What’s new in Python 3.14

Editor:

TBD

This article explains the new features in Python 3.14, compared to 3.13.

For full details, see the changelog.

Note

Prerelease users should be aware that this document is currently in draft form. It will be updated substantially as Python 3.14 moves towards release, so it’s worth checking back even after reading earlier versions.

Summary – release highlights

Incompatible changes

On platforms other than macOS and Windows, the default start method for multiprocessing and ProcessPoolExecutor switches from fork to forkserver.

See (1) and (2) for details.

If you encounter NameErrors or pickling errors coming out of multiprocessing or concurrent.futures, see the forkserver restrictions.

New features

PEP 649: deferred evaluation of annotations

The annotations on functions, classes, and modules are no longer evaluated eagerly. Instead, annotations are stored in special-purpose annotate functions and evaluated only when necessary. This is specified in PEP 649 and PEP 749.

This change is designed to make annotations in Python more performant and more usable in most circumstances. The runtime cost for defining annotations is minimized, but it remains possible to introspect annotations at runtime. It is usually no longer necessary to enclose annotations in strings if they contain forward references.

The new annotationlib module provides tools for inspecting deferred annotations. Annotations may be evaluated in the VALUE format (which evaluates annotations to runtime values, similar to the behavior in earlier Python versions), the FORWARDREF format (which replaces undefined names with special markers), and the STRING format (which returns annotations as strings).

This example shows how these formats behave:

>>> from annotationlib import get_annotations, Format
>>> def func(arg: Undefined):
...     pass
>>> get_annotations(func, format=Format.VALUE)
Traceback (most recent call last):
  ...
NameError: name 'Undefined' is not defined
>>> get_annotations(func, format=Format.FORWARDREF)
{'arg': ForwardRef('Undefined')}
>>> get_annotations(func, format=Format.STRING)
{'arg': 'Undefined'}

Implications for annotated code

If you define annotations in your code (for example, for use with a static type checker), then this change probably does not affect you: you can keep writing annotations the same way you did with previous versions of Python.

You will likely be able to remove quoted strings in annotations, which are frequently used for forward references. Similarly, if you use from __future__ import annotations to avoid having to write strings in annotations, you may well be able to remove that import. However, if you rely on third-party libraries that read annotations, those libraries may need changes to support unquoted annotations before they work as expected.

Implications for readers of __annotations__

If your code reads the __annotations__ attribute on objects, you may want to make changes in order to support code that relies on deferred evaluation of annotations. For example, you may want to use annotationlib.get_annotations() with the FORWARDREF format, as the dataclasses module now does.

from __future__ import annotations

In Python 3.7, PEP 563 introduced the from __future__ import annotations directive, which turns all annotations into strings. This directive is now considered deprecated and it is expected to be removed in a future version of Python. However, this removal will not happen until after Python 3.13, the last version of Python without deferred evaluation of annotations, reaches its end of life in 2029. In Python 3.14, the behavior of code using from __future__ import annotations is unchanged.

Improved error messages

  • When unpacking assignment fails due to incorrect number of variables, the error message prints the received number of values in more cases than before. (Contributed by Tushar Sadhwani in gh-122239.)

    >>> x, y, z = 1, 2, 3, 4
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
    x, y, z = 1, 2, 3, 4
    ^^^^^^^
ValueError: too many values to unpack (expected 3, got 4)

  • If a statement (pass, del, return, yield, raise, break, continue, assert, import, from) is passed to the Conditional expressions after else, or one of pass, break, or continue is passed before if, then the error message highlights where the expression is required. (Contributed by Sergey Miryanov in gh-129515.)

    >>> x = 1 if True else pass
Traceback (most recent call last):
  File "<string>", line 1
    x = 1 if True else pass
                       ^^^^
SyntaxError: expected expression after 'else', but statement is given

>>> x = continue if True else break
Traceback (most recent call last):
  File "<string>", line 1
    x = continue if True else break
        ^^^^^^^^
SyntaxError: expected expression before 'if', but statement is given

  • When incorrectly closed strings are detected, the error message suggests that the string may be intended to be part of the string. (Contributed by Pablo Galindo in gh-88535.)

    >>> "The interesting object "The important object" is very important"
Traceback (most recent call last):
SyntaxError: invalid syntax. Is this intended to be part of the string?

PEP 741: Python Configuration C API

Add a PyInitConfig C API to configure the Python initialization without relying on C structures and the ability to make ABI-compatible changes in the future.

Complete the PEP 587 PyConfig C API by adding PyInitConfig_AddModule() which can be used to add a built-in extension module; feature previously referred to as the “inittab”.

Add PyConfig_Get() and PyConfig_Set() functions to get and set the current runtime configuration.

PEP 587 “Python Initialization Configuration” unified all the ways to configure the Python initialization. This PEP unifies also the configuration of the Python preinitialization and the Python initialization in a single API. Moreover, this PEP only provides a single choice to embed Python, instead of having two “Python” and “Isolated” choices (PEP 587), to simplify the API further.

The lower level PEP 587 PyConfig API remains available for use cases with an intentionally higher level of coupling to CPython implementation details (such as emulating the full functionality of CPython’s CLI, including its configuration mechanisms).

(Contributed by Victor Stinner in gh-107954.)

See also

PEP 741.

A new type of interpreter

A new type of interpreter has been added to CPython. It uses tail calls between small C functions that implement individual Python opcodes, rather than one large C case statement. For certain newer compilers, this interpreter provides significantly better performance. Preliminary numbers on our machines suggest anywhere up to 30% faster Python code, and a geometric mean of 3-5% faster on pyperformance depending on platform and architecture. The baseline is Python 3.14 built with Clang 19 without this new interpreter.

This interpreter currently only works with Clang 19 and newer on x86-64 and AArch64 architectures. However, we expect that a future release of GCC will support this as well.

This feature is opt-in for now. We highly recommend enabling profile-guided optimization with the new interpreter as it is the only configuration we have tested and can validate its improved performance. For further information on how to build Python, see --with-tail-call-interp.

Note

This is not to be confused with tail call optimization of Python functions, which is currently not implemented in CPython.

This new interpreter type is an internal implementation detail of the CPython interpreter. It doesn’t change the visible behavior of Python programs at all. It can improve their performance, but doesn’t change anything else.

Attention

This section previously reported a 9-15% geometric mean speedup. This number has since been cautiously revised down to 3-5%. While we expect performance results to be better than what we report, our estimates are more conservative due to a compiler bug found in Clang/LLVM 19, which causes the normal interpreter to be slower. We were unaware of this bug, resulting in inaccurate results. We sincerely apologize for communicating results that were only accurate for certain versions of LLVM 19 and 20. At the time of writing, this bug has not yet been fixed in LLVM 19-21. Thus any benchmarks with those versions of LLVM may produce inaccurate numbers. (Thanks to Nelson Elhage for bringing this to light.)

(Contributed by Ken Jin in gh-128563, with ideas on how to implement this in CPython by Mark Shannon, Garrett Gu, Haoran Xu, and Josh Haberman.)

Other language changes

  • The map() built-in now has an optional keyword-only strict flag like zip() to check that all the iterables are of equal length. (Contributed by Wannes Boeykens in gh-119793.)

  • Incorrect usage of await and asynchronous comprehensions is now detected even if the code is optimized away by the -O command-line option. For example, python -O -c 'assert await 1' now produces a SyntaxError. (Contributed by Jelle Zijlstra in gh-121637.)

  • Writes to __debug__ are now detected even if the code is optimized away by the -O command-line option. For example, python -O -c 'assert (__debug__ := 1)' now produces a SyntaxError. (Contributed by Irit Katriel in gh-122245.)

  • Add class methods float.from_number() and complex.from_number() to convert a number to float or complex type correspondingly. They raise an error if the argument is a string. (Contributed by Serhiy Storchaka in gh-84978.)

  • Implement mixed-mode arithmetic rules combining real and complex numbers as specified by C standards since C99. (Contributed by Sergey B Kirpichev in gh-69639.)

  • All Windows code pages are now supported as “cpXXX” codecs on Windows. (Contributed by Serhiy Storchaka in gh-123803.)

  • super objects are now pickleable and copyable. (Contributed by Serhiy Storchaka in gh-125767.)

  • The memoryview type now supports subscription, making it a generic type. (Contributed by Brian Schubert in gh-126012.)

  • Support underscore and comma as thousands separators in the fractional part for floating-point presentation types of the new-style string formatting (with format() or f-strings). (Contrubuted by Sergey B Kirpichev in gh-87790.)

  • The bytes.fromhex() and bytearray.fromhex() methods now accept ASCII bytes and bytes-like objects. (Contributed by Daniel Pope in gh-129349.)

  • \B in regular expression now matches empty input string. Now it is always the opposite of \b. (Contributed by Serhiy Storchaka in gh-124130.)

  • iOS and macOS apps can now be configured to redirect stdout and stderr content to the system log. (Contributed by Russell Keith-Magee in gh-127592.)

  • The iOS testbed is now able to stream test output while the test is running. The testbed can also be used to run the test suite of projects other than CPython itself. (Contributed by Russell Keith-Magee in gh-127592.)

New modules

Improved modules

argparse

  • The default value of the program name for argparse.ArgumentParser now reflects the way the Python interpreter was instructed to find the __main__ module code. (Contributed by Serhiy Storchaka and Alyssa Coghlan in gh-66436.)

  • Introduced the optional suggest_on_error parameter to argparse.ArgumentParser, enabling suggestions for argument choices and subparser names if mistyped by the user. (Contributed by Savannah Ostrowski in gh-124456.)

ast

  • Add ast.compare() for comparing two ASTs. (Contributed by Batuhan Taskaya and Jeremy Hylton in gh-60191.)

  • Add support for copy.replace() for AST nodes. (Contributed by Bénédikt Tran in gh-121141.)

  • Docstrings are now removed from an optimized AST in optimization level 2. (Contributed by Irit Katriel in gh-123958.)

  • The repr() output for AST nodes now includes more information. (Contributed by Tomas R in gh-116022.)

  • ast.parse(), when called with an AST as input, now always verifies that the root node type is appropriate. (Contributed by Irit Katriel in gh-130139.)

calendar

concurrent.futures

  • Add InterpreterPoolExecutor, which exposes “subinterpreters (multiple Python interpreters in the same process) to Python code. This is separate from the proposed API in PEP 734. (Contributed by Eric Snow in gh-124548.)

contextvars

ctypes

datetime

decimal

difflib

  • Comparison pages with highlighted changes generated by the difflib.HtmlDiff class now support dark mode. (Contributed by Jiahao Li in gh-129939.)

dis

errno

fractions

functools

getopt

  • Add support for options with optional arguments. (Contributed by Serhiy Storchaka in gh-126374.)

  • Add support for returning intermixed options and non-option arguments in order. (Contributed by Serhiy Storchaka in gh-126390.)

http

  • Directory lists and error pages generated by the http.server module allow the browser to apply its default dark mode. (Contributed by Yorik Hansen in gh-123430.)

imaplib

inspect

io

json

  • Add notes for JSON serialization errors that allow to identify the source of the error. (Contributed by Serhiy Storchaka in gh-122163.)

  • Enable the json module to work as a script using the -m switch: python -m json. See the JSON command-line interface documentation. (Contributed by Trey Hunner in gh-122873.)

mimetypes

  • Add MS and RFC 8081 MIME types for fonts:

    • Embedded OpenType: application/vnd.ms-fontobject

    • OpenType Layout (OTF) font/otf

    • TrueType: font/ttf

    • WOFF 1.0 font/woff

    • WOFF 2.0 font/woff2

    (Contributed by Sahil Prajapati and Hugo van Kemenade in gh-84852.)

  • Add RFC 9559 MIME types for Matroska audiovisual data container structures, containing:

    • audio with no video: audio/matroska (.mka)

    • video: video/matroska (.mkv)

    • stereoscopic video: video/matroska-3d (.mk3d)

    (Contributed by Hugo van Kemenade in gh-89416.)

  • Add MIME types for images with RFCs:

    • RFC 1494: CCITT Group 3 (.g3)

    • RFC 3362: Real-time Facsimile, T.38 (.t38)

    • RFC 3745: JPEG 2000 (.jp2), extension (.jpx) and compound (.jpm)

    • RFC 3950: Tag Image File Format Fax eXtended, TIFF-FX (.tfx)

    • RFC 4047: Flexible Image Transport System (.fits)

    • RFC 7903: Enhanced Metafile (.emf) and Windows Metafile (.wmf)

    (Contributed by Hugo van Kemenade in gh-85957.)

  • More MIME type changes:

    • RFC 2361: Change type for .avi to video/vnd.avi and for .wav to audio/vnd.wave

    • RFC 4337: Add MPEG-4 audio/mp4 (.m4a))

    • RFC 5334: Add Ogg media (.oga, .ogg and .ogx)

    • RFC 9639: Add FLAC audio/flac (.flac)

    • De facto: Add WebM audio/webm (.weba)

    • ECMA-376: Add .docx, .pptx and .xlsx types

    • OASIS: Add OpenDocument .odg, .odp, .ods and .odt types

    • W3C: Add EPUB application/epub+zip (.epub)

    (Contributed by Hugo van Kemenade in gh-129965.)

multiprocessing

operator

  • Two new functions operator.is_none() and operator.is_not_none() have been added, such that operator.is_none(obj) is equivalent to obj is None and operator.is_not_none(obj) is equivalent to obj is not None. (Contributed by Raymond Hettinger and Nico Mexis in gh-115808.)

os

pathlib

  • Add methods to pathlib.Path to recursively copy or move files and directories:

    • copy() copies a file or directory tree to a destination.

    • copy_into() copies into a destination directory.

    • move() moves a file or directory tree to a destination.

    • move_into() moves into a destination directory.

    (Contributed by Barney Gale in gh-73991.)

  • Add pathlib.Path.info attribute, which stores an object implementing the pathlib.types.PathInfo protocol (also new). The object supports querying the file type and internally caching stat() results. Path objects generated by iterdir() are initialized with file type information gleaned from scanning the parent directory. (Contributed by Barney Gale in gh-125413.)

pdb

  • Hardcoded breakpoints (breakpoint() and pdb.set_trace()) now reuse the most recent Pdb instance that calls set_trace(), instead of creating a new one each time. As a result, all the instance specific data like display and commands are preserved across hardcoded breakpoints. (Contributed by Tian Gao in gh-121450.)

  • Add a new argument mode to pdb.Pdb. Disable the restart command when pdb is in inline mode. (Contributed by Tian Gao in gh-123757.)

  • A confirmation prompt will be shown when the user tries to quit pdb in inline mode. y, Y, <Enter> or EOF will confirm the quit and call sys.exit(), instead of raising bdb.BdbQuit. (Contributed by Tian Gao in gh-124704.)

  • Inline breakpoints like breakpoint() or pdb.set_trace() will always stop the program at calling frame, ignoring the skip pattern (if any). (Contributed by Tian Gao in gh-130493.)

  • <tab> at the beginning of the line in pdb multi-line input will fill in a 4-space indentation now, instead of inserting a \t character. (Contributed by Tian Gao in gh-130471.)

pickle

  • Set the default protocol version on the pickle module to 5. For more details, see pickle protocols.

  • Add notes for pickle serialization errors that allow to identify the source of the error. (Contributed by Serhiy Storchaka in gh-122213.)

platform

pydoc

  • Annotations in help output are now usually displayed in a format closer to that in the original source. (Contributed by Jelle Zijlstra in gh-101552.)

ssl

  • Indicate through ssl.HAS_PHA whether the ssl module supports TLSv1.3 post-handshake client authentication (PHA). (Contributed by Will Childs-Klein in gh-128036.)

symtable

sys

  • The previously undocumented special function sys.getobjects(), which only exists in specialized builds of Python, may now return objects from other interpreters than the one it’s called in.

  • Add sys._is_immortal() for determining if an object is immortal. (Contributed by Peter Bierma in gh-128509.)

  • On FreeBSD, sys.platform doesn’t contain the major version anymore. It is always 'freebsd', instead of 'freebsd13' or 'freebsd14'.

sys.monitoring

threading

tkinter

  • Make tkinter widget methods after() and after_idle() accept arguments passed by keyword. (Contributed by Zhikang Yan in gh-126899.)

turtle

unicodedata

  • The Unicode database has been updated to Unicode 16.0.0.

unittest

urllib

  • Upgrade HTTP digest authentication algorithm for urllib.request by supporting SHA-256 digest authentication as specified in RFC 7616. (Contributed by Calvin Bui in gh-128193.)

uuid

zipinfo

Optimizations

asyncio

  • asyncio now uses double linked list implementation for native tasks which speeds up execution by 10% on standard pyperformance benchmarks and reduces memory usage. (Contributed by Kumar Aditya in gh-107803.)

  • asyncio has new utility functions for introspecting and printing the program’s call graph: asyncio.capture_call_graph() and asyncio.print_call_graph(). (Contributed by Yury Selivanov, Pablo Galindo Salgado, and Łukasz Langa in gh-91048.)

base64

  • Improve the performance of base64.b16decode() by up to ten times, and reduce the import time of base64 by up to six times. (Contributed by Bénédikt Tran, Chris Markiewicz, and Adam Turner in gh-118761.)

io

  • io which provides the built-in open() makes less system calls when opening regular files as well as reading whole files. Reading a small operating system cached file in full is up to 15% faster. pathlib.Path.read_bytes() has the most optimizations for reading a file’s bytes in full. (Contributed by Cody Maloney and Victor Stinner in gh-120754 and gh-90102.)

uuid

  • Improve generation of UUID objects via their dedicated functions:

    • uuid3() and uuid5() are both roughly 40% faster for 16-byte names and 20% faster for 1024-byte names. Performance for longer names remains unchanged.

    • uuid4() and uuid8() are 30% and 40% faster respectively.

    (Contributed by Bénédikt Tran in gh-128150.)

Deprecated

Pending removal in Python 3.15

  • The import system:

    • Setting __cached__ on a module while failing to set __spec__.cached is deprecated. In Python 3.15, __cached__ will cease to be set or take into consideration by the import system or standard library. (gh-97879)

    • Setting __package__ on a module while failing to set __spec__.parent is deprecated. In Python 3.15, __package__ will cease to be set or take into consideration by the import system or standard library. (gh-97879)

  • ctypes:

    • The undocumented ctypes.SetPointerType() function has been deprecated since Python 3.13.

  • http.server:

    • The obsolete and rarely used CGIHTTPRequestHandler has been deprecated since Python 3.13. No direct replacement exists. Anything is better than CGI to interface a web server with a request handler.

    • The --cgi flag to the python -m http.server command-line interface has been deprecated since Python 3.13.

  • importlib:

    • load_module() method: use exec_module() instead.

  • locale:

  • pathlib:

  • platform:

    • java_ver() has been deprecated since Python 3.13. This function is only useful for Jython support, has a confusing API, and is largely untested.

  • sysconfig:

  • threading:

    • RLock() will take no arguments in Python 3.15. Passing any arguments has been deprecated since Python 3.14, as the Python version does not permit any arguments, but the C version allows any number of positional or keyword arguments, ignoring every argument.

  • types:

  • typing:

    • The undocumented keyword argument syntax for creating NamedTuple classes (for example, Point = NamedTuple("Point", x=int, y=int)) has been deprecated since Python 3.13. Use the class-based syntax or the functional syntax instead.

    • The typing.no_type_check_decorator() decorator function has been deprecated since Python 3.13. After eight years in the typing module, it has yet to be supported by any major type checker.

  • wave:

  • zipimport:

Pending removal in Python 3.16

Pending removal in future versions

The following APIs will be removed in the future, although there is currently no date scheduled for their removal.

  • argparse:

    • Nesting argument groups and nesting mutually exclusive groups are deprecated.

    • Passing the undocumented keyword argument prefix_chars to add_argument_group() is now deprecated.

    • The argparse.FileType type converter is deprecated.

  • array’s 'u' format code (gh-57281)

  • builtins:

    • bool(NotImplemented).

    • Generators: throw(type, exc, tb) and athrow(type, exc, tb) signature is deprecated: use throw(exc) and athrow(exc) instead, the single argument signature.

    • 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. (gh-87999)

    • Support for __index__() and __int__() method returning non-int type: these methods will be required to return an instance of a strict subclass of int.

    • Support for __float__() method returning a strict subclass of float: these methods will be required to return an instance of float.

    • Support for __complex__() method returning a strict subclass of complex: these methods will be required to return an instance of complex.

    • Delegation of int() to __trunc__() method.

    • Passing a complex number as the real or imag argument in the complex() constructor is now deprecated; it should only be passed as a single positional argument. (Contributed by Serhiy Storchaka in gh-109218.)

  • calendar: calendar.January and calendar.February constants are deprecated and replaced by calendar.JANUARY and calendar.FEBRUARY. (Contributed by Prince Roshan in gh-103636.)

  • codeobject.co_lnotab: use the codeobject.co_lines() method instead.

  • datetime:

    • utcnow(): use datetime.datetime.now(tz=datetime.UTC).

    • utcfromtimestamp(): use datetime.datetime.fromtimestamp(timestamp, tz=datetime.UTC).

  • gettext: Plural value must be an integer.

  • importlib:

    • cache_from_source() debug_override parameter is deprecated: use the optimization parameter instead.

  • importlib.metadata:

    • EntryPoints tuple interface.

    • Implicit None on return values.

  • logging: the warn() method has been deprecated since Python 3.3, use warning() instead.

  • mailbox: Use of StringIO input and text mode is deprecated, use BytesIO and binary mode instead.

  • os: Calling os.register_at_fork() in multi-threaded process.

  • pydoc.ErrorDuringImport: A tuple value for exc_info parameter is deprecated, use an exception instance.

  • re: 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 gh-91760.)

  • sre_compile, sre_constants and sre_parse modules.

  • shutil: rmtree()’s onerror parameter is deprecated in Python 3.12; use the onexc parameter instead.

  • ssl options and protocols:

    • ssl.SSLContext without protocol argument is deprecated.

    • ssl.SSLContext: set_npn_protocols() and selected_npn_protocol() are deprecated: use ALPN instead.

    • ssl.OP_NO_SSL* options

    • ssl.OP_NO_TLS* options

    • ssl.PROTOCOL_SSLv3

    • ssl.PROTOCOL_TLS

    • ssl.PROTOCOL_TLSv1

    • ssl.PROTOCOL_TLSv1_1

    • ssl.PROTOCOL_TLSv1_2

    • ssl.TLSVersion.SSLv3

    • ssl.TLSVersion.TLSv1

    • ssl.TLSVersion.TLSv1_1

  • sysconfig.is_python_build() check_home parameter is deprecated and ignored.

  • threading methods:

  • typing.Text (gh-92332).

  • The internal class typing._UnionGenericAlias is no longer used to implement typing.Union. To preserve compatibility with users using this private class, a compatibility shim will be provided until at least Python 3.17. (Contributed by Jelle Zijlstra in gh-105499.)

  • unittest.IsolatedAsyncioTestCase: it is deprecated to return a value that is not None from a test case.

  • urllib.parse deprecated functions: urlparse() instead

    • splitattr()

    • splithost()

    • splitnport()

    • splitpasswd()

    • splitport()

    • splitquery()

    • splittag()

    • splittype()

    • splituser()

    • splitvalue()

    • to_bytes()

  • wsgiref: SimpleHandler.stdout.write() should not do partial writes.

  • xml.etree.ElementTree: Testing the truth value of an Element is deprecated. In a future release it will always return True. Prefer explicit len(elem) or elem is not None tests instead.

Removed

argparse

  • Remove the type, choices, and metavar parameters of argparse.BooleanOptionalAction. They were deprecated since 3.12.

  • Calling add_argument_group() on an argument group, and calling add_argument_group() or add_mutually_exclusive_group() on a mutually exclusive group now raise exceptions. This nesting was never supported, often failed to work correctly, and was unintentionally exposed through inheritance. This functionality has been deprecated since Python 3.11. (Contributed by Savannah Ostrowski in gh-127186.)

ast

  • Remove the following classes. They were all deprecated since Python 3.8, and have emitted deprecation warnings since Python 3.12:

    • ast.Bytes

    • ast.Ellipsis

    • ast.NameConstant

    • ast.Num

    • ast.Str

    Use ast.Constant instead. As a consequence of these removals, user-defined visit_Num, visit_Str, visit_Bytes, visit_NameConstant and visit_Ellipsis methods on custom ast.NodeVisitor subclasses will no longer be called when the NodeVisitor subclass is visiting an AST. Define a visit_Constant method instead.

    Also, remove the following deprecated properties on ast.Constant, which were present for compatibility with the now-removed AST classes:

    • ast.Constant.n

    • ast.Constant.s

    Use ast.Constant.value instead. (Contributed by Alex Waygood in gh-119562.)

asyncio

  • Remove the following classes and functions. They were all deprecated and emitted deprecation warnings since Python 3.12:

    • asyncio.get_child_watcher()

    • asyncio.set_child_watcher()

    • asyncio.AbstractEventLoopPolicy.get_child_watcher()

    • asyncio.AbstractEventLoopPolicy.set_child_watcher()

    • asyncio.AbstractChildWatcher

    • asyncio.FastChildWatcher

    • asyncio.MultiLoopChildWatcher

    • asyncio.PidfdChildWatcher

    • asyncio.SafeChildWatcher

    • asyncio.ThreadedChildWatcher

    (Contributed by Kumar Aditya in gh-120804.)

  • Removed implicit creation of event loop by asyncio.get_event_loop(). It now raises a RuntimeError if there is no current event loop. (Contributed by Kumar Aditya in gh-126353.)

    There’s a few patterns that use asyncio.get_event_loop(), most of them can be replaced with asyncio.run().

    If you’re running an async function, simply use asyncio.run().

    Before:

    async def main():
    ...


loop = asyncio.get_event_loop()
try:
    loop.run_until_complete(main())
finally:
    loop.close()

    After:

    async def main():
    ...

asyncio.run(main())

    If you need to start something, e.g. a server listening on a socket and then run forever, use asyncio.run() and an asyncio.Event.

    Before:

    def start_server(loop):
    ...

loop = asyncio.get_event_loop()
try:
    start_server(loop)
    loop.run_forever()
finally:
    loop.close()

    After:

    def start_server(loop):
    ...

async def main():
    start_server(asyncio.get_running_loop())
    await asyncio.Event().wait()

asyncio.run(main())

    If you need to run something in an event loop, then run some blocking code around it, use asyncio.Runner.

    Before:

    async def operation_one():
    ...

def blocking_code():
    ...

async def operation_two():
    ...

loop = asyncio.get_event_loop()
try:
    loop.run_until_complete(operation_one())
    blocking_code()
    loop.run_until_complete(operation_two())
finally:
    loop.close()

    After:

    async def operation_one():
    ...

def blocking_code():
    ...

async def operation_two():
    ...

with asyncio.Runner() as runner:
    runner.run(operation_one())
    blocking_code()
    runner.run(operation_two())

collections.abc

  • Remove collections.abc.ByteString. It had previously raised a DeprecationWarning since Python 3.12.

email

importlib

itertools

  • Remove itertools support for copy, deepcopy, and pickle operations. These had previously raised a DeprecationWarning since Python 3.12. (Contributed by Raymond Hettinger in gh-101588.)

pathlib

  • Remove support for passing additional keyword arguments to pathlib.Path. In previous versions, any such arguments are ignored.

  • Remove support for passing additional positional arguments to pathlib.PurePath.relative_to() and is_relative_to(). In previous versions, any such arguments are joined onto other.

pkgutil

  • Remove deprecated pkgutil.get_loader() and pkgutil.find_loader(). These had previously raised a DeprecationWarning since Python 3.12. (Contributed by Bénédikt Tran in gh-97850.)

pty

sqlite3

typing

urllib

Others

CPython Bytecode Changes

  • Replaced the opcode BINARY_SUBSCR by BINARY_OP with oparg NB_SUBSCR. (Contributed by Irit Katriel in gh-100239.)

Porting to Python 3.14

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

Changes in the Python API

  • functools.partial is now a method descriptor. Wrap it in staticmethod() if you want to preserve the old behavior. (Contributed by Serhiy Storchaka and Dominykas Grigonis in gh-121027.)

  • The locale.nl_langinfo() function now sets temporarily the LC_CTYPE locale in some cases. This temporary change affects other threads. (Contributed by Serhiy Storchaka in gh-69998.)

Build changes

  • GNU Autoconf 2.72 is now required to generate configure. (Contributed by Erlend Aasland in gh-115765.)

  • #pragma-based linking with python3*.lib can now be switched off with Py_NO_LINK_LIB. (Contributed by Jean-Christophe Fillion-Robin in gh-82909.)

PEP 761: Discontinuation of PGP signatures

PGP signatures will not be available for CPython 3.14 and onwards. Users verifying artifacts must use Sigstore verification materials for verifying CPython artifacts. This change in release process is specified in PEP 761.

C API changes

New features

Limited C API changes

Porting to Python 3.14

Deprecated

Pending removal in Python 3.15

Pending removal in Python 3.18

Pending removal in future versions

The following APIs are deprecated and will be removed, although there is currently no date scheduled for their removal.

Removed

  • Creating immutable types with mutable bases was deprecated since 3.12 and now raises a TypeError.

  • Remove PyDictObject.ma_version_tag member which was deprecated since Python 3.12. Use the PyDict_AddWatcher() API instead. (Contributed by Sam Gross in gh-124296.)

  • Remove the private _Py_InitializeMain() function. It was a provisional API added to Python 3.8 by PEP 587. (Contributed by Victor Stinner in gh-129033.)