3.15.0b3 - Cpython — ContextQMD

.. date: 2026-06-16-14-58-02 .. gh-issue: 151544 .. nonce: _bexVy .. release date: 2026-06-23 .. section: Security

:file:Modules/Setup.local is no longer used as a landmark to discover whether Python is running in a source tree, as it could potentially affect actual installs. The :file:pybuilddir.txt file is now the sole indicator of running in a source tree.

.. date: 2026-06-09-23-38-08 .. gh-issue: 151159 .. nonce: ds-9f8 .. section: Security

Update macOS installer to use OpenSSL 3.5.7.

.. date: 2026-06-09-10-23-57 .. gh-issue: 151159 .. nonce: 91GpWQ .. section: Security

Update Android and iOS installers to use OpenSSL 3.5.7.

.. date: 2026-05-30-09-36-20 .. gh-issue: 150599 .. nonce: nlHqU- .. section: Security

Fix a possible stack buffer overflow in :mod:bz2 when a :class:bz2.BZ2Decompressor is reused after a decompression error. The decompressor now becomes unusable after libbz2 reports an error.

.. date: 2026-05-18-17-46-00 .. gh-issue: 149835 .. nonce: EebFlk .. section: Security

:func:shutil.move now resolves symlinks via :func:os.path.realpath when checking whether the destination is inside the source directory, preventing a symlink-based bypass of that guard.

.. date: 2026-06-22-06-26-34 .. gh-issue: 151905 .. nonce: FOLMYg .. section: Core and Builtins

Fix OOM error handling in :c:func:PyFrame_GetBack to propagate exceptions instead of masking them as None.

.. date: 2026-06-20-00-30-47 .. gh-issue: 151722 .. nonce: RPMPIY .. section: Core and Builtins

Defer GC tracking of :class:frozendict to end of construction. Patch by Donghee Na.

.. date: 2026-06-16-17-23-37 .. gh-issue: 151546 .. nonce: LhiaZz .. section: Core and Builtins

Fix the stack limit check if Python is linked to musl (ex: Alpine Linux). Use the stack size set by the linker to compute the stack limits. Patch by Victor Stinner.

.. date: 2026-06-16-00-45-42 .. gh-issue: 151510 .. nonce: HJ-kGn .. section: Core and Builtins

Fix a crash in :func:!__lazy_import__ when called without an explicit globals argument and without a current Python frame.

.. date: 2026-06-14-05-05-15 .. gh-issue: 151461 .. nonce: 5q0s88 .. section: Core and Builtins

Fix direct execution of files with invalid source encodings to report the underlying codec lookup or decoding error instead of the generic SyntaxError: encoding problem message. Patch by Bartosz Sławecki.

.. date: 2026-06-12-15-30-25 .. gh-issue: 151218 .. nonce: 5M_nv8 .. section: Core and Builtins

:c:func:PyConfig_Set and :func:sys.set_int_max_str_digits now replace :data:sys.flags (create a new object), instead of modifying :data:sys.flags in-place. Patch by Victor Stinner.

.. date: 2026-06-11-16-03-23 .. gh-issue: 151297 .. nonce: NGPkUM .. section: Core and Builtins

Fix an invalid pointer dereference that could occur when calling :c:func:PyObject_Realloc with a NULL pointer in :term:free-threaded builds <free-threaded build> or with :envvar:PYTHONMALLOC set to mimalloc.

.. date: 2026-06-10-15-42-46 .. gh-issue: 151253 .. nonce: 7MMQ8P .. section: Core and Builtins

If import encodings (first import) fails at Python startup, dump the Python path configuration to help users debugging their configuration. Patch by Victor Stinner.

.. date: 2026-06-10-15-19-58 .. gh-issue: 151238 .. nonce: C9Wu4x .. section: Core and Builtins

Fix a crash when compiling a concatenated f-string or t-string if an error occurs when processing one of it's parts.

.. date: 2026-06-09-12-24-35 .. gh-issue: 151112 .. nonce: 4RKCkD .. section: Core and Builtins

Fix a crash in the compiler that could occur when running out of memory.

.. date: 2026-06-09-10-28-30 .. gh-issue: 151126 .. nonce: DKa6Sl .. section: Core and Builtins

Fix a crash, when there's no memory left on a device, which happened in: code compilation, :mod:!_interpchannels module, :func:!_winapi.CreateProcess function.

Now these places raise proper :exc:MemoryError errors.

.. date: 2026-06-08-13-14-42 .. gh-issue: 150902 .. nonce: -CWZ66 .. section: Core and Builtins

Apply an existing optimization of PyCriticalSection (single mutex) to PyCriticalSection2: avoid acquiring the same locks that the current CS has already acquired.

.. date: 2026-06-08-05-31-22 .. gh-issue: 151065 .. nonce: _o_31F .. section: Core and Builtins

Fix memory leak when using the :ref:mimalloc memory allocator <mimalloc>.

.. date: 2026-06-05-22-52-41 .. gh-issue: 150988 .. nonce: fDKfMJ .. section: Core and Builtins

Fix a reference leak in :exc:OSError when attributes are set before super().__init__().

.. date: 2026-06-01-19-24-12 .. gh-issue: 150723 .. nonce: WlcL_- .. section: Core and Builtins

Fix perf jitdump timestamps on macOS. Events were stamped using CLOCK_MONOTONIC, but macOS profilers timestamp their samples with mach_absolute_time(). The mismatch prevented the JIT code mappings from lining up with the samples, so no Python frame could be resolved.

.. date: 2026-06-01-19-21-01 .. gh-issue: 150723 .. nonce: Hb3JDG .. section: Core and Builtins

Fix malformed perf jitdump thread ids on macOS. The thread_id field of the JR_CODE_LOAD record was written as a 64-bit value instead of the 32-bit value required by the jitdump format, which shifted every following field and prevented profilers from resolving Python frames.

.. date: 2026-06-01-19-00-00 .. gh-issue: 150700 .. nonce: W8CzVR .. section: Core and Builtins

Fix a :exc:SystemError when compiling a class-scope comprehension containing a lambda that references __class__, __classdict__, or __conditional_annotations__. Patch by Bartosz Sławecki.

.. date: 2026-05-30-20-19-35 .. gh-issue: 150633 .. nonce: XkNul0 .. section: Core and Builtins

Fix the frozen importer accepting module names with embedded null bytes, which caused it to bypass the :data:sys.modules cache and create duplicate module objects.

.. date: 2026-05-24-22-46-49 .. gh-issue: 148613 .. nonce: PLpmyd .. section: Core and Builtins

Fix a data race in the free-threaded build between :func:gc.set_threshold and garbage collection scheduling during object allocation.

.. date: 2026-05-22-21-52-38 .. gh-issue: 150207 .. nonce: l2BUtI .. section: Core and Builtins

Fix a crash when a memory allocation fails during tokenizer initialization. A proper :exc:MemoryError is now raised instead.

.. date: 2026-05-13-21-26-26 .. gh-issue: 149805 .. nonce: IG6cza .. section: Core and Builtins

Fix a :exc:SystemError when compiling a compiling __classdict__ class annotation. Found by OSS-Fuzz in :oss-fuzz:512907042.

.. date: 2026-05-05-12-00-00 .. gh-issue: 149321 .. nonce: remove-lazy-imports-none .. section: Core and Builtins

Do not support none as a lazy imports mode.

.. date: 2026-06-20-15-00-00 .. gh-issue: 75666 .. nonce: Kt9xQ2 .. section: Library

Fix a reference leak in :mod:tkinter: the Tcl commands created for event callbacks are now deleted when a binding is replaced or unbound.

.. date: 2026-06-20-15-00-00 .. gh-issue: 151770 .. nonce: dtiso0 .. section: Library

Fix :meth:datetime.datetime.fromisoformat raising :exc:AssertionError instead of :exc:ValueError for an out-of-range month combined with a 24:00 time.

.. date: 2026-06-20-14-47-55 .. gh-issue: 151665 .. nonce: 82fmzx .. section: Library

:func:inspect.signature now works on the lazy evaluators of type aliases and type parameters instead of raising :exc:ValueError.

.. date: 2026-06-19-07-26-20 .. gh-issue: 151695 .. nonce: IBDlkN .. section: Library

Fix a use-after-free in the :mod:curses module. The encoding of the initial screen, used by :func:curses.unctrl and :func:curses.ungetch to encode non-ASCII characters, is now kept as a private copy instead of a borrowed pointer to a window object that may be deallocated.

.. date: 2026-06-13-11-57-48 .. gh-issue: 151436 .. nonce: UEDowO .. section: Library

Fix skewed stack trackes in the Tachyon profiler when caching is enabled and when generators and coroutines are profiled, by updating tstate->last_profiled_frame at every frame-removal site. The issue resulted in total erasure of some callers. Patch by Maurycy Pawłowski-Wieroński.

.. date: 2026-06-13-04-11-00 .. gh-issue: 151426 .. nonce: f2V67e .. section: Library

Fix impossible stack traces (callers and callees cross called, orphans and incorrect lines) in the Tachyon profiler when caching frames, by snapshotting the stack chunks before walking the frame chain on a cache miss. Patch by Maurycy Pawłowski-Wieroński.

.. date: 2026-06-12-22-46-31 .. gh-issue: 151403 .. nonce: DalZWh .. section: Library

Fixed a crash in :class:subprocess.Popen (and _posixsubprocess.fork_exec) when an argv item's :meth:~os.PathLike.__fspath__ concurrently mutates the args sequence being converted.

.. date: 2026-06-12-07-20-08 .. gh-issue: 151390 .. nonce: CmYN9EeJ .. section: Library

Colorize match in the :term:REPL when followed by a unary + or - operator. Patch by Bartosz Sławecki.

.. date: 2026-06-12-00-04-34 .. gh-issue: 151126 .. nonce: aHaBYq .. section: Library

Fix crash on unset :exc:MemoryError on allocation failure in :func:ctypes.get_errno.

.. date: 2026-06-11-21-43-24 .. gh-issue: 151337 .. nonce: JSVV18 .. section: Library

Avoid possible memory leak in tkinter.c on Windows.

.. date: 2026-06-11-16-25-38 .. gh-issue: 151126 .. nonce: bh_Usy .. section: Library

Fix a crash when :exc:MemoryError in :func:!os._path_splitroot was not set properly.

.. date: 2026-06-11-11-52-23 .. gh-issue: 149671 .. nonce: 6Rpr5r .. section: Library

Restore compatibility with setuptools -nspkg.pth files in the :mod:site module. Inject sitedir variable in the frame which executes pth code. Patch by Victor Stinner.

.. date: 2026-06-11-00-00-00 .. gh-issue: 151295 .. nonce: NQYUzW .. section: Library

Fixed a crash (use-after-free) in :meth:bytes.join and :meth:bytearray.join that could occur if an item's :meth:~object.__buffer__ concurrently mutates the sequence being joined. The mutation is now reported as a :exc:RuntimeError instead.

.. date: 2026-06-10-00-00-02 .. gh-issue: 109940 .. nonce: Cx1099 .. section: Library

Fix Windows :mod:venv activation in cmd.exe to respect VIRTUAL_ENV_DISABLE_PROMPT.

.. date: 2026-06-09-12-00-00 .. gh-issue: 150771 .. nonce: K7mNx2 .. section: Library

Fix :mod:email messages created with shift_jis or euc-jp charsets. set_content() now stores the payload using the output charset (iso-2022-jp) so printing the message no longer raises :exc:UnicodeEncodeError.

.. date: 2026-06-07-17-29-33 .. gh-issue: 151039 .. nonce: AZ0qBn .. section: Library

Fix a crash when static :mod:datetime types outlive the _datetime module.

.. date: 2026-06-06-15-20-54 .. gh-issue: 151021 .. nonce: J4qk2A .. section: Library

Fix :meth:mmap.mmap.find and :meth:~mmap.mmap.rfind to return -1 when searching for an empty subsequence with a start position past the end of the mapping.

.. date: 2026-06-04-23-10-31 .. gh-issue: 62825 .. nonce: BtG_yQ .. section: Library

Encodings "KS_C_5601-1987", "KS X 1001", etc are now aliases of "CP949" instead of "EUC-KR".

.. date: 2026-06-04-21-49-18 .. gh-issue: 150913 .. nonce: EmptyBl .. section: Library

Fix :class:sqlite3.Blob slice assignment to raise :exc:TypeError and :exc:IndexError for type and size mismatches respectively, even when the target slice is empty.

.. date: 2026-06-04-18-22-56 .. gh-issue: 143008 .. nonce: z5tw-J .. section: Library

Fix race conditions when re-initializing a :class:io.TextIOWrapper object.

.. date: 2026-06-03-13-51-29 .. gh-issue: 150662 .. nonce: ELT8Vg .. section: Library

Fix the --gecko collector in :mod:profiling.sampling that kept every sample in memory. It now writes sample and marker data to temporary files and reads them back, ultimately building the output file at the end. Patch by Pablo Galindo and Maurycy Pawłowski-Wieroński.

.. date: 2026-06-02-14-21-46 .. gh-issue: 150750 .. nonce: SVS2o0 .. section: Library

Fix a race condition in :meth:collections.deque.index with free-threading.

.. date: 2026-05-27-23-47-31 .. gh-issue: 148932 .. nonce: Y1xmvA .. section: Library

Fix profiling.sampling on Windows virtual environments to resolve the actual Python PID from a virtual environment shim.

.. date: 2026-05-18-22-45-54 .. gh-issue: 149816 .. nonce: T68vc_ .. section: Library

Fix race condition in :attr:ssl.SSLContext.sni_callback

.. date: 2026-05-17-12-37-59 .. gh-issue: 53144 .. nonce: c5tr1p .. section: Library

The :mod:email package now supports all aliases of Python codecs and uses MIME/IANA names for all IANA registered charsets.

.. date: 2026-05-15-19-52-41 .. gh-issue: 149891 .. nonce: BJUIGB .. section: Library

Add support for more encoding aliases officially registered in IANA <https://www.iana.org/assignments/character-sets/character-sets.xhtml>__.

.. date: 2026-05-13-12-16-54 .. gh-issue: 149473 .. nonce: nOQZqn .. section: Library

Calling os.environ.clear() now emits os._clearenv auditing event. Patch by Victor Stinner.

.. date: 2026-04-24-19-54-00 .. gh-issue: 148954 .. nonce: v1 .. section: Library

Fix XML injection vulnerability in :func:xmlrpc.client.dumps where the methodname was not being escaped before interpolation into the XML body.

.. date: 2026-01-18-06-42-47 .. gh-issue: 143988 .. nonce: MtLtCP .. section: Library

Fixed crashes in :meth:socket.socket.sendmsg and :meth:socket.socket.recvmsg_into that could occur if buffer sequences are concurrently mutated.

.. date: 2024-06-18-04-08-37 .. gh-issue: 120665 .. nonce: x7T1hV .. section: Library

Fixed an issue where unittest loaders would load and instantiate :class:unittest.TestCase-derived subclasses that are also abstract base classes, which can't be instantiated.

.. date: 2023-02-26-14-07-18 .. gh-issue: 91099 .. nonce: _QPbEL .. section: Library

:meth:imaplib.IMAP4.login now raises exceptions with :class:str instead of :class:bytes. Patch by Florian Best.

.. date: 2023-01-23-21-23-50 .. gh-issue: 101267 .. nonce: _f-cFH .. section: Library

When a worker process terminates unexpectedly, :class:concurrent.futures.ProcessPoolExecutor now sets a separate :exc:~concurrent.futures.process.BrokenProcessPool exception on each pending future instead of sharing a single instance among them all. Sharing one exception produced malformed tracebacks: each :meth:Future.result() <concurrent.futures.Future.result> call re-raised the same object, appending another copy of the traceback to it.

.. date: 2026-06-17-12-00-00 .. gh-issue: 86726 .. nonce: __bOgH .. section: Documentation

Greatly expand the :mod:tkinter documentation to cover the full public API of the package and its submodules. The descriptions are oriented towards Python rather than Tcl/Tk, with corrected return types and versionadded/versionchanged information.

.. date: 2026-05-23-17-27-41 .. gh-issue: 150319 .. nonce: ol9tWK .. section: Documentation

Generic builtin and standard library types now document the meaning of their type parameters.

.. date: 2023-09-16-23-42-27 .. gh-issue: 109503 .. nonce: mZ-kdU .. section: Documentation

Fix documentation for :func:shutil.move on usage of :func:os.rename since nonatomic move might be used even if the files are on the same filesystem. Patch by Fang Li

.. date: 2026-06-09-11-52-52 .. gh-issue: 151130 .. nonce: 1vslPH .. section: Tests

Add more tests for PyWeakref_* C API.

.. date: 2026-06-06-16-22-00 .. gh-issue: 150966 .. nonce: 7N9x5Q .. section: Tests

Avoid prematurely terminating failing live sampling profiler test targets, which made stderr assertions flaky on ASAN buildbots.

.. date: 2026-04-24-01-38-56 .. gh-issue: 148853 .. nonce: _uM4_Q .. section: Tests

Fix tests failing on FreeBSD in test.support's in_systemd_nspawn_sync_suppressed() due to unreadable /run directory.

.. date: 2026-06-09-11-54-13 .. gh-issue: 151163 .. nonce: vFAtjv .. section: Build

Updated Android build to include SQLite version 3.53.2.

.. date: 2026-06-09-11-55-41 .. gh-issue: 151163 .. nonce: oizZYV .. section: Windows

Updated Windows builds to include SQLite version 3.53.2.

.. date: 2026-06-09-11-40-48 .. gh-issue: 151159 .. nonce: JKVfme .. section: Windows

Updated bundled version of OpenSSL to 3.5.7.

.. date: 2026-06-04-18-53-18 .. gh-issue: 150836 .. nonce: Wci7bZ .. section: Windows

Make installed tkinter work with Tcl/Tk 9 builds that embed the Tk script library in the Tk DLL on Windows.

.. date: 2026-06-09-11-52-35 .. gh-issue: 151163 .. nonce: RlPXHq .. section: macOS

Updated macOS installer to include SQLite version 3.53.2.

.. bpo: 6699 .. date: 2019-12-12-03-18-02 .. nonce: 1CqJFG .. section: IDLE

Warn the user if a file will be overwritten when saving.

.. date: 2026-06-18-18-24-11 .. gh-issue: 141510 .. nonce: -EOHJ1 .. section: C API

Add :class:frozendict to the fast paths of :c:func:PyMapping_GetOptionalItem, :c:func:PyMapping_Keys, :c:func:PyMapping_Values, and :c:func:PyMapping_Items.

.. date: 2026-06-10-16-43-37 .. gh-issue: 123619 .. nonce: dV82r6 .. section: C API

:c:func:PyUnstable_Object_EnableDeferredRefcount now returns 0 if the object is not tracked by the garbage collector: if :func:gc.is_tracked is false. Patch by Victor Stinner.

.. date: 2026-06-10-15-22-44 .. gh-issue: 149044 .. nonce: O7KEcs .. section: C API

Improved error message when specifying non-type base classes in :c:macro:Py_tp_bases, :c:macro:Py_tp_base, and bases argument to :c:func:PyType_FromMetaclass and other PyType_From* functions.

.. date: 2026-06-04-14-26-17 .. gh-issue: 150907 .. nonce: CA91_B .. section: C API

Fix dynamic_annotations.h header file when built with C++ and Valgrind: add extern "C++" scope for the C++ template. Patch by Victor Stinner.