3.14.0a2.rst

Update credits command output.

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

Fixes venv failure due to missing redirector executables in experimental free-threaded installs.

Removed unnecessary DLLs from Windows embeddable package

Avoid crashing in :mod:`platform` due to slow WMI calls on some Windows machines.

Fix venvwlauncher to launch pythonw instead of python so no extra console window is created.

Fix a :exc:`SystemError` when :func:`sys.exit` is called with 0xffffffff on Windows.

Enable the :ref:`launcher` to detect Python 3.14 installs from the Windows Store.

All Windows code pages are now supported as "cpXXX" codecs on Windows.

Fix extraction warnings in :program:`pygettext.py` caused by mistaking function definitions for function calls.

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

Fix test_os extended attribute tests to work on filesystems with 1 KiB xattr size limit.

Change make test to not run GUI tests by default. Use make ci to run tests with GUI tests instead.

Add translation tests to the :mod:`argparse` module.

Upgrade libexpat to 2.6.4

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

Fix the prefix and exec_prefix keys from :py:func:`sysconfig.get_config_vars` incorrectly having the same value as :py:const:`sys.base_prefix` and :py:const:`sys.base_exec_prefix`, respectively, inside virtual environments. They now accurately reflect :py:const:`sys.prefix` and :py:const:`sys.exec_prefix`.

Fix memory leaks when :mod:`regular expression <re>` matching terminates abruptly, either because of a signal or because memory allocation fails.

:mod:`marshal` now supports :class:`slice` objects. The marshal format version was increased to 5.

Fixed the values of :py:func:`sysconfig.get_config_vars`, :py:func:`sysconfig.get_paths`, and their siblings when the :py:mod:`site` initialization happens after :py:mod:`sysconfig` has built a cache for :py:func:`sysconfig.get_config_vars`.

Update bundled pip to 24.3.1

Fix issue where :func:`urllib.request.url2pathname` failed to discard two leading slashes introducing an empty authority section.

Allow :class:`os.PathLike` to be a base for Protocols.

Allow :class:`collections.abc.AsyncIterator` to be a base for Protocols.

Fix crash when non-dict was passed to several functions in _interpreters module.

Limit starting a patcher (from :func:`unittest.mock.patch` or :func:`unittest.mock.patch.object`) more than once without stopping it

Fix a crash when instantiating :class:`itertools.count` with an initial count of :data:`sys.maxsize` on debug builds. Patch by Bénédikt Tran.

Fix issue where :func:`urllib.request.pathname2url` mishandled Windows paths with embedded forward slashes.

Improve performances of :meth:`zipfile.Path.open` for non-reading modes.

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

Fixed the :mod:`multiprocessing` "forkserver" start method forkserver process to correctly inherit the parent's :data:`sys.path` during the importing of :func:`multiprocessing.set_forkserver_preload` modules in the same manner as :data:`sys.path` is configured in workers before executing work items.

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

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

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

The :class:`multiprocessing.Lock` and :class:`multiprocessing.RLock` repr values no longer say "unknown" on macOS.

Raise :class:`calendar.IllegalMonthError` (now a subclass of :class:`IndexError`) for :func:`calendar.month` when the input month is not correct.

The Python implementation of :mod:`pickle` no longer calls :meth:`pickle.Pickler.persistent_id` for the result of :meth:`!persistent_id`.

Register the :class:`contextvars.Context` type to :class:`collections.abc.Mapping`.

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

Add RFC 9559 MIME types for Matroska audiovisual container formats. Patch by Hugo van Kemenade.

Register the :class:`!multiprocessing.managers.DictProxy` and :class:`!multiprocessing.managers.ListProxy` types in :mod:`multiprocessing.managers` to :class:`collections.abc.MutableMapping` and :class:`collections.abc.MutableSequence`, respectively.

Add support for returning intermixed options and non-option arguments in order in :func:`getopt.gnu_getopt`.

Add support for options with optional arguments in the :mod:`getopt` module.

Speed up pattern parsing in :meth:`pathlib.Path.glob` by skipping creation of a :class:`pathlib.Path` object for the pattern.

:func:`asyncio.get_event_loop` now does not implicitly creates an event loop. It now raises a :exc:`RuntimeError` if there is no set event loop. Patch by Kumar Aditya.

Fix an issue in :func:`curses.napms` when :func:`curses.initscr` has not yet been called. Patch by Bénédikt Tran.

Fix pickling and copying of :class:`os.sched_param` objects.

Fix a use-after-free crash on :class:`asyncio.Task` objects whose underlying coroutine yields an object that implements an evil :meth:`~object.__getattribute__`. Patch by Nico Posada.

Replace the os.environ.refresh() method with a new :func:`os.reload_environ` function. Patch by Victor Stinner.

Fix crash in :class:`!cProfile.Profile` and :class:`!_lsprof.Profiler` when their callbacks were directly called with 0 arguments.

Fix issue where :func:`urllib.request.pathname2url` and :func:`~urllib.request.url2pathname` removed slashes from Windows DOS drive paths and URLs.

Raise a :exc:`UnicodeEncodeError` instead of a :exc:`SystemError` upon calling :func:`!_interpreters.create` with an invalid Unicode character.

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

Improved performances of creating :py:class:`~http.cookies.Morsel` objects by a factor of 3.8x.

Fix a crash in :mod:`ast` when the :attr:`ast.AST._fields` attribute is deleted.

Fixes a possible NULL pointer dereference in :mod:`ssl`.

Fix a use-after-free crash on :class:`asyncio.Task` objects for which the underlying event loop implements an evil :meth:`~object.__getattribute__`. Reported by Nico-Posada. Patch by Bénédikt Tran.

Correct detection of complex numbers support in libffi.

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

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

Add :meth:`!pathlib.Path.scandir` method to efficiently fetch directory children and their file attributes. This is a trivial wrapper of :func:`os.scandir`.

Fix use-after-free crashes on :class:`asyncio.Future` objects for which the underlying event loop implements an evil :meth:`~object.__getattribute__`. Reported by Nico-Posada. Patch by Bénédikt Tran.

Fix :func:`urllib.parse.urljoin` for base URI with undefined authority. Although RFC 3986 only specify reference resolution for absolute base URI, :func:`!urljoin` should continue to return sensible result for relative base URI.

Fix an out-of-bounds crash when an evil :meth:`asyncio.loop.call_soon` mutates the length of the internal callbacks list. Patch by Bénédikt Tran.

Fix a use-after-free crash in :meth:`asyncio.Future.remove_done_callback`. Patch by Bénédikt Tran.

Fix possible crash when mutating list of callbacks returned by :attr:`!asyncio.Future._callbacks`. It now always returns a new copy in C implementation :mod:`!_asyncio`. Patch by Kumar Aditya.

Allow the initial parameter of :func:`functools.reduce` to be passed as a keyword argument. Patch by Sayandip Dutta.

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

:class:`!argparse.BooleanOptionalAction` now rejects option names starting with --no-.

Fixed the bug for :mod:`pdb` where it can't set breakpoints on functions with certain annotations.

Fix several bugs in :meth:`argparse.ArgumentParser.parse_intermixed_args`.

• The parser no longer changes temporarily during parsing.
• Default values are not processed twice.
• Required mutually exclusive groups containing positional arguments are now supported.
• The missing arguments report now includes the names of all required optional and positional arguments.
• Unknown options can be intermixed with positional arguments in parse_known_intermixed_args().

:class:`super` objects are now :mod:`pickleable <pickle>` and :mod:`copyable <copy>`.

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

Remove :class:`!URLopener` and :class:`!FancyURLopener` classes from :mod:`urllib.request`. They had previously raised :exc:`DeprecationWarning` since Python 3.3.

Avoid the exiting the interpreter if a null byte is given as input in the new REPL.

[Enum] fix hashable<->nonhashable comparisons for member values

Restore ability to set :attr:`~pickle.Pickler.persistent_id` and :attr:`~pickle.Unpickler.persistent_load` attributes of instances of the :class:`!Pickler` and :class:`!Unpickler` classes in the :mod:`pickle` module.

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

Reject non-ASCII digits in the Python implementation of :func:`json.loads` conforming to the JSON specification.

Reject invalid unicode escapes for Python implementation of :func:`json.loads`.

Use :c:func:`!wcsftime` to implement :func:`time.strftime` on Windows.

Fix the notes removal logic for errors thrown in enum initialization.

Add function :func:`inspect.ispackage` to determine whether an object is a :term:`package` or not.

In the :data:`~annotationlib.Format.FORWARDREF` format of :mod:`annotationlib`, fix bug where nested expressions were not returned as :class:`annotationlib.ForwardRef` format.

Allow FrameLocalsProxy to delete and pop if the key is not a fast variable.

Only show stale code warning in :mod:`pdb` when we display source code.

Deprecate passing keyword-only prefix_chars argument to :meth:`argparse.ArgumentParser.add_argument_group`.

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

Improve traceback if :func:`importlib.reload` is called with an object that is not a module. Patch by Alex Waygood.

Fix deadlock when :class:`concurrent.futures.ProcessPoolExecutor` shuts down concurrently with an error when feeding a job to a worker process.

Fixed a bug in :mod:`pdb` where arguments starting with - can't be passed to the debugged script.

Fix the conversion of the :envvar:`!VIRTUAL_ENV` path in the activate script in :mod:`venv` when running in Git Bash for Windows.

Fix race condition when importing :mod:`collections.abc`, which could incorrectly return an empty module.

Fix encoding issues in :func:`time.strftime`, the :meth:`~datetime.datetime.strftime` method of the :mod:`datetime` classes :class:`~datetime.datetime`, :class:`~datetime.date` and :class:`~datetime.time` and formatting of these classes. Characters not encodable in the current locale are now acceptable in the format string. Surrogate pairs and sequence of surrogatescape-encoded bytes are no longer recombinated. Embedded null character no longer terminates the format string.

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

Properly quote template strings in :mod:`venv` activation scripts.

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

This addition is unrelated to PEP 734.

Deprecate the :class:`argparse.FileType` type converter.

Adds a feature to optionally enable suggestions for argument choices and subparser names if mistyped by the user.

Fixed a bug in :mod:`pdb` where sometimes the breakpoint won't trigger if it was set on a function which is already in the call stack.

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

unittest discovery supports PEP 420 namespace packages as start directory again.

Fix the canvas not clearing after running turtledemo clock.

Add :func:`uuid.uuid8` for generating UUIDv8 objects as specified in RFC 9562. Patch by Bénédikt Tran

Add :func:`platform.invalidate_caches` to invalidate cached results.

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

Improve the performance of :mod:`tarfile` when writing files, by caching user names and group names.

Fixed an issue where :func:`inspect.getclosurevars` would incorrectly classify an attribute name as a global variable when the name exists both as an attribute name and a global variable.

:func:`!posixpath.realpath` now raises :exc:`NotADirectoryError` when strict mode is enabled and a non-directory path with a trailing slash is supplied.

Always return an absolute path for :func:`os.path.abspath` on Windows.

Remove deprecated :func:`!pkgutil.get_loader` and :func:`!pkgutil.find_loader`.

Add :data:`!socket.IPV6_RECVERR` constant (available since Linux 2.2).

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

Fix SystemError when match regular expression pattern containing some combination of possessive quantifier, alternative and capture group.

Fix a race condition in :class:`multiprocessing.pool.Pool`.

Strip :class:`unittest.IsolatedAsyncioTestCase` stack frames from reported stacktraces.

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

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

Require Sphinx 7.2.6 or later to build the Python documentation. Patch by Adam Turner.

Include the :class:`object` type in the lists of documented types. Change by Furkan Onder and Martin Panter.

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

Now :exc:`ValueError` is raised instead of :exc:`SystemError` when trying to iterate over a released :class:`memoryview` object.

Fix a crash when calling :func:`os.fork` on some operating systems, including SerenityOS.

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

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

Fix crash when using yield from on an object that raises an exception in its __iter__.

Fix an issue with skip_file_prefixes parameter which resulted in an inconsistent behaviour between the C and Python implementations of :func:`warnings.warn`. Patch by Daehee Kim.

Fix crash during garbage collection on an object frozen by :func:`gc.freeze` on the free-threaded build.

Relax optimization requirements to allow fast attribute access to module subclasses.

Following :gh:`126101`, for :ref:`codeobjects` like lambda, annotation and type alias, we no longer add None to its :attr:`~codeobject.co_consts`.

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

Provide better error location when attempting to use a :term:`future statement <__future__>` with an unknown future feature.

Add a new attribute in :attr:`~codeobject.co_flags` to indicate whether the first item in :attr:`~codeobject.co_consts` is the docstring. If a code object has no docstring, None will NOT be inserted.

Relocated objects such as tuple, bytes and str objects are properly tracked by :mod:`tracemalloc` and its associated hooks. Patch by Pablo Galindo.

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

Fix a crash in :func:`sys.audit` when passing a non-string as first argument and Python was compiled in debug mode.

The :class:`memoryview` type now supports subscription, making it a :term:`generic type`.

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

On Android, the errors setting of :any:`sys.stdout` was changed from surrogateescape to backslashreplace.

Fix a crash in the free threading build when :func:`gc.get_objects` or :func:`gc.get_referrers` is called during an in-progress garbage collection.

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

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

Correctly honour :mod:`tracemalloc` hooks in specialized Py_DECREF paths. Patch by Pablo Galindo

Use color to highlight error locations in traceback from exception group

Fix crash on certain accesses to the __annotations__ of :class:`staticmethod` and :class:`classmethod` objects.

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

Fix illegal instruction for older Arm architectures. Patch by Diego Russo, testing by Ross Burton.

Add a new INSTRUCTION_SIZE macro to the cases generator which returns the current instruction size.

Fix crash when iterating over a generator expression after direct changes on gi_frame.f_locals. Patch by Mikhail Efimov.

Don't allow the JIT and perf support to be active at the same time. Patch by Pablo Galindo

Update JIT compilation to use LLVM 19

Improve the error message when a script shadowing a module from the standard library causes :exc:`ImportError` to be raised during a "from" import. Similarly, improve the error message when a script shadowing a third party module attempts to "from" import an attribute from that third party module while still initialising.

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

Fix bug where SSLProtocol.connection_lost wasn't getting called when OSError was thrown on writing to socket.

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

Fix error handling in :class:`ctypes.CDLL` objects which could result in a crash in rare situations.

Add :c:func:`PyLong_IsPositive`, :c:func:`PyLong_IsNegative` and :c:func:`PyLong_IsZero` for checking if a :c:type:`PyLongObject` is positive, negative, or zero, respectively.

Fix a bug where dictionary watchers (e.g., :c:func:`PyDict_Watch`) on an object's attribute dictionary (:attr:`~object.__dict__`) were not triggered when the object's attributes were modified.

Added the :c:func:`PyUnstable_Object_EnableDeferredRefcount` function for enabling PEP 703 deferred reference counting.

Add :c:func:`PyType_Freeze` function to make a type immutable. Patch by Victor Stinner.

The :c:macro:`!Py_HUGE_VAL` macro is :term:`soft deprecated`.

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

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

Disable SIMD support for HACL under WASI.

Hard-code float word ordering as little endian on WASM.

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

Introduced Tools/wasm/emscripten.py to simplify doing Emscripten builds.

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

The minimum supported Android version is now 7.0 (API level 24).

The Android build now supports 16 KB page sizes.

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

Emscripten builds now require node >= 18.

Fix cross compile failures when the host and target SOABIs match.