Changelog¶

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.

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.