now returns the new absolute position. Patch by Donghee Na.

• gh-111804: Remove posix.fallocate() under WASI as the underlying posix_fallocate() is not available in WASI preview2.

• gh-111841: Fix truncating arguments on an embedded null character in os.putenv() and os.unsetenv() on Windows.

• gh-111768: wsgiref.util.is_hop_by_hop() is now exposed correctly in __all__.

• gh-80731: Avoid executing the default function in cmd.Cmd in an except block

• gh-111541: Fix doctest for SyntaxError not-builtin subclasses.

• gh-111719: Add extra argument validation for alias command in pdb

• gh-111482: time: Make time.clock_gettime() and time.clock_gettime_ns() functions up to 2x faster by faster calling convention. Patch by Victor Stinner.

• gh-110894: Call loop exception handler for exceptions in client_connected_cb of asyncio.start_server() so that applications can handle it. Patch by Kumar Aditya.

• gh-111531: Fix reference leaks in bind_class() and bind_all() methods of tkinter widgets.

• gh-111246: asyncio.loop.create_unix_server() will now automatically remove the Unix socket when the server is closed.

• gh-111356: Added io.text_encoding(), io.DEFAULT_BUFFER_SIZE, and io.IncrementalNewlineDecoder to io.__all__.

• gh-66425: Remove the code to set the REMOTE_HOST header from wsgiref module, as it is unreachable. This header is used for performance reasons, which is not necessary in the wsgiref module.

• gh-111429: Speed up pathlib.PurePath.relative_to() and is_relative_to().

• gh-111342: Fixed typo in math.sumprod().

• gh-68166: Remove mention of not supported “vsapi” element type in tkinter.ttk.Style.element_create(). Add tests for element_create() and other ttk.Style methods. Add examples for element_create() in the documentation.

• gh-111388: Add show_group parameter to traceback.format_exception_only(), which allows to format ExceptionGroup instances.

• gh-79033: Another attempt at fixing asyncio.Server.wait_closed(). It now blocks until both conditions are true: the server is closed, and there are no more active connections. (This means that in some cases where in 3.12.0 this function would incorrectly have returned immediately, it will now block; in particular, when there are no active connections but the server hasn’t been closed yet.)

• gh-111259: Optimize recursive wildcards in pathlib.

• gh-111295: Fix time not checking for errors when initializing.

• gh-111253: Add error checking during _socket module init.

• gh-111251: Fix _blake2 not checking for errors when initializing.

• gh-111233: Fix select not checking for errors when initializing.

• gh-111230: Fix ssl not checking for errors when initializing.

• gh-111174: Fix crash in io.BytesIO.getbuffer() called repeatedly for empty BytesIO.

• gh-111187: Postpone removal version for locale.getdefaultlocale() to Python 3.15.

• gh-111159: Fix doctest output comparison for exceptions with notes.

• gh-110910: Fix invalid state handling in asyncio.TaskGroup and asyncio.Timeout. They now raise proper RuntimeError if they are improperly used and are left in consistent state after this.

• gh-111092: Make turtledemo run without default root enabled.

• gh-110944: Support alias and convenience vars for pdb completion

• gh-110745: Added newline parameter to pathlib.Path.read_text(). Patch by Junya Okabe.

• gh-84583: Make pdb enter post-mortem mode even for SyntaxError

• gh-80675: Set f_trace_lines = True on all frames upon pdb.set_trace()

• gh-110771: Expose the setup and cleanup portions of asyncio.run_forever() as the standalone methods asyncio.run_forever_setup() and asyncio.run_forever_cleanup(). This allows for tighter integration with GUI event loops.

• gh-110774: Support setting the asyncio.Runner loop_factory kwarg in unittest.IsolatedAsyncioTestCase

• gh-110392: Fix tty.setraw() and tty.setcbreak(): previously they returned partially modified list of the original tty attributes. tty.cfmakeraw() and tty.cfmakecbreak() now make a copy of the list of special characters before modifying it.

• gh-59013: Make line number of function breakpoint more precise in pdb

• gh-88434: Emit deprecation warning for non-integer numbers in gettext functions and methods that consider plural forms even if the translation was not found.

• gh-110395: Ensure that select.kqueue() objects correctly appear as closed in forked children, to prevent operations on an invalid file descriptor.

• gh-110196: Add __reduce__ method to IPv6Address in order to keep scope_id

• gh-109747: Improve errors for unsupported look-behind patterns. Now re.error is raised instead of OverflowError or RuntimeError for too large width of look-behind pattern.

• gh-109466: Add the ipaddress.IPv4Address.ipv6_mapped property, which returns the IPv4-mapped IPv6 address.

• gh-85098: Implement the CLI of the symtable module and improve the repr of Symbol.

• gh-108791: Improved error handling in pdb command line interface, making it produce more concise error messages.

• gh-105931: Change compileall to only strip the stripdir prefix from the full path recorded in the compiled .pyc file, when the prefix matches the start of the full path in its entirety. When the prefix does not match, no stripping is performed and a warning to this effect is displayed.

  Previously all path components of the stripdir prefix that matched the full path were removed, while those that did not match were left alone (including ones interspersed between matching components).

• gh-107431: Make the DictProxy and ListProxy types in multiprocessing.managers Generic Alias Types for [] use in typing contexts.

• gh-72904: Add glob.translate(). This function converts a pathname with shell-style wildcards to a regular expression.

• gh-90026: Define USE_XATTRS on Cygwin so that XATTR-related functions in the os module become available.

• gh-90890: New methods mailbox.Maildir.get_info(), mailbox.Maildir.set_info(), mailbox.Maildir.get_flags(), mailbox.Maildir.set_flags(), mailbox.Maildir.add_flag(), mailbox.Maildir.remove_flag(). These methods speed up accessing a message’s info and/or flags and are useful when it is not necessary to access the message’s contents, as when iterating over a Maildir to find messages with specific flags.

• gh-102956: Fix returning of empty byte strings after seek in zipfile module

• gh-102895: Added a parameter local_exit for code.interact() to prevent exit() and quit from closing sys.stdin and raise SystemExit.

• gh-97928: Change the behavior of tkinter.Text.count(). It now always returns an integer if one or less counting options are specified. Previously it could return a single count as a 1-tuple, an integer (only if option "update" was specified) or None if no items found. The result is now the same if wantobjects is set to 0.

• gh-96954: Switch the storage of the unicode codepoint names to use a different data-structure, a directed acyclic word graph. This makes the unicodedata shared library about 440 KiB smaller. Contributed by Carl Friedrich Bolz-Tereick using code from the PyPy project.

• gh-73561: Omit the interface scope from an IPv6 address when used as Host header by http.client.

• gh-86826: zipinfo now supports the full range of values in the TZ string determined by RFC 8536 and detects all invalid formats. Both Python and C implementations now raise exceptions of the same type on invalid data.

Tests

• gh-111808: Make the default value of test.support.infinite_recursion() to be conditional based on whether optimizations were used when compiling the interpreter. This helps with platforms like WASI whose stack size is greatly restricted in debug builds.

• gh-110722: Gathering line coverage of standard libraries within the regression test suite is now precise, as well as much faster. Patch by Łukasz Langa.

• gh-110367: Make regrtest --verbose3 option compatible with --huntrleaks -jN options. The ./python -m test -j1 -R 3:3 --verbose3 command now works as expected. Patch by Victor Stinner.

• gh-111165: Remove no longer used functions run_unittest() and run_doctest() from the test.support module.

• gh-110932: Fix regrtest if the SOURCE_DATE_EPOCH environment variable is defined: use the variable value as the random seed. Patch by Victor Stinner.

• gh-110995: test_gdb: Fix detection of gdb built without Python scripting support. Patch by Victor Stinner.

• gh-110918: Test case matching patterns specified by options --match, --ignore, --matchfile and --ignorefile are now tested in the order of specification, and the last match determines whether the test case be run or ignored.

• gh-108747: Add unit test for usercustomize and sitecustomize hooks from site.

Build

• gh-96954: Make make regen-unicodedata work for out-of-tree builds of CPython.

• gh-112088: Add Tools/build/regen-configure.sh script to regenerate the configure with an Ubuntu container image. The quay.io/tiran/cpython_autoconf:271 container image (tiran/cpython_autoconf) is no longer used. Patch by Victor Stinner.

• gh-111046: For wasi-threads, memory is now exported to fix compatibility issues with some wasm runtimes.

• gh-110828: AIX 32bit needs -latomic to build the _testcapi extension module.

• gh-85283: The errno, md5, resource, winsound, _ctypes_test, _multiprocessing.posixshmem, _scproxy, _stat, _testimportmultiple and _uuid C extensions are now built with the limited C API. Patch by Victor Stinner.

Windows

• gh-111856: Fixes fstat() on file systems that do not support file ID requests. This includes FAT32 and exFAT.

• gh-111293: Fix os.DirEntry.inode dropping higher 64 bits of a file id on some filesystems on Windows.

• gh-110913: WindowsConsoleIO now correctly chunks large buffers without splitting up UTF-8 sequences.

macOS

• gh-59703: For macOS framework builds, in getpath.c use the system dladdr function to find the path to the shared library rather than depending on deprecated macOS APIs.

• gh-110950: Update macOS installer to include an upstream Tcl/Tk fix for the Secure coding is not enabled for restorable state! warning encountered in Tkinter on macOS 14 Sonoma.

• gh-111015: Ensure that IDLE.app and Python Launcher.app are installed with appropriate permissions on macOS builds.

• gh-71383: Update macOS installer to include an upstream Tcl/Tk fix for the ttk::ThemeChanged error encountered in Tkinter.

• gh-92603: Update macOS installer to include a fix accepted by upstream Tcl/Tk for a crash encountered after the first tkinter.Tk() instance is destroyed.

IDLE

• bpo-35668: Add docstrings to the IDLE debugger module. Fix two bugs: initialize Idb.botframe (should be in Bdb); in Idb.in_rpc_code, check whether prev_frame is None before trying to use it. Greatly expand test_debugger.

Tools/Demos

• gh-111903: Argument Clinic now supports the @critical_section directive that instructs Argument Clinic to generate a critical section around the function call, which locks the self object in --disable-gil builds. Patch by Sam Gross.

C API

• gh-112026: Add again the private _PyThreadState_UncheckedGet() function as an alias to the new public PyThreadState_GetUnchecked() function. Patch by Victor Stinner.

• gh-112026: Restore the removed _PyDict_GetItemStringWithError() function. It is used by numpy. Patch by Victor Stinner.

• gh-112026: Restore removed private C API functions, macros and structures which have no simple replacement for now:

  • _PyDict_GetItem_KnownHash()

  • _PyDict_NewPresized()

  • _PyHASH_BITS

  • _PyHASH_IMAG

  • _PyHASH_INF

  • _PyHASH_MODULUS

  • _PyHASH_MULTIPLIER

  • _PyLong_Copy()

  • _PyLong_FromDigits()

  • _PyLong_New()

  • _PyLong_Sign()

  • _PyObject_CallMethodId()

  • _PyObject_CallMethodNoArgs()

  • _PyObject_CallMethodOneArg()

  • _PyObject_CallOneArg()

  • _PyObject_EXTRA_INIT

  • _PyObject_FastCallDict()

  • _PyObject_GetAttrId()

  • _PyObject_Vectorcall()

  • _PyObject_VectorcallMethod()

  • _PyStack_AsDict()

  • _PyThread_CurrentFrames()

  • _PyUnicodeWriter structure

  • _PyUnicodeWriter_Dealloc()

  • _PyUnicodeWriter_Finish()

  • _PyUnicodeWriter_Init()

  • _PyUnicodeWriter_Prepare()

  • _PyUnicodeWriter_PrepareKind()

  • _PyUnicodeWriter_WriteASCIIString()

  • _PyUnicodeWriter_WriteChar()

  • _PyUnicodeWriter_WriteLatin1String()

  • _PyUnicodeWriter_WriteStr()

  • _PyUnicodeWriter_WriteSubstring()

  • _PyUnicode_AsString()

  • _PyUnicode_FromId()

  • _PyVectorcall_Function()

  • _Py_IDENTIFIER()

  • _Py_c_abs()

  • _Py_c_diff()

  • _Py_c_neg()

  • _Py_c_pow()

  • _Py_c_prod()

  • _Py_c_quot()

  • _Py_c_sum()

  • _Py_static_string()

  • _Py_static_string_init()

  Patch by Victor Stinner.

• gh-112026: Add again <ctype.h> and <unistd.h> includes in Python.h, but don’t include them in the limited C API version 3.13 and newer. Patch by Victor Stinner.

• gh-111956: Add internal-only one-time initialization API: _PyOnceFlag and _PyOnceFlag_CallOnce.

• gh-111262: Add PyDict_Pop() and PyDict_PopString() functions: remove a key from a dictionary and optionally return the removed value. This is similar to dict.pop(), but without the default value and not raising KeyError if the key missing. Patch by Stefan Behnel and Victor Stinner.

• gh-111863: Rename Py_NOGIL to Py_GIL_DISABLED. Patch by Hugo van Kemenade.

• gh-111138: Add PyList_Extend() and PyList_Clear() functions: similar to Python list.extend() and list.clear() methods. Patch by Victor Stinner.

• gh-108765: On Windows, Python.h no longer includes the <stddef.h> standard header file. If needed, it should now be included explicitly. Patch by Victor Stinner.

• gh-111569: Implement “Python Critical Sections” from PEP 703. These are macros to help replace the GIL with per-object locks in the --disable-gil build of CPython. The macros are no-ops in the default build.

• gh-111506: In the limited C API version 3.13, Py_SET_REFCNT() function is now implemented as an opaque function call. Patch by Victor Stinner.

• gh-108082: Add PyErr_FormatUnraisable() function.

• gh-110964: Move the undocumented private _PyArg functions and _PyArg_Parser structure to internal C API (pycore_modsupport.h). Patch by Victor Stinner.

• gh-110815: Support non-ASCII keyword