3.15.0a8 - Cpython — ContextQMD

.. date: 2026-03-14-17-31-39 .. gh-issue: 145986 .. nonce: ifSSr8 .. release date: 2026-04-07 .. section: Security

:mod:xml.parsers.expat: Fixed a crash caused by unbounded C recursion when converting deeply nested XML content models with :meth:~xml.parsers.expat.xmlparser.ElementDeclHandler. This addresses :cve:2026-4224.

.. date: 2026-03-06-17-03-38 .. gh-issue: 145599 .. nonce: kchwZV .. section: Security

Reject control characters in :class:http.cookies.Morsel :meth:~http.cookies.Morsel.update and :meth:~http.cookies.BaseCookie.js_output. This addresses :cve:2026-3644.

.. date: 2026-01-16-12-04-49 .. gh-issue: 143930 .. nonce: zYC5x3 .. section: Security

Reject leading dashes in URLs passed to :func:webbrowser.open.

.. date: 2026-04-06-11-15-46 .. gh-issue: 148157 .. nonce: JFnZDn .. section: Core and Builtins

Fix an unlikely crash when parsing an invalid type comments for function parameters. Found by OSS Fuzz in :oss-fuzz:492782951.

.. date: 2026-04-06-00-00-00 .. gh-issue: 100239 .. nonce: binopxt .. section: Core and Builtins

Propagate result type and uniqueness information through _BINARY_OP_EXTEND in the tier 2 optimizer, enabling elimination of downstream type guards and selection of inplace float operations.

.. date: 2026-04-05-15-20-00 .. gh-issue: 148144 .. nonce: f7qA0x .. section: Core and Builtins

Initialize _PyInterpreterFrame.visited when copying interpreter frames so incremental GC does not read an uninitialized byte from generator and frame-object copies.

.. date: 2026-04-05-00-00-00 .. gh-issue: 148072 .. nonce: xid9Pe .. section: Core and Builtins

Cache pickle.dumps and pickle.loads per interpreter in the XIData framework, avoiding repeated module lookups on every cross-interpreter data transfer. This speeds up :class:~concurrent.futures.InterpreterPoolExecutor for mutable types (list, dict) by 1.7x--3.3x.

.. date: 2026-04-04-22-20-00 .. gh-issue: 148110 .. nonce: cL5x2Q .. section: Core and Builtins

Fix :func:sys.set_lazy_imports_filter so relative lazy imports pass the resolved imported module name to the filter callback. Patch by Pablo Galindo.

.. date: 2026-04-04-20-59-12 .. gh-issue: 148083 .. nonce: 9ZHNBN .. section: Core and Builtins

Constant-fold _CONTAINS_OP_SET for :class:frozenset. Patch by Donghee Na.

.. date: 2026-04-01-12-52-31 .. gh-issue: 144319 .. nonce: iZk4hs .. section: Core and Builtins

Fix a bug that could cause applications with specific allocation patterns to leak memory via Huge Pages if compiled with Huge Page support. Patch by Pablo Galindo

.. date: 2026-04-01-12-35-55 .. gh-issue: 147985 .. nonce: YVirHJ .. section: Core and Builtins

Make :c:func:PySet_Contains attempt a lock-free lookup, similar to :meth:!set.__contains__. This avoids acquiring the set object mutex in the normal case.

.. date: 2026-03-31-18-07-53 .. gh-issue: 147856 .. nonce: 62Dwee .. section: Core and Builtins

Allow the count argument of :meth:bytes.replace to be a keyword.

.. date: 2026-03-31-01-06-35 .. gh-issue: 146615 .. nonce: fix-method-get .. section: Core and Builtins

Fix a crash in :meth:~object.__get__ for :c:expr:METH_METHOD descriptors when an invalid (non-type) object is passed as the second argument. Patch by Steven Sun.

.. date: 2026-03-30-20-00-00 .. gh-issue: 146306 .. nonce: C45609 .. section: Core and Builtins

Optimize compact integer arithmetic in the JIT by mutating uniquely-referenced operands in place, avoiding allocation of a new int object. Speeds up the pyperformance spectral_norm benchmark by ~10%.

.. date: 2026-03-29-11-39-05 .. gh-issue: 146587 .. nonce: YJicXt .. section: Core and Builtins

Fix type slot assignment incase of multiple slots for same name in type object implementation. Patch by Kumar Aditya.

.. date: 2026-03-27-17-14-18 .. gh-issue: 126910 .. nonce: hooVFQ .. section: Core and Builtins

Set frame pointers in aarch64-unknown-linux-gnu JIT code, allowing most native profilers and debuggers to unwind through them. Patch by Diego Russo

.. date: 2026-03-26-11-18-45 .. gh-issue: 146388 .. nonce: O0u1c3 .. section: Core and Builtins

Adds a null check to handle when the JIT optimizer runs out of space when dealing with contradictions in make_bottom.

.. date: 2026-03-24-13-06-52 .. gh-issue: 146369 .. nonce: 6wDI6S .. section: Core and Builtins

Ensure -X lazy_imports=none and PYTHON_LAZY_IMPORTS=none override :attr:~module.__lazy_modules__. Patch by Hugo van Kemenade.

.. date: 2026-03-22-19-30-00 .. gh-issue: 146308 .. nonce: AxnRVA .. section: Core and Builtins

Fixed multiple error handling issues in the :mod:!_remote_debugging module including a double-free in code object caching, memory leaks on allocation failure, missing exception checks in binary format varint decoding, reference leaks on error paths in frame chain processing, and inconsistent thread status error reporting across platforms. Patch by Pablo Galindo.

.. date: 2026-03-22-12-00-00 .. gh-issue: 146306 .. nonce: 870ef4 .. section: Core and Builtins

Optimize float arithmetic in the JIT by mutating uniquely-referenced operands in place, avoiding allocation of a new float object. Speeds up the pyperformance nbody benchmark by ~19%.

.. date: 2026-03-21-15-05-14 .. gh-issue: 146128 .. nonce: DG1Hfa .. section: Core and Builtins

Fix a bug which could cause constant values to be partially corrupted in AArch64 JIT code. This issue is theoretical, and hasn't actually been observed in unmodified Python interpreters.

.. date: 2026-03-21-11-55-16 .. gh-issue: 146250 .. nonce: ahl3O2 .. section: Core and Builtins

Fixed a memory leak in :exc:SyntaxError when re-initializing it.

.. date: 2026-03-21-08-48-25 .. gh-issue: 146245 .. nonce: cqM3_4 .. section: Core and Builtins

Fixed reference leaks in :mod:socket when audit hooks raise exceptions in :func:socket.getaddrinfo and :meth:!socket.sendto.

.. date: 2026-03-21-08-11-58 .. gh-issue: 146151 .. nonce: 4-lhim .. section: Core and Builtins

:class:memoryview now supports the :c:expr:float complex and :c:expr:double complex C types: formatting characters 'F' and 'D' respectively. Patch by Sergey B Kirpichev.

.. date: 2026-03-20-13-55-14 .. gh-issue: 146196 .. nonce: Zg70Kb .. section: Core and Builtins

Fix potential Undefined Behavior in :c:func:PyUnicodeWriter_WriteASCII by adding a zero-length check. Patch by Shamil Abdulaev.

.. date: 2026-03-20-13-07-33 .. gh-issue: 146227 .. nonce: MqBPEo .. section: Core and Builtins

Fix wrong type in _Py_atomic_load_uint16 in the C11 atomics backend (pyatomic_std.h), which used a 32-bit atomic load instead of 16-bit. Found by Mohammed Zuhaib.

.. date: 2026-03-20-12-52-55 .. gh-issue: 146205 .. nonce: M4yKdf .. section: Core and Builtins

Fixed a bug where :meth:select.epoll.close, :meth:select.kqueue.close, and :meth:select.devpoll.close silently ignored errors.

.. date: 2026-03-20-12-26-24 .. gh-issue: 146199 .. nonce: vV8V9s .. section: Core and Builtins

Comparison of code objects now handles errors correctly.

.. date: 2026-03-20-11-34-17 .. gh-issue: 145667 .. nonce: _Agp9o .. section: Core and Builtins

Remove the GET_ITER_YIELD_FROM instruction, modifying SEND to pair with GET_ITER when compiling yield from expressions.

.. date: 2026-03-20-00-39-25 .. gh-issue: 146192 .. nonce: 8aQ6sC .. section: Core and Builtins

Add Base32 support to :mod:binascii and improve the performance of the Base32 converters in :mod:base64. Patch by James Seo.

.. date: 2026-03-19-16-16-40 .. gh-issue: 135871 .. nonce: jSExZ3 .. section: Core and Builtins

Improve multithreaded scaling of PyMutex in low-contention scenarios by reloading the lock's internal state, without slowing down high-contention scenarios.

.. date: 2026-03-19-01-19-34 .. gh-issue: 146096 .. nonce: R9tkJX .. section: Core and Builtins

Fixed segmentation fault when called repr for BaseExceptionGroup with empty or 1-size tuple args.

.. date: 2026-03-18-18-52-00 .. gh-issue: 146056 .. nonce: r1tVSo .. section: Core and Builtins

Fix :func:repr for lists and tuples containing NULL\ s.

.. date: 2026-03-17-14-20-56 .. gh-issue: 145059 .. nonce: aB3xKm .. section: Core and Builtins

Fixed sys.lazy_modules to include lazy modules without submodules. Patch by Bartosz Sławecki.

.. date: 2026-03-17-00-00-00 .. gh-issue: 146041 .. nonce: 7799bb .. section: Core and Builtins

Fix free-threading scaling bottleneck in :func:sys.intern and :c:func:PyObject_SetAttr by avoiding the interpreter-wide lock when the string is already interned and immortalized.

.. date: 2026-03-15-21-45-35 .. gh-issue: 145990 .. nonce: tmXwRB .. section: Core and Builtins

python --help-env sections are now sorted by environment variable name.

.. date: 2026-03-15-20-47-34 .. gh-issue: 145990 .. nonce: 14BUzw .. section: Core and Builtins

python --help-xoptions is now sorted by -X option name.

.. date: 2026-03-13-12-24-17 .. gh-issue: 145876 .. nonce: LWFO2K .. section: Core and Builtins

:exc:AttributeError\ s and :exc:KeyError\ s raised in :meth:!keys or :meth:!__getitem__ during dictionary unpacking ({**mymapping} or func(**mymapping)) are no longer masked by :exc:TypeError.

.. date: 2026-03-13-09-48-57 .. gh-issue: 127958 .. nonce: U-znTv .. section: Core and Builtins

Support tracing from function entrypoints in the JIT. Patch by Ken Jin.

.. date: 2026-03-11-21-27-28 .. gh-issue: 145376 .. nonce: LfDvyw .. section: Core and Builtins

Fix GC tracking in structseq.__replace__().

.. date: 2026-03-11-19-09-47 .. gh-issue: 145792 .. nonce: X5KUhc .. section: Core and Builtins

Fix out-of-bounds access when invoking faulthandler on a CPython build compiled without support for VLAs.

.. date: 2026-03-11-00-13-59 .. gh-issue: 142183 .. nonce: 2iVhJH .. section: Core and Builtins

Avoid a pathological case where repeated calls at a specific stack depth could be significantly slower.

.. date: 2026-03-10-22-38-40 .. gh-issue: 145779 .. nonce: 5375381d80 .. section: Core and Builtins

Improve scaling of :func:classmethod and :func:staticmethod calls in the free-threaded build by avoiding the descriptor __get__ call.

.. date: 2026-03-10-19-00-39 .. gh-issue: 145783 .. nonce: dS5TM9 .. section: Core and Builtins

Fix an unlikely crash in the parser when certain errors were erroneously not propagated. Found by OSS Fuzz in :oss-fuzz:491369109.

.. date: 2026-03-10-12-52-06 .. gh-issue: 145685 .. nonce: 80B7gK .. section: Core and Builtins

Improve scaling of type attribute lookups in the :term:free-threaded build by avoiding contention on the internal type lock.

.. date: 2026-03-09-00-00-00 .. gh-issue: 145713 .. nonce: KR6azvzI .. section: Core and Builtins

Make :meth:bytearray.resize thread-safe in the free-threaded build by using a critical section and calling the lock-held variant of the resize function.

.. date: 2026-02-28-18-42-36 .. gh-issue: 145036 .. nonce: 70Kbfz .. section: Core and Builtins

In free-threaded build, fix race condition when calling :meth:!__sizeof__ on a :class:list

.. date: 2026-02-14-15-51-16 .. gh-issue: 134584 .. nonce: 6WFSuB .. section: Core and Builtins

Eliminate redundant refcounting for MATCH_CLASS in the JIT.

.. date: 2026-02-14-13-07-08 .. gh-issue: 69605 .. nonce: 4aL4hn .. section: Core and Builtins

Add :mod:math.integer to :term:REPL auto-completion of imports.

.. date: 2026-02-08-01-19-50 .. gh-issue: 131798 .. nonce: PaWDNH .. section: Core and Builtins

Optimize _ITER_CHECK_RANGE and _ITER_CHECK_LIST in the JIT

.. date: 2026-01-31-15-15-43 .. gh-issue: 143414 .. nonce: Jgl4xu .. section: Core and Builtins

Add tracking to the JIT optimizer to determine whether a reference is uniquely owned or shared

.. date: 2026-01-10-12-59-58 .. gh-issue: 143636 .. nonce: dzr26e .. section: Core and Builtins

Fix a crash when calling :class:SimpleNamespace.__replace__() <types.SimpleNamespace> on non-namespace instances. Patch by Bénédikt Tran.

.. date: 2026-01-07-23-07-17 .. gh-issue: 126910 .. nonce: d8zdm- .. section: Core and Builtins

Set frame pointers in x86_64-unknown-linux-gnu JIT code, allowing most native profilers and debuggers to unwind through them.

.. date: 2025-11-02-16-23-17 .. gh-issue: 140594 .. nonce: YIWUpl .. section: Core and Builtins

Fix an out of bounds read when a single NUL character is read from the standard input. Patch by Shamil Abdulaev.

.. date: 2025-11-01-01-49-52 .. gh-issue: 140870 .. nonce: iknc12 .. section: Core and Builtins

Add support for module attributes in the :term:REPL auto-completion of imports.

.. date: 2026-04-07-01-04-00 .. gh-issue: 144503 .. nonce: argvfs .. section: Library

Fix a regression introduced in 3.14.3 and 3.13.12 where the :mod:multiprocessing forkserver start method would fail with :exc:BrokenPipeError when the parent process had a very large :data:sys.argv. The argv is now passed to the forkserver as separate command-line arguments rather than being embedded in the -c command string, avoiding the operating system's per-argument length limit.

.. date: 2026-04-06-11-20-24 .. gh-issue: 148153 .. nonce: ZtsuTl .. section: Library

:func:base64.b32encode now always raises :exc:ValueError instead of :exc:AssertionError for the value of map01 with invalid length.

.. date: 2026-04-01-18-17-55 .. gh-issue: 73613 .. nonce: PLEebm .. section: Library

Add the padded parameter in functions related to Base32 and Base64 codecs in the :mod:binascii and :mod:base64 modules. In the encoding functions it controls whether the pad character can be added in the output, in the decoding functions it controls whether padding is required in input. Padding of input no longer required in :func:base64.urlsafe_b64decode by default.

.. date: 2026-04-01-11-05-36 .. gh-issue: 146613 .. nonce: GzjUFK .. section: Library

:mod:itertools: Fix a crash in :func:itertools.groupby when the grouper iterator is concurrently mutated.

.. date: 2026-03-31-19-54-32 .. gh-issue: 147944 .. nonce: 3dn8GZ .. section: Library

Accepted range for the bytes_per_sep argument of :meth:bytes.hex, :meth:bytearray.hex, :meth:memoryview.hex, and :func:binascii.b2a_hex is now increased, so passing sys.maxsize and -sys.maxsize is now valid.

.. date: 2026-03-28-13-19-20 .. gh-issue: 146080 .. nonce: srN12a .. section: Library

:mod:ssl: fix a crash when an SNI callback tries to use an SSL object that has already been garbage-collected. Patch by Bénédikt Tran.

.. date: 2026-03-28-12-20-19 .. gh-issue: 146556 .. nonce: Y8Eson .. section: Library

Fix :func:annotationlib.get_annotations hanging indefinitely when called with eval_str=True on a callable that has a circular __wrapped__ chain (e.g. f.__wrapped__ = f). Cycle detection using an id-based visited set now stops the traversal and falls back to the globals found so far, mirroring the approach of :func:inspect.unwrap.

.. date: 2026-03-28-12-05-34 .. gh-issue: 146090 .. nonce: wf9_ef .. section: Library

:mod:sqlite3: fix a crash when :meth:sqlite3.Connection.create_collation fails with SQLITE_BUSY <https://sqlite.org/rescode.html#busy>__. Patch by Bénédikt Tran.

.. date: 2026-03-28-12-01-48 .. gh-issue: 146090 .. nonce: wh1qJR .. section: Library

:mod:sqlite3: properly raise :exc:MemoryError instead of :exc:SystemError when a context callback fails to be allocated. Patch by Bénédikt Tran.

.. date: 2026-03-27-12-00-00 .. gh-issue: 146507 .. nonce: 1D95A7 .. section: Library

Make :meth:asyncio.SelectorEventLoop stream transport's :meth:~asyncio.WriteTransport.get_write_buffer_size O(1) by maintaining a running byte counter instead of iterating the buffer on every call.

.. date: 2026-03-26-14-51-55 .. gh-issue: 145056 .. nonce: QS-6l1 .. section: Library

Fix merging of :class:collections.OrderedDict and :class:frozendict.

.. date: 2026-03-26-14-44-07 .. gh-issue: 145056 .. nonce: L9KPC3 .. section: Library

Add support for merging :class:collections.UserDict and :class:frozendict.

.. date: 2026-03-26-11-04-42 .. gh-issue: 145633 .. nonce: RWjlaX .. section: Library

Fix struct.pack('f', float): use :c:func:PyFloat_Pack4 to raise :exc:OverflowError. Patch by Sergey B Kirpichev and Victor Stinner.

.. date: 2026-03-26-02-06-52 .. gh-issue: 146440 .. nonce: HXjhQO .. section: Library

:mod:json: Add the array_hook parameter to :func:~json.load and :func:~json.loads functions: allow a callback for JSON literal array types to customize Python lists in the resulting decoded object. Passing combined :class:frozendict to object_pairs_hook param and :class:tuple to array_hook will yield a deeply nested immutable Python structure representing the JSON data.

.. date: 2026-03-25-21-08-51 .. gh-issue: 146431 .. nonce: zERPwe .. section: Library

Add the wrapcol parameter to :mod:base64 functions :func:~base64.b16encode, :func:~base64.b32encode, :func:~base64.b32hexencode, :func:~base64.b85encode and :func:~base64.z85encode, and :mod:binascii functions :func:~binascii.b2a_base32 and :func:~binascii.b2a_base85. Add the ignorechars parameter to :mod:base64 functions :func:~base64.b16decode, :func:~base64.b32decode, :func:~base64.b32hexdecode, :func:~base64.b85decode and :func:~base64.z85decode, and :mod:binascii functions :func:~binascii.a2b_hex, :func:~binascii.unhexlify, :func:~binascii.a2b_base32 and :func:~binascii.a2b_base85.

.. date: 2026-03-24-03-49-50 .. gh-issue: 146310 .. nonce: WhlDir .. section: Library

The :mod:ensurepip module no longer looks for pip-*.whl wheel packages in the current directory.

.. date: 2026-03-21-16-03-16 .. gh-issue: 141510 .. nonce: tKptA7 .. section: Library

Support :class:frozendict in :mod:plistlib, for serialization only. Patch by Hugo van Kemenade.

.. date: 2026-03-21-10-02-20 .. gh-issue: 146238 .. nonce: 2WpMOj .. section: Library

Support half-floats (type code 'e' of the :mod:struct module) in the :mod:array module. Patch by Sergey B Kirpichev.

.. date: 2026-03-21-08-23-26 .. gh-issue: 140947 .. nonce: owZ4r_ .. section: Library

Fix incorrect contextvars handling in server tasks created by :mod:asyncio. Patch by Kumar Aditya.

.. date: 2026-03-21-06-21-38 .. gh-issue: 146151 .. nonce: yNpgml .. section: Library

Support the :c:expr:float complex and :c:expr:double complex C types in the :mod:array module: formatting characters 'F' and 'D' respectively. Patch by Sergey B Kirpichev.

.. date: 2026-03-20-16-17-31 .. gh-issue: 143387 .. nonce: 9Waopa .. section: Library

In importlib.metadata, when a distribution file is corrupt and there is no metadata file, calls to Distribution.metadata() (including implicit calls from other properties like .name and .requires) will now raise a MetadataNotFound Exception. This allows callers to distinguish between missing metadata and a degenerate (empty) metadata. Previously, if the file was missing, an empty PackageMetadata would be returned and would be indistinguishable from the presence of an empty file.

.. date: 2026-03-20-14-53-00 .. gh-issue: 146228 .. nonce: OJVEDL .. section: Library

Cached FastPath objects in importlib.metadata are now cleared on fork, avoiding broken references to zip files during fork.

.. date: 2026-03-20-00-28-00 .. gh-issue: 146171 .. nonce: P5Jk2R7v .. section: Library

Nested :exc:AttributeError suggestions now include property-backed attributes on nested objects without executing the property getter.

.. date: 2026-03-18-23-54-36 .. gh-issue: 145410 .. nonce: NvLWj5 .. section: Library

On Windows, :func:sysconfig.get_platform now gets the platform from the _sysconfig module instead of parsing :data:sys.version string. Patch by Victor Stinner.

.. date: 2026-03-18-16-58-17 .. gh-issue: 146091 .. nonce: lBbo1L .. section: Library

Fix a bug in :func:termios.tcsetwinsize where passing a sequence that raises an exception in __getitem__ would cause a :exc:SystemError instead of propagating the original exception.

.. date: 2026-03-17-20-52-24 .. gh-issue: 146083 .. nonce: NxZa_c .. section: Library

Update bundled libexpat <https://libexpat.github.io/>_ to version 2.7.5.

.. date: 2026-03-17-20-41-27 .. gh-issue: 146076 .. nonce: yoBNnB .. section: Library

:mod:zoneinfo: fix crashes when deleting _weak_cache from a :class:zoneinfo.ZoneInfo subclass.

.. date: 2026-03-17-19-51-05 .. gh-issue: 123471 .. nonce: oY4UR5 .. section: Library

Make concurrent iteration over :class:itertools.zip_longest safe under free-threading.

.. date: 2026-03-17-19-30-45 .. gh-issue: 146075 .. nonce: 85sCSh .. section: Library

Errors when calling :func:functools.partial with a malformed keyword will no longer crash the interpreter.

.. date: 2026-03-17-11-46-20 .. gh-issue: 146054 .. nonce: udYcqn .. section: Library

Limit the size of :func:encodings.search_function cache. Found by OSS Fuzz in :oss-fuzz:493449985.

.. date: 2026-03-16-00-00-00 .. gh-issue: 146004 .. nonce: xOptProp .. section: Library

All :option:-X options from the Python command line are now propagated to child processes spawned by :mod:multiprocessing, not just a hard-coded subset. This makes the behavior consistent between default "spawn" and "forkserver" start methods and the old "fork" start method. The options that were previously not propagated are: context_aware_warnings, cpu_count, disable-remote-debug, int_max_str_digits, lazy_imports, no_debug_ranges, pathconfig_warnings, perf, perf_jit, presite, pycache_prefix, thread_inherit_context, and warn_default_encoding.

.. date: 2026-03-15-16-38-48 .. gh-issue: 145980 .. nonce: mRze5H .. section: Library

Added the alphabet parameter in :func:~binascii.b2a_base64, :func:~binascii.a2b_base64, :func:~binascii.b2a_base85 and :func:~binascii.a2b_base85 and a number of *_ALPHABET constants in the :mod:binascii module. Removed :func:!b2a_z85 and :func:!a2b_z85.

.. date: 2026-03-15-10-17-51 .. gh-issue: 145968 .. nonce: gZexry .. section: Library

Fix translation in :func:base64.b64decode when altchars overlaps with the standard ones.

.. date: 2026-03-15-00-00-00 .. gh-issue: 145966 .. nonce: tCI0uD4I .. section: Library

Non-:exc:AttributeError exceptions raised during dialect attribute lookup in :mod:csv are no longer silently suppressed.

.. date: 2026-03-12-21-01-48 .. gh-issue: 145883 .. nonce: lUvXcc .. section: Library

:mod:zoneinfo: Fix heap buffer overflow reads from malformed TZif data. Found by OSS Fuzz, issues :oss-fuzz:492245058 and :oss-fuzz:492230068.

.. date: 2026-03-12-12-17-39 .. gh-issue: 145850 .. nonce: uW3stt .. section: Library

Changed some implementation details in :class:struct.Struct: calling it with non-ASCII string format will now raise a :exc:ValueError instead of :exc:UnicodeEncodeError, calling it with non-ASCII bytes format will now raise a :exc:ValueError instead of :exc:struct.error, getting the :attr:!format attribute of uninitialized object will now raise an :exc:AttributeError instead of :exc:RuntimeError.

.. date: 2026-03-11-10-25-32 .. gh-issue: 123720 .. nonce: TauFRx .. section: Library

asyncio: Fix :func:asyncio.Server.serve_forever shutdown regression. Since 3.12, cancelling serve_forever() could hang waiting for a handler blocked on a read from a client that never closed (effectively requiring two interrupts to stop); the shutdown sequence now ensures client streams are closed so serve_forever() exits promptly and handlers observe EOF.

.. date: 2026-03-10-19-50-59 .. gh-issue: 138122 .. nonce: CsoBEo .. section: Library

The profiling.sampling module now supports differential flamegraph visualization via --diff-flamegraph to compare two profiling runs. Functions are colored red (regressions), blue (improvements), gray (neutral), or purple (new). Elided stacks show code paths that disappeared between runs.

.. date: 2026-03-10-14-57-15 .. gh-issue: 145754 .. nonce: YBL5Ko .. section: Library

Request signature during mock autospec with FORWARDREF annotation format. This prevents runtime errors when an annotation uses a name that is not defined at runtime.

.. date: 2026-03-10-14-13-12 .. gh-issue: 145750 .. nonce: iQsTeX .. section: Library

Avoid undefined behaviour from signed integer overflow when parsing format strings in the :mod:struct module. Found by OSS Fuzz in :oss-fuzz:488466741.

.. date: 2026-03-10-01-54-34 .. gh-issue: 145719 .. nonce: okJRoK .. section: Library

Add application/efi MIME type to :mod:mimetypes.

.. date: 2026-03-10-01-48-12 .. gh-issue: 145717 .. nonce: dPc0Rt .. section: Library

Add a few Microsoft-specific MIME types.

.. date: 2026-03-09-19-59-05 .. gh-issue: 145703 .. nonce: 4EEP7J .. section: Library

:mod:asyncio: Make sure that :meth:loop.call_at <asyncio.loop.call_at> and :meth:loop.call_later <asyncio.loop.call_later> trigger scheduled events on time when the clock resolution becomes too small.

.. date: 2026-03-09-18-33-16 .. gh-issue: 145697 .. nonce: d6hFmm .. section: Library

Add application/sql and application/vnd.sqlite3 into mimetypes.

.. date: 2026-03-09-00-00-00 .. gh-issue: 145492 .. nonce: 457Afc .. section: Library

Fix infinite recursion in :class:collections.defaultdict __repr__ when a defaultdict contains itself. Based on analysis by KowalskiThomas in :gh:145492.

.. date: 2026-03-08-00-00-00 .. gh-issue: 145650 .. nonce: LgRepr .. section: Library

Add :meth:~object.__repr__ support to :class:logging.Formatter and :class:logging.Filter, showing the format string and filter name respectively.

.. date: 2026-03-07-14-34-39 .. gh-issue: 145587 .. nonce: flFQ5- .. section: Library

Resolved a performance regression in multiprocessing.connection.wait on Windows that caused infinite busy loops when called with no objects. The function now properly yields control to the OS to conserve CPU resources. Patch By Shrey Naithani

.. date: 2026-03-07-02-44-52 .. gh-issue: 145616 .. nonce: x8Mf23 .. section: Library

Detect Android sysconfig ABI correctly on 32-bit ARM Android on 64-bit ARM kernel

.. date: 2026-03-05-14-13-10 .. gh-issue: 145546 .. nonce: 3tnlxx .. section: Library

Fix unittest.util.sorted_list_difference() to deduplicate remaining elements when one input list is exhausted before the other.

.. date: 2026-03-03-23-21-40 .. gh-issue: 145446 .. nonce: 0c-TJX .. section: Library

Now :mod:functools is safer in free-threaded build when using keywords in :func:functools.partial

.. date: 2026-02-26-20-13-16 .. gh-issue: 145264 .. nonce: 4pggX_ .. section: Library

Base64 decoder (see :func:binascii.a2b_base64, :func:base64.b64decode, etc) no longer ignores excess data after the first padded quad in non-strict (default) mode. Instead, in conformance with :rfc:4648, section 3.3, it now ignores the pad character, "=", if it is present before the end of the encoded data.

.. date: 2026-02-23-21-28-12 .. gh-issue: 145035 .. nonce: J5UjS6 .. section: Library

Allows omitting the internal library _pyrepl with limited loss of functionality. This allows complete removal of the modern REPL, which is an unsupported configuration, but still desirable for some distributions.

.. date: 2026-02-19-16-34-18 .. gh-issue: 144270 .. nonce: wJRtSr .. section: Library

Made the tag parameter of :class:xml.etree.ElementTree.Element and the parent and tag parameters of :func:xml.etree.ElementTree.SubElement positional-only, matching the behavior of the C accelerator.

.. date: 2026-02-19-12-00-00 .. gh-issue: 144984 .. nonce: b93995c982 .. section: Library

Fix crash in :meth:xml.parsers.expat.xmlparser.ExternalEntityParserCreate when an allocation fails. The error paths could dereference NULL handlers and double-decrement the parent parser's reference count.

.. date: 2026-02-18-21-45-00 .. gh-issue: 144975 .. nonce: Ab3XyZ .. section: Library

:meth:wave.Wave_write.setframerate now validates the frame rate after rounding to an integer, preventing values like 0.5 from being accepted and causing confusing errors later. Patch by Michiel Beijen.

.. date: 2026-02-17-03-43-07 .. gh-issue: 140715 .. nonce: twmcM_ .. section: Library

Add %n and %t support to :meth:~datetime.datetime.strptime.

.. date: 2026-02-11-21-01-30 .. gh-issue: 144259 .. nonce: OAhOR8 .. section: Library

Fix inconsistent display of long multiline pasted content in the REPL.

.. date: 2026-02-08-22-04-06 .. gh-issue: 140814 .. nonce: frzSpn .. section: Library

:func:multiprocessing.freeze_support no longer sets the default start method as a side effect, which previously caused a subsequent :func:multiprocessing.set_start_method call to raise :exc:RuntimeError.

.. date: 2026-02-04-20-30-59 .. gh-issue: 123471 .. nonce: 1dnPvs .. section: Library

Make concurrent iteration over :class:itertools.accumulate safe under free-threading.

.. date: 2026-01-10-16-23-21 .. gh-issue: 143715 .. nonce: HZrfSA .. section: Library

Calling the Struct.__new__() without required argument now is deprecated. Calling :meth:~object.__init__ method on initialized :class:~struct.Struct objects is deprecated.

.. date: 2025-12-18-00-00-00 .. gh-issue: 142763 .. nonce: AJpZPVG5 .. section: Library

Fix a race condition between :class:zoneinfo.ZoneInfo creation and :func:zoneinfo.ZoneInfo.clear_cache that could raise :exc:KeyError.

.. date: 2025-11-18-06-35-53 .. gh-issue: 141707 .. nonce: DBmQIy .. section: Library

Don't change :class:tarfile.TarInfo type from AREGTYPE to DIRTYPE when parsing GNU long name or link headers.

.. date: 2025-11-15-23-14-30 .. gh-issue: 138577 .. nonce: KbShrt .. section: Library

:func:getpass.getpass with non-empty echo_char now handles keyboard shortcuts including Ctrl+A/E (cursor movement), Ctrl+K/U (kill line), Ctrl+W (erase word), and Ctrl+V (literal next) by reading the terminal's control character settings and processing them appropriately in non-canonical mode. Patch by Sanyam Khurana.

.. date: 2025-10-13-16-43-36 .. gh-issue: 140049 .. nonce: VvmAzN .. section: Library

:func:traceback.format_exception_only now colorizes exception notes.

.. date: 2025-10-11-11-50-59 .. gh-issue: 139933 .. nonce: 05MHlx .. section: Library

Improve :exc:AttributeError suggestions for classes with a custom :meth:~object.__dir__ method returning a list of unsortable values. Patch by Bénédikt Tran.

.. date: 2025-10-05-15-38-02 .. gh-issue: 139633 .. nonce: l3P839 .. section: Library

The :mod:netrc security check is now run once per parse rather than once per entry.

.. date: 2025-09-19-13-54-54 .. gh-issue: 130472 .. nonce: LODfdk .. section: Library

Add fancycompleter and enable it by default when using pyrepl. This gives colored tab completion.

.. date: 2025-02-07-00-48-07 .. gh-issue: 112632 .. nonce: 95MM0C .. section: Library

Add an expand keyword argument for :func:pprint.pprint, :func:pprint.pformat, :func:pprint.pp by passing on all kwargs and :class:pprint.PrettyPrinter. Contributed by Stefan Todoran and Semyon Moroz.

.. date: 2024-09-25-12-47-50 .. gh-issue: 66419 .. nonce: DVSukU .. section: Library

Optional argument with :ref:nargs equals to argparse.REMAINDER now consumes all remaining arguments including '--'.

.. date: 2023-03-10-13-10-06 .. gh-issue: 60729 .. nonce: KCCHTe .. section: Library

Add support for floating point audio wave files in :mod:wave.

.. bpo: 36461 .. date: 2019-04-25-21-11-37 .. nonce: TO5YyP .. section: Library

Make the target time of :meth:timeit.Timer.autorange configurable and add --target-time option to the command-line interface of :mod:timeit.

.. date: 2026-03-25-00-00-00 .. gh-issue: 126676 .. nonce: 052336 .. section: Documentation

Expand :mod:argparse documentation for type=bool with a demonstration of the surprising behavior and pointers to common alternatives.

.. date: 2026-03-09-00-00-00 .. gh-issue: 145649 .. nonce: 8BcbAB .. section: Documentation

Fix text wrapping and formatting of -X option descriptions in the :manpage:python(1) man page by using proper roff markup.

.. date: 2026-04-03-21-37-18 .. gh-issue: 144418 .. nonce: PusC0S .. section: Tests

The Android testbed's emulator RAM has been increased from 2 GB to 4 GB.

.. date: 2026-03-24-00-15-58 .. gh-issue: 146202 .. nonce: LgH6Bj .. section: Tests

Fix a race condition in regrtest: make sure that the temporary directory is created in the worker process. Previously, temp_cwd() could fail on Windows if the "build" directory was not created. Patch by Victor Stinner.

.. date: 2026-03-28-02-48-51 .. gh-issue: 146541 .. nonce: k-zlM6 .. section: Build

The Android testbed can now be built for 32-bit ARM and x86 targets.

.. date: 2026-03-27-06-55-10 .. gh-issue: 146498 .. nonce: uOiCab .. section: Build

The iOS XCframework build script now ensures libpython isn't included in installed app content, and is more robust in identifying standard library binary content that requires processing.

.. date: 2026-03-26-14-35-29 .. gh-issue: 146450 .. nonce: 9Kmp5Q .. section: Build

The Android build script was modified to improve parity with other platform build scripts.

.. date: 2026-03-26-12-48-42 .. gh-issue: 146446 .. nonce: 0GyMu4 .. section: Build

The clean target for the Apple/iOS XCframework build script is now more selective when targeting a single architecture.

.. date: 2026-03-26-12-27-42 .. gh-issue: 146444 .. nonce: JKJuEa .. section: Build

The Apple/iOS build script has been moved to the Platforms directory.

.. date: 2026-03-23-20-06-35 .. gh-issue: 146210 .. nonce: C01Rmq .. section: Build

Fix building the jit stencils on Windows when the interpreter is built with a different clang version. Patch by Chris Eibl.

.. date: 2026-03-12-12-30-24 .. gh-issue: 145844 .. nonce: VOPeCU .. section: Build

Update to WASI SDK 32.

.. date: 2026-03-11-11-58-42 .. gh-issue: 145801 .. nonce: iCXa3v .. section: Build

When Python build is optimized with GCC using PGO, use -fprofile-update=atomic option to use atomic operations when updating profile information. This option reduces the risk of gcov Data Files (.gcda) corruption which can cause random GCC crashes. Patch by Victor Stinner.

.. date: 2026-03-10-16-58-55 .. gh-issue: 138850 .. nonce: CkqTw6 .. section: Build

Add :option:--disable-epoll to configure

.. date: 2026-03-08-06-18-26 .. gh-issue: 145633 .. nonce: Ogu-RF .. section: Build

Remove support for ancient ARM platforms (ARMv4L and ARMv5L OABI boards), using mixed-endian representation for doubles. Patch by Sergey B Kirpichev.

.. date: 2026-01-08-22-27-07 .. gh-issue: 85277 .. nonce: TotySi .. section: Build

Fix building without stropts.h or empty stropts.h

.. date: 2025-10-19-23-44-46 .. gh-issue: 140131 .. nonce: AABF2k .. section: Windows

Fix REPL cursor position on Windows when module completion suggestion line hits console width.

.. date: 2025-10-17-01-07-03 .. gh-issue: 137586 .. nonce: kVzxvp .. section: macOS

Invoke :program:osascript with absolute path in :mod:webbrowser and :mod:!turtledemo.

.. date: 2026-03-22-00-00-00 .. gh-issue: 135953 .. nonce: IptOwg .. section: Tools/Demos

Properly identify the main thread in the Gecko profiler collector by using a status flag from the interpreter state instead of relying on :func:threading.main_thread in the collector process.

.. date: 2026-03-15-20-59-29 .. gh-issue: 145976 .. nonce: rEdUI- .. section: Tools/Demos

Remove :file:Misc/indent.pro, a configuration file for GNU :manpage:indent(1).

.. date: 2026-03-15-11-32-35 .. gh-issue: 145976 .. nonce: mqhzmB .. section: Tools/Demos

Remove :file:Misc/vgrindefs and :file:Misc/Porting.

.. date: 2026-03-31-13-33-41 .. gh-issue: 146636 .. nonce: 5do3wt .. section: C API

The :c:data:Py_mod_abi slot is now mandatory for modules created from a slots array (using :c:func:PyModule_FromSlotsAndSpec or the :c:func:PyModExport_* <PyModExport_modulename> export hook).

.. date: 2026-03-19-16-50-27 .. gh-issue: 146175 .. nonce: pISQGX .. section: C API

The following macros are :term:soft deprecated: :c:macro:Py_ALIGNED, :c:macro:PY_FORMAT_SIZE_T, :c:macro:Py_LL, :c:macro:Py_ULL, :c:macro:PY_LONG_LONG, :c:macro:PY_LLONG_MIN, :c:macro:PY_LLONG_MAX, :c:macro:PY_ULLONG_MAX, :c:macro:PY_INT32_T, :c:macro:PY_UINT32_T, :c:macro:PY_INT64_T, :c:macro:PY_UINT64_T, :c:macro:PY_SIZE_MAX, :c:macro:Py_UNICODE_SIZE, :c:macro:Py_VA_COPY.

The macro :c:macro:Py_UNICODE_WIDE, which was scheduled for removal, is :term:soft deprecated instead.

.. date: 2026-03-18-23-44-29 .. gh-issue: 146143 .. nonce: pwIrJq .. section: C API

:c:func:PyUnicodeWriter_WriteUCS4 now accepts a pointer to a constant buffer of Py_UCS4.

.. date: 2026-03-18-20-18-59 .. gh-issue: 146056 .. nonce: nnZIgp .. section: C API

:c:func:PyUnicodeWriter_WriteRepr now supports NULL argument.

.. date: 2026-02-19-18-39-11 .. gh-issue: 145010 .. nonce: mKzjci .. section: C API

Use GCC dialect alternatives for inline assembly in object.h so that the Python headers compile correctly with -masm=intel.