Changelog¶

Tests¶

• gh-142836: Accommodated Solaris in test_pdb.test_script_target_anonymous_pipe.

Library¶

• gh-142783: Fix zoneinfo use-after-free with descriptor _weak_cache. a descriptor as _weak_cache could cause crashes during object creation. The fix ensures proper reference counting for descriptor-provided objects.

• gh-142594: Fix crash in TextIOWrapper.close() when the underlying buffer’s closed property calls detach().

• gh-142451: hmac: Ensure that the HMAC.block_size attribute is correctly copied by HMAC.copy. Patch by Bénédikt Tran.

• gh-142495: collections.defaultdict now prioritizes __setitem__() when inserting default values from default_factory. This prevents race conditions where a default value would overwrite a value set before default_factory returns.

• gh-142651: unittest.mock: fix a thread safety issue where Mock.call_count may return inaccurate values when the mock is called concurrently from multiple threads.

• gh-142595: Added type check during initialization of the decimal module to prevent a crash in case of broken stdlib. Patch by Sergey B Kirpichev.

• gh-142556: Fix crash when a task gets re-registered during finalization in asyncio. Patch by Kumar Aditya.

• gh-123241: Avoid reference count operations in garbage collection of ctypes objects.

• gh-112527: The help text for required options in argparse no longer extended with “ (default: None)”.

• gh-142346: Fix usage formatting for mutually exclusive groups in argparse when they are preceded by positional arguments or followed or intermixed with other optional arguments.

• gh-142315: Pdb can now run scripts from anonymous pipes used in process substitution. Patch by Bartosz Sławecki.

• gh-142332: Fix usage formatting for positional arguments in mutually exclusive groups in argparse. in argparse.

• gh-142282: Fix winreg.QueryValueEx() to not accidentally read garbage buffer under race condition.

• gh-75949: Fix argparse to preserve | separators in mutually exclusive groups when the usage line wraps due to length.

• gh-142267: Improve argparse performance by caching the formatter used for argument validation.

• gh-68552: MisplacedEnvelopeHeaderDefect and Missing header name defects are now correctly passed to the handle_defect method of policy in FeedParser.

• gh-142006: Fix a bug in the email.policy.default folding algorithm which incorrectly resulted in a doubled newline when a line ending at exactly max_line_length was followed by an unfoldable token.

• gh-105836: Fix asyncio.run_coroutine_threadsafe() leaving underlying cancelled asyncio task running.

Core and Builtins¶

• gh-142737: Tracebacks will be displayed in fallback mode even if io.open() is lost. Previously, this would crash the interpreter. Patch by Bartosz Sławecki.

• gh-142554: Fix a crash in divmod() when _pylong.int_divmod() does not return a tuple of length two exactly. Patch by Bénédikt Tran.

• gh-142531: Fix a free-threaded GC performance regression. If there are many untracked tuples, the GC will run too often, resulting in poor performance. The fix is to include untracked tuples in the “long lived” object count. The number of frozen objects is also now included since the free-threaded GC must scan those too.

• gh-142402: Fix reference counting when adjacent literal parts are merged while constructing string.templatelib.Template, preventing the displaced string object from leaking.

• gh-133932: Fix crash in the free threading build when clearing frames that hold tagged integers.

• gh-142343: Fix SIGILL crash on m68k due to incorrect assembly constraint.

• gh-137007: Fix a bug during JIT compilation failure which caused garbage collection debug assertions to fail.

C API¶

• gh-142589: Fix PyUnstable_Object_IsUniqueReferencedTemporary() handling of tagged ints on the interpreter stack.

• gh-142571: PyUnstable_CopyPerfMapFile() now checks that opening the file succeeded before flushing.

Build¶

• gh-142454: When calculating the digest of the JIT stencils input, sort the hashed files by filenames before adding their content to the hasher. This ensures deterministic hash input and hence deterministic hash, independent on filesystem order.

• gh-141808: When running make clean-retain-profile, keep the generated JIT stencils. That way, the stencils are not generated twice when Profile-guided optimization (PGO) is used. It also allows distributors to supply their own pre-built JIT stencils.

• gh-138061: Ensure reproducible builds by making JIT stencil header generation deterministic.

Security¶

• gh-142145: Remove quadratic behavior in xml.minidom node ID cache clearing.

• gh-119452: Fix a potential memory denial of service in the http.server module. When a malicious user is connected to the CGI server on Windows, it could cause an arbitrary amount of memory to be allocated. This could have led to symptoms including a MemoryError, swapping, out of memory (OOM) killed processes or containers, or even system crashes.

Library¶

• gh-140797: Revert changes to the undocumented re.Scanner class. Capturing groups are still allowed for backward compatibility, although using them can lead to incorrect result. They will be forbidden in future Python versions.

• gh-142206: The resource tracker in the multiprocessing module now uses the original communication protocol, as in Python 3.14.0 and below, by default. This avoids issues with upgrading Python while it is running. (Note that such ‘in-place’ upgrades are not tested.) The tracker remains compatible with subprocesses that use new protocol (that is, subprocesses using Python 3.13.10, 3.14.1 and 3.15).

• gh-142214: Fix two regressions in dataclasses in Python 3.14.1 related to annotations.

  • An exception is no longer raised if slots=True is used and the __init__ method does not have an __annotate__ attribute (likely because init=False was used).

  • An exception is no longer raised if annotations are requested on the __init__ method and one of the fields is not present in the class annotations. This can occur in certain dynamic scenarios.

  Patch by Jelle Zijlstra.

Core and Builtins¶

• gh-142218: Fix crash when inserting into a split table dictionary with a non str key that matches an existing key.

Library¶

• gh-116738: Fix cmath data race when initializing trigonometric tables with subinterpreters.

Windows¶

• gh-139810: Installing with py install 3[.x]-dev will now select final versions as well as prereleases.

Tools/Demos¶

• gh-141692: Each slice of an iOS XCframework now contains a lib folder that contains a symlink to the libpython dylib. This allows binary modules to be compiled for iOS using dynamic libreary linking, rather than Framework linking.

• gh-141442: The iOS testbed now correctly handles test arguments that contain spaces.

• gh-140702: The iOS testbed app will now expose the GITHUB_ACTIONS environment variable to iOS apps being tested.

• gh-137484: Have Tools/wasm/wasi put the build Python into a directory named after the build triple instead of “build”.

• gh-137248: Add a --logdir option to Tools/wasm/wasi for specifying where to write log files.

• gh-137243: Have Tools/wasm/wasi detect a WASI SDK install in /opt when it was directly extracted from a release tarball.

Tests¶

• gh-140482: Preserve and restore the state of stty echo as part of the test environment.

• gh-140082: Update python -m test to set FORCE_COLOR=1 when being run with color enabled so that unittest which is run by it with redirected output will output in color.

• gh-139208: Fix regrtest --fast-ci --verbose: don’t ignore the --verbose option anymore. Patch by Victor Stinner.

• gh-136442: Use exitcode 1 instead of 5 if unittest.TestCase.setUpClass() raises an exception

Security¶

• gh-139700: Check consistency of the zip64 end of central directory record. Support records with “zip64 extensible data” if there are no bytes prepended to the ZIP file.

• gh-139283: sqlite3: correctly handle maximum number of rows to fetch in Cursor.fetchmany and reject negative values for Cursor.arraysize. Patch by Bénédikt Tran.

• gh-137836: Add support of the “plaintext” element, RAWTEXT elements “xmp”, “iframe”, “noembed” and “noframes”, and optionally RAWTEXT element “noscript” in html.parser.HTMLParser.

• gh-136063: email.message: ensure linear complexity for legacy HTTP parameters parsing. Patch by Bénédikt Tran.

• gh-136065: Fix quadratic complexity in os.path.expandvars().

• gh-119451: Fix a potential memory denial of service in the http.client module. When connecting to a malicious server, it could cause an arbitrary amount of memory to be allocated. This could have led to symptoms including a MemoryError, swapping, out of memory (OOM) killed processes or containers, or even system crashes.

• gh-119342: Fix a potential memory denial of service in the plistlib module. When reading a Plist file received from untrusted source, it could cause an arbitrary amount of memory to be allocated. This could have led to symptoms including a MemoryError, swapping, out of memory (OOM) killed processes or containers, or even system crashes.

Library¶

• gh-74389: When the stdin being used by a subprocess.Popen instance is closed, this is now ignored in subprocess.Popen.communicate() instead of leaving the class in an inconsistent state.

• gh-87512: Fix subprocess.Popen.communicate() timeout handling on Windows when writing large input. Previously, the timeout was ignored during stdin writing, causing the method to block indefinitely if the child process did not consume input quickly. The stdin write is now performed in a background thread, allowing the timeout to be properly enforced.

• gh-141473: When subprocess.Popen.communicate() was called with input and a timeout and is called for a second time after a TimeoutExpired exception before the process has died, it should no longer hang.

• gh-59000: Fix pdb breakpoint resolution for class methods when the module defining the class is not imported.

• gh-141570: Support file-like object raising OSError from fileno() in color detection (_colorize.can_colorize()). This can occur when sys.stdout is redirected.

• gh-141659: Fix bad file descriptor errors from _posixsubprocess on AIX.

• gh-141600: Fix musl version detection on Void Linux.

• gh-141497: ipaddress: ensure that the methods IPv4Network.hosts() and IPv6Network.hosts() always return an iterator.

• gh-140938: The statistics.stdev() and statistics.pstdev() functions now raise a ValueError when the input contains an infinity or a NaN.

• gh-124111: Updated Tcl threading configuration in _tkinter to assume that threads are always available in Tcl 9 and later.

• gh-137109: The os.fork and related forking APIs will no longer warn in the common case where Linux or macOS platform APIs return the number of threads in a process and find the answer to be 1 even when a os.register_at_fork() after_in_parent= callback (re)starts a thread.

• gh-141314: Fix assertion failure in io.TextIOWrapper.tell() when reading files with standalone carriage return (\r) line endings.

• gh-141311: Fix assertion failure in io.BytesIO.readinto() and undefined behavior arising when read position is above capcity in io.BytesIO.

• gh-141141: Fix a thread safety issue with base64.b85decode(). Contributed by Benel Tayar.

• gh-137969: Fix annotationlib.ForwardRef.evaluate() returning ForwardRef objects which don’t update with new globals.

• gh-140911: collections: Ensure that the methods UserString.rindex() and UserString.index() accept collections.UserString instances as the sub argument.

• gh-140797: The undocumented re.Scanner class now forbids regular expressions containing capturing groups in its lexicon patterns. Patterns using capturing groups could previously lead to crashes with segmentation fault. Use non-capturing groups (?:…) instead.

• gh-125115: Refactor the pdb parsing issue so positional arguments can pass through intuitively.

• gh-140815: faulthandler now detects if a frame or a code object is invalid or freed. Patch by Victor Stinner.

• gh-100218: Correctly set errno when socket.if_nametoindex() or socket.if_indextoname() raise an OSError. Patch by Bénédikt Tran.

• gh-140875: Fix handling of unclosed character references (named and numerical) followed by the end of file in html.parser.HTMLParser with convert_charrefs=False.

• gh-140734: multiprocessing: fix off-by-one error when checking the length of a temporary socket file path. Patch by Bénédikt Tran.

• gh-140874: Bump the version of pip bundled in ensurepip to version 25.3

• gh-140691: In urllib.request, when opening a FTP URL fails because a data connection cannot be made, the control connection’s socket is now closed to avoid a ResourceWarning.

• gh-103847: Fix hang when cancelling process created by asyncio.create_subprocess_exec() or asyncio.create_subprocess_shell(). Patch by Kumar Aditya.

• gh-120057: Add os.reload_environ() to os.__all__.

• gh-140228: Avoid making unnecessary filesystem calls for frozen modules in linecache when the global module cache is not present.

• gh-140590: Fix arguments checking for the functools.partial.__setstate__() that may lead to internal state corruption and crash. Patch by Sergey Miryanov.

• gh-125434: Display thread name in faulthandler on Windows. Patch by Victor Stinner.

• gh-140634: Fix a reference counting bug in os.sched_param.__reduce__().

• gh-140633: Ignore AttributeError when setting a module’s __file__ attribute when loading an extension module packaged as Apple Framework.

• gh-140593: xml.parsers.expat: Fix a memory leak that could affect users with ElementDeclHandler() set to a custom element declaration handler. Patch by Sebastian Pipping.

• gh-140607: Inside io.RawIOBase.read(), validate that the count of bytes returned by io.RawIOBase.readinto() is valid (inside the provided buffer).

• gh-138162: Fix logging.LoggerAdapter with merge_extra=True and without the extra argument.

• gh-138774: ast.unparse() now generates full source code when handling ast.Interpolation nodes that do not have a specified source.

• gh-140474: Fix memory leak in array.array when creating arrays from an empty str and the u type code.

• gh-137530: dataclasses Fix annotations for generated __init__ methods by replacing the annotations that were in-line in the generated source code with __annotate__ functions attached to the methods.

• gh-140348: Fix regression in Python 3.14.0 where using the | operator on a typing.Union object combined with an object that is not a type would raise an error.

• gh-140272: Fix memory leak in the clear() method of the dbm.gnu database.

• gh-140041: Fix import of ctypes on Android and Cygwin when ABI flags are present.

• gh-140120: Fixed a memory leak in hmac when it was using the hacl-star backend. Discovered by @ashm-dev using AddressSanitizer.

• gh-139905: Add suggestion to error message for typing.Generic subclasses when cls.__parameters__ is missing due to a parent class failing to call super().__init_subclass__() in its __init_subclass__.

• gh-139894: Fix incorrect sharing of current task with the child process while forking in asyncio. Patch by Kumar Aditya.

• gh-139845: Fix to not print KeyboardInterrupt twice in default asyncio REPL.

• gh-139783: Fix inspect.getsourcelines() for the case when a decorator is followed by a comment or an empty line.

• gh-139809: Prevent premature colorization of subparser prog in argparse.ArgumentParser.add_subparsers() to respect color environment variable changes after parser creation.

• gh-139736: Fix excessive indentation in the default argparse HelpFormatter. Patch by Alexander Edland.

• gh-70765: http.server: fix default handling of HTTP/0.9 requests in BaseHTTPRequestHandler. Previously, BaseHTTPRequestHandler.parse_request() incorrectly waited for headers in the request although those are not supported in HTTP/0.9. Patch by Bénédikt Tran.

• gh-63161: Fix tokenize.detect_encoding(). Support non-UTF-8 shebang and comments if non-UTF-8 encoding is specified. Detect decoding error for non-UTF-8 encoding. Detect null bytes in source code.

• gh-139391: Fix an issue when, on non-Windows platforms, it was not possible to gracefully exit a python -m asyncio process suspended by Ctrl+Z and later resumed by fg other than with kill.

• gh-101828: Fix 'shift_jisx0213', 'shift_jis_2004', 'euc_jisx0213' and 'euc_jis_2004' codecs truncating null chars as they were treated as part of multi-character sequences.

• gh-139289: Do a real lazy-import on rlcompleter in pdb and restore the existing completer after importing rlcompleter.

• gh-139246: fix: paste zero-width in default repl width is wrong.

• gh-90949: Add SetAllocTrackerActivationThreshold() and SetAllocTrackerMaximumAmplification() to xmlparser objects to prevent use of disproportional amounts of dynamic memory from within an Expat parser. Patch by Bénédikt Tran.

• gh-139210: Fix use-after-free when reporting unknown event in xml.etree.ElementTree.iterparse(). Patch by Ken Jin.

• gh-138860: Lazy import rlcompleter in pdb to avoid deadlock in subprocess.

• gh-112729: Fix crash when calling concurrent.interpreters.create() when the process is out of memory.

• gh-135729: Fix unraisable exception during finalization when using concurrent.interpreters in the REPL.

• gh-139076: Fix a bug in the pydoc module that was hiding functions in a Python module if they were implemented in an extension module and the module did not have __all__.

• gh-139065: Fix trailing space before a wrapped long word if the line length is exactly width in textwrap.

• gh-139001: Fix race condition in pathlib.Path on the internal _raw_paths field.

• gh-138813: multiprocessing.BaseProcess defaults kwargs to None instead of a shared dictionary.

• gh-138993: Dedent credits text.

• gh-138891: Fix SyntaxError when inspect.get_annotations(f, eval_str=True) is called on a function annotated with a PEP 646 star_expression

• gh-130567: Fix possible crash in locale.strxfrm() due to a platform bug on macOS.

• gh-138859: Fix generic type parameterization raising a TypeError when omitting a ParamSpec that has a default which is not a list of types.

• gh-138764: Prevent annotationlib.call_annotate_function() from calling __annotate__ functions that don’t support VALUE_WITH_FAKE_GLOBALS in a fake globals namespace with empty globals.

  Make FORWARDREF and STRING annotations fall back to using VALUE annotations in the case that neither their own format, nor VALUE_WITH_FAKE_GLOBALS are supported.

• gh-138775: Use of python -m with base64 has been fixed to detect input from a terminal so that it properly notices EOF.

• gh-138779: Support device numbers larger than 2**63-1 for the st_rdev field of the os.stat_result structure.

• gh-137706: Fix the partial evaluation of annotations that use typing.Annotated[T, x] where T is a forward reference.

• gh-88375: Fix normalization of the robots.txt rules and URLs in the urllib.robotparser module. No longer ignore trailing ?. Distinguish raw special characters ?, = and & from the percent-encoded ones.

• gh-111788: Fix parsing errors in the urllib.robotparser module. Don’t fail trying to parse weird paths. Don’t fail trying to decode non-UTF-8 robots.txt files.

• gh-98896: Fix a failure in multiprocessing resource_tracker when SharedMemory names contain colons. Patch by Rani Pinchuk.

• gh-138425: Fix partial evaluation of annotationlib.ForwardRef objects which rely on names defined as globals.

• gh-138432: zoneinfo.reset_tzpath() will now convert any os.PathLike objects it receives into strings before adding them to TZPATH. It will raise TypeError if anything other than a string is found after this conversion. If given an os.PathLike object that represents a relative path, it will now raise ValueError instead of TypeError, and present a more informative error message.

• gh-138008: Fix segmentation faults in the ctypes module due to invalid argtypes. Patch by Dung Nguyen.

• gh-60462: Fix locale.strxfrm() on Solaris (and possibly other platforms).

• gh-138239: The REPL now highlights type as a soft keyword in type statements.

• gh-138204: Forbid expansion of shared anonymous memory maps on Linux, which caused a bus error.

• gh-138010: Fix an issue where defining a class with an @warnings.deprecated-decorated base class may not invoke the correct __init_subclass__() method in cases involving multiple inheritance. Patch by Brian Schubert.

• gh-138151: In annotationlib, improve evaluation of forward references to nonlocal variables that are not yet defined when the annotations are initially evaluated.

• gh-137317: inspect.signature() now correctly handles classes that use a descriptor on a wrapped __init__() or __new__() method. Contributed by Yongyu Yan.

• gh-137754: Fix import of the zoneinfo module if the C implementation of the datetime module is not available.

• gh-137490: Handle ECANCELED in the same way as EINTR in signal.sigwaitinfo() on NetBSD.

• gh-137477: Fix inspect.getblock(), inspect.getsourcelines() and inspect.getsource() for generator expressions.

• gh-137044: Return large limit values as positive integers instead of negative integers in resource.getrlimit(). Accept large values and reject negative values (except RLIM_INFINITY) for limits in resource.setrlimit().

• gh-75989: tarfile.TarFile.extractall() and tarfile.TarFile.extract() now overwrite symlinks when extracting hardlinks. (Contributed by Alexander Enrique Urieles Nieto in gh-75989.)

• gh-137017: Fix threading.Thread.is_alive to remain True until the underlying OS thread is fully cleaned up. This avoids false negatives in edge cases involving thread monitoring or premature threading.Thread.is_alive calls.

• gh-137273: Fix debug assertion failure in locale.setlocale() on Windows.

• gh-137239: heapq: Update heapq.__all__ with *_max functions.

• gh-81325: tarfile.TarFile now accepts a path-like when working on a tar archive. (Contributed by Alexander Enrique Urieles Nieto in gh-81325.)

• gh-137185: Fix a potential async-signal-safety issue in faulthandler when printing C stack traces.

• gh-136914: Fix retrieval of doctest.DocTest.lineno for objects decorated with functools.cache() or functools.cached_property.

• gh-136912: hmac.digest() now properly handles large keys and messages by falling back to the pure Python implementation when necessary. Patch by Bénédikt Tran.

• gh-83424: Allows creating a ctypes.CDLL without name when passing a handle as an argument.

• gh-136234: Fix asyncio.WriteTransport.writelines() to be robust to connection failure, by using the same behavior as write().

• gh-136507: Fix mimetypes CLI to handle multiple file parameters.

• gh-136057: Fixed the bug in pdb and bdb where next and step can’t go over the line if a loop exists in the line.

• gh-135386: Fix opening a dbm.sqlite3 database for reading from read-only file or directory.

• gh-135444: Fix asyncio.DatagramTransport.sendto() to account for datagram header size when data cannot be sent.

• gh-126631: Fix multiprocessing forkserver bug which prevented __main__ from being preloaded.

• gh-135307: email: Fix exception in set_content() when encoding text and max_line_length is set to 0 or None (unlimited).

• gh-134453: Fixed subprocess.Popen.communicate() input= handling of memoryview instances that were non-byte shaped on POSIX platforms. Those are now properly cast to a byte shaped view instead of truncating the input. Windows platforms did not have this bug.

• gh-134698: Fix a crash when calling methods of ssl.SSLContext or ssl.SSLSocket across multiple threads.

• gh-125996: Fix thread safety of collections.OrderedDict. Patch by Kumar Aditya.

• gh-133789: Fix unpickling of pathlib objects that were pickled in Python 3.13.

• gh-127081: Fix libc thread safety issues with dbm by performing stateful operations in critical sections.

• gh-132551: Make io.BytesIO safe in free-threaded build.

• gh-131788: Make ResourceTracker.send from multiprocessing re-entrant safe

• gh-118981: Fix potential hang in multiprocessing.popen_spawn_posix that can happen when the child proc dies early by closing the child fds right away.

• gh-102431: Clarify constraints for “logical” arguments in methods of decimal.Context.

• gh-78319: UTF8 support for the IMAP APPEND command has been made RFC compliant.

• bpo-38735: Fix failure when importing a module from the root directory on unix-like platforms with sys.pycache_prefix set.

• bpo-41839: Allow negative priority values from os.sched_get_priority_min() and os.sched_get_priority_max() functions.

IDLE¶

• gh-96491: Deduplicate version number in IDLE shell title bar after saving to a file.

• gh-139742: Colorize t-string prefixes for template strings in IDLE, as done for f-string prefixes.

Documentation¶

• gh-141994: xml.sax.handler: Make Documentation of xml.sax.handler.feature_external_ges warn of opening up to external entity attacks. Patch by Sebastian Pipping.

• gh-140578: Remove outdated sencence in the documentation for multiprocessing, that implied that concurrent.futures.ThreadPoolExecutor did not exist.

Core and Builtins¶

• gh-142048: Fix quadratically increasing garbage collection delays in free-threaded build.

Library¶

• gh-116738: Fix thread safety issue with re scanner objects in free-threaded builds.

Core and Builtins¶

• gh-141930: When importing a module, use Python’s regular file object to ensure that writes to .pyc files are complete or an appropriate error is raised.

• gh-120158: Fix inconsistent state when enabling or disabling monitoring events too many times.

• gh-139653: Only raise a RecursionError or trigger a fatal error if the stack pointer is both below the limit pointer and above the stack base. If outside of these bounds assume that it is OK. This prevents false positives when user-space threads swap stacks.

• gh-139103: Improve multithreaded scaling of dataclasses on the free-threaded build.

• gh-141579: Fix sys.activate_stack_trampoline() to properly support the perf_jit backend. Patch by Pablo Galindo.

• gh-114203: Skip locking if object is already locked by two-mutex critical section.

• gh-141528: Suggest using concurrent.interpreters.Interpreter.close() instead of the private _interpreters.destroy function when warning about remaining subinterpreters. Patch by Sergey Miryanov.

• gh-141312: Fix the assertion failure in the __setstate__ method of the range iterator when a non-integer argument is passed. Patch by Sergey Miryanov.

Library¶

• gh-116738: Make csv module thread-safe on the free threaded build.

Core and Builtins¶

• gh-140939: Fix memory leak when bytearray or bytes is formated with the %*b format with a large width that results in a MemoryError.

Library¶

• gh-140260: Fix struct data race in endian table initialization with subinterpreters. Patch by Shamil Abdulaev.

Core and Builtins¶

• gh-140530: Fix a reference leak when raise exc from cause fails. Patch by Bénédikt Tran.

• gh-140373: Correctly emit PY_UNWIND event when generator object is closed. Patch by Mikhail Efimov.

• gh-140576: Fixed crash in tokenize.generate_tokens() in case of specific incorrect input. Patch by Mikhail Efimov.

• gh-140551: Fixed crash in dict if dict.clear() is called at the lookup stage. Patch by Mikhail Efimov and Inada Naoki.

• gh-140517: Fixed a reference leak when iterating over the result of map() with strict=True when the input iterables have different lengths. Patch by Mikhail Efimov.

• gh-140471: Fix potential buffer overflow in ast.AST node initialization when encountering malformed _fields containing non-str.

• gh-140431: Fix a crash in Python’s garbage collector due to partially initialized coroutine objects when coroutine origin tracking depth is enabled (sys.set_coroutine_origin_tracking_depth()).

Library¶

• gh-140398: Fix memory leaks in readline functions read_init_file(), read_history_file(), write_history_file(), and append_history_file() when PySys_Audit() fails.

Core and Builtins¶

• gh-140406: Fix memory leak when an object’s __hash__() method returns an object that isn’t an int.

• gh-140358: Restore elapsed time and unreachable object count in GC debug output. These were inadvertently removed during a refactor of gc.c. The debug log now again reports elapsed collection time and the number of unreachable objects. Contributed by Pål Grønås Drange.

• gh-140306: Fix memory leaks in cross-interpreter channel operations and shared namespace handling.

• gh-140301: Fix memory leak of PyConfig in subinterpreters.

• gh-140257: Fix data race between interpreter_clear() and take_gil() on eval_breaker during finalization with daemon threads.

• gh-139951: Fixes a regression in GC performance for a growing heap composed mostly of small tuples.

  • Counts number of actually tracked objects, instead of trackable objects. This ensures that untracking tuples has the desired effect of reducing GC overhead.

  • Does not track most untrackable tuples during creation. This prevents large numbers of small tuples causing excessive GCs.

• gh-140104: Fix a bug with exception handling in the JIT. Patch by Ken Jin. Bug reported by Daniel Diniz.

• gh-140061: Fixing the checking of whether an object is uniquely referenced to ensure free-threaded compatibility. Patch by Sergey Miryanov.

• gh-140067: Fix memory leak in sub-interpreter creation.

• gh-140000: Fix potential memory leak when a reference cycle exists between an instance of typing.TypeAliasType, typing.TypeVar, typing.ParamSpec, or typing.TypeVarTuple and its __name__ attribute. Patch by Mikhail Efimov.

• gh-139914: Restore support for HP PA-RISC, which has an upwards-growing stack.

• gh-139988: Fix a memory leak when failing to create a Union type. Patch by Bénédikt Tran.

• gh-139748: Fix reference leaks in error branches of functions accepting path strings or bytes such as compile() and os.system(). Patch by Bénédikt Tran.

• gh-139516: Fix lambda colon erroneously start format spec in f-string in tokenizer.

• gh-139640: ast.parse() no longer emits syntax warnings for return/break/continue in finally (see PEP 765) – they are only emitted during compilation.

• gh-139640: Fix swallowing some syntax warnings in different modules if they accidentally have the same message and are emitted from the same line. Fix duplicated warnings in the finally block.

• gh-63161: Support non-UTF-8 shebang and comments in Python source files if non-UTF-8 encoding is specified. Detect decoding error in comments for default (UTF-8) encoding. Show the line and position of decoding error for default encoding in a traceback. Show the line containing the coding cookie when it conflicts with the BOM in a traceback.

Library¶

• gh-116738: Make mmap thread-safe on the free threaded build.

Core and Builtins¶

• gh-138558: Fix handling of unusual t-string annotations in annotationlib. Patch by Dave Peck.

• gh-134466: Don’t run PyREPL in a degraded environment where setting termios attributes is not allowed.

• gh-138944: Fix SyntaxError message when invalid syntax appears on the same line as a valid import ... as ... or from ... import ... as ... statement. Patch by Brian Schubert.

• gh-105487: Remove non-existent __copy__(), __deepcopy__(), and __bases__ from the __dir__() entries of types.GenericAlias.

• gh-69605: Fix some standard library submodules missing from the REPL auto-completion of imports.

Library¶

• gh-116738: Make cProfile thread-safe on the free threaded build.

• gh-138004: On Solaris/Illumos platforms, thread names are now encoded as ASCII to avoid errors on systems (e.g. OpenIndiana) that don’t support non-ASCII names.

Core and Builtins¶

• gh-137433: Fix a potential deadlock in the free threading build when daemon threads enable or disable profiling or tracing while the main thread is shutting down the interpreter.

• gh-137400: Fix a crash in the free threading build when disabling profiling or tracing across all threads with PyEval_SetProfileAllThreads() or PyEval_SetTraceAllThreads() or their Python equivalents threading.settrace_all_threads() and threading.setprofile_all_threads().

• gh-58124: Fix name of the Python encoding in Unicode errors of the code page codec: use “cp65000” and “cp65001” instead of “CP_UTF7” and “CP_UTF8” which are not valid Python code names. Patch by Victor Stinner.

• gh-132657: Improve performance of frozenset by removing locks in the free-threading build.

• gh-133400: Fixed Ctrl+D (^D) behavior in _pyrepl module to match old pre-3.13 REPL behavior.

• gh-128640: Fix a crash when using threads inside of a subinterpreter.

C API¶

• gh-137422: Fix free threading race condition in PyImport_AddModuleRef(). It was previously possible for two calls to the function return two different objects, only one of which was stored in sys.modules.

• gh-140042: Removed the sqlite3_shutdown call that could cause closing connections for sqlite when used with multiple sub interpreters.

• gh-141042: Make qNaN in PyFloat_Pack2() and PyFloat_Pack4(), if while conversion to a narrower precision floating-point format — the remaining after truncation payload will be zero. Patch by Sergey B Kirpichev.

• gh-140487: Fix Py_RETURN_NOTIMPLEMENTED in limited C API 3.11 and older: don’t treat Py_NotImplemented as immortal. Patch by Victor Stinner.

• gh-140153: Fix Py_REFCNT() definition on limited C API 3.11-3.13. Patch by Victor Stinner.

• gh-139653: Add PyUnstable_ThreadState_SetStackProtection() and PyUnstable_ThreadState_ResetStackProtection() functions to set the stack protection base address and stack protection size of a Python thread state. Patch by Victor Stinner.

Build¶

• gh-141808: Do not generate the jit stencils twice in case of PGO builds on Windows.

• gh-141784: Fix _remote_debugging_module.c compilation on 32-bit Linux. Include Python.h before system headers to make sure that _remote_debugging_module.c uses the same types (ABI) than Python. Patch by Victor Stinner.

• gh-140768: Warn when the WASI SDK version doesn’t match what’s supported.

• gh-140513: Generate a clear compilation error when _Py_TAIL_CALL_INTERP is enabled but either preserve_none or musttail is not supported.

• gh-140189: iOS builds were added to CI.

• gh-138489: When cross-compiling for WASI by build_wasm or build_emscripten, the build-details.json step is now included in the build process, just like with native builds.

  This fixes the libinstall task which requires the build-details.json file during the process.

• gh-137618: PYTHON_FOR_REGEN now requires Python 3.10 to Python 3.15. Patch by Adam Turner.

• gh-123681: Check the strftime() behavior at runtime instead of at the compile time to support cross-compiling. Remove the internal macro _Py_NORMALIZE_CENTURY.

macOS¶

• gh-124111: Update macOS installer to use Tcl/Tk 8.6.17.

• gh-139573: Updated bundled version of OpenSSL to 3.0.18.

Windows¶

• gh-139573: Updated bundled version of OpenSSL to 3.0.18.

Tools/Demos¶

• gh-139330: SBOM generation tool didn’t cross-check the version and checksum values against the Modules/expat/refresh.sh script, leading to the values becoming out-of-date during routine updates.

• gh-132006: XCframeworks now include privacy manifests to satisfy Apple App Store submission requirements.

• gh-138171: A script for building an iOS XCframework was added. As part of this change, the top level iOS folder has been moved to be a subdirectory of the Apple folder.

Security¶

• gh-139400: xml.parsers.expat: Make sure that parent Expat parsers are only garbage-collected once they are no longer referenced by subparsers created by ExternalEntityParserCreate(). Patch by Sebastian Pipping.

Library¶

• gh-139312: Upgrade bundled libexpat to 2.7.3

Windows¶

• gh-138896: Fix error installing C runtime on non-updated Windows machines

Tools/Demos¶

• gh-137873: The iOS test runner has been simplified, resolving some issues that have been observed using the runner in GitHub Actions and Azure Pipelines test environments.

Security¶

• gh-135661: Fix CDATA section parsing in html.parser.HTMLParser according to the HTML5 standard: ] ]> and ]] > no longer end the CDATA section. Add private method _set_support_cdata() which can be used to specify how to parse <[CDATA[ — as a CDATA section in foreign content (SVG or MathML) or as a bogus comment in the HTML namespace.

Library¶

• gh-138998: Update bundled libexpat to 2.7.2

• gh-118803: Add back collections.abc.ByteString and typing.ByteString. Both had been removed in prior alpha, beta and release candidates for Python 3.14, but their removal has now been postponed to Python 3.17.

• gh-137226: Fix typing.get_type_hints() calls on generic typing.TypedDict classes defined with string annotations.

• gh-138804: Raise TypeError instead of AttributeError when an argument of incorrect type is passed to shlex.quote(). This restores the behavior of the function prior to 3.14.

• gh-128636: Fix crash in PyREPL when os.environ is overwritten with an invalid value for mac

• gh-138514: Raise ValueError when a multi-character string is passed to the echo_char parameter of getpass.getpass(). Patch by Benjamin Johnson.

• gh-138515: email is added to Emscripten build.

• gh-99948: ctypes.util.find_library() now works in Emscripten build.

• gh-138253: Add the block parameter in the put() and get() methods of the concurrent.interpreters queues for compatibility with the queue.Queue interface.

• gh-138133: Prevent infinite traceback loop when sending CTRL^C to Python through strace.

• gh-134869: Fix an issue where pressing Ctrl+C during tab completion in the REPL would leave the autocompletion menu in a corrupted state.

• gh-90548: Fix musl detection for platform.libc_ver() on Alpine Linux if compiled with –strip-all.

• gh-136134: SMTP.auth_cram_md5() now raises an SMTPException instead of a ValueError if Python has been built without MD5 support. In particular, SMTP clients will not attempt to use this method even if the remote server is assumed to support it. Patch by Bénédikt Tran.

• gh-136134: IMAP4.login_cram_md5 now raises an IMAP4.error if CRAM-MD5 authentication is not supported. Patch by Bénédikt Tran.

• gh-134953: Expand _colorize theme with keyword_constant and implement in repl.

Core and Builtins¶

• gh-71810: Raise OverflowError for (-1).to_bytes() for signed conversions when bytes count is zero. Patch by Sergey B Kirpichev.

• gh-138192: Fix contextvars initialization so that all subinterpreters are assigned the MISSING value.

• gh-138479: Fix a crash when a generic object’s __typing_subst__ returns an object that isn’t a tuple.

• gh-138372: Fix SyntaxWarning emitted for erroneous subscript expressions involving template string literals. Patch by Brian Schubert.

• gh-138318: The default REPL now avoids highlighting built-in names (for instance set or format()) when they are used as attribute names (for instance in value.set or text.format).

• gh-138349: Fix crash in certain cases where a module contains both a module-level annotation and a comprehension.

• gh-137384: Fix a crash when using the warnings module in a finalizer at shutdown. Patch by Kumar Aditya.

• gh-137883: Fix runaway recursion when calling a function with keyword arguments.

• gh-137079: Fix keyword typo recognition when parsing files. Patch by Pablo Galindo.

• gh-137728: Fix the JIT’s handling of many local variables. This previously caused a segfault.

• gh-137576: Fix for incorrect source code being shown in tracebacks from the Basic REPL when PYTHONSTARTUP is given. Patch by Adam Hartz.

macOS¶

• gh-137450: macOS installer shell path management improvements: separate the installer Shell profile updater postinstall script from the Update Shell Profile.command to enable more robust error handling.

• gh-137134: Update macOS installer to ship with SQLite version 3.50.4.

Windows¶

• gh-137134: Update Windows installer to ship with SQLite 3.50.4.

Library¶

• gh-137426: Remove the code deprecation of importlib.abc.ResourceLoader. It is documented as deprecated, but left for backwards compatibility with other classes in importlib.abc.

• gh-137282: Fix tab completion and dir() on concurrent.futures.

• gh-137257: Bump the version of pip bundled in ensurepip to version 25.2

• gh-137226: Fix behavior of annotationlib.ForwardRef.evaluate() when the type_params parameter is passed and the name of a type param is also present in an enclosing scope.

• gh-130522: Fix unraisable TypeError raised during interpreter shutdown in the threading module.

• gh-137059: Fix handling of file URLs with a Windows drive letter in the URL authority by urllib.request.url2pathname(). This fixes a regression in earlier pre-releases of Python 3.14.

• gh-130577: tarfile now validates archives to ensure member offsets are non-negative. (Contributed by Alexander Enrique Urieles Nieto in gh-130577.)

• gh-135228: When dataclasses replaces a class with a slotted dataclass, the original class can now be garbage collected again. Earlier changes in Python 3.14 caused this class to always remain in existence together with the replacement class synthesized by dataclasses.

Documentation¶

• gh-136155: We are now checking for fatal errors in EPUB builds in CI.

Core and Builtins¶

• gh-137400: Fix a crash in the free threading build when disabling profiling or tracing across all threads with PyEval_SetProfileAllThreads() or PyEval_SetTraceAllThreads() or their Python equivalents threading.settrace_all_threads() and threading.setprofile_all_threads().

• gh-137314: Fixed a regression where raw f-strings incorrectly interpreted escape sequences in format specifications. Raw f-strings now properly preserve literal backslashes in format specs, matching the behavior from Python 3.11. For example, rf"{obj:\xFF}" now correctly produces '\\xFF' instead of 'ÿ'. Patch by Pablo Galindo.

• gh-137308: A standalone docstring in a node body is optimized as a pass statement to ensure that the node’s body is never empty. There was a ValueError in compile() otherwise.

• gh-137288: Fix bug where some bytecode instructions of a boolean expression are not associated with the correct exception handler.

• gh-134291: Remove some newer macOS API usage from the JIT compiler in order to restore compatibility with older OSX 10.15 deployment targets.

• gh-131338: Disable computed stack limit checks on non-glibc linux platforms to fix crashes on deep recursion.

• gh-136870: Fix data races while de-instrumenting bytecode of code objects running concurrently in threads.

C API¶

• gh-137573: Mark _PyOptimizer_Optimize as Py_NO_INLINE to prevent stack overflow crashes on macOS.

Build¶

• gh-132339: Add support for OpenSSL 3.5.

Tools/Demos¶

• gh-136251: Fixes and usability improvements for Tools/wasm/emscripten/web_example

Security¶

• gh-135661: Fix parsing attributes with whitespaces around the = separator in html.parser.HTMLParser according to the HTML5 standard.

• gh-118350: Fix support of escapable raw text mode (elements “textarea” and “title”) in html.parser.HTMLParser.

Library¶

• gh-136170: Removed the unreleased zipfile.ZipFile.data_offset property added in 3.14.0a7 as it wasn’t fully clear which behavior it should have in some situations so the result was not always what a user might expect.

• gh-124621: pyrepl now works in Emscripten.

• gh-136874: Discard URL query and fragment in urllib.request.url2pathname().

• gh-130645: Enable color help by default in argparse.

• gh-136549: Fix signature of threading.excepthook().

• gh-136523: Fix wave.Wave_write emitting an unraisable when open raises.

• gh-52876: Add missing keepends (default True) parameter to codecs.StreamReaderWriter.readline() and codecs.StreamReaderWriter.readlines().

• gh-136470: Correct concurrent.futures.InterpreterPoolExecutor’s default thread name.

• gh-136476: Fix a bug that was causing the get_async_stack_trace function to miss some frames in the stack trace.

• gh-136434: Fix docs generation of UnboundItem in concurrent.interpreters when running with -OO.

• gh-136380: Raises AttributeError when accessing concurrent.futures.InterpreterPoolExecutor and subinterpreters are not available.

• gh-134759: Fix UnboundLocalError in email.message.Message.get_payload() when the payload to decode is a bytes object. Patch by Kliment Lamonov.

• gh-134657: asyncio: Remove some private names from asyncio.__all__.

Core and Builtins¶

• gh-136801: Fix PyREPL syntax highlighting on match cases after multi-line case. Contributed by Olga Matoula.

Library¶

• gh-136421: Fix crash when initializing datetime concurrently.

Core and Builtins¶

• gh-136541: Fix some issues with the perf trampolines on x86-64 and aarch64. The trampolines were not being generated correctly for some cases, which could lead to the perf integration not working correctly. Patch by Pablo Galindo.

• gh-136517: Fixed a typo that prevented printing of uncollectable objects when the gc.DEBUG_UNCOLLECTABLE mode was set.

• gh-136525: Fix issue where per-thread bytecode was not instrumented for newly created threads.

• gh-132661: Interpolation.expression now has a default, the empty string.

• gh-132661: Reflect recent PEP 750 change.

  Disallow concatenation of string.templatelib.Template and str. Also, disallow implicit concatenation of t-string literals with string or f-string literals.

Library¶

• gh-116738: Make functions in grp thread-safe on the free threaded build.

Core and Builtins¶

• gh-135148: Fixed a bug where f-string debug expressions (using =) would incorrectly strip out parts of strings containing escaped quotes and # characters. Patch by Pablo Galindo.

• gh-133136: Limit excess memory usage in the free threading build when a large dictionary or list is resized and accessed by multiple threads.

• gh-91153: Fix a crash when a bytearray is concurrently mutated during item assignment.

• gh-127971: Fix off-by-one read beyond the end of a string in string search.

C API¶

• gh-112068: Revert support of nullable arguments in PyArg_Parse().

• gh-133296: New variants for the critical section API that accept one or two PyMutex pointers rather than PyObject instances are now public in the non-limited C API.

• gh-134009: Expose PyMutex_IsLocked() as part of the public C API.

Build¶

• gh-135621: PyREPL no longer depends on the curses standard library. Contributed by Łukasz Langa.

Tools/Demos¶

• gh-135968: Stubs for strip are now provided as part of an iOS install.

• gh-133600: Backport file reorganization for Tools/wasm/wasi.

  This should make backporting future code changes easier. It also simplifies instructions around how to do WASI builds in the devguide.

Tests¶

• gh-135966: The iOS testbed now handles the app_packages folder as a site directory.

• gh-135494: Fix regrtest to support excluding tests from --pgo tests. Patch by Victor Stinner.

Security¶

• gh-136053: marshal: fix a possible crash when deserializing slice objects.

• gh-135661: Fix parsing start and end tags in html.parser.HTMLParser according to the HTML5 standard.

  • Whitespaces no longer accepted between </ and the tag name. E.g. </ script> does not end the script section.

  • Vertical tabulation (\v) and non-ASCII whitespaces no longer recognized as whitespaces. The only whitespaces are \t\n\r\f and space.

  • Null character (U+0000) no longer ends the tag name.

  • Attributes and slashes after the tag name in end tags are now ignored, instead of terminating after the first > in quoted attribute value. E.g. </script/foo=">"/>.

  • Multiple slashes and whitespaces between the last attribute and closing > are now ignored in both start and end tags. E.g. <a foo=bar/ //>.

  • Multiple = between attribute name and value are no longer collapsed. E.g. <a foo==bar> produces attribute “foo” with value “=bar”.

  • [Reverted in gh-136927] Whitespaces between the = separator and attribute name or value are no longer ignored. E.g. <a foo =bar> produces two attributes “foo” and “=bar”, both with value None; <a foo= bar> produces two attributes: “foo” with value “” and “bar” with value None.

• gh-102555: Fix comment parsing in html.parser.HTMLParser according to the HTML5 standard. --!> now ends the comment. -- > no longer ends the comment. Support abnormally ended empty comments <--> and <--->.

Library¶

• gh-136286: Fix pickling failures for protocols 0 and 1 for many objects realted to subinterpreters.

• gh-136316: Improve support for evaluating nested forward references in typing.evaluate_forward_ref().

• gh-85702: If zoneinfo._common.load_tzdata is given a package without a resource a zoneinfo.ZoneInfoNotFoundError is raised rather than a PermissionError. Patch by Victor Stinner.

• gh-136028: Fix parsing month names containing “İ” (U+0130, LATIN CAPITAL LETTER I WITH DOT ABOVE) in time.strptime(). This affects locales az_AZ, ber_DZ, ber_MA and crh_UA.

• gh-135995: In the palmos encoding, make byte 0x9b decode to › (U+203A - SINGLE RIGHT-POINTING ANGLE QUOTATION MARK).

• gh-53203: Fix time.strptime() for %c and %x formats on locales byn_ER, wal_ET and lzh_TW, and for %X format on locales ar_SA, bg_BG and lzh_TW.

• gh-91555: An earlier change, which was introduced in 3.14.0b2, has been reverted. It disabled logging for a logger during handling of log messages for that logger. Since the reversion, the behaviour should be as it was before 3.14.0b2.

• gh-135878: Fixes a crash of types.SimpleNamespace on free threading builds, when several threads were calling its __repr__() method at the same time.

• gh-135836: Fix IndexError in asyncio.loop.create_connection() that could occur when non-OSError exception is raised during connection and socket’s close() raises OSError.

• gh-135836: Fix IndexError in asyncio.loop.create_connection() that could occur when the Happy Eyeballs algorithm resulted in an empty exceptions list during connection attempts.

• gh-135855: Raise TypeError instead of SystemError when _interpreters.set___main___attrs() is passed a non-dict object. Patch by Brian Schubert.

• gh-135815: netrc: skip security checks if os.getuid() is missing. Patch by Bénédikt Tran.

• gh-135640: Address bug where it was possible to call xml.etree.ElementTree.ElementTree.write() on an ElementTree object with an invalid root element. This behavior blanked the file passed to write if it already existed.

• gh-135645: Added supports_isolated_interpreters field to sys.implementation.

• gh-135646: Raise consistent NameError exceptions in annotationlib.ForwardRef.evaluate()

• gh-135557: Fix races on heapq updates and list reads on the free threaded build.

• gh-119180: Only fetch globals and locals if necessary in annotationlib.get_annotations()

• gh-135561: Fix a crash on DEBUG builds when an HACL* HMAC routine fails. Patch by Bénédikt Tran.

• gh-135487: Fix reprlib.Repr.repr_int() when given integers with more than sys.get_int_max_str_digits() digits. Patch by Bénédikt Tran.

• gh-135335: multiprocessing: Flush stdout and stderr after preloading modules in the forkserver.

• gh-135069: Fix the “Invalid error handling” exception in encodings.idna.IncrementalDecoder to correctly replace the ‘errors’ parameter.

• gh-130662: +Accept leading zeros in precision and width fields for +:class:Decimal formatting, for example format(Decimal(1.25), '.016f').

• gh-130662: Accept leading zeros in precision and width fields for Fraction formatting, for example format(Fraction(1, 3), '.016f').

• gh-87790: Support underscore and comma as thousands separators in the fractional part for Fraction’s formatting. Patch by Sergey B Kirpichev.

• gh-87790: Support underscore and comma as thousands separators in the fractional part for Decimal’s formatting. Patch by Sergey B Kirpichev.

• gh-130664: Handle corner-case for Fraction’s formatting: treat zero-padding (preceding the width field by a zero ('0') character) as an equivalent to a fill character of '0' with an alignment type of '=', just as in case of float’s.

Documentation¶

• gh-136155: EPUB builds are fixed by excluding non-XHTML-compatible tags.

Core and Builtins¶

• gh-109700: Fix memory error handling in PyDict_SetDefault().

• gh-78465: Fix error message for cls.__new__(cls, ...) where cls is not instantiable builtin or extension type (with tp_new set to NULL).

• gh-129958: Differentiate between t-strings and f-strings in syntax error for newlines in format specifiers of single-quoted interpolated strings.

• gh-135871: Non-blocking mutex lock attempts now return immediately when the lock is busy instead of briefly spinning in the free threading build.

• gh-135106: Restrict the trashcan mechanism to GC’ed objects and untrack them while in the trashcan to prevent the GC and trashcan mechanisms conflicting.

• gh-135607: Fix potential weakref races in an object’s destructor on the free threaded build.

• gh-135608: Fix a crash in the JIT involving attributes of modules.

• gh-135543: Emit sys.remote_exec audit event when sys.remote_exec() is called and migrate remote_debugger_script to cpython.remote_debugger_script.

• gh-134280: Disable constant folding for ~ with a boolean argument. This moves the deprecation warning from compile time to runtime.

C API¶

• gh-135906: Fix compilation errors when compiling the internal headers with a C++ compiler.

Build¶

• gh-134273: Add support for configuring compiler flags for the JIT with CFLAGS_JIT

Windows¶

• gh-135099: Fix a crash that could occur on Windows when a background thread waits on a PyMutex while the main thread is shutting down the interpreter.

Tests¶

• gh-132815: Fix test__opcode: add JUMP_BACKWARD to specialization stats.

• gh-135489: Show verbose output for failing tests during PGO profiling step with –enable-optimizations.

• gh-135120: Add test.support.subTests().

Security¶

• gh-135462: Fix quadratic complexity in processing specially crafted input in html.parser.HTMLParser. End-of-file errors are now handled according to the HTML5 specs – comments and declarations are automatically closed, tags are ignored.

• gh-135034: Fixes multiple issues that allowed tarfile extraction filters (filter="data" and filter="tar") to be bypassed using crafted symlinks and hard links.

  Addresses CVE 2024-12718, CVE 2025-4138, CVE 2025-4330, and CVE 2025-4517.

Library¶

• gh-65697: configparser’s error message when attempting to write an invalid key is now more helpful.

• gh-135497: Fix os.getlogin() failing for longer usernames on BSD-based platforms.

• gh-135429: Fix the argument mismatch in _lsprof for PY_THROW event.

• gh-135368: Fix unittest.mock.Mock generation on dataclasses.dataclass() objects. Now all special attributes are set as it was before gh-124429.

• gh-133967: Do not normalize locale name ‘C.UTF-8’ to ‘en_US.UTF-8’.

• gh-135321: Raise a correct exception for values greater than 0x7fffffff for the BINSTRING opcode in the C implementation of pickle.

• gh-135276: Backported bugfixes in zipfile.Path from zipp 3.23. Fixed .name, .stem and other basename-based properties on Windows when working with a zipfile on disk.

• gh-135244: uuid: when the MAC address cannot be determined, the 48-bit node ID is now generated with a cryptographically-secure pseudo-random number generator (CSPRNG) as per RFC 9562, §6.10.3. This affects uuid1() and uuid6().

• gh-134970: Fix the “unknown action” exception in argparse.ArgumentParser.add_argument_group() to correctly replace the action class.

• gh-134718: ast.dump() now only omits None and [] values if they are default values.

• gh-134939: Add the concurrent.interpreters module. See PEP 734.

• gh-134885: Fix possible crash in the compression.zstd module related to setting parameter types. Patch by Jelle Zijlstra.

• gh-134857: Improve error report for doctests run with unittest. Remove doctest module frames from tracebacks and redundant newline character from a failure message.

• gh-128840: Fix parsing long IPv6 addresses with embedded IPv4 address.

• gh-134637: Fix performance regression in calling a ctypes function pointer in free threading.

• gh-134696: Built-in HACL* and OpenSSL implementations of hash function constructors now correctly accept the same documented named arguments. For instance, md5() could be previously invoked as md5(data=data) or md5(string=string) depending on the underlying implementation but these calls were not compatible. Patch by Bénédikt Tran.

• gh-134151: email: Fix TypeError in email.utils.decode_params() when sorting RFC 2231 continuations that contain an unnumbered section.

• gh-134210: curses.window.getch() now correctly handles signals. Patch by Bénédikt Tran.

• gh-134152: email: Fix parsing of email message ID with invalid domain.

• gh-133489: random.getrandbits() can now generate more that 2³¹ bits. random.randbytes() can now generate more that 256 MiB.

• gh-132813: Improve error messages for incorrect types and values of csv.Dialect attributes.

• gh-132969: Prevent the ProcessPoolExecutor executor thread, which remains running when shutdown(wait=False), from attempting to adjust the pool’s worker processes after the object state has already been reset during shutdown. A combination of conditions, including a worker process having terminated abormally, resulted in an exception and a potential hang when the still-running executor thread attempted to replace dead workers within the pool.

• gh-127081: Fix libc thread safety issues with os by replacing getlogin with getlogin_r re-entrant version.

• gh-131884: Fix formatting issues in json.dump() when both indent and skipkeys are used.

• gh-130999: Avoid exiting the new REPL and offer suggestions even if there are non-string candidates when errors occur.

Documentation¶

• gh-135171: Document that the iterator for the leftmost for clause in the generator expression is created immediately.

• bpo-45210: Document that error indicator may be set in tp_dealloc, and how to avoid clobbering it.

Core and Builtins¶

• gh-135496: Fix typo in the f-string conversion type error (“exclamanation” -> “exclamation”).

• gh-135371: Fixed asyncio debugging tools to properly display internal coroutine call stacks alongside external task dependencies. The python -m asyncio ps and python -m asyncio pstree commands now show complete execution context. Patch by Pablo Galindo.

Library¶

• gh-127319: Set the allow_reuse_port class variable to False on the XMLRPC, logging, and HTTP servers. This matches the behavior in prior Python releases, which is to not allow port reuse.

Core and Builtins¶

• gh-135171: Reverts the behavior of async generator expressions when created with object w/o __aiter__ method to the pre-3.13 behavior of raising a TypeError.

• gh-130077: Properly raise custom syntax errors when incorrect syntax containing names that are prefixes of soft keywords is encountered. Patch by Pablo Galindo.

• gh-135171: Reverts the behavior of generator expressions when created with a non-iterable to the pre-3.13 behavior of raising a TypeError. It is no longer possible to cause a crash in the debugger by altering the generator expression’s local variables. This is achieved by moving the GET_ITER instruction back to the creation of the generator expression and adding an additional check to FOR_ITER.

Library¶

• gh-116738: Make methods in heapq thread-safe on the free threaded build.

Core and Builtins¶

• gh-134876: Add support to PEP 768 remote debugging for Linux kernels which don’t have CONFIG_CROSS_MEMORY_ATTACH configured.

• gh-134889: Fix handling of a few opcodes that leave operands on the stack when optimizing LOAD_FAST.

Library¶

• gh-134908: Fix crash when iterating over lines in a text file on the free threaded build.

Core and Builtins¶

• gh-132617: Fix dict.update() modification check that could incorrectly raise a “dict mutated during update” error when a different dictionary was modified that happens to share the same underlying keys object.

• gh-134679: Fix crash in the free threading build’s QSBR code that could occur when changing an object’s __dict__ attribute.

• gh-127682: No longer call __iter__ twice in list comprehensions. This brings the behavior of list comprehensions in line with other forms of iteration

• gh-133912: Fix the C API function PyObject_GenericSetDict to handle extension classes with inline values.

C API¶

• gh-134989: Fix Py_RETURN_NONE, Py_RETURN_TRUE and Py_RETURN_FALSE macros in the limited C API 3.11 and older: don’t treat Py_None, Py_True and Py_False as immortal. Patch by Victor Stinner.

• gh-134989: Implement PyObject_DelAttr() and PyObject_DelAttrString() as macros in the limited C API 3.12 and older. Patch by Victor Stinner.

• gh-133968: Add PyUnicodeWriter_WriteASCII() function to write an ASCII string into a PyUnicodeWriter. The function is faster than PyUnicodeWriter_WriteUTF8(), but has an undefined behavior if the input string contains non-ASCII characters. Patch by Victor Stinner.

Build¶

• gh-119132: Remove “experimental” tag from the CPython free-threading build.

• gh-135497: Fix the detection of MAXLOGNAME in the configure.ac script.

• gh-134923: Windows builds with profile-guided optimization enabled now use /GENPROFILE and /USEPROFILE instead of deprecated /LTCG: options.

• gh-134774: Fix Py_DEBUG macro redefinition warnings on Windows debug builds. Patch by Chris Eibl.

• gh-134632: Fixed build-details.json generation to use INCLUDEPY, in order to reference the pythonX.Y subdirectory of the include directory, as required in PEP 739, instead of the top-level include directory.

Windows¶

• gh-130727: Fix a race in internal calls into WMI that can result in an “invalid handle” exception under high load. Patch by Chris Eibl.

• gh-76023: Make os.path.realpath() ignore Windows error 1005 when in non-strict mode.

• gh-133779: Reverts the change to generate different pyconfig.h files based on compiler settings, as it was frequently causing extension builds to break. In particular, the Py_GIL_DISABLED preprocessor variable must now always be defined explicitly when compiling for the experimental free-threaded runtime. The sysconfig.get_config_var() function can be used to determine whether the current runtime was compiled with that flag or not.

• gh-133626: Ensures packages are not accidentally bundled into the traditional installer.

Tools/Demos¶

• gh-134215: REPL import autocomplete only suggests private modules when explicitly specified.

Tests¶

• gh-133744: Fix multiprocessing interrupt test. Add an event to synchronize the parent process with the child process: wait until the child process starts sleeping. Patch by Victor Stinner.

• gh-133682: Fixed test case test.test_annotationlib.TestStringFormat.test_displays which ensures proper handling of complex data structures (lists, sets, dictionaries, and tuples) in string annotations.

• gh-133639: Fix TestPyReplAutoindent.test_auto_indent_default() doesn’t run input_code.

Security¶

• gh-133767: Fix use-after-free in the “unicode-escape” decoder with a non-“strict” error handler.

• gh-128840: Short-circuit the processing of long IPv6 addresses early in ipaddress to prevent excessive memory consumption and a minor denial-of-service.

Library¶

• gh-132710: If possible, ensure that uuid.getnode() returns the same result even across different processes. Previously, the result was constant only within the same process. Patch by Bénédikt Tran.

• gh-80334: multiprocessing.freeze_support() now checks for work on any “spawn” start method platform rather than only on Windows.

• gh-134582: Fix tokenize.untokenize() round-trip errors related to t-strings braces escaping

• gh-134546: Ensure pdb remote debugging script is readable by remote Python process.

• gh-134451: Converted asyncio.tools.CycleFoundException from dataclass to a regular exception type.

• gh-114177: Fix asyncio to not close subprocess pipes which would otherwise error out when the event loop is already closed.

• gh-90871: Fixed an off by one error concerning the backlog parameter in create_unix_server(). Contributed by Christian Harries.

• gh-134323: Fix the threading.RLock.locked() method.

• gh-86802: Fixed asyncio memory leak in cancelled shield tasks. For shielded tasks where the shield was cancelled, log potential exceptions through the exception handler. Contributed by Christian Harries.

• gh-134209: curses: The curses.window.instr() and curses.window.getstr() methods now allocate their internal buffer on the heap instead of the stack; in addition, the max buffer size is increased from 1023 to 2047.

• gh-134235: Updated tab completion on REPL to include builtin modules. Contributed by Tom Wang, Hunter Young

• gh-134152: Fixed UnboundLocalError that could occur during email header parsing if an expected trailing delimiter is missing in some contexts.

• gh-134168: http.server: Fix IPv6 address binding and --directory handling when using HTTPS.

• gh-62184: Remove import of C implementation of io.FileIO from Python implementation which has its own implementation

• gh-133982: Emit RuntimeWarning in the Python implementation of io when the file-like object is not closed explicitly in the presence of multiple I/O layers.

• gh-133890: The tarfile module now handles UnicodeEncodeError in the same way as OSError when cannot extract a member.

• gh-134097: Fix interaction of the new REPL and -X showrefcount command line option.

• gh-133889: The generated directory listing page in http.server.SimpleHTTPRequestHandler now only shows the decoded path component of the requested URL, and not the query and fragment.

• gh-134098: Fix handling paths that end with a percent-encoded slash (%2f or %2F) in http.server.SimpleHTTPRequestHandler.

• gh-132124: On POSIX-compliant systems, multiprocessing.util.get_temp_dir() now ignores TMPDIR (and similar environment variables) if the path length of AF_UNIX socket files exceeds the platform-specific maximum length when using the forkserver start method. Patch by Bénédikt Tran.

• gh-134062: ipaddress: fix collisions in __hash__() for IPv4Network and IPv6Network objects.

• gh-133970: Make string.templatelib.Template and string.templatelib.Interpolation generic.

• gh-71253: Raise ValueError in open() if opener returns a negative file-descriptor in the Python implementation of io to match the C implementation.

• gh-133960: Simplify and improve typing.evaluate_forward_ref(). It now no longer raises errors on certain invalid types. In several situations, it is now able to evaluate forward references that were previously unsupported.

• gh-133925: Make the private class typing._UnionGenericAlias hashable.

• gh-133653: Fix argparse.ArgumentParser with the formatter_class argument. Fix TypeError when formatter_class is a custom subclass of HelpFormatter. Fix TypeError when formatter_class is not a subclass of HelpFormatter and non-standard prefix_char is used. Fix support of colorizing when formatter_class is not a subclass of HelpFormatter.

• gh-132641: Fixed a race in functools.lru_cache() under free-threading.

• gh-133783: Fix bug with applying copy.replace() to ast objects. Attributes that default to None were incorrectly treated as required for manually created AST nodes.

• gh-133684: Fix bug where annotationlib.get_annotations() would return the wrong result for certain classes that are part of a class hierarchy where from __future__ import annotations is used.

• gh-77057: Fix handling of invalid markup declarations in html.parser.HTMLParser.

• gh-130328: Speedup pasting in PyREPL on Windows in a legacy console. Patch by Chris Eibl.

• gh-133701: Fix bug where typing.TypedDict classes defined under from __future__ import annotations and inheriting from another TypedDict had an incorrect __annotations__ attribute.

• gh-133581: Improve unparsing of t-strings in ast.unparse() and from __future__ import annotations. Empty t-strings now round-trip correctly and formatting in interpolations is preserved. Patch by Jelle Zijlstra.

• gh-133551: Support t-strings (PEP 750) in annotationlib. Patch by Jelle Zijlstra.

• gh-133439: Fix dot commands with trailing spaces are mistaken for multi-line SQL statements in the sqlite3 command-line interface.

• gh-132493: Avoid accessing __annotations__ unnecessarily in inspect.signature().

• gh-132876: ldexp() on Windows doesn’t round subnormal results before Windows 11, but should. Python’s math.ldexp() wrapper now does round them, so results may change slightly, in rare cases of very small results, on Windows versions before 11.

• gh-133009: xml.etree.ElementTree: Fix a crash in Element.__deepcopy__ when the element is concurrently mutated. Patch by Bénédikt Tran.

• gh-91555: Ignore log messages generated during handling of log messages, to avoid deadlock or infinite recursion. [NOTE: This change has since been reverted.]

• gh-125028: functools.Placeholder cannot be passed to functools.partial() as a keyword argument.

• gh-62824: Fix aliases for iso8859_8 encoding. Patch by Dave Goncalves.

• gh-86155: html.parser.HTMLParser.close() no longer loses data when the <script> tag is not closed. Patch by Waylan Limberg.

• gh-69426: Fix html.parser.HTMLParser to not unescape character entities in attribute values if they are followed by an ASCII alphanumeric or an equals sign.

• bpo-28494: Improve Zip file validation false positive rate in zipfile.is_zipfile().

• gh-134381: Fix RuntimeError when using a not-started threading.Thread after calling os.fork()

Core and Builtins¶

• gh-127960: PyREPL interactive shell no longer starts with __package__ and __file__ global names set to _pyrepl package internals. Contributed by Yuichiro Tachibana.

• gh-130397: Remove special-casing for C stack depth limits for WASI. Due to WebAssembly’s built-in stack protection this does not pose a security concern.

• gh-128066: Fixes an edge case where PyREPL improperly threw an error when Python is invoked on a read only filesystem while trying to write history file entries.

• gh-69605: When auto-completing an import in the REPL, finding no candidates now issues no suggestion, rather than suggestions from the current namespace.

• gh-134158: Fix coloring of double braces in f-strings and t-strings in the REPL.

• gh-134119: Fix crash when calling next() on an exhausted template string iterator. Patch by Jelle Zijlstra.

• gh-134100: Fix a use-after-free bug that occurs when an imported module isn’t in sys.modules after its initial import. Patch by Nico-Posada.

• gh-133999: Fix SyntaxError regression in except parsing after gh-123440.

• gh-133886: Fix sys.remote_exec() for non-ASCII paths in non-UTF-8 locales and non-UTF-8 paths in UTF-8 locales.

• gh-133703: Fix hashtable in dict can be bigger than intended in some situations.

• gh-133778: Fix bug where assigning to the __annotations__ attributes of classes defined under from __future__ import annotations had no effect.

• gh-132762: fromkeys() no longer loops forever when adding a small set of keys to a large base dict. Patch by Angela Liss.

• gh-133541: Inconsistent indentation in user input crashed the new REPL when syntax highlighting was active. This is now fixed.

• gh-133516: Raise ValueError when constants True, False or None are used as an identifier after NFKC normalization.

• gh-132542: Update Thread.native_id after fork(2) to ensure accuracy. Patch by Noam Cohen.

C API¶

• gh-134144: Fix crash when calling Py_EndInterpreter() with a thread state that isn’t the initial thread for the interpreter.

Build¶

• gh-134455: Fixed build-details.json generation to use the correct c_api.headers as defined in PEP 739, instead of c_api.include.

• gh-131769: Fix detecting when the build Python in a cross-build is a pydebug build.

• gh-117088: AIX linker don’t support -h option, so avoid it through platform check

Windows¶

• gh-132930: Marks the installer for Windows as deprecated and updates documentation to cover the new Python install manager.

• gh-127405: Add ABIFLAGS to sysconfig.get_config_vars() on Windows. Patch by Xuehai Pan.

Tools/Demos¶

• gh-130453: Allow passing multiple keyword arguments with the same function name in pygettext.

• gh-130195: Add warning messages when pygettext unimplemented -a/--extract-all option is called.

Tests¶

• gh-133131: The iOS testbed will now select the most recently released “SE-class” device for testing if a device isn’t explicitly specified.

• gh-91048: Add ability to externally inspect all pending asyncio tasks, even if no task is currently entered on the event loop.

• gh-109981: The test helper that counts the list of open file descriptors now uses the optimised /dev/fd approach on all Apple platforms, not just macOS. This avoids crashes caused by guarded file descriptors.

• gh-132678: Add --prioritize to -m test. This option allows the user to specify which selected tests should execute first, even if the order is otherwise randomized. This is particularly useful for tests that run the longest.

• gh-131290: Tests in Lib/test can now be correctly executed as standalone scripts.

Security¶

• gh-115322: The underlying extension modules behind readline:, subprocess, and ctypes now raise audit events on previously uncovered code paths that could lead to file system access related to C function calling and external binary execution. The ctypes.call_function audit hook has also been fixed to use an unsigned value for its function pointer.

Library¶

• gh-133490: Add color support to PDB in remote mode.

• gh-132493: Avoid eagerly evaluating annotations in functions decorated with reprlib.recursive_repr().

• gh-130645: Add color to stdlib argparse CLIs. Patch by Hugo van Kemenade.

• gh-119180: Make annotationlib.get_annotations() succeed with the FORWARDREF format if evaluating the annotations throws an exception other than NameError or AttributeError.

• gh-133351: Fix remote PDB to correctly request tab completions for Python expressions from the server when completing a continuation line of a multi-line Python block.

• gh-133367: Add the --feature-version, --optimize, and --show-empty options to the ast command-line interface. Patch by Semyon Moroz.

• gh-133363: The cmd.Cmd class has been fixed to reliably call the completedefault method whenever the do_shell method is not defined and tab completion is requested for a line beginning with !.

• gh-113081: Highlight syntax on source code in pdb.

• gh-133349: Introduced auto-indent in pdb multi-line input.

• gh-133306: Use \z instead of \Z in fnmatch.translate() and glob.translate().

• gh-133306: Support \z as a synonym for \Z in regular expressions.

• gh-133300: Make argparse.ArgumentParser’s suggest_on_error a keyword-only parameter. Patch by Hugo van Kemenade.

• gh-133290: Fix attribute caching issue when setting ctypes._Pointer._type_ in the undocumented and deprecated ctypes.SetPointerType() function and the undocumented set_type() method.

• gh-133223: When PDB is attached to a remote process, do a better job of intercepting Ctrl+C and forwarding it to the remote process.

• gh-133153: Do not complete pdb commands in interact mode of pdb.

• gh-133139: Add the curses.assume_default_colors() function, a refinement of the curses.use_default_colors() function which allows to change the color pair 0.

• gh-133089: Use original timeout value for subprocess.TimeoutExpired when the func subprocess.run() is called with a timeout instead of sometimes a confusing partial remaining time out value used internally on the final wait().

• gh-133036: codecs.open() is now deprecated. Use open() instead. Contributed by Inada Naoki.

• gh-132987: Many builtin and extension functions which accept an unsigned integer argument, now use __index__() if available.

• gh-124703: Set return code to 1 when aborting process from pdb.

• gh-133005: Support passing preset option to tarfile.open() when using 'w|xz' mode.

• gh-115032: Support for custom logging handlers with the strm argument is deprecated and scheduled for removal in Python 3.16. Define handlers with the stream argument instead. Patch by Mariusz Felisiak.

• gh-132991: Add socket.IP_FREEBIND constant on Linux 2.4 and later.

• gh-132995: Bump the version of pip bundled in ensurepip to version 25.1.1

• gh-132933: The zipapp module now applies the filter when creating the list of files to add, rather than waiting until the file is being added to the archive.

• gh-121249: Always support the float complex and double complex C types in the struct module. Patch by Sergey B Kirpichev.

• gh-132915: fcntl.fcntl() and fcntl.ioctl() can now detect a buffer overflow and raise SystemError. The stack and memory can be corrupted in such case, so treat this error as fatal.

• gh-132017: Fix error when pyrepl is suspended, then resumed and terminated.

• gh-132893: Improved statistics.NormalDist.cdf() accuracy for inputs smaller than the mean.

• gh-130328: Speedup pasting in PyREPL on Windows. Fix by Chris Eibl.

• gh-132882: Fix copying of typing.Union objects containing objects that do not support the | operator.

• gh-93696: Fixed the breakpoint display error for frozen modules in pdb.

• gh-129965: Add MIME types for .7z, .apk, .deb, .glb, .gltf, .gz, .m4v, .php, .rar, .rpm, .stl and .wmv. Patch by Hugo van Kemenade.

• gh-132742: fcntl.fcntl() now supports arbitrary bytes-like objects, not only bytes. fcntl.ioctl() now automatically retries system calls failing with EINTR and releases the GIL during a system call even for large bytes-like object.

• gh-132451: The CLI for the PDB debugger now accepts a -p PID argument to allow attaching to a running process. The process must be running the same version of Python as the one running PDB.

• gh-125618: Add a format parameter to annotationlib.ForwardRef.evaluate(). Evaluating annotations in the FORWARDREF format now succeeds in more cases that would previously have raised an exception.

• gh-132805: Fix incorrect handling of nested non-constant values in the FORWARDREF format in annotationlib.

• gh-132734: Add new constants for Bluetooth sockets.

• gh-132673: Fix AssertionError raised on ctypes.Structure with _align_ = 0 and _fields_ = [].

• gh-132578: Rename the threading.Thread._handle field to avoid shadowing methods defined on subclasses of threading.Thread.

• gh-132561: Fix the public locked method of multiprocessing.SemLock class. Also adding 2 tests for the derivated multiprocessing.Lock and multiprocessing.RLock classes.

• gh-121468: Add pdb.set_trace_async() function to support await statements in pdb.

• gh-132493: typing.Protocol now uses annotationlib.get_annotations() when checking whether or not an instance implements the protocol with isinstance(). This enables support for isinstance checks against classes with deferred annotations.

• gh-132536: Do not disable PY_THROW event in bdb because it can’t be disabled.

• gh-132527: Include the valid typecode ‘w’ in the error message when an invalid typecode is passed to array.array.

• gh-132099: The Bluetooth socket with the BTPROTO_HCI protocol on Linux now accepts an address in the format of an integer device_id, not only a tuple (device_id,).

• gh-81793: Fix os.link() on platforms (like Linux) where the system link() function does not follow symlinks. On Linux, it now follows symlinks by default or if follow_symlinks=True is specified. On Windows, it now raises an error if follow_symlinks=True is passed. On macOS, it now raises an error if follow_symlinks=False is passed and the system linkat() function is not available at runtime.

• gh-132493: Support creation of typing.Protocol classes with annotations that cannot be resolved at class creation time.

• gh-132491: Rename annotationlib.value_to_string to annotationlib.type_repr() and provide better handling for function objects.

• gh-132426: Add annotationlib.get_annotate_from_class_namespace() as a helper for accessing annotations in metaclasses, and remove annotationlib.get_annotate_function.

• gh-70145: Add support for channels in Bluetooth HCI protocol (BTPROTO_HCI).

• gh-131913: Add a shortcut function multiprocessing.Process.interrupt() alongside the existing multiprocessing.Process.terminate() and multiprocessing.Process.kill() for an improved control over child process termination.

• gh-132439: Fix PyREPL on Windows: characters entered via AltGr are swallowed. Patch by Chris Eibl.

• gh-132429: Fix support of Bluetooth sockets on NetBSD and DragonFly BSD. Add support for cid and bdaddr_type in the BTPROTO_L2CAP address on FreeBSD. Return cid in getsockname() for BTPROTO_L2CAP if it is not zero.

• gh-132106: QueueListener.start now raises a RuntimeError if the listener is already started.

• gh-132417: Fix a NULL pointer dereference when a C function called using ctypes with restype py_object returns NULL.

• gh-132385: Fix instance error suggestions trigger potential exceptions in object.__getattr__() in traceback.

• gh-125866: Add optional add_scheme argument to urllib.request.pathname2url(); when set to true, a complete URL is returned. Likewise add optional require_scheme argument to url2pathname(); when set to true, a complete URL is accepted.

• gh-132308: A traceback.TracebackException now correctly renders the __context__ and __cause__ attributes from falsey Exception, and the exceptions attribute from falsey ExceptionGroup.

• gh-130645: Add colour to argparse help output. Patch by Hugo van Kemenade.

• gh-127495: In PyREPL, append a new entry to the PYTHON_HISTORY file after every statement. This should preserve command-line history after interpreter is terminated. Patch by Sergey B Kirpichev.

• gh-129463: Comparison of annotationlib.ForwardRef objects no longer uses the internal __code__ and __ast_node__ attributes, which are used as caches.

• gh-132250: Fixed the SystemError in cProfile when locating the actual C function of a method raises an exception.

• gh-132064: annotationlib.get_annotations() now uses the __annotate__ attribute if it is present, even if __annotations__ is not present. Additionally, the function now raises a TypeError if it is passed an object that does not have any annotatins.

• gh-130664: Support the '_' digit separator in formatting of the integral part of Decimal’s. Patch by Sergey B Kirpichev.

• gh-131952: Add color output to the json CLI. Patch by Tomas Roun.

• gh-132063: Prevent exceptions that evaluate as falsey (namely, when their __bool__ method returns False or their __len__ method returns 0) from being ignored by concurrent.futures.ProcessPoolExecutor and concurrent.futures.ThreadPoolExecutor.

• gh-132106: logging.handlers.QueueListener now implements the context manager protocol, allowing it to be used in a with statement.

• gh-132054: The application/yaml mime type (RFC 9512) is now supported by mimetypes. Patch by Sasha “Nelie” Chernykh and Hugo van Kemenade.

• gh-119605: Respect follow_wrapped for __init__() and __new__() methods when getting the class signature for a class with inspect.signature(). Preserve class signature after wrapping with warnings.deprecated(). Patch by Xuehai Pan.

• gh-118761: Improve import times by up to 33x for the shlex module, and improve the performance of shlex.quote() by up to 12x. Patch by Adam Turner.

• gh-85302: Add support for BTPROTO_SCO in sockets on FreeBSD.

• gh-131757: Make functools.lru_cache() call the cached function unlocked to allow concurrency.

• gh-131423: ssl can show descriptions for errors added in OpenSSL 3.4.1. Patch by Bénédikt Tran.

• gh-131434: Improve error reporting for incorrect format in time.strptime().

• gh-131524: Add help message to platform command-line interface. Contributed by Harry Lees.

• gh-100926: Move ctypes.POINTER() types cache from a global internal cache (_pointer_type_cache) to the ctypes._CData.__pointer_type__ attribute of the corresponding ctypes types. This will stop the cache from growing without limits in some situations.

• gh-85702: If zoneinfo._common.load_tzdata is given a package without a resource a ZoneInfoNotFoundError is raised rather than a IsADirectoryError.

• gh-123471: Make concurrent iterations over itertools.repeat safe under free-threading.

• gh-131127: Systems using LibreSSL now successfully build.

• gh-89157: Make the pure Python implementation of datetime.date.fromisoformat(), only accept ASCII strings for consistency with the C implementation.

• gh-130941: Fix configparser.ConfigParser parsing empty interpolation with allow_no_value set to True.

• gh-110067: Make heapq max-heap functions heapq.heapify_max(), heapq.heappush_max(), heapq.heappop_max(), and heapq.heapreplace_max() public. Previous underscored naming is kept for backwards compatibility. Additionally, the missing function heapq.heappushpop_max() has been added to both the C and Python implementations.

• gh-129098: Fix REPL traceback reporting when using compile() with an inexisting file. Patch by Bénédikt Tran.

• gh-130631: http.cookiejar.join_header_words() is now more similar to the original Perl version. It now quotes the same set of characters and always quote values that end with "\n".

• gh-130482: Add ability to specify name for tkinter.OptionMenu and tkinter.ttk.OptionMenu.

• gh-77065: Add keyword-only optional argument echo_char for getpass.getpass() for optional visual keyboard feedback support. Patch by Semyon Moroz.

• gh-130317: Fix PyFloat_Pack2() and PyFloat_Unpack2() for NaN’s with payload. This corrects round-trip for struct.unpack() and struct.pack() in case of the IEEE 754 binary16 “half precision” type. Patch by Sergey B Kirpichev.

• gh-130402: Joining running daemon threads during interpreter shutdown now raises PythonFinalizationError.

• gh-130167: Improve speed of difflib.IS_LINE_JUNK(). Patch by Semyon Moroz.

• gh-101410: Added more detailed messages for domain errors in the math module.

• gh-128384: Make warnings.catch_warnings use a context variable for holding the warning filtering state if the sys.flags.context_aware_warnings flag is set to true. This makes using the context manager thread-safe in multi-threaded programs. The flag is true by default in free-threaded builds and is otherwise false. The value of the flag can be overridden by the the -X context_aware_warnings command-line option or by the PYTHON_CONTEXT_AWARE_WARNINGS environment variable.

• gh-129719: Fix missing socket.CAN_RAW_ERR_FILTER constant in the socket module on Linux systems. It was missing since Python 3.11.

• gh-129027: Raise DeprecationWarning for sys._clear_type_cache(). This function was deprecated in Python 3.13 but it didn’t raise a runtime warning.

• gh-128307: Add eager_start keyword argument to asyncio.loop.create_task()

• gh-127604: Add support for printing the C stack trace on systems that support it via faulthandler.dump_c_stack() or via the c_stack argument in faulthandler.enable().

• gh-127385: Add the F_DUPFD_QUERY constant to the fcntl module.

• gh-126838: Add resolve_host keyword-only parameter to urllib.request.url2pathname(), and fix handling of file URLs with authorities.

• gh-82129: Fix NameError when calling typing.get_type_hints() on a dataclasses.dataclass() created by dataclasses.make_dataclass() with un-annotated fields.

• gh-122559: Remove __reduce__() and __reduce_ex__() methods that always raise TypeError in the C implementation of io.FileIO, io.BufferedReader, io.BufferedWriter and io.BufferedRandom and replace them with default __getstate__() methods that raise TypeError. This restores fine details of behavior of Python 3.11 and older versions.

• gh-122179: hashlib.file_digest() now raises BlockingIOError when no data is available during non-blocking I/O. Before, it added spurious null bytes to the digest.

• gh-53032: Expose decimal.IEEEContext() to support creation of contexts corresponding to the IEEE 754 (2008) decimal interchange formats. Patch by Sergey B Kirpichev.

• gh-120220: Deprecate the tkinter.Variable methods trace_variable(), trace_vdelete() and trace_vinfo(). Methods trace_add(), trace_remove() and trace_info() can be used instead.

• gh-113539: webbrowser: Names in the BROWSER environment variable can now refer to already registered web browsers, instead of always generating a new browser command.

  This makes it possible to set BROWSER to the value of one of the supported browsers on macOS.

• bpo-44172: Keep a reference to original curses windows in subwindows so that the original window does not get deleted before subwindows.

• gh-75223: Deprecate undotted extensions in mimetypes.MimeTypes.add_type(). Patch by Hugo van Kemenade.

IDLE¶

• gh-112936: fix IDLE: no Shell menu item in single-process mode.

Documentation¶

• gh-107006: Move documentation and example code for threading.local from its docstring to the official docs.

• gh-125142: As part of the builtin help intro text, show the keyboard shortcuts for the new, non-basic REPL (F1, F2, and F3).

Core and Builtins¶

• gh-133336: -J is no longer reserved for use by Jython. Patch by Adam Turner.

• gh-133261: Fix bug where the cycle GC could untrack objects in the trashcan because they looked like they were immortal. When objects are added to the trashcan, we take care to ensure they keep a mortal reference count.

• gh-133346: Added experimental color theming support to the _colorize module.

• gh-132917: For the free-threaded build, check the process memory usage increase before triggering a full automatic garbage collection. If the memory used has not increased 10% since the last collection then defer it.

• gh-91048: Add a new python -m asyncio ps PID command-line interface to inspect asyncio tasks in a running Python process. Displays a flat table of await relationships. A variant showing a tree view is also available as python -m asyncio pstree PID. Both are useful for debugging async code. Patch by Pablo Galindo, Łukasz Langa, Yury Selivanov, and Marta Gomez Macias.

• gh-133304: Workaround NaN’s “canonicalization” in PyFloat_Pack4() and PyFloat_Unpack4() on RISC-V.

• gh-133197: Improve SyntaxError error messages for incompatible string / bytes prefixes.

• gh-133231: Add new utilities of observing JIT compilation: sys._jit.is_available(), sys._jit.is_enabled(), and sys._jit.is_active().

Library¶

• gh-133194: ast.parse() will no longer parse new PEP 758 syntax with older feature_version passed.

Core and Builtins¶

• gh-131798: Split CALL_LEN into several uops allowing the JIT to remove them when optimizing. Patch by Diego Russo.

• gh-131798: Use sym_new_type instead of sym_new_not_null for _BUILD_STRING, _BUILD_SET

• gh-132942: Fix two races in the type lookup cache. This affected the free-threaded build and could cause crashes (apparently quite difficult to trigger).

• gh-131798: Propagate the return type of _BINARY_OP_SUBSCR_TUPLE_INT in JIT. Patch by Tomas Roun

• gh-132952: Speed up startup with the -S argument by importing the private _io module instead of io. This fixes a performance regression introduced earlier in Python 3.14 development and restores performance to the level of Python 3.13.

• gh-131798: Allow the JIT to remove int guards after _CALL_LEN by setting the return type to int. Patch by Diego Russo

• gh-131798: Split CALL_TUPLE_1 into several uops allowing the JIT to remove some of them. Patch by Tomas Roun

• gh-131798: Split CALL_STR_1 into several uops allowing the JIT to remove some of them. Patch by Tomas Roun

• gh-132825: Enhance unhashable key/element error messages for dict and set. Patch by Victor Stinner.

• gh-131591: Reset any PEP 768 remote debugging pending call in children after os.fork() calls.

• gh-132713: Fix repr(list) race condition: hold a strong reference to the item while calling repr(item). Patch by Victor Stinner.

• gh-132661: Implement PEP 750 (Template Strings). Add new syntax for t-strings and implement new internal string.templatelib.Template and string.templatelib.Interpolation types.

• gh-132479: Fix compiler crash in certain circumstances where multiple module-level annotations include comprehensions and other nested scopes.

• gh-132747: Fix a crash when calling __get__() of a method with a None second argument.

• gh-132744: Certain calls now check for runaway recursion and respect the system recursion limit.

• gh-132449: Syntax errors that look like misspellings of Python keywords now provide a helpful fix suggestion for the typo. Contributed by Pablo Galindo Salgado.

Library¶

• gh-132737: Support profiling code that requires __main__, such as pickle.

Core and Builtins¶

• gh-132639: Added PyLong_AsNativeBytes(), PyLong_FromNativeBytes() and PyLong_FromUnsignedNativeBytes() to the limited C API.

• gh-100239: Add specialisation for BINARY_OP/SUBSCR on list and slice.

• gh-132508: Uses tagged integers on the evaluation stack to represent the instruction offsets when reraising an exception. This avoids the need to box the integer which could fail in low memory conditions.

• gh-124476: Fix decoding from the locale encoding in the C.UTF-8 locale.

• gh-131927: Compiler warnings originating from the same module and line number are now only emitted once, matching the behaviour of warnings emitted from user code. This can also be configured with warnings filters.

• gh-132457: Make staticmethod() and classmethod() generic.

• gh-131798: Use sym_new_type instead of sym_new_not_null for _BUILD_LIST, _BUILD_SET, _BUILD_MAP

• gh-131798: Split CALL_TYPE_1 into several uops allowing the JIT to remove some of them.

• gh-132386: Fix crash when passing a dict subclass as the globals parameter to exec().

• gh-127682: No longer call __iter__ twice when creating and executing a generator expression. Creating a generator expression from a non-interable will raise only when the generator expression is executed. This brings the behavior of generator expressions in line with other generators.

• gh-132261: The internal storage for annotations and annotate functions on classes now uses different keys in the class dictionary. This eliminates various edge cases where access to the __annotate__ and __annotations__ attributes would behave unpredictably.

• gh-132284: Don’t wrap base PyCFunction slots on class creation if not overridden.

• gh-130415: Improve the JIT’s ability to remove unused constant and local variable loads, and fix an issue where deallocating unused values could cause JIT code to crash or behave incorrectly.

• gh-126703: Fix possible use after free in cases where a method’s definition has the same lifetime as its self.

• gh-132286: Fix that type.__annotate__ was not deleted, when type.__annotations__ was deleted.

• gh-131798: Allow the JIT to remove an extra _TO_BOOL_BOOL instruction after _CONTAINS_OP_DICT by setting the return type to bool.

• gh-124715: Prevents against stack overflows when calling Py_DECREF(). Third-party extension objects no longer need to use the “trashcan” mechanism, as protection is now built into the Py_DECREF() macro.

• gh-131798: Allow the JIT compiler to remove some type checks for operations on lists, tuples, dictionaries, and sets.

• gh-128398: Improve error message when an object supporting the synchronous (resp. asynchronous) context manager protocol is entered using async with (resp. with) instead of with (resp. async with). Patch by Bénédikt Tran.

• gh-131798: Allow the JIT to remove unicode guards after _BINARY_OP_SUBSCR_STR_INT by setting the return type to string.

• gh-131878: Handle uncaught exceptions in the main input loop for the new REPL.

• gh-131878: Fix support of unicode characters with two or more codepoints on Windows in the new REPL.

• gh-126835: Move constant folding to the peephole optimizer. Rename AST optimization related files (Python/ast_opt.c -> Python/ast_preprocess.c), structs (_PyASTOptimizeState -> _PyASTPreprocessState) and functions (_PyAST_Optimize -> _PyAST_Preprocess, _PyCompile_AstOptimize -> _PyCompile_AstPreprocess).

• gh-114809: Add support for macOS multi-arch builds with the JIT enabled

• gh-131507: PyREPL now supports syntax highlighting. Contributed by Łukasz Langa.

• gh-130907: If the __annotations__ of a module object are accessed while the module is executing, return the annotations that have been defined so far, without caching them.

• gh-130104: Three-argument pow() now try calling __rpow__() if necessary. Previously it was only called in two-argument pow() and the binary power operator.

• gh-130070: Fixed an assertion error for exec() passed a string source and a non-None closure. Patch by Bartosz Sławecki.

• gh-129958: Fix a bug that was allowing newlines inconsistently in format specifiers for single-quoted f-strings. Patch by Pablo Galindo.

• gh-129858: elif statements that follow an else block now have a specific error message.

• gh-69605: Add module autocomplete to PyREPL.

• gh-128555: Add the sys.flags.thread_inherit_context flag.

  • This flag is set to true by default on the free-threaded build and false otherwise. If the flag is true, starting a new thread using threading.Thread will, by default, use a copy of the contextvars.Context from the caller of threading.Thread.start() rather than using an empty context.

  • Add the -X thread_inherit_context command-line option and PYTHON_THREAD_INHERIT_CONTEXT environment variable, which set the thread_inherit_context flag.

  • Add the context keyword parameter to Thread. It can be used to explicitly pass a context value to be used by a new thread.

  • Make the _contextvars module built-in.

• gh-123539: Improve SyntaxError message for using import ... as and from ... import ... as with not a name.

• gh-102567: -X importtime now accepts value 2, which indicates that an importtime entry should also be printed if an imported module has already been loaded. Patch by Noah Kim and Adam Turner.

• gh-116436: Improve error message when TypeError occurs during dict.update()

• gh-103997: String arguments passed to “-c” are now automatically dedented as if by textwrap.dedent(). This allows “python -c” invocations to be indented in shell scripts without causing indentation errors. (Patch by Jon Crall and Steven Sun)

Library¶

• gh-89562: Remove hostflags member from PySSLContext struct.

C API¶

• gh-133166: Fix regression where PyType_GetModuleByDef() returns NULL without setting TypeError when a static type is passed.

• gh-133164: Add PyUnstable_Object_IsUniqueReferencedTemporary() function for determining if an object exists as a unique temporary variable on the interpreter’s stack. This is a replacement for some cases where checking that Py_REFCNT() is one is no longer sufficient to determine if it’s safe to modify a Python object in-place with no visible side effects.

• gh-133140: Add PyUnstable_Object_IsUniquelyReferenced() as a replacement for Py_REFNCT(op) == 1 on free threaded builds of Python.

• gh-131747: On non-Windows platforms, deprecate using ctypes.Structure._pack_ to use a Windows-compatible layout on non-Windows platforms. The layout should be specified explicitly by setting ctypes.Structure._layout_ to 'ms'.

• gh-128972: For non-free-threaded builds, the memory layout of PyASCIIObject is reverted to match Python 3.13. (Note that the structure is not part of stable ABI and so its memory layout is guaranteed to remain stable.)

• gh-133079: The undocumented APIs Py_C_RECURSION_LIMIT and PyThreadState.c_recursion_remaining, added in 3.13, are removed without a deprecation period.

• gh-132987: The k and K formats in PyArg_Parse() now support the __index__() special method, like all other integer formats.

• gh-132909: Fix an overflow when handling the K format in Py_BuildValue(). Patch by Bénédikt Tran.

• gh-132798: Deprecated and undocumented functions PyUnicode_AsEncodedObject(), PyUnicode_AsDecodedObject(), PyUnicode_AsEncodedUnicode() and PyUnicode_AsDecodedUnicode() are scheduled for removal in 3.15.

• gh-132470: Creating a ctypes.CField with a byte_size that does not match the actual type size now raises a ValueError instead of crashing the interpreter.

• gh-112068: [Reverted in gh-136991] Add support of nullable arguments in PyArg_Parse() and similar functions. Adding ? after any format unit makes None be accepted as a value.

• gh-50333: Non-tuple sequences are deprecated as argument for the (items) format unit in PyArg_ParseTuple() and other argument parsing functions if items contains format units which store a borrowed buffer or a borrowed reference.

Build¶

• gh-113464: Use the cpython-bin-deps “externals” repository for Windows LLVM dependency management. Installing LLVM manually is no longer necessary for Windows JIT builds.

• gh-133183: iOS compiler shims now include IPHONEOS_DEPLOYMENT_TARGET in target triples, ensuring that SDK version minimums are honored.

• gh-133167: Fix compilation process with --enable-optimizations and --without-docstrings.

• gh-133171: Since free-threaded builds do not support the experimental JIT compiler, prevent these configurations from being combined.

• gh-132758: Fix building with tail call interpreter and pystats.

• gh-132649: The PClayout script now allows passing --include-tcltk on Windows ARM64.

• gh-132257: Change the default LTO flags on GCC to not pass -flto-partition=none, and allow parallelization of LTO. For newer GNU makes and GCC, this has a multiple factor speedup for LTO build times, with no noticeable loss in performance.

• gh-132026: Fix use of undefined identifiers in platform triplet detection on MIPS Linux platforms.

macOS¶

• gh-124111: Update macOS installer to use Tcl/Tk 8.6.16.

• gh-131423: Update macOS installer to use OpenSSL 3.0.16. Patch by Bénédikt Tran.

• gh-131025: Update macOS installer to ship with SQLite 3.49.1.

Windows¶

• gh-131423: Update bundled version of OpenSSL to 3.0.16. The new build also disables uplink support, which may be relevant to embedders but has no impact on normal use.

• gh-131453: Some SND_* and MB_* constants are added to winsound.

• gh-91349: Replaces our copy of zlib with zlib-ng, for performance improvements in zlib.

• gh-131025: Update Windows installer to ship with SQLite 3.49.1.

Tools/Demos¶

• gh-132121: Always escape non-printable Unicode characters in pygettext.

• gh-131852: msgfmt no longer adds the POT-Creation-Date to generated .mo files for consistency with GNU msgfmt.

Tests¶

• gh-131277: Allow to unset one or more environment variables at once via EnvironmentVarGuard.unset(). Patch by Bénédikt Tran.

• gh-131050: test_ssl.test_dh_params is skipped if the underlying TLS library does not support finite-field ephemeral Diffie-Hellman.

Security¶

• gh-131809: Update bundled libexpat to 2.7.1

• gh-131261: Upgrade to libexpat 2.7.0

• gh-121284: Fix bug in the folding of rfc2047 encoded-words when flattening an email message using a modern email policy. Previously when an encoded-word was too long for a line, it would be decoded, split across lines, and re-encoded. But commas and other special characters in the original text could be left unencoded and unquoted. This could theoretically be used to spoof header lines using a carefully constructed encoded-word if the resulting rendered email was transmitted or re-parsed.

Library¶

• gh-132174: Fix function name in error message of _interpreters.run_string.

• gh-132171: Fix crash of _interpreters.run_string on string subclasses.

• gh-129204: Introduce new _PYTHON_SUBPROCESS_USE_POSIX_SPAWN environment variable knob in subprocess to control the use of os.posix_spawn().

• gh-132159: Do not shadow user arguments in generated __new__() by decorator warnings.deprecated. Patch by Xuehai Pan.

• gh-132168: The ctypes.py_object type now supports subscription, making it a generic type.

• gh-84481: Add the zipfile.ZipFile.data_offset attribute, which stores the offset to the beginning of ZIP data in a file when available. When the zipfile.ZipFile is opened in either mode 'w' or 'x' and the underlying file does not support tell(), the value will be None instead.

• gh-132075: Fix possible use of socket address structures with uninitialized members. Now all structure members are initialized with zeroes by default.

• gh-118761: Improve import times by up to 27x for the string module. Patch by Adam Turner.

• gh-125434: Display thread name in faulthandler. Patch by Victor Stinner.

• gh-132002: Fix crash when deallocating contextvars.ContextVar with weird unahashable string names.

• gh-131938: xml.etree.ElementTree: update the error message when an element to remove via Element.remove is not found. Patch by Bénédikt Tran.

• gh-115942: Add threading.RLock.locked(), multiprocessing.Lock.locked(), multiprocessing.RLock.locked(), and allow multiprocessing.managers.SyncManager.Lock() and multiprocessing.managers.SyncManager.RLock() to proxy locked() call.

• gh-131974: Fix several thread-safety issues in ctypes on the free threaded build.

• gh-118761: Improve the import time of the ast module by extracting the unparse() function to a helper module.

• gh-107369: Improved performance of textwrap.indent() by an average of ~1.3x. Patch by Adam Turner.

• gh-131792: Improved performance of textwrap.dedent() by an average of ~2.4x, (with improvements of up to 4x for large inputs), and fixed a bug where blank lines with whitespace characters other than space or horizontal tab were not normalised to the newline. Patch by Adam Turner, Marius Juston, and Pieter Eendebak.

• gh-131668: socket: Fix code parsing AF_BLUETOOTH socket addresses.

• gh-60115: Support frozen modules for linecache.getline().

• gh-131492: Fix a resource leak when constructing a gzip.GzipFile with a filename fails, for example when passing an invalid compresslevel.

• gh-131435: 10-20% performance improvement of random.randint().

• gh-131461: Fix ResourceWarning when constructing a gzip.GzipFile in write mode with a broken file object.

• gh-125866: Deprecate the nturl2path module. Call urllib.request.url2pathname() and pathname2url() instead.

• gh-126367: Fix issue where urllib.request.url2pathname() raised OSError when given a Windows URI containing a colon character not following a drive letter, such as before an NTFS alternate data stream.

• gh-120144: Disable CALL event in bdb in monitoring backend when we don’t need any new events on the code object to get a better performance.

• gh-131358: Register cseuckr as an encoding alias for euc_kr.

• gh-131325: Fix sendfile fallback implementation to drain data after writing to transport in asyncio.

• gh-90548: platform.libc_ver() can now detect and report the version of musl on Alpine Linux.

• gh-129843: Fix incorrect argument passing in warnings.warn_explicit().

• gh-70647: When creating a datetime object with an out of range date a more informative error is raised.

• gh-130914: Allow graphlib.TopologicalSorter.prepare() to be called more than once as long as sorting has not started. Patch by Daniel Pope.

• gh-131236: Allow to generate multiple UUIDs at once via python -m uuid --count.

• gh-126895: Fix readline in free-threaded build.

• gh-121468: $_asynctask is added as a pdb convenience variable to access the current asyncio task if applicable.

• gh-118761: Improve import time of locale using lazy import re. Patch by Semyon Moroz.

• gh-129598: Fix ast.unparse() when ast.Interactive contains multiple statements.

• gh-85162: The http.server module now includes built-in support for HTTPS servers exposed by http.server.HTTPSServer. This functionality is exposed by the command-line interface (python -m http.server) through the --tls-cert, --tls-key and --tls-password-file options. Patch by Semyon Moroz.

• gh-129463: The implementations of equality and hashing for annotationlib.ForwardRef now use all attributes on the object. Two ForwardRef objects are equal only if all attributes are equal.

• gh-128593: annotationlib.ForwardRef objects no longer cache their value when they are successfully evaluated. Successive calls to annotationlib.ForwardRef.evaluate() may return different values.

• gh-117779: Fix reading duplicated entries in zipfile by name. Reading duplicated entries (except the last one) by ZipInfo now emits a warning instead of raising an exception.

• gh-128715: The class of Structure/Union field descriptors is now available as CField, and has new attributes to aid debugging and introspection.

• gh-128055: Fix test.test_sysconfig.test_sysconfigdata_json when running outside the build directory (eg. after installing).

• gh-126037: xml.etree.ElementTree: Fix a crash in Element.find, Element.findtext and Element.findall when the tag to find implements an __eq__() method mutating the element being queried. Patch by Bénédikt Tran.

• gh-127794: When headers are added to email.message.Message objects, either through email.message.Message.__setitem__() or email.message.Message.add_header(), the field name is now validated according to RFC 5322, Section 2.2 and a ValueError is raised if the field name contains any invalid characters.

• gh-123599: Deprecate pathlib.PurePath.as_uri(); use pathlib.Path.as_uri() instead.

• gh-126033: xml.etree.ElementTree: Fix a crash in Element.remove when the element is concurrently mutated. Patch by Bénédikt Tran.

• gh-120144: Add the optional backend of sys.monitoring to bdb and use it for pdb.

• gh-74598: Add fnmatch.filterfalse() for excluding names matching a pattern. Patch by Bénédikt Tran.

• gh-114917: Add support for AI_NUMERICSERV in getaddrinfo emulation

• bpo-17254: Added aliases for Thai Language using Microsoft Code Pages.

Documentation¶

• gh-131417: Mention asyncio.Future and asyncio.Task in generic classes list.

Core and Builtins¶

• gh-131798: Allow the JIT to remove an extra _TO_BOOL_BOOL instruction after _CONTAINS_OP_SET by setting the return type to bool.

• gh-132011: Fix crash when calling list.append() as an unbound method.

• gh-131998: Fix a crash when using an unbound method descriptor object in a function where a bound method descriptor was used.

• gh-131591: Implement PEP 768 (Safe external debugger interface for CPython). Add a new sys.remote_exec() function to the sys module. This function schedules the execution of a Python file in a separate process. Patch by Pablo Galindo, Matt Wozniski and Ivona Stojanovic.

• gh-131798: Allow JIT to omit str guard in truthiness test when str type is known.

• gh-131833: Add support for optionally dropping grouping parentheses when using multiple exception types as per PEP 758. Patch by Pablo Galindo

• gh-130924: Usage of a name in a function-scope annotation no longer triggers creation of a cell for that variable. This fixes a regression in earlier alphas of Python 3.14.

• gh-131800: Improve the experimental JIT’s ability to remove type checks for certain subscripting operations.

• gh-131738: Compiler emits optimized code for builtin any/all/tuple calls over a generator expression.

• gh-131719: Fix missing NULL check in _PyMem_FreeDelayed in free-threaded build.

• gh-131670: Fix anext() failing on sync __anext__() raising an exception.

• gh-131666: Fix signature of anext_awaitable.close objects. Patch by Bénédikt Tran.

• gh-130415: Optimize comparison of two constants in JIT builds

• gh-129149: Add fast path for small and medium-size integers in PyLong_FromInt32(), PyLong_FromUInt32(), PyLong_FromInt64() and PyLong_FromUInt64(). Patch by Chris Eibl.

• gh-130887: Optimize the AArch64 code generation for the JIT. Patch by Diego Russo

• gh-130956: Optimize the AArch64 code generation for the JIT. Patch by Diego Russo

• gh-130928: Fix error message when formatting bytes using the 'i' flag. Patch by Maxim Ageev.

• gh-130935: Annotations at the class and module level that are conditionally defined are now only reflected in __annotations__ if the block they are in is executed. Patch by Jelle Zijlstra.

• gh-130775: Do not crash on negative column and end_column in ast locations.

• gh-130704: Optimize LOAD_FAST and its superinstruction form to reduce reference counting overhead. These instructions are replaced with faster variants that load borrowed references onto the operand stack when we can prove that the reference in the frame outlives the reference loaded onto the stack.

• gh-88887: Fixing multiprocessing Resource Tracker process leaking, usually observed when running Python as PID 1.

• gh-130115: Fix an issue with thread identifiers being sign-extended on some platforms.

Library¶

• gh-99108: Add support for built-in implementation of HMAC (RFC 2104) based on HACL*. Patch by Bénédikt Tran.

Core and Builtins¶

• gh-130080: Implement PEP 765: Disallow return/break/continue that exit a finally block.

• gh-129900: Fix return codes inside SystemExit not getting returned by the REPL.

• gh-128632: Disallow __classdict__ as the name of a type parameter. Using this name would previously crash the interpreter in some circumstances.

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

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

C API¶

• gh-131740: Update PyUnstable_GC_VisitObjects to traverse perm gen.

• gh-131525: The PyTupleObject now caches the computed hash value in the new field ob_hash.

Build¶

• gh-131865: The DTrace build now properly passes the CC and CFLAGS variables to the dtrace command when utilizing SystemTap on Linux.

• gh-131675: Fix mimalloc library builds for 32-bit ARM targets.

• gh-131691: clang-cl on Windows needs option /EHa to support SEH (structured exception handling) correctly. Fix by Chris Eibl.

• gh-131278: Add optimizing flag WITH_COMPUTED_GOTOS to Windows builds for when using a compiler that supports it (currently clang-cl). Patch by Chris Eibl.

• gh-130213: Update the vendored HACL* library to fix build issues with older clang compilers.

• gh-130673: Fix potential KeyError when handling object sections during JIT building process.

macOS¶

• gh-128540: Ensure web browser is launched by webbrowser.open() on macOS, even for file:// URLs.

Windows¶

• gh-131020: pylauncher correctly detects a BOM when searching for the shebang. Fix by Chris Eibl.

Tools/Demos¶

• gh-130453: Make it possible to override default keywords in pygettext.

• gh-85012: Correctly reset msgctxt when compiling messages in msgfmt.

• gh-130453: Extend support for specifying custom keywords in pygettext.

• gh-130195: Add warning messages when pygettext unimplemented -a/--extract-all option is called.

• gh-130057: Add support for translator comments in pygettext.py.

• gh-130025: The iOS testbed now correctly handles symlinks used as Python framework references.

• gh-129911: Fix the keyword entry in the help output of pygettext.

Tests¶

• gh-129200: Multiple iOS testbed runners can now be started at the same time without introducing an ambiguity over simulator ownership.

• gh-130292: The iOS testbed will now run successfully on a machine that has not previously run Xcode tests (such as CI configurations).

• gh-130293: The tests of terminal colorization are no longer sensitive to the value of the TERM variable in the testing environment.

• gh-129401: Fix a flaky test in test_repr_rlock that checks the representation of multiprocessing.RLock.

• gh-126332: Add unit tests for pyrepl.

Security¶

• gh-127371: Avoid unbounded buffering for tempfile.SpooledTemporaryFile.writelines(). Previously, disk spillover was only checked after the lines iterator had been exhausted. This is now done after each line is written.

Library¶

• gh-131204: Use monospace font from System Font Stack for cross-platform support in difflib.HtmlDiff.

• gh-131196: Improve performance of uuid.UUID.hex and uuid.UUID.__str__.

• gh-130940: The behavior of PyConfig.use_system_logger was modified to be enabled by default on iOS. It remains disabled by default on macOS.

• gh-131123: Supported completions for attributes of convenience variables in pdb.

• gh-93096: Removed undocumented CLI python -m difflib. Use python -m doctest Lib/difflib.py -v instead. Patch by Semyon Moroz.

• gh-93096: Removed undocumented -t and -v arguments of python -m pickle. Use python -m doctest Lib/pickle.py -v instead. Patch by Semyon Moroz.

• gh-81267: Correct time.sleep() error message when an object that cannot be interpreted as an integer or float is provided.

• gh-93096: Removed undocumented -t and -v arguments of python -m pickletools. Use python -m doctest Lib/pickletools.py -v instead. Patch by Semyon Moroz.

• gh-131045: Fix issue with __contains__, values, and pseudo-members for enum.Flag.

• gh-130959: Fix pure-Python implementation of datetime.time.fromisoformat() to reject times with spaces in fractional part (for example, 12:34:56.400 +02:00), matching the C implementation. Patch by Michał Gorny.

• gh-130806: Deleting gzip.GzipFile before it is closed now emits a ResourceWarning.

• gh-130637: Add validation for numeric response data in poplib.POP3.stat() method

• gh-130665: Only apply locale to calendar CLI when set via --locale and not via LANG environment variable.

• gh-130660: sys.ps1 and sys.ps2 are now restored after code.interact() call.

• gh-130608: Remove dirs_exist_ok argument from pathlib.Path.copy() and copy_into(). These methods are new in Python 3.14.

• gh-130461: Remove .. index:: directives from the uuid module documentation. These directives previously created entries in the general index for getnode() as well as the uuid1(), uuid3(), uuid4(), uuid5(), and uuid8() constructor functions.

• gh-130379: The zipapp module now calculates the list of files to be added to the archive before creating the archive. This avoids accidentally including the target when it is being created in the source directory.

• gh-82987: Inline breakpoints like breakpoint() or pdb.set_trace() will always stop the program at calling frame, ignoring the skip pattern (if any).

• gh-125377: <tab> at the beginning of the line in pdb multi-line input will fill in a 4-space indentation now, instead of inserting a \t character.

• gh-125413: Ensure the path returned from pathlib.Path.copy() or move() has fresh info.

• gh-65697: stdlib configparser will now attempt to validate that keys it writes will not result in file corruption (creating a file unable to be accurately parsed by a future read() call from the same parser). Attempting a corrupting write() will raise an InvalidWriteError.

• gh-125413: Speed up Path.copy by making better use of info internally.

• gh-130285: Fix corner case for random.sample() allowing the counts parameter to specify an empty population. So now, sample([], 0, counts=[]) and sample('abc', k=0, counts=[0, 0, 0]) both give the same result as sample([], 0).

• gh-124703: Executing quit command in pdb will raise bdb.BdbQuit when pdb is started from an interactive console using breakpoint() or pdb.set_trace().

• gh-107773: Make datetime subclass __repr__() consistent both implementations. Patch by Semyon Moroz.

• gh-130250: Fix regression in traceback.print_last().

• gh-123471: Make concurrent iterations over itertools.batched safe under free-threading.

• gh-57537: Support breakpoints for zipimport modules on pdb

• gh-130230: Fix crash in pow() with only Decimal third argument.

• gh-126944: Show explicit errors when required arguments of pdb commands are missing

• gh-127750: Improve repr of functools.singledispatchmethod methods and descriptors.

• gh-128520: Apply type conversion consistently in pathlib.PurePath and Path methods can accept a path object as an argument, such as match() and rename(). The argument is now converted to path object if it lacks a with_segments() attribute, and not otherwise.

• gh-118761: Reverts a change in the previous release attempting to make some stdlib imports used within the subprocess module lazy as this was causing errors during __del__ finalizers calling methods such as terminate, or kill, or send_signal.

• gh-130164: Fixed failure to raise TypeError in inspect.Signature.bind() for positional-only arguments provided by keyword when a variadic keyword argument (e.g. **kwargs) is present.

• gh-130151: Fix reference leaks in _hashlib.hmac_new() and _hashlib.hmac_digest(). Patch by Bénédikt Tran.

• gh-130145: Fix asyncio.AbstractEventloop.run_forever() when another loop is already running.

• gh-130139: Fix bug where ast.parse() did not error on AST input which is not of the correct type, when called with optimize=False.

• gh-127260: Forbid the use of colon (“:”) as a fractional component separator and other improvements to the consistency of error raising between the C and Python implementations of datetime.time.fromisoformat() and datetime.datetime.fromisoformat(). Patch by Semyon Moroz.

• gh-85795: Using super() and __class__ closure variable in user-defined methods of typing.NamedTuple subclasses is now explicitly prohibited at runtime. Contributed by Bartosz Sławecki in gh-130082.

• gh-118761: Improve import time of cmd by lazy importing inspect and removing string. Patch by Semyon Moroz.

• gh-129726: Fix gzip.GzipFile raising an unraisable exception during garbage collection when referring to a temporary object by breaking the reference loop with weakref.

• gh-127750: Remove broken functools.singledispatchmethod() caching introduced in gh-85160. Achieve the same performance using different optimization.

• gh-129948: Add support for shared set to multiprocessing.managers.SyncManager via SyncManager.set().

• gh-129965: Update MIME types for .avi and .wav. Add MIME types for .docx, .pptx, .xlsx, .epub, .flac, .m4a, .odg, .odp, .ods, .odt, .oga, .ogg, .ogx and .weba. Patch by Hugo van Kemenade.

• gh-129889: Support context manager protocol by contextvars.Token. Patch by Andrew Svetlov.

• gh-97850: Update the deprecation warning of importlib.abc.Loader.load_module().

• gh-129678: configparser.ConfigParser: do not write an empty unnamed section

• gh-128641: Restore configparser.ConfigParser.read() performance.

• gh-129569: Fix unicodedata.normalize() to always return a built-in str object when given an input of a str subclass, regardless of whether the string is already normalized.

• gh-128231: Execution of multiple statements in the new REPL now stops immediately upon the first exception encountered. Patch by Bartosz Sławecki.

• gh-96092: Fix bug in traceback.walk_stack() called with None where it was skipping more frames than in prior versions. This bug fix also changes walk_stack to walk the stack in the frame where it was called rather than where it first gets used.

• gh-129288: Add optional l2_cid and l2_bdaddr_type fields to socket BTPROTO_L2CAP sockaddr tuple.

• gh-128703: Fix mimetypes.guess_type() to use default mapping for empty Content-Type in registry.

• gh-128647: Eagerly write to buffers passed to gzip.GzipFile’s readinto() and readinto1() implementations, avoiding unnecessary allocations. Patch by Chris Markiewicz.

• gh-128184: Improve display of annotationlib.ForwardRef object within inspect.Signature representations. This also fixes a NameError that was raised when using dataclasses.dataclass() on classes with unresolvable forward references.

• gh-128041: Add concurrent.futures.ProcessPoolExecutor.terminate_workers() and concurrent.futures.ProcessPoolExecutor.kill_workers() as ways to terminate or kill all living worker processes in the given pool. (Contributed by Charles Machalow in gh-130849.)

• gh-127647: Add protocols io.Reader and io.Writer as alternatives to typing.IO, typing.TextIO, and typing.BinaryIO.

• gh-109798: Added additional information into error messages in datetime, and made the messages more consistent between the C and Python implementations. Patch by Semyon Moroz.

• gh-125746: Delay deprecated zipimport.zipimporter.load_module() removal time to 3.15. Use zipimport.zipimporter.exec_module() instead.

• gh-74028: Add the optional buffersize parameter to concurrent.futures.Executor.map() to limit the number of submitted tasks whose results have not yet been yielded. If the buffer is full, iteration over the iterables pauses until a result is yielded from the buffer.

• gh-124927: Non-printing characters are now properly handled in the new REPL.

• gh-124096: Turn on virtual terminal mode and enable bracketed paste in REPL on Windows console. (If the terminal does not support bracketed paste, enabling it does nothing.)

• gh-89083: Add uuid.uuid7() for generating UUIDv7 objects as specified in RFC 9562. Patch by Bénédikt Tran.

• gh-89083: Add uuid.uuid6() for generating UUIDv6 objects as specified in RFC 9562. Patch by Bénédikt Tran.

• gh-117151: Increase io.DEFAULT_BUFFER_SIZE from 8k to 128k and adjust open() on platforms where os.fstat() provides a st_blksize field (such as Linux) to use max(min(blocksize, 8 MiB), io.DEFAULT_BUFFER_SIZE) rather than always using the device block size. This should improve I/O performance. Patch by Romain Morotti.

• gh-105499: Make types.UnionType an alias for typing.Union. Both int | str and Union[int, str] now create instances of the same type. Patch by Jelle Zijlstra.

• gh-93096: Document the command-line for mimetypes. It now exits with 1 on failure instead of 0 and 2 on incorrect command-line parameters instead of 1. Also, errors are printed to stderr instead of stdout and their text is made tighter. Patch by Oleg Iarygin and Hugo van Kemenade.

Documentation¶

• gh-125722: Require Sphinx 8.2.0 or later to build the Python documentation. Patch by Adam Turner.

• gh-129712: The wheel tags supported by each macOS universal SDK option are now documented.

• gh-46236: C API: Document PyUnicode_RSplit(), PyUnicode_Partition() and PyUnicode_RPartition().

Core and Builtins¶

• gh-131141: Fix data race in sys.monitoring instrumentation while registering callback.

• gh-130804: Fix support of unicode characters on Windows in the new REPL.

• gh-130932: Fix incorrect exception handling in _PyModule_IsPossiblyShadowing

• gh-122029: sys.setprofile() and sys.settrace() will not generate a c_call event for INSTRUMENTED_CALL_FUNCTION_EX if the callable is a method with a C function wrapped, because we do not generate c_return event in such case.

• gh-129964: Fix JIT crash on Windows on Arm. Patch by Diego Russo and Brandt Bucher.

• gh-130851: Fix a crash in the free threading build when constructing a code object with co_consts that contains instances of types that are not otherwise generated by the bytecode compiler.

• gh-128534: Ensure that both left and right branches have the same source for async for loops. Add these branches to the co_branches() iterator.

• gh-130794: Fix memory leak in the free threaded build when resizing a shared list or dictionary from multiple short-lived threads.

• gh-130415: Improve JIT understanding of integers in boolean context.

• gh-130382: Fix PyRefTracer_DESTROY not being sent from Python/ceval.c Py_DECREF().

• gh-130574: Renumber RESUME from 149 to 128.

• gh-124878: Fix race conditions during runtime finalization that could lead to accessing freed memory.

• gh-130415: Improve the experimental JIT’s ability to narrow boolean values based on the results of truthiness tests.

• gh-130618: Fix a bug that was causing UnicodeDecodeError or SystemError to be raised when using f-strings with lambda expressions with non-ASCII characters. Patch by Pablo Galindo

• gh-123044: Make sure that the location of branch targets in match cases is in the body, not the pattern.

• gh-128534: Add branch monitoring (BRANCH_LEFT and BRANCH_RIGHT events) for async for loops.

• gh-130163: Fix possible crashes related to concurrent change and use of the sys module attributes.

• gh-122029: INSTRUMENTED_CALL_KW will expand the method before monitoring to reflect the actual behavior more accurately.

• gh-130415: Improve JIT’s ability to optimize strings in boolean contexts.

• gh-130396: Use actual stack limits (from pthread_getattr_np(3)) for linux, and other systems with _GNU_SOURCE defined, when determining limits for C stack protection.

• gh-128396: Fix a crash that occurs when calling locals() inside an inline comprehension that uses the same local variable as the outer frame scope where the variable is a free or cell var.

• gh-129107: Fix two more bytearray functions for free threading.

• gh-127705: Use tagged references (_PyStackRef) for the default build as well as for the free-threading build. This has a small negative performance impact short-term but will enable larger speedups in the future and significantly reduce maintenance costs by allowing a single implementation of tagged references in the future.

• gh-130094: Fix two race conditions involving concurrent imports that could lead to spurious failures with ModuleNotFoundError.

• gh-129107: Make bytearray iterator safe under free threading.

• gh-115802: Use the more efficient “medium” code model for JIT-compiled code on supported platforms.

• gh-107956: A build-details.json file is now install in the platform-independent standard library directory (PEP 739 implementation).

• gh-116042: Fix location for SyntaxErrors of invalid escapes in the tokenizer. Patch by Pablo Galindo

• gh-91079: Change C stack overflow protection to consider the amount of stack consumed, rather than a counter. This allows deeper recursion in many cases, but remains safe.

• gh-129715: Improve the experimental JIT’s handling of returns to unknown callers.

Library¶

• gh-129983: Fix data race in compile_template in sre.c.

Core and Builtins¶

• gh-129967: Fix a race condition in the free threading build when repr(set) is called concurrently with set.clear().

• gh-129953: The internal (evaluation) stack is now spilled to memory whenever execution escapes from the interpreter or JIT compiled code. This should have no observable effect in either Python or builtin extensions, but will allow various important optimizations in the future.

• gh-129515: Clarify syntax error messages for conditional expressions when a statement is specified before an if or after an else keyword.

• gh-129349: bytes.fromhex() and bytearray.fromhex() now accepts ASCII bytes and bytes-like objects.

• gh-129149: Add fast path for medium-size integers in PyLong_FromSsize_t(). Patch by Chris Eibl.

• gh-129107: Make the bytearray safe under free threading.

• gh-128974: Fix a crash in UnicodeError.__str__ when custom attributes implement __str__() with side-effects. Patch by Bénédikt Tran.

• gh-126085: typing.TypeAliasType now supports star unpacking.

• gh-125331: from __future__ import barry_as_FLUFL now works in more contexts, including when it is used in files, with the -c flag, and in the REPL when there are multiple statements on the same line. Previously, it worked only on subsequent lines in the REPL, and when the appropriate flags were passed directly to compile(). Patch by Pablo Galindo.

• gh-121464: Make concurrent iterations over the same enumerate() iterator safe under free-threading. See Strategy for Iterators in Free Threading.

• gh-87790: Support underscore and comma as thousands separators in the fractional part for floating-point presentation types of the new-style string formatting (with format() or f-strings). Patch by Sergey B Kirpichev.

• gh-124445: Fix specialization of generic aliases that are generic over a typing.ParamSpec and have been specialized with a nested type variable.

• gh-120608: Adapt reversed() for use in the free-threading build. The reversed() is still not thread-safe in the sense that concurrent iterations may see the same object, but they will not corrupt the interpreter state.

Library¶

• gh-100388: Fix the platform._sys_version() method when __DATE__ is undefined at buildtime by changing default buildtime datetime string to the UNIX epoch.

Core and Builtins¶

• bpo-44369: Improve syntax errors for incorrectly closed strings. Patch by Pablo Galindo

C API¶

• gh-111178: Fix PyCMethod API: replace size_t nargs with Py_ssize_t nargs in PyCMethod. Patch by Victor Stinner.

• gh-130947: Add again PySequence_Fast() to the limited C API. Patch by Victor Stinner.

• gh-128863: The following private functions are deprecated and planned for removal in Python 3.18:

  • _PyUnicodeWriter_Init(): replace _PyUnicodeWriter_Init(&writer) with writer = PyUnicodeWriter_Create(0).

  • _PyUnicodeWriter_Finish(): replace _PyUnicodeWriter_Finish(&writer) with PyUnicodeWriter_Finish(writer).

  • _PyUnicodeWriter_Dealloc(): replace _PyUnicodeWriter_Dealloc(&writer) with PyUnicodeWriter_Discard(writer).

  • _PyUnicodeWriter_WriteChar(): replace _PyUnicodeWriter_WriteChar(&writer, ch) with PyUnicodeWriter_WriteChar(writer, ch).

  • _PyUnicodeWriter_WriteStr(): replace _PyUnicodeWriter_WriteStr(&writer, str) with PyUnicodeWriter_WriteStr(writer, str).

  • _PyUnicodeWriter_WriteSubstring(): replace _PyUnicodeWriter_WriteSubstring(&writer, str, start, end) with PyUnicodeWriter_WriteSubstring(writer, str, start, end).

  • _PyUnicodeWriter_WriteASCIIString(): replace _PyUnicodeWriter_WriteASCIIString(&writer, str) with PyUnicodeWriter_WriteUTF8(writer, str).

  • _PyUnicodeWriter_WriteLatin1String(): replace _PyUnicodeWriter_WriteLatin1String(&writer, str) with PyUnicodeWriter_WriteUTF8(writer, str).

  • _PyUnicodeWriter_Prepare(): (no replacement).

  • _PyUnicodeWriter_PrepareKind(): (no replacement).

  The pythoncapi-compat project can be used to get these new public functions on Python 3.13 and older.

  Patch by Victor Stinner.

• gh-45325: Add a new p format parameter to Py_BuildValue() that allows to take a C integer and produce a Python bool object. Patch by Pablo Galindo.

Build¶

• gh-131035: Use -flto=thin for faster build times using clang-cl on Windows. Patch by Chris Eibl.

• gh-130740: Ensure that Python.h is included before stdbool.h unless pyconfig.h is included before or in some platform-specific contexts.

• gh-130090: Building with PlatformToolset=ClangCL on Windows now supports PGO (profile guided optimization). Patch by Chris Eibl with invaluable support from Steve Dover.

• gh-129819: Allow building the JIT with the tailcall interpreter.

• gh-129989: Fix a bug where the tailcall interpreter was enabled when --without-tail-call-interp was provided to the configure script.

• gh-129838: Don’t redefine _Py_NO_SANITIZE_UNDEFINED when compiling with a recent GCC version and undefined sanitizer enabled.

• gh-82909: #pragma-based linking with python3*.lib can now be switched off with Py_NO_LINK_LIB. Patch by Jean-Christophe Fillion-Robin.

macOS