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What's New In Python 3.12

Release
Date

This article explains the new features in Python 3.12, compared to 3.11.

For full details, see the changelog <changelog>.

Note

Prerelease users should be aware that this document is currently in draft form. It will be updated substantially as Python 3.12 moves towards release, so it's worth checking back even after reading earlier versions.

Summary -- Release highlights

New typing features:

  • 688: Making the buffer protocol accessible in Python
  • whatsnew312-pep692
  • 698: Override Decorator for Static Typing

Important deprecations, removals or restrictions:

  • 623: Remove wstr from Unicode
  • 632: Remove the distutils package

Improved Error Messages

  • Modules from the standard library are now potentially suggested as part of the error messages displayed by the interpreter when a NameError is raised to the top level. Contributed by Pablo Galindo in 98254.

    >>> sys.version_info Traceback (most recent call last): File "<stdin>", line 1, in <module> NameError: name 'sys' is not defined. Did you forget to import 'sys'?

  • Improve the error suggestion for NameError exceptions for instances. Now if a NameError is raised in a method and the instance has an attribute that's exactly equal to the name in the exception, the suggestion will include self.<NAME> instead of the closest match in the method scope. Contributed by Pablo Galindo in 99139.

    >>> class A: ... def __init__(self): ... self.blech = 1 ... ... def foo(self): ... somethin = blech

    >>> A().foo() Traceback (most recent call last): File "<stdin>", line 1 somethin = blech ^^^^^ NameError: name 'blech' is not defined. Did you mean: 'self.blech'?

  • Improve the SyntaxError error message when the user types import x from y instead of from y import x. Contributed by Pablo Galindo in 98931.

    >>> import a.y.z from b.y.z Traceback (most recent call last): File "<stdin>", line 1 import a.y.z from b.y.z ^^^^^^^^^^^^^^^^^^^^^^^ SyntaxError: Did you mean to use 'from ... import ...' instead?

  • ImportError exceptions raised from failed from <module> import <name> statements now include suggestions for the value of <name> based on the available names in <module>. Contributed by Pablo Galindo in 91058.

    >>> from collections import chainmap Traceback (most recent call last): File "<stdin>", line 1, in <module> ImportError: cannot import name 'chainmap' from 'collections'. Did you mean: 'ChainMap'?

New Features

  • Add perf_profiling through the new environment variable PYTHONPERFSUPPORT, the new command-line option -X perf <-X>, as well as the new sys.activate_stack_trampoline, sys.deactivate_stack_trampoline, and sys.is_stack_trampoline_active APIs. (Design by Pablo Galindo. Contributed by Pablo Galindo and Christian Heimes with contributions from Gregory P. Smith [Google] and Mark Shannon in 96123.)
  • The extraction methods in tarfile, and shutil.unpack_archive, have a new a filter argument that allows limiting tar features than may be surprising or dangerous, such as creating files outside the destination directory. See tarfile-extraction-filter for details. In Python 3.14, the default will switch to 'data'. (Contributed by Petr Viktorin in 706.)

PEP 709: Comprehension inlining

Dictionary, list, and set comprehensions are now inlined, rather than creating a new single-use function object for each execution of the comprehension. This speeds up execution of a comprehension by up to 2x.

Comprehension iteration variables remain isolated; they don't overwrite a variable of the same name in the outer scope, nor are they visible after the comprehension. This isolation is now maintained via stack/locals manipulation, not via separate function scope.

Inlining does result in a few visible behavior changes:

  • There is no longer a separate frame for the comprehension in tracebacks, and tracing/profiling no longer shows the comprehension as a function call.
  • Calling locals inside a comprehension now includes variables from outside the comprehension, and no longer includes the synthetic .0 variable for the comprehension "argument".

Contributed by Carl Meyer and Vladimir Matveev in 709.

PEP 688: Making the buffer protocol accessible in Python

688 introduces a way to use the buffer protocol <bufferobjects> from Python code. Classes that implement the ~object.__buffer__ method are now usable as buffer types.

The new collections.abc.Buffer ABC provides a standard way to represent buffer objects, for example in type annotations. The new inspect.BufferFlags enum represents the flags that can be used to customize buffer creation. (Contributed by Jelle Zijlstra in 102500.)

New Features Related to Type Hints

This section covers major changes affecting 484 type hints and the typing module.

PEP 692: Using TypedDict for more precise **kwargs typing

Typing **kwargs in a function signature as introduced by 484 allowed for valid annotations only in cases where all of the **kwargs were of the same type.

This PEP specifies a more precise way of typing **kwargs by relying on typed dictionaries:

from typing import TypedDict, Unpack

class Movie(TypedDict):
  name: str
  year: int

def foo(**kwargs: Unpack[Movie]): ...

See 692 for more details.

(PEP written by Franek Magiera)

Other Language Changes

  • types.MappingProxyType instances are now hashable if the underlying mapping is hashable. (Contributed by Serhiy Storchaka in 87995.)
  • memoryview now supports the half-float type (the "e" format code). (Contributed by Dong-hee Na and Antoine Pitrou in 90751.)
  • The parser now raises SyntaxError when parsing source code containing null bytes. (Contributed by Pablo Galindo in 96670.)
  • ast.parse now raises SyntaxError instead of ValueError when parsing source code containing null bytes. (Contributed by Pablo Galindo in 96670.)
  • The Garbage Collector now runs only on the eval breaker mechanism of the Python bytecode evaluation loop instead of object allocations. The GC can also run when :cPyErr_CheckSignals is called so C extensions that need to run for a long time without executing any Python code also have a chance to execute the GC periodically. (Contributed by Pablo Galindo in 97922.)
  • A backslash-character pair that is not a valid escape sequence now generates a SyntaxWarning, instead of DeprecationWarning. For example, re.compile("\d+\.\d+") now emits a SyntaxWarning ("\d" is an invalid escape sequence), use raw strings for regular expression: re.compile(r"\d+\.\d+"). In a future Python version, SyntaxError will eventually be raised, instead of SyntaxWarning. (Contributed by Victor Stinner in 98401.)
  • Octal escapes with value larger than 0o377 (ex: "\477"), deprecated in Python 3.11, now produce a SyntaxWarning, instead of DeprecationWarning. In a future Python version they will be eventually a SyntaxError. (Contributed by Victor Stinner in 98401.)
  • All builtin and extension callables expecting boolean parameters now accept arguments of any type instead of just bool and int. (Contributed by Serhiy Storchaka in 60203.)
  • Variables used in the target part of comprehensions that are not stored to can now be used in assignment expressions (:=). For example, in [(b := 1) for a, b.prop in some_iter], the assignment to b is now allowed. Note that assigning to variables stored to in the target part of comprehensions (like a) is still disallowed, as per 572. (Contributed by Nikita Sobolev in 100581.)
  • slice objects are now hashable, allowing them to be used as dict keys and set items. (Contributed by Will Bradshaw and Furkan Onder in 101264.)
  • Exceptions raised in a typeobject's __set_name__ method are no longer wrapped by a RuntimeError. Context information is added to the exception as a 678 note. (Contributed by Irit Katriel in 77757.)
  • When a try-except* construct handles the entire ExceptionGroup and raises one other exception, that exception is no longer wrapped in an ExceptionGroup. Also changed in version 3.11.4. (Contributed by Irit Katriel in 103590.)

New Modules

  • None yet.

Improved Modules

array

  • The array.array class now supports subscripting, making it a generic type. (Contributed by Jelle Zijlstra in 98658.)

asyncio

  • The performance of writing to sockets in asyncio has been significantly improved. asyncio now avoids unnecessary copying when writing to sockets and uses ~socket.socket.sendmsg if the platform supports it. (Contributed by Kumar Aditya in 91166.)
  • Added asyncio.eager_task_factory and asyncio.create_eager_task_factory functions to allow opting an event loop in to eager task execution, making some use-cases 2x to 5x faster. (Contributed by Jacob Bower & Itamar O in 102853, 104140, and 104138)
  • On Linux, asyncio uses ~asyncio.PidfdChildWatcher by default if os.pidfd_open is available and functional instead of ~asyncio.ThreadedChildWatcher. (Contributed by Kumar Aditya in 98024.)
  • The child watcher classes ~asyncio.MultiLoopChildWatcher, ~asyncio.FastChildWatcher, ~asyncio.AbstractChildWatcher and ~asyncio.SafeChildWatcher are deprecated and will be removed in Python 3.14. It is recommended to not manually configure a child watcher as the event loop now uses the best available child watcher for each platform (~asyncio.PidfdChildWatcher if supported and ~asyncio.ThreadedChildWatcher otherwise). (Contributed by Kumar Aditya in 94597.)
  • asyncio.set_child_watcher, asyncio.get_child_watcher, asyncio.AbstractEventLoopPolicy.set_child_watcher and asyncio.AbstractEventLoopPolicy.get_child_watcher are deprecated and will be removed in Python 3.14. (Contributed by Kumar Aditya in 94597.)
  • Add loop_factory parameter to asyncio.run to allow specifying a custom event loop factory. (Contributed by Kumar Aditya in 99388.)
  • Add C implementation of asyncio.current_task for 4x-6x speedup. (Contributed by Itamar Ostricher and Pranav Thulasiram Bhat in 100344.)
  • asyncio.iscoroutine now returns False for generators as asyncio does not support legacy generator-based coroutines. (Contributed by Kumar Aditya in 102748.)
  • asyncio.wait and asyncio.as_completed now accepts generators yielding tasks. (Contributed by Kumar Aditya in 78530.)

calendar

  • Add enums ~calendar.Month and ~calendar.Day. (Contributed by Prince Roshan in 103636.)

csv

  • Add ~csv.QUOTE_NOTNULL and ~csv.QUOTE_STRINGS flags to provide finer grained control of None and empty strings by ~csv.writer objects.

inspect

  • Add inspect.markcoroutinefunction to mark sync functions that return a coroutine for use with inspect.iscoroutinefunction. (Contributed Carlton Gibson in 99247.)
  • Add inspect.getasyncgenstate and inspect.getasyncgenlocals for determining the current state of asynchronous generators. (Contributed by Thomas Krennwallner in 35759.)
  • The performance of inspect.getattr_static has been considerably improved. Most calls to the function should be at least 2x faster than they were in Python 3.11, and some may be 6x faster or more. (Contributed by Alex Waygood in 103193.)

pathlib

  • Add support for subclassing pathlib.PurePath and ~pathlib.Path, plus their Posix- and Windows-specific variants. Subclasses may override the ~pathlib.PurePath.with_segments method to pass information between path instances.
  • Add ~pathlib.Path.walk for walking the directory trees and generating all file or directory names within them, similar to os.walk. (Contributed by Stanislav Zmiev in 90385.)
  • Add walk_up optional parameter to pathlib.PurePath.relative_to to allow the insertion of .. entries in the result; this behavior is more consistent with os.path.relpath. (Contributed by Domenico Ragusa in 40358.)
  • Add pathlib.Path.is_junction as a proxy to os.path.isjunction. (Contributed by Charles Machalow in 99547.)
  • Add case_sensitive optional parameter to pathlib.Path.glob, pathlib.Path.rglob and pathlib.PurePath.match for matching the path's case sensitivity, allowing for more precise control over the matching process.

dis

  • Pseudo instruction opcodes (which are used by the compiler but do not appear in executable bytecode) are now exposed in the dis module. HAVE_ARGUMENT is still relevant to real opcodes, but it is not useful for pseudo instructions. Use the new ~dis.hasarg collection instead. (Contributed by Irit Katriel in 94216.)

fractions

  • Objects of type fractions.Fraction now support float-style formatting. (Contributed by Mark Dickinson in 100161.)

itertools

  • Added itertools.batched() for collecting into even-sized tuples where the last batch may be shorter than the rest. (Contributed by Raymond Hettinger in 98363.)

math

  • Added math.sumprod for computing a sum of products. (Contributed by Raymond Hettinger in 100485.)

os

  • Add os.PIDFD_NONBLOCK to open a file descriptor for a process with os.pidfd_open in non-blocking mode. (Contributed by Kumar Aditya in 93312.)
  • os.DirEntry now includes an os.DirEntry.is_junction method to check if the entry is a junction. (Contributed by Charles Machalow in 99547.)
  • Add os.listdrives, os.listvolumes and os.listmounts functions on Windows for enumerating drives, volumes and mount points. (Contributed by Steve Dower in 102519.)
  • os.stat and os.lstat are now more accurate on Windows. The st_birthtime field will now be filled with the creation time of the file, and st_ctime is deprecated but still contains the creation time (but in the future will return the last metadata change, for consistency with other platforms). st_dev may be up to 64 bits and st_ino up to 128 bits depending on your file system, and st_rdev is always set to zero rather than incorrect values. Both functions may be significantly faster on newer releases of Windows. (Contributed by Steve Dower in 99726.)

os.path

  • Add os.path.isjunction to check if a given path is a junction. (Contributed by Charles Machalow in 99547.)
  • Add os.path.splitroot to split a path into a triad (drive, root, tail). (Contributed by Barney Gale in 101000.)

pdb

  • Add convenience variables to hold values temporarily for debug session and provide quick access to values like the current frame or the return value. (Contributed by Tian Gao in 103693.)

shutil

  • shutil.make_archive now passes the root_dir argument to custom archivers which support it. In this case it no longer temporarily changes the current working directory of the process to root_dir to perform archiving. (Contributed by Serhiy Storchaka in 74696.)
  • shutil.rmtree now accepts a new argument onexc which is an error handler like onerror but which expects an exception instance rather than a (typ, val, tb) triplet. onerror is deprecated and will be removed in Python 3.14. (Contributed by Irit Katriel in 102828.)

  • shutil.which now consults the PATHEXT environment variable to find matches within PATH on Windows even when the given cmd includes a directory component. (Contributed by Charles Machalow in 103179.)

    shutil.which will call NeedCurrentDirectoryForExePathW when querying for executables on Windows to determine if the current working directory should be prepended to the search path. (Contributed by Charles Machalow in 103179.)

    shutil.which will return a path matching the cmd with a component from PATHEXT prior to a direct match elsewhere in the search path on Windows. (Contributed by Charles Machalow in 103179.)

sqlite3

  • Add a command-line interface <sqlite3-cli>. (Contributed by Erlend E. Aasland in 77617.)
  • Add the ~sqlite3.Connection.autocommit attribute to ~sqlite3.Connection and the autocommit parameter to ~sqlite3.connect to control 249-compliant transaction handling <sqlite3-transaction-control-autocommit>. (Contributed by Erlend E. Aasland in 83638.)
  • Add entrypoint keyword-only parameter to ~sqlite3.Connection.load_extension, for overriding the SQLite extension entry point. (Contributed by Erlend E. Aasland in 103015.)
  • Add ~sqlite3.Connection.getconfig and ~sqlite3.Connection.setconfig to ~sqlite3.Connection to make configuration changes to a database connection. (Contributed by Erlend E. Aasland in 103489.)

threading

  • Add threading.settrace_all_threads and threading.setprofile_all_threads that allow to set tracing and profiling functions in all running threads in addition to the calling one. (Contributed by Pablo Galindo in 93503.)

tkinter

  • tkinter.Canvas.coords() now flattens its arguments. It now accepts not only coordinates as separate arguments (x1, y1, x2, y2, ...) and a sequence of coordinates ([x1, y1, x2, y2, ...]), but also coordinates grouped in pairs ((x1, y1), (x2, y2), ... and [(x1, y1), (x2, y2), ...]), like create_*() methods. (Contributed by Serhiy Storchaka in 94473.)

types

  • Add types.get_original_bases to allow for further introspection of user-defined-generics when subclassed. (Contributed by James Hilton-Balfe and Alex Waygood in 101827.)

unicodedata

  • The Unicode database has been updated to version 15.0.0. (Contributed by Benjamin Peterson in 96734).

unittest

Added --durations command line option, showing the N slowest test cases:

python3 -m unittest --durations=3 lib.tests.test_threading
.....
Slowest test durations
----------------------------------------------------------------------
1.210s     test_timeout (Lib.test.test_threading.BarrierTests)
1.003s     test_default_timeout (Lib.test.test_threading.BarrierTests)
0.518s     test_timeout (Lib.test.test_threading.EventTests)

(0.000 durations hidden.  Use -v to show these durations.)
----------------------------------------------------------------------
Ran 158 tests in 9.869s

OK (skipped=3)

(Contributed by Giampaolo Rodola in 4080)

uuid

  • Add a command-line interface <uuid-cli>. (Contributed by Adam Chhina in 88597.)

tempfile

  • The tempfile.NamedTemporaryFile function has a new optional parameter delete_on_close (Contributed by Evgeny Zorin in 58451.)
  • tempfile.mkdtemp now always returns an absolute path, even if the argument provided to the dir parameter is a relative path.

typing

  • Add typing.override, an override decorator telling to static type checkers to verify that a method overrides some method or attribute of the same name on a base class, as per 698. (Contributed by Steven Troxler in 101564.)
  • isinstance checks against runtime-checkable protocols <typing.runtime_checkable> now use inspect.getattr_static rather than hasattr to lookup whether attributes exist. This means that descriptors and ~object.__getattr__ methods are no longer unexpectedly evaluated during isinstance() checks against runtime-checkable protocols. However, it may also mean that some objects which used to be considered instances of a runtime-checkable protocol may no longer be considered instances of that protocol on Python 3.12+, and vice versa. Most users are unlikely to be affected by this change. (Contributed by Alex Waygood in 102433.)

  • The members of a runtime-checkable protocol are now considered "frozen" at runtime as soon as the class has been created. Monkey-patching attributes onto a runtime-checkable protocol will still work, but will have no impact on isinstance checks comparing objects to the protocol. For example:

    >>> from typing import Protocol, runtime_checkable
>>> @runtime_checkable
... class HasX(Protocol):
...     x = 1
...
>>> class Foo: ...
...
>>> f = Foo()
>>> isinstance(f, HasX)
False
>>> f.x = 1
>>> isinstance(f, HasX)
True
>>> HasX.y = 2
>>> isinstance(f, HasX)  # unchanged, even though HasX now also has a "y" attribute
True

    This change was made in order to speed up isinstance() checks against runtime-checkable protocols.

  • The performance profile of isinstance checks against runtime-checkable protocols <typing.runtime_checkable> has changed significantly. Most isinstance() checks against protocols with only a few members should be at least 2x faster than in 3.11, and some may be 20x faster or more. However, isinstance() checks against protocols with fourteen or more members may be slower than in Python 3.11. (Contributed by Alex Waygood in 74690 and 103193.)

sys

  • Add sys.activate_stack_trampoline and sys.deactivate_stack_trampoline for activating and deactivating stack profiler trampolines, and sys.is_stack_trampoline_active for querying if stack profiler trampolines are active. (Contributed by Pablo Galindo and Christian Heimes with contributions from Gregory P. Smith [Google] and Mark Shannon in 96123.)
  • Add sys.last_exc which holds the last unhandled exception that was raised (for post-mortem debugging use cases). Deprecate the three fields that have the same information in its legacy form: sys.last_type, sys.last_value and sys.last_traceback. (Contributed by Irit Katriel in 102778.)
  • sys._current_exceptions now returns a mapping from thread-id to an exception instance, rather than to a (typ, exc, tb) tuple. (Contributed by Irit Katriel in 103176.)

Optimizations

  • Removed wstr and wstr_length members from Unicode objects. It reduces object size by 8 or 16 bytes on 64bit platform. (623) (Contributed by Inada Naoki in 92536.)
  • Added experimental support for using the BOLT binary optimizer in the build process, which improves performance by 1-5%. (Contributed by Kevin Modzelewski in 90536 and tuned by Dong-hee Na in 101525)
  • Speed up the regular expression substitution (functions re.sub and re.subn and corresponding !re.Pattern methods) for replacement strings containing group references by 2--3 times. (Contributed by Serhiy Storchaka in 91524.)
  • Speed up asyncio.Task creation by deferring expensive string formatting. (Contributed by Itamar O in 103793.)

CPython bytecode changes

  • Removed the LOAD_METHOD instruction. It has been merged into LOAD_ATTR. LOAD_ATTR will now behave like the old LOAD_METHOD instruction if the low bit of its oparg is set. (Contributed by Ken Jin in 93429.)
  • Removed the !JUMP_IF_FALSE_OR_POP and !JUMP_IF_TRUE_OR_POP instructions. (Contributed by Irit Katriel in 102859.)

Demos and Tools

  • Remove the Tools/demo/ directory which contained old demo scripts. A copy can be found in the old-demos project. (Contributed by Victor Stinner in 97681.)
  • Remove outdated example scripts of the Tools/scripts/ directory. A copy can be found in the old-demos project. (Contributed by Victor Stinner in 97669.)

Deprecated

  • typing.Hashable and typing.Sized aliases for collections.abc.Hashable and collections.abc.Sized. (94309.)
  • The sqlite3 default adapters and converters <sqlite3-default-converters> are now deprecated. Instead, use the sqlite3-adapter-converter-recipes and tailor them to your needs. (Contributed by Erlend E. Aasland in 90016.)
  • In ~sqlite3.Cursor.execute, DeprecationWarning is now emitted when named placeholders <sqlite3-placeholders> are used together with parameters supplied as a sequence instead of as a dict. Starting from Python 3.14, using named placeholders with parameters supplied as a sequence will raise a ~sqlite3.ProgrammingError. (Contributed by Erlend E. Aasland in 101698.)
  • The 3-arg signatures (type, value, traceback) of ~coroutine.throw, ~generator.throw and ~agen.athrow are deprecated and may be removed in a future version of Python. Use the single-arg versions of these functions instead. (Contributed by Ofey Chan in 89874.)
  • DeprecationWarning is now raised when __package__ on a module differs from __spec__.parent (previously it was ImportWarning). (Contributed by Brett Cannon in 65961.)
  • The ~asyncio.get_event_loop method of the default event loop policy now emits a DeprecationWarning if there is no current event loop set and it decides to create one. (Contributed by Serhiy Storchaka and Guido van Rossum in 100160.)
  • The xml.etree.ElementTree module now emits DeprecationWarning when testing the truth value of an xml.etree.ElementTree.Element. Before, the Python implementation emitted FutureWarning, and the C implementation emitted nothing.
  • In accordance with 699, the ma_version_tag field in :cPyDictObject is deprecated for extension modules. Accessing this field will generate a compiler warning at compile time. This field will be removed in Python 3.14. (Contributed by Ramvikrams and Kumar Aditya in 101193. PEP by Ken Jin.)
  • The st_ctime fields return by os.stat and os.lstat on Windows are deprecated. In a future release, they will contain the last metadata change time, consistent with other platforms. For now, they still contain the creation time, which is also available in the new st_birthtime field. (Contributed by Steve Dower in 99726.)
  • The sys.last_type, sys.last_value and sys.last_traceback fields are deprecated. Use sys.last_exc instead. (Contributed by Irit Katriel in 102778.)
  • The onerror argument of shutil.rmtree is deprecated as will be removed in Python 3.14. Use onexc instead. (Contributed by Irit Katriel in 102828.)
  • Extracting tar archives without specifying filter is deprecated until Python 3.14, when 'data' filter will become the default. See tarfile-extraction-filter for details.
  • calendar.January and calendar.February constants are deprecated and replaced by calendar.Month.JANUARY and calendar.Month.FEBRUARY. (Contributed by Prince Roshan in 103636.)
  • The bitwise inversion operator (~) on bool is deprecated. It will throw an error in Python 3.14. Use not for logical negation of bools instead. In the rare case that you really need the bitwise inversion of the underlying int, convert to int explicitly with ~int(x). (Contributed by Tim Hoffmann in 103487.)
  • datetime.datetime's ~datetime.datetime.utcnow and ~datetime.datetime.utcfromtimestamp are deprecated and will be removed in a future version. Instead, use timezone-aware objects to represent datetimes in UTC: respectively, call ~datetime.datetime.now and ~datetime.datetime.fromtimestamp with the tz parameter set to datetime.UTC. (Contributed by Paul Ganssle in 103857.)

Pending Removal in Python 3.13

The following modules and APIs have been deprecated in earlier Python releases, and will be removed in Python 3.13.

Modules (see 594):

  • aifc
  • audioop
  • cgi
  • cgitb
  • chunk
  • crypt
  • imghdr
  • mailcap
  • msilib
  • nis
  • nntplib
  • ossaudiodev
  • pipes
  • sndhdr
  • spwd
  • sunau
  • telnetlib
  • uu
  • xdrlib

APIs:

  • !configparser.LegacyInterpolation (90765)
  • locale.getdefaultlocale (90817)
  • !turtle.RawTurtle.settiltangle (50096)
  • !unittest.findTestCases (50096)
  • !unittest.makeSuite (50096)
  • !unittest.getTestCaseNames (50096)
  • !webbrowser.MacOSX (86421)

Pending Removal in Python 3.14

  • Deprecated the following importlib.abc classes, scheduled for removal in Python 3.14:

    • !importlib.abc.ResourceReader
    • !importlib.abc.Traversable
    • !importlib.abc.TraversableResources

    Use importlib.resources.abc classes instead:

    • importlib.resources.abc.Traversable
    • importlib.resources.abc.TraversableResources

    (Contributed by Jason R. Coombs and Hugo van Kemenade in 93963.)

  • Deprecated collections.abc.ByteString. Prefer Sequence or collections.abc.Buffer. For use in typing, prefer a union, like bytes | bytearray, or collections.abc.Buffer. (Contributed by Shantanu Jain in 91896.)
  • typing.ByteString, deprecated since Python 3.9, now causes a DeprecationWarning to be emitted when it is used.
  • Creating immutable types (Py_TPFLAGS_IMMUTABLETYPE) with mutable bases using the C API.
  • Deprecated the isdst parameter in email.utils.localtime. (Contributed by Alan Williams in 72346.)
  • __package__ and __cached__ will cease to be set or taken into consideration by the import system (97879).
  • Testing the truth value of an xml.etree.ElementTree.Element is deprecated and will raise an exception in Python 3.14.
  • The default multiprocessing start method will change to a safer one on Linux, BSDs, and other non-macOS POSIX platforms where 'fork' is currently the default (84559). Adding a runtime warning about this was deemed too disruptive as the majority of code is not expected to care. Use the ~multiprocessing.get_context or ~multiprocessing.set_start_method APIs to explicitly specify when your code requires 'fork'. See multiprocessing-start-methods.
  • pty has two undocumented master_open() and slave_open() functions that have been deprecated since Python 2 but only gained a proper DeprecationWarning in 3.12. Remove them in 3.14.
  • Accessing co_lnotab was deprecated in 626 since 3.10 and was planned to be removed in 3.12 but it only got a proper DeprecationWarning in 3.12. May be removed in 3.14. (Contributed by Nikita Sobolev in 101866.)
  • The onerror argument of shutil.rmtree is deprecated in 3.12, and will be removed in 3.14.
  • The type, choices, and metavar parameters of !argparse.BooleanOptionalAction are deprecated and will be removed in 3.14. (Contributed by Nikita Sobolev in 92248.)
  • pkgutil.find_loader and pkgutil.get_loader now raise DeprecationWarning; use importlib.util.find_spec instead. (Contributed by Nikita Sobolev in 97850.)

  • The following ast features have been deprecated in documentation since Python 3.8, now cause a DeprecationWarning to be emitted at runtime when they are accessed or used, and will be removed in Python 3.14:

    • !ast.Num
    • !ast.Str
    • !ast.Bytes
    • !ast.NameConstant
    • !ast.Ellipsis

    Use ast.Constant instead. (Contributed by Serhiy Storchaka in 90953.)

Pending Removal in Future Versions

The following APIs were deprecated in earlier Python versions and will be removed, although there is currently no date scheduled for their removal.

  • typing.Text (92332)
  • Currently Python accepts numeric literals immediately followed by keywords, for example 0in x, 1or x, 0if 1else 2. It allows confusing and ambiguous expressions like [0x1for x in y] (which can be interpreted as [0x1 for x in y] or [0x1f or x in y]). A syntax warning is raised if the numeric literal is immediately followed by one of keywords and, else, for, if, in, is and or. In a future release it will be changed to a syntax error. (87999)

Removed

  • Remove the distutils package. It was deprecated in Python 3.10 by 632 "Deprecate distutils module". For projects still using distutils and cannot be updated to something else, the setuptools project can be installed: it still provides distutils. (Contributed by Victor Stinner in 92584.)

  • Remove the bundled setuptools wheel from ensurepip, and stop installing setuptools in environments created by venv.

    pip (>= 22.1) does not require setuptools to be installed in the environment. setuptools-based (and distutils-based) packages can still be used with pip install, since pip will provide setuptools in the build environment it uses for building a package.

    easy_install, pkg_resources, setuptools and distutils are no longer provided by default in environments created with venv or bootstrapped with ensurepip, since they are part of the setuptools package. For projects relying on these at runtime, the setuptools project should be declared as a dependency and installed separately (typically, using pip).

    (Contributed by Pradyun Gedam in 95299.)

  • Removed many old deprecated unittest features:

    • A number of ~unittest.TestCase method aliases:

      Deprecated alias Method Name Deprecated in

      failUnless

      .assertTrue

      3.1

      failIf

      .assertFalse

      3.1

      failUnlessEqual

      .assertEqual

      3.1

      failIfEqual

      .assertNotEqual

      3.1

      failUnlessAlmostEqual

      .assertAlmostEqual

      3.1

      failIfAlmostEqual

      .assertNotAlmostEqual

      3.1

      failUnlessRaises

      .assertRaises

      3.1

      assert_

      .assertTrue

      3.2

      assertEquals

      .assertEqual

      3.2

      assertNotEquals

      .assertNotEqual

      3.2

      assertAlmostEquals

      .assertAlmostEqual

      3.2

      assertNotAlmostEquals

      .assertNotAlmostEqual

      3.2

      assertRegexpMatches

      .assertRegex

      3.2

      assertRaisesRegexp

      .assertRaisesRegex

      3.2

      assertNotRegexpMatches

      .assertNotRegex

      3.5

      You can use https://github.com/isidentical/teyit to automatically modernise your unit tests.

    • Undocumented and broken ~unittest.TestCase method assertDictContainsSubset (deprecated in Python 3.2).
    • Undocumented TestLoader.loadTestsFromModule <unittest.TestLoader.loadTestsFromModule> parameter use_load_tests (deprecated and ignored since Python 3.2).
    • An alias of the ~unittest.TextTestResult class: _TextTestResult (deprecated in Python 3.2).

    (Contributed by Serhiy Storchaka in 45162.)

  • Several names deprecated in the configparser way back in 3.2 have been removed per 89336:
    • configparser.ParsingError no longer has a filename attribute or argument. Use the source attribute and argument instead.
    • configparser no longer has a SafeConfigParser class. Use the shorter ~configparser.ConfigParser name instead.
    • configparser.ConfigParser no longer has a readfp method. Use ~configparser.ConfigParser.read_file instead.

  • The following undocumented sqlite3 features, deprecated in Python 3.10, are now removed:

    • sqlite3.enable_shared_cache()
    • sqlite3.OptimizedUnicode

    If a shared cache must be used, open the database in URI mode using the cache=shared query parameter.

    The sqlite3.OptimizedUnicode text factory has been an alias for str since Python 3.3. Code that previously set the text factory to OptimizedUnicode can either use str explicitly, or rely on the default value which is also str.

    (Contributed by Erlend E. Aasland in 92548.)

  • smtpd has been removed according to the schedule in 594, having been deprecated in Python 3.4.7 and 3.5.4. Use aiosmtpd PyPI module or any other asyncio-based server instead. (Contributed by Oleg Iarygin in 93243.)
  • asynchat and asyncore have been removed according to the schedule in 594, having been deprecated in Python 3.6. Use asyncio instead. (Contributed by Nikita Sobolev in 96580.)
  • Remove io.OpenWrapper and _pyio.OpenWrapper, deprecated in Python 3.10: just use open instead. The open (io.open) function is a built-in function. Since Python 3.10, !_pyio.open is also a static method. (Contributed by Victor Stinner in 94169.)
  • Remove the !ssl.RAND_pseudo_bytes function, deprecated in Python 3.6: use os.urandom or ssl.RAND_bytes instead. (Contributed by Victor Stinner in 94199.)
  • gzip: Remove the filename attribute of gzip.GzipFile, deprecated since Python 2.6, use the ~gzip.GzipFile.name attribute instead. In write mode, the filename attribute added '.gz' file extension if it was not present. (Contributed by Victor Stinner in 94196.)
  • Remove the !ssl.match_hostname function. It was deprecated in Python 3.7. OpenSSL performs hostname matching since Python 3.7, Python no longer uses the !ssl.match_hostname function. (Contributed by Victor Stinner in 94199.)
  • Remove the !locale.format function, deprecated in Python 3.7: use locale.format_string instead. (Contributed by Victor Stinner in 94226.)
  • hashlib: Remove the pure Python implementation of hashlib.pbkdf2_hmac(), deprecated in Python 3.10. Python 3.10 and newer requires OpenSSL 1.1.1 (644): this OpenSSL version provides a C implementation of ~hashlib.pbkdf2_hmac() which is faster. (Contributed by Victor Stinner in 94199.)
  • xml.etree.ElementTree: Remove the ElementTree.Element.copy() method of the pure Python implementation, deprecated in Python 3.10, use the copy.copy function instead. The C implementation of xml.etree.ElementTree has no copy() method, only a __copy__() method. (Contributed by Victor Stinner in 94383.)
  • zipimport: Remove find_loader() and find_module() methods, deprecated in Python 3.10: use the find_spec() method instead. See 451 for the rationale. (Contributed by Victor Stinner in 94379.)
  • Remove the !ssl.wrap_socket function, deprecated in Python 3.7: instead, create a ssl.SSLContext object and call its ssl.SSLContext.wrap_socket method. Any package that still uses !ssl.wrap_socket is broken and insecure. The function neither sends a SNI TLS extension nor validates server hostname. Code is subject to CWE-295: Improper Certificate Validation. (Contributed by Victor Stinner in 94199.)
  • Many previously deprecated cleanups in importlib have now been completed:
    • References to, and support for !module_repr() has been removed. (Contributed by Barry Warsaw in 97850.)
    • importlib.util.set_package has been removed. (Contributed by Brett Cannon in 65961.)
    • Support for find_loader() and find_module() APIs have been removed. (Contributed by Barry Warsaw in 98040.)
    • importlib.abc.Finder, pkg.ImpImporter, and pkg.ImpLoader have been removed. (Contributed by Barry Warsaw in 98040.)
    • The !imp module has been removed. (Contributed by Barry Warsaw in 98040.)
  • Removed the suspicious rule from the documentation Makefile, and removed Doc/tools/rstlint.py, both in favor of sphinx-lint. (Contributed by Julien Palard in 98179.)
  • Remove the keyfile and certfile parameters from the ftplib, imaplib, poplib and smtplib modules, and the key_file, cert_file and check_hostname parameters from the http.client module, all deprecated since Python 3.6. Use the context parameter (ssl_context in imaplib) instead. (Contributed by Victor Stinner in 94172.)
  • ftplib: Remove the FTP_TLS.ssl_version class attribute: use the context parameter instead. (Contributed by Victor Stinner in 94172.)
  • Remove support for obsolete browsers from webbrowser. Removed browsers include: Grail, Mosaic, Netscape, Galeon, Skipstone, Iceape, Firebird, and Firefox versions 35 and below (102871).

Porting to Python 3.12

This section lists previously described changes and other bugfixes that may require changes to your code.

Changes in the Python API

  • More strict rules are now applied for numerical group references and group names in regular expressions. Only sequence of ASCII digits is now accepted as a numerical reference. The group name in bytes patterns and replacement strings can now only contain ASCII letters and digits and underscore. (Contributed by Serhiy Storchaka in 91760.)
  • Removed randrange() functionality deprecated since Python 3.10. Formerly, randrange(10.0) losslessly converted to randrange(10). Now, it raises a TypeError. Also, the exception raised for non-integral values such as randrange(10.5) or randrange('10') has been changed from ValueError to TypeError. This also prevents bugs where randrange(1e25) would silently select from a larger range than randrange(10**25). (Originally suggested by Serhiy Storchaka 86388.)
  • argparse.ArgumentParser changed encoding and error handler for reading arguments from file (e.g. fromfile_prefix_chars option) from default text encoding (e.g. locale.getpreferredencoding(False) <locale.getpreferredencoding>) to filesystem encoding and error handler. Argument files should be encoded in UTF-8 instead of ANSI Codepage on Windows.
  • Removed the asyncore-based smtpd module deprecated in Python 3.4.7 and 3.5.4. A recommended replacement is the asyncio-based aiosmtpd PyPI module.
  • shlex.split: Passing None for s argument now raises an exception, rather than reading sys.stdin. The feature was deprecated in Python 3.9. (Contributed by Victor Stinner in 94352.)
  • The os module no longer accepts bytes-like paths, like bytearray and memoryview types: only the exact bytes type is accepted for bytes strings. (Contributed by Victor Stinner in 98393.)
  • syslog.openlog and syslog.closelog now fail if used in subinterpreters. syslog.syslog may still be used in subinterpreters, but now only if syslog.openlog has already been called in the main interpreter. These new restrictions do not apply to the main interpreter, so only a very small set of users might be affected. This change helps with interpreter isolation. Furthermore, syslog is a wrapper around process-global resources, which are best managed from the main interpreter. (Contributed by Dong-hee Na in 99127.)
  • The undocumented locking behavior of ~functools.cached_property is removed, because it locked across all instances of the class, leading to high lock contention. This means that a cached property getter function could now run more than once for a single instance, if two threads race. For most simple cached properties (e.g. those that are idempotent and simply calculate a value based on other attributes of the instance) this will be fine. If synchronization is needed, implement locking within the cached property getter function or around multi-threaded access points.
  • sys._current_exceptions now returns a mapping from thread-id to an exception instance, rather than to a (typ, exc, tb) tuple. (Contributed by Irit Katriel in 103176.)
  • When extracting tar files using tarfile or shutil.unpack_archive, pass the filter argument to limit features that may be surprising or dangerous. See tarfile-extraction-filter for details.

Build Changes

  • Python no longer uses setup.py to build shared C extension modules. Build parameters like headers and libraries are detected in configure script. Extensions are built by Makefile. Most extensions use pkg-config and fall back to manual detection. (Contributed by Christian Heimes in 93939.)
  • va_start() with two parameters, like va_start(args, format), is now required to build Python. va_start() is no longer called with a single parameter. (Contributed by Kumar Aditya in 93207.)
  • CPython now uses the ThinLTO option as the default link time optimization policy if the Clang compiler accepts the flag. (Contributed by Dong-hee Na in 89536.)
  • Add COMPILEALL_OPTS variable in Makefile to override compileall options (default: -j0) in make install. Also merged the 3 compileall commands into a single command to build .pyc files for all optimization levels (0, 1, 2) at once. (Contributed by Victor Stinner in 99289.)

  • Add platform triplets for 64-bit LoongArch:

    • loongarch64-linux-gnusf
    • loongarch64-linux-gnuf32
    • loongarch64-linux-gnu

    (Contributed by Zhang Na in 90656.)

  • PYTHON_FOR_REGEN now require Python 3.10 or newer.

C API Changes

New Features

  • 697: Introduced the Unstable C API tier <unstable-c-api>, intended for low-level tools like debuggers and JIT compilers. This API may change in each minor release of CPython without deprecation warnings. Its contents are marked by the PyUnstable_ prefix in names.

    Code object constructors:

    • PyUnstable_Code_New() (renamed from PyCode_New)
    • PyUnstable_Code_NewWithPosOnlyArgs() (renamed from PyCode_NewWithPosOnlyArgs)

    Extra storage for code objects (523):

    • PyUnstable_Eval_RequestCodeExtraIndex() (renamed from _PyEval_RequestCodeExtraIndex)
    • PyUnstable_Code_GetExtra() (renamed from _PyCode_GetExtra)
    • PyUnstable_Code_SetExtra() (renamed from _PyCode_SetExtra)

    The original names will continue to be available until the respective API changes.

    (Contributed by Petr Viktorin in 101101.)

  • 697: Added API for extending types whose instance memory layout is opaque:

    • :cPyType_Spec.basicsize can be zero or negative to specify inheriting or extending the base class size.
    • :cPyObject_GetTypeData and :cPyType_GetTypeDataSize added to allow access to subclass-specific instance data.
    • Py_TPFLAGS_ITEMS_AT_END and :cPyObject_GetItemData added to allow safely extending certain variable-sized types, including :cPyType_Type.
    • :cPy_RELATIVE_OFFSET added to allow defining :cmembers <PyMemberDef> in terms of a subclass-specific struct.

    (Contributed by Petr Viktorin in 103509.)

  • Added the new limited C API function :cPyType_FromMetaclass, which generalizes the existing :cPyType_FromModuleAndSpec using an additional metaclass argument. (Contributed by Wenzel Jakob in 93012.)

  • API for creating objects that can be called using the vectorcall protocol <vectorcall> was added to the Limited API <stable>:

    • Py_TPFLAGS_HAVE_VECTORCALL
    • :cPyVectorcall_NARGS
    • :cPyVectorcall_Call
    • :cvectorcallfunc

    The Py_TPFLAGS_HAVE_VECTORCALL flag is now removed from a class when the class's :py~object.__call__ method is reassigned. This makes vectorcall safe to use with mutable types (i.e. heap types without the immutable flag, Py_TPFLAGS_IMMUTABLETYPE). Mutable types that do not override :c~PyTypeObject.tp_call now inherit the Py_TPFLAGS_HAVE_VECTORCALL flag. (Contributed by Petr Viktorin in 93274.)

    The Py_TPFLAGS_MANAGED_DICT and Py_TPFLAGS_MANAGED_WEAKREF flags have been added. This allows extensions classes to support object __dict__ and weakrefs with less bookkeeping, using less memory and with faster access.

  • API for performing calls using the vectorcall protocol <vectorcall> was added to the Limited API <stable>:

    • :cPyObject_Vectorcall
    • :cPyObject_VectorcallMethod
    • PY_VECTORCALL_ARGUMENTS_OFFSET

    This means that both the incoming and outgoing ends of the vector call protocol are now available in the Limited API <stable>. (Contributed by Wenzel Jakob in 98586.)

  • Added two new public functions, :cPyEval_SetProfileAllThreads and :cPyEval_SetTraceAllThreads, that allow to set tracing and profiling functions in all running threads in addition to the calling one. (Contributed by Pablo Galindo in 93503.)
  • Added new function :cPyFunction_SetVectorcall to the C API which sets the vectorcall field of a given :cPyFunctionObject. (Contributed by Andrew Frost in 92257.)
  • The C API now permits registering callbacks via :cPyDict_AddWatcher, :cPyDict_Watch and related APIs to be called whenever a dictionary is modified. This is intended for use by optimizing interpreters, JIT compilers, or debuggers. (Contributed by Carl Meyer in 91052.)
  • Added :cPyType_AddWatcher and :cPyType_Watch API to register callbacks to receive notification on changes to a type. (Contributed by Carl Meyer in 91051.)
  • Added :cPyCode_AddWatcher and :cPyCode_ClearWatcher APIs to register callbacks to receive notification on creation and destruction of code objects. (Contributed by Itamar Ostricher in 91054.)
  • Add :cPyFrame_GetVar and :cPyFrame_GetVarString functions to get a frame variable by its name. (Contributed by Victor Stinner in 91248.)
  • Add :cPyErr_GetRaisedException and :cPyErr_SetRaisedException for saving and restoring the current exception. These functions return and accept a single exception object, rather than the triple arguments of the now-deprecated :cPyErr_Fetch and :cPyErr_Restore. This is less error prone and a bit more efficient. (Contributed by Mark Shannon in 101578.)
  • Add _PyErr_ChainExceptions1, which takes an exception instance, to replace the legacy-API _PyErr_ChainExceptions, which is now deprecated. (Contributed by Mark Shannon in 101578.)
  • Add :cPyException_GetArgs and :cPyException_SetArgs as convenience functions for retrieving and modifying the ~BaseException.args passed to the exception's constructor. (Contributed by Mark Shannon in 101578.)
  • Add :cPyErr_DisplayException, which takes an exception instance, to replace the legacy-api :c!PyErr_Display. (Contributed by Irit Katriel in 102755).

  • 683: Introduced Immortal Objects to Python which allows objects to bypass reference counts and introduced changes to the C-API:

    • _Py_IMMORTAL_REFCNT: The reference count that defines an object

      as immortal.

    • _Py_IsImmortal Checks if an object has the immortal reference count.
    • PyObject_HEAD_INIT This will now initialize reference count to

      _Py_IMMORTAL_REFCNT when used with Py_BUILD_CORE.

    • SSTATE_INTERNED_IMMORTAL An identifier for interned unicode objects

      that are immortal.

    • SSTATE_INTERNED_IMMORTAL_STATIC An identifier for interned unicode

      objects that are immortal and static

    • sys.getunicodeinternedsize This returns the total number of unicode

      objects that have been interned. This is now needed for refleak.py to correctly track reference counts and allocated blocks

    (Contributed by Eddie Elizondo in 84436.)

Porting to Python 3.12

  • Legacy Unicode APIs based on Py_UNICODE* representation has been removed. Please migrate to APIs based on UTF-8 or wchar_t*.
  • Argument parsing functions like :cPyArg_ParseTuple doesn't support Py_UNICODE* based format (e.g. u, Z) anymore. Please migrate to other formats for Unicode like s, z, es, and U.
  • tp_weaklist for all static builtin types is always NULL. This is an internal-only field on PyTypeObject but we're pointing out the change in case someone happens to be accessing the field directly anyway. To avoid breakage, consider using the existing public C-API instead, or, if necessary, the (internal-only) _PyObject_GET_WEAKREFS_LISTPTR() macro.

  • This internal-only :cPyTypeObject.tp_subclasses may now not be a valid object pointer. Its type was changed to :cvoid * to reflect this. We mention this in case someone happens to be accessing the internal-only field directly.

    To get a list of subclasses, call the Python method :py~class.__subclasses__ (using :cPyObject_CallMethod, for example).

  • Add support of more formatting options (left aligning, octals, uppercase hexadecimals, intmax_t, ptrdiff_t, wchar_t C strings, variable width and precision) in :cPyUnicode_FromFormat and :cPyUnicode_FromFormatV. (Contributed by Serhiy Storchaka in 98836.)
  • An unrecognized format character in :cPyUnicode_FromFormat and :cPyUnicode_FromFormatV now sets a SystemError. In previous versions it caused all the rest of the format string to be copied as-is to the result string, and any extra arguments discarded. (Contributed by Serhiy Storchaka in 95781.)
  • Fixed wrong sign placement in :cPyUnicode_FromFormat and :cPyUnicode_FromFormatV. (Contributed by Philip Georgi in 95504.)
  • Extension classes wanting to add a __dict__ or weak reference slot should use Py_TPFLAGS_MANAGED_DICT and Py_TPFLAGS_MANAGED_WEAKREF instead of tp_dictoffset and tp_weaklistoffset, respectively. The use of tp_dictoffset and tp_weaklistoffset is still supported, but does not fully support multiple inheritance (95589), and performance may be worse. Classes declaring Py_TPFLAGS_MANAGED_DICT should call :c!_PyObject_VisitManagedDict and :c!_PyObject_ClearManagedDict to traverse and clear their instance's dictionaries. To clear weakrefs, call :cPyObject_ClearWeakRefs, as before.
  • The :cPyUnicode_FSDecoder function no longer accepts bytes-like paths, like bytearray and memoryview types: only the exact bytes type is accepted for bytes strings. (Contributed by Victor Stinner in 98393.)
  • The :cPy_CLEAR, :cPy_SETREF and :cPy_XSETREF macros now only evaluate their arguments once. If an argument has side effects, these side effects are no longer duplicated. (Contributed by Victor Stinner in 98724.)
  • The interpreter's error indicator is now always normalized. This means that :cPyErr_SetObject, :cPyErr_SetString and the other functions that set the error indicator now normalize the exception before storing it. (Contributed by Mark Shannon in 101578.)
  • _Py_RefTotal is no longer authoritative and only kept around for ABI compabitility. Note that it is an internal global and only available on debug builds. If you happen to be using it then you'll need to start using _Py_GetGlobalRefTotal().

  • The following functions now select an appropriate metaclass for the newly created type:

    • :cPyType_FromSpec
    • :cPyType_FromSpecWithBases
    • :cPyType_FromModuleAndSpec

    Creating classes whose metaclass overrides :c~PyTypeObject.tp_new is deprecated, and in Python 3.14+ it will be disallowed. Note that these functions ignore tp_new of the metaclass, possibly allowing incomplete initialization.

    Note that :cPyType_FromMetaclass (added in Python 3.12) already disallows creating classes whose metaclass overrides tp_new.

  • :cPyOS_InputHook and :cPyOS_ReadlineFunctionPointer are no longer called in subinterpreters <sub-interpreter-support>. This is because clients generally rely on process-wide global state (since these callbacks have no way of recovering extension module state).

    This also avoids situations where extensions may find themselves running in a subinterpreter that they don't support (or haven't yet been loaded in). See 104668 for more info.

Deprecated

  • Deprecate global configuration variable:

    • :cPy_DebugFlag: use :cPyConfig.parser_debug
    • :cPy_VerboseFlag: use :cPyConfig.verbose
    • :cPy_QuietFlag: use :cPyConfig.quiet
    • :cPy_InteractiveFlag: use :cPyConfig.interactive
    • :cPy_InspectFlag: use :cPyConfig.inspect
    • :cPy_OptimizeFlag: use :cPyConfig.optimization_level
    • :cPy_NoSiteFlag: use :cPyConfig.site_import
    • :cPy_BytesWarningFlag: use :cPyConfig.bytes_warning
    • :cPy_FrozenFlag: use :cPyConfig.pathconfig_warnings
    • :cPy_IgnoreEnvironmentFlag: use :cPyConfig.use_environment
    • :cPy_DontWriteBytecodeFlag: use :cPyConfig.write_bytecode
    • :cPy_NoUserSiteDirectory: use :cPyConfig.user_site_directory
    • :cPy_UnbufferedStdioFlag: use :cPyConfig.buffered_stdio
    • :cPy_HashRandomizationFlag: use :cPyConfig.use_hash_seed and :cPyConfig.hash_seed
    • :cPy_IsolatedFlag: use :cPyConfig.isolated
    • :cPy_LegacyWindowsFSEncodingFlag: use :cPyPreConfig.legacy_windows_fs_encoding
    • :cPy_LegacyWindowsStdioFlag: use :cPyConfig.legacy_windows_stdio
    • :c!Py_FileSystemDefaultEncoding: use :cPyConfig.filesystem_encoding
    • :c!Py_FileSystemDefaultEncodeErrors: use :cPyConfig.filesystem_errors
    • :c!Py_UTF8Mode: use :cPyPreConfig.utf8_mode (see :cPy_PreInitialize)

    The :cPy_InitializeFromConfig API should be used with :cPyConfig instead. (Contributed by Victor Stinner in 77782.)

  • Creating immutable types (Py_TPFLAGS_IMMUTABLETYPE) with mutable bases is deprecated and will be disabled in Python 3.14.

  • The structmember.h header is deprecated, though it continues to be available and there are no plans to remove it.

    Its contents are now available just by including Python.h, with a Py prefix added if it was missing:

    • :cPyMemberDef, :cPyMember_GetOne and :cPyMember_SetOne
    • Type macros like :cPy_T_INT, :cPy_T_DOUBLE, etc. (previously T_INT, T_DOUBLE, etc.)
    • The flags :cPy_READONLY (previously READONLY) and :cPy_AUDIT_READ (previously all uppercase)

    Several items are not exposed from Python.h:

    • :cT_OBJECT (use :cPy_T_OBJECT_EX)
    • :cT_NONE (previously undocumented, and pretty quirky)
    • The macro WRITE_RESTRICTED which does nothing.
    • The macros RESTRICTED and READ_RESTRICTED, equivalents of :cPy_AUDIT_READ.
    • In some configurations, <stddef.h> is not included from Python.h. It should be included manually when using offsetof().

    The deprecated header continues to provide its original contents under the original names. Your old code can stay unchanged, unless the extra include and non-namespaced macros bother you greatly.

    (Contributed in 47146 by Petr Viktorin, based on earlier work by Alexander Belopolsky and Matthias Braun.)

  • :cPyErr_Fetch and :cPyErr_Restore are deprecated. Use :cPyErr_GetRaisedException and :cPyErr_SetRaisedException instead. (Contributed by Mark Shannon in 101578.)
  • :c!PyErr_Display is deprecated. Use :cPyErr_DisplayException instead. (Contributed by Irit Katriel in 102755).
  • _PyErr_ChainExceptions is deprecated. Use _PyErr_ChainExceptions1 instead. (Contributed by Irit Katriel in 102192.)
  • Using :cPyType_FromSpec, :cPyType_FromSpecWithBases or :cPyType_FromModuleAndSpec to create a class whose metaclass overrides :c~PyTypeObject.tp_new is deprecated. Call the metaclass instead.

Removed

  • Remove the token.h header file. There was never any public tokenizer C API. The token.h header file was only designed to be used by Python internals. (Contributed by Victor Stinner in 92651.)

  • Legacy Unicode APIs have been removed. See 623 for detail.

    • :c!PyUnicode_WCHAR_KIND
    • :c!PyUnicode_AS_UNICODE
    • :c!PyUnicode_AsUnicode
    • :c!PyUnicode_AsUnicodeAndSize
    • :c!PyUnicode_AS_DATA
    • :c!PyUnicode_FromUnicode
    • :c!PyUnicode_GET_SIZE
    • :c!PyUnicode_GetSize
    • :c!PyUnicode_GET_DATA_SIZE
  • Remove the PyUnicode_InternImmortal() function macro. (Contributed by Victor Stinner in 85858.)
  • Remove Jython compatibility hacks from several stdlib modules and tests. (Contributed by Nikita Sobolev in 99482.)
  • Remove _use_broken_old_ctypes_structure_semantics_ flag from ctypes module. (Contributed by Nikita Sobolev in 99285.)