Doc/whatsnew/3.14.rst
What's new in Python 3.14
:Editors: Adam Turner and Hugo van Kemenade
.. Rules for maintenance:
Anyone can add text to this document. Do not spend very much time on the wording of your changes, because your text will probably get rewritten to some degree.
The maintainer will go through Misc/NEWS periodically and add changes; it's therefore more important to add your changes to Misc/NEWS than to this file.
This is not a complete list of every single change; completeness is the purpose of Misc/NEWS. Some changes I consider too small or esoteric to include. If such a change is added to the text, I'll just remove it. (This is another reason you shouldn't spend too much time on writing your addition.)
If you want to draw your new text to the attention of the maintainer, add 'XXX' to the beginning of the paragraph or section.
It's OK to just add a fragmentary note about a change. For example: "XXX Describe the transmogrify() function added to the socket module." The maintainer will research the change and write the necessary text.
You can comment out your additions if you like, but it's not necessary (especially when a final release is some months away).
Credit the author of a patch or bugfix. Just the name is sufficient; the e-mail address isn't necessary.
It's helpful to add the issue number as a comment:
XXX Describe the transmogrify() function added to the socket
module.
(Contributed by P.Y. Developer in :gh:12345.)
This saves the maintainer the effort of going through the VCS log when researching a change.
This article explains the new features in Python 3.14, compared to 3.13.
Python 3.14 was released on 7 October 2025.
For full details, see the :ref:changelog <changelog>.
.. seealso::
:pep:745 -- Python 3.14 release schedule
.. This section singles out the most important changes in Python 3.14. Brevity is key.
Python 3.14 is the latest stable release of the Python programming
language, with a mix of changes to the language, the implementation,
and the standard library.
The biggest changes include :ref:template string literals <whatsnew314-template-string-literals>,
:ref:deferred evaluation of annotations <whatsnew314-deferred-annotations>,
and support for :ref:subinterpreters <whatsnew314-multiple-interpreters> in
the standard library.
The library changes include significantly improved capabilities for
:ref:introspection in asyncio <whatsnew314-asyncio-introspection>,
:ref:support for Zstandard <whatsnew314-zstandard> via a new
:mod:compression.zstd module, syntax highlighting in the REPL,
as well as the usual deprecations and removals,
and improvements in user-friendliness and correctness.
This article doesn't attempt to provide a complete specification
of all new features, but instead gives a convenient overview.
For full details refer to the documentation,
such as the :ref:Library Reference <library-index>
and :ref:Language Reference <reference-index>.
To understand the complete implementation and design rationale for a change,
refer to the PEP for a particular new feature;
but note that PEPs usually are not kept up-to-date
once a feature has been fully implemented.
See Porting to Python 3.14_ for guidance on upgrading from
earlier versions of Python.
.. PEP-sized items next.
Interpreter improvements:
649 and :pep:749: :ref:Deferred evaluation of annotations <whatsnew314-deferred-annotations>734: :ref:Multiple interpreters in the standard library <whatsnew314-multiple-interpreters>750: :ref:Template strings <whatsnew314-template-string-literals>758: :ref:Allow except and except* expressions without brackets <whatsnew314-bracketless-except>765: :ref:Control flow in finally blocks <whatsnew314-finally-syntaxwarning>768: :ref:Safe external debugger interface for CPython <whatsnew314-remote-debugging>A new type of interpreter <whatsnew314-tail-call-interpreter>Free-threaded mode improvements <whatsnew314-free-threaded-cpython>Improved error messages <whatsnew314-improved-error-messages>Incremental garbage collection <whatsnew314-incremental-gc>Significant improvements in the standard library:
784: :ref:Zstandard support in the standard library <whatsnew314-zstandard>whatsnew314-asyncio-introspectionwhatsnew314-concurrent-warnings-controlSyntax highlighting in the default interactive shell <whatsnew314-pyrepl-highlighting>, and color output in several
standard library CLIsC API improvements:
741: :ref:Python configuration C API <whatsnew314-capi-config>Platform support:
776: Emscripten is now an :ref:officially supported platform <whatsnew314-build-changes>, at :pep:tier 3 <11#tier-3>.Release changes:
779: :ref:Free-threaded Python is officially supported <whatsnew314-free-threaded-now-supported>761: :ref:PGP signatures have been discontinued for official releases <whatsnew314-no-more-pgp>Windows and macOS binary releases now support the experimental just-in-time compiler <whatsnew314-jit-compiler>Binary releases for Android are now provided <whatsnew314-build-changes>.. _whatsnew314-deferred-annotations:
649 & :pep:749: Deferred evaluation of annotationsThe :term:annotations <annotation> on functions, classes, and modules are no
longer evaluated eagerly. Instead, annotations are stored in special-purpose
:term:annotate functions <annotate function> and evaluated only when
necessary (except if from __future__ import annotations is used).
This change is designed to improve performance and usability of annotations in Python in most circumstances. The runtime cost for defining annotations is minimized, but it remains possible to introspect annotations at runtime. It is no longer necessary to enclose annotations in strings if they contain forward references.
The new :mod:annotationlib module provides tools for inspecting deferred
annotations. Annotations may be evaluated in the :attr:~annotationlib.Format.VALUE
format (which evaluates annotations to runtime values, similar to the behavior in
earlier Python versions), the :attr:~annotationlib.Format.FORWARDREF format
(which replaces undefined names with special markers), and the
:attr:~annotationlib.Format.STRING format (which returns annotations as strings).
This example shows how these formats behave:
.. doctest::
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', owner=<function func at 0x...>)} get_annotations(func, format=Format.STRING) {'arg': 'Undefined'}
The :ref:porting <whatsnew314-porting-annotations> section contains guidance
on changes that may be needed due to these changes, though in the majority of
cases, code will continue working as-is.
(Contributed by Jelle Zijlstra in :pep:749 and :gh:119180;
:pep:649 was written by Larry Hastings.)
.. seealso::
:pep:649
Deferred Evaluation Of Annotations Using Descriptors
:pep:749
Implementing PEP 649
.. _whatsnew314-multiple-interpreters:
734: Multiple interpreters in the standard libraryThe CPython runtime supports running multiple copies of Python in the
same process simultaneously and has done so for over 20 years.
Each of these separate copies is called an 'interpreter'.
However, the feature had been available only through
the :ref:C-API <sub-interpreter-support>.
That limitation is removed in Python 3.14,
with the new :mod:concurrent.interpreters module.
There are at least two notable reasons why using multiple interpreters has significant benefits:
For some use cases, concurrency in software improves efficiency and
can simplify design, at a high level.
At the same time, implementing and maintaining all but the simplest concurrency
is often a struggle for the human brain.
That especially applies to plain threads (for example, :mod:threading),
where all memory is shared between all threads.
With multiple isolated interpreters, you can take advantage of a class of concurrency models, like Communicating Sequential Processes (CSP) or the actor model, that have found success in other programming languages, like Smalltalk, Erlang, Haskell, and Go. Think of multiple interpreters as threads but with opt-in sharing.
Regarding multi-core parallelism: as of Python 3.12, interpreters
are now sufficiently isolated from one another to be used in parallel
(see :pep:684). This unlocks a variety of CPU-intensive use cases
for Python that were limited by the :term:GIL.
Using multiple interpreters is similar in many ways to
:mod:multiprocessing, in that they both provide isolated logical
"processes" that can run in parallel, with no sharing by default.
However, when using multiple interpreters, an application will use
fewer system resources and will operate more efficiently (since it
stays within the same process). Think of multiple interpreters as
having the isolation of processes with the efficiency of threads.
.. XXX Add an example or two. .. XXX Link to the not-yet-added HOWTO doc.
While the feature has been around for decades, multiple interpreters have not been used widely, due to low awareness and the lack of a standard library module. Consequently, they currently have several notable limitations, which are expected to improve significantly now that the feature is going mainstream.
Current limitations:
memoryview)The impact of these limitations will depend on future CPython improvements, how interpreters are used, and what the community solves through PyPI packages. Depending on the use case, the limitations may not have much impact, so try it out!
Furthermore, future CPython releases will reduce or eliminate overhead
and provide utilities that are less appropriate on PyPI. In the
meantime, most of the limitations can also be addressed through
extension modules, meaning PyPI packages can fill any gap for 3.14, and
even back to 3.12 where interpreters were finally properly isolated and
stopped sharing the :term:GIL. Likewise, libraries on PyPI are expected
to emerge for high-level abstractions on top of interpreters.
Regarding extension modules, work is in progress to update some PyPI
projects, as well as tools like Cython, pybind11, nanobind, and PyO3.
The steps for isolating an extension module are found at
:ref:isolating-extensions-howto.
Isolating a module has a lot of overlap with what is required to support
:ref:free-threading <whatsnew314-free-threaded-cpython>, so the ongoing
work in the community in that area will help accelerate support
for multiple interpreters.
Also added in 3.14: :ref:concurrent.futures.InterpreterPoolExecutor <whatsnew314-concurrent-futures-interp-pool>.
(Contributed by Eric Snow in :gh:134939.)
.. seealso:: :pep:734
.. _whatsnew314-template-string-literals:
750: Template string literalsTemplate strings are a new mechanism for custom string processing.
They share the familiar syntax of f-strings but, unlike f-strings,
return an object representing the static and interpolated parts of
the string, instead of a simple :class:str.
To write a t-string, use a 't' prefix instead of an 'f':
.. doctest::
variety = 'Stilton' template = t'Try some {variety} cheese!' type(template) <class 'string.templatelib.Template'>
:class:~string.templatelib.Template objects provide access to the static
and interpolated (in curly braces) parts of a string before they are combined.
Iterate over :class:!Template instances to access their parts in order:
.. testsetup::
variety = 'Stilton' template = t'Try some {variety} cheese!'
.. doctest::
list(template) ['Try some ', Interpolation('Stilton', 'variety', None, ''), ' cheese!']
It's easy to write (or call) code to process :class:!Template instances.
For example, here's a function that renders static parts lowercase and
:class:~string.templatelib.Interpolation instances uppercase:
.. code-block:: python
from string.templatelib import Interpolation
def lower_upper(template): """Render static parts lowercase and interpolations uppercase.""" parts = [] for part in template: if isinstance(part, Interpolation): parts.append(str(part.value).upper()) else: parts.append(part.lower()) return ''.join(parts)
name = 'Wenslydale' template = t'Mister {name}' assert lower_upper(template) == 'mister WENSLYDALE'
Because :class:!Template instances distinguish between static strings and
interpolations at runtime, they can be useful for sanitising user input.
Writing a :func:!html function that escapes user input in HTML is an exercise
left to the reader!
Template processing code can provide improved flexibility.
For instance, a more advanced :func:!html function could accept
a :class:!dict of HTML attributes directly in the template:
.. code-block:: python
attributes = {'src': 'limburger.jpg', 'alt': 'lovely cheese'} template = t'' assert html(template) == ''
Of course, template processing code does not need to return a string-like result.
An even more advanced :func:!html could return a custom type representing
a DOM-like structure.
With t-strings in place, developers can write systems that sanitise SQL, make safe shell operations, improve logging, tackle modern ideas in web development (HTML, CSS, and so on), and implement lightweight custom business DSLs.
(Contributed by Jim Baker, Guido van Rossum, Paul Everitt, Koudai Aono,
Lysandros Nikolaou, Dave Peck, Adam Turner, Jelle Zijlstra, Bénédikt Tran,
and Pablo Galindo Salgado in :gh:132661.)
.. seealso:: :pep:750.
.. _whatsnew314-remote-debugging:
768: Safe external debugger interfacePython 3.14 introduces a zero-overhead debugging interface that allows debuggers and profilers to safely attach to running Python processes without stopping or restarting them. This is a significant enhancement to Python's debugging capabilities, meaning that unsafe alternatives are no longer required.
The new interface provides safe execution points for attaching debugger code without modifying the interpreter's normal execution path or adding any overhead at runtime. Due to this, tools can now inspect and interact with Python applications in real-time, which is a crucial capability for high-availability systems and production environments.
For convenience, this interface is implemented in the :func:sys.remote_exec
function. For example:
.. code-block:: python
import sys from tempfile import NamedTemporaryFile
with NamedTemporaryFile(mode='w', suffix='.py', delete=False) as f: script_path = f.name f.write(f'import my_debugger; my_debugger.connect({os.getpid()})')
print('Behold! An offering:') sys.remote_exec(1234, script_path)
This function allows sending Python code to be executed in a target process at the next safe execution point. However, tool authors can also implement the protocol directly as described in the PEP, which details the underlying mechanisms used to safely attach to running processes.
The debugging interface has been carefully designed with security in mind and includes several mechanisms to control access:
PYTHON_DISABLE_REMOTE_DEBUG environment variable.-X disable-remote-debug command-line option.--without-remote-debug configure flag to completely disable
the feature at build time.(Contributed by Pablo Galindo Salgado, Matt Wozniski, and Ivona Stojanovic
in :gh:131591.)
.. seealso:: :pep:768.
.. _whatsnew314-tail-call-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 benchmarks suggest a geometric
mean of 3-5% faster on the standard pyperformance benchmark suite,
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, a future release of GCC is expected to support this as well.
This feature is opt-in for now. Enabling profile-guided optimization is highly
recommended when using the new interpreter as it is the only configuration
that has been tested and validated for improved performance.
For further information, see :option:--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.
__ https://en.wikipedia.org/wiki/Tail_call
(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.)
.. _whatsnew314-free-threaded-cpython:
CPython's free-threaded mode (:pep:703), initially added in 3.13,
has been significantly improved in Python 3.14.
The implementation described in PEP 703 has been finished, including C API
changes, and temporary workarounds in the interpreter were replaced with
more permanent solutions.
The specializing adaptive interpreter (:pep:659) is now enabled
in free-threaded mode, which along with many other optimizations
greatly improves its performance.
The performance penalty on single-threaded code in free-threaded mode
is now roughly 5-10%, depending on the platform and C compiler used.
From Python 3.14, when compiling extension modules for the free-threaded build of
CPython on Windows, the preprocessor variable Py_GIL_DISABLED now needs to
be specified by the build backend, as it will no longer be determined
automatically by the C compiler. For a running interpreter, the setting that
was used at compile time can be found using :func:sysconfig.get_config_var.
The new :option:-X context_aware_warnings <-X> flag controls if
:ref:concurrent safe warnings control <whatsnew314-concurrent-warnings-control>
is enabled. The flag defaults to true for the free-threaded build
and false for the GIL-enabled build.
A new :data:~sys.flags.thread_inherit_context flag has been added,
which if enabled means that threads created with :class:threading.Thread
start with a copy of the :class:~contextvars.Context() of the caller of
:meth:~threading.Thread.start. Most significantly, this makes the warning
filtering context established by :class:~warnings.catch_warnings be
"inherited" by threads (or asyncio tasks) started within that context. It also
affects other modules that use context variables, such as the :mod:decimal
context manager.
This flag defaults to true for the free-threaded build and false for
the GIL-enabled build.
(Contributed by Sam Gross, Matt Page, Neil Schemenauer, Thomas Wouters, Donghee Na, Kirill Podoprigora, Ken Jin, Itamar Oren, Brett Simmers, Dino Viehland, Nathan Goldbaum, Ralf Gommers, Lysandros Nikolaou, Kumar Aditya, Edgar Margffoy, and many others. Some of these contributors are employed by Meta, which has continued to provide significant engineering resources to support this project.)
.. _whatsnew314-improved-error-messages:
The interpreter now provides helpful suggestions when it detects typos in Python keywords. When a word that closely resembles a Python keyword is encountered, the interpreter will suggest the correct keyword in the error message. This feature helps programmers quickly identify and fix common typing mistakes. For example:
.. code-block:: pycon
whille True: ... pass Traceback (most recent call last): File "<stdin>", line 1 whille True: ^^^^^^ SyntaxError: invalid syntax. Did you mean 'while'?
While the feature focuses on the most common cases, some variations of
misspellings may still result in regular syntax errors.
(Contributed by Pablo Galindo in :gh:132449.)
:keyword:elif statements that follow an :keyword:else block now have
a specific error message.
(Contributed by Steele Farnsworth in :gh:129902.)
.. code-block:: pycon
>>> if who == "me":
... print("It's me!")
... else:
... print("It's not me!")
... elif who is None:
... print("Who is it?")
File "<stdin>", line 5
elif who is None:
^^^^
SyntaxError: 'elif' block follows an 'else' block
If a statement is passed to the :ref:if_expr after :keyword:else,
or one of :keyword:pass, :keyword:break, or :keyword:continue
is passed before :keyword:if, then the
error message highlights where the :token:~python-grammar:expression is
required. (Contributed by Sergey Miryanov in :gh:129515.)
.. code-block:: pycon
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.)
.. code-block:: pycon
"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?
When strings have incompatible prefixes, the error now shows
which prefixes are incompatible.
(Contributed by Nikita Sobolev in :gh:133197.)
.. code-block:: pycon
ub'abc' File "<python-input-0>", line 1 ub'abc' ^^ SyntaxError: 'u' and 'b' prefixes are incompatible
Improved error messages when using as with incompatible targets in:
import ... as ...from ... import ... as ...except ... as ...case ... as ...(Contributed by Nikita Sobolev in :gh:123539, :gh:123562, and :gh:123440.)
Improved error message when trying to add an instance of an unhashable type to
a :class:dict or :class:set.
(Contributed by CF Bolz-Tereick and Victor Stinner in :gh:132828.)
.. code-block:: pycon
s = set() s.add({'pages': 12, 'grade': 'A'}) Traceback (most recent call last): File "<python-input-1>", line 1, in <module> s.add({'pages': 12, 'grade': 'A'}) ~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ TypeError: cannot use 'dict' as a set element (unhashable type: 'dict') d = {} l = [1, 2, 3] d[l] = 12 Traceback (most recent call last): File "<python-input-4>", line 1, in <module> d[l] = 12 ~^^^ TypeError: cannot use 'list' as a dict key (unhashable type: 'list')
Improved error message when an object supporting the synchronous
context manager protocol is entered using :keyword:async with
instead of :keyword:with,
and vice versa for the asynchronous context manager protocol.
(Contributed by Bénédikt Tran in :gh:128398.)
.. _whatsnew314-zstandard:
784: Zstandard support in the standard libraryThe new :mod:!compression package contains modules :mod:!compression.lzma,
:mod:!compression.bz2, :mod:!compression.gzip and :mod:!compression.zlib
which re-export the :mod:lzma, :mod:bz2, :mod:gzip and :mod:zlib
modules respectively. The new import names under :mod:!compression are the
preferred names for importing these compression modules from Python 3.14. However,
the existing modules names have not been deprecated. Any deprecation or removal
of the existing compression modules will occur no sooner than five years after
the release of 3.14.
The new :mod:!compression.zstd module provides compression and decompression
APIs for the Zstandard format via bindings to Meta's zstd library <https://facebook.github.io/zstd/>__. Zstandard is a widely adopted, highly
efficient, and fast compression format. In addition to the APIs introduced in
:mod:!compression.zstd, support for reading and writing Zstandard compressed
archives has been added to the :mod:tarfile, :mod:zipfile, and
:mod:shutil modules.
Here's an example of using the new module to compress some data:
.. code-block:: python
from compression import zstd
import math
data = str(math.pi).encode() * 20
compressed = zstd.compress(data)
ratio = len(compressed) / len(data)
print(f"Achieved compression ratio of {ratio}")
As can be seen, the API is similar to the APIs of the :mod:!lzma and
:mod:!bz2 modules.
(Contributed by Emma Harper Smith, Adam Turner, Gregory P. Smith, Tomas Roun,
Victor Stinner, and Rogdham in :gh:132983.)
.. seealso:: :pep:784.
.. _whatsnew314-asyncio-introspection:
Added a new command-line interface to inspect running Python processes
using asynchronous tasks, available via python -m asyncio ps PID
or python -m asyncio pstree PID.
The ps subcommand inspects the given process ID (PID) and displays
information about currently running asyncio tasks.
It outputs a task table: a flat listing of all tasks, their names,
their coroutine stacks, and which tasks are awaiting them.
The pstree subcommand fetches the same information, but instead renders a
visual async call tree, showing coroutine relationships in a hierarchical format.
This command is particularly useful for debugging long-running or stuck
asynchronous programs.
It can help developers quickly identify where a program is blocked,
what tasks are pending, and how coroutines are chained together.
For example given this code:
.. code-block:: python
import asyncio
async def play_track(track): await asyncio.sleep(5) print(f'🎵 Finished: {track}')
async def play_album(name, tracks): async with asyncio.TaskGroup() as tg: for track in tracks: tg.create_task(play_track(track), name=track)
async def main(): async with asyncio.TaskGroup() as tg: tg.create_task( play_album('Sundowning', ['TNDNBTG', 'Levitate']), name='Sundowning') tg.create_task( play_album('TMBTE', ['DYWTYLM', 'Aqua Regia']), name='TMBTE')
if name == 'main': asyncio.run(main())
Executing the new tool on the running process will yield a table like this:
.. code-block:: bash
python -m asyncio ps 12345
1935500 0x7fc930c18050 Task-1 TaskGroup._aexit -> TaskGroup.aexit -> main 0x0 1935500 0x7fc930c18230 Sundowning TaskGroup._aexit -> TaskGroup.aexit -> album TaskGroup._aexit -> TaskGroup.aexit -> main Task-1 0x7fc930c18050 1935500 0x7fc93173fa50 TMBTE TaskGroup._aexit -> TaskGroup.aexit -> album TaskGroup._aexit -> TaskGroup.aexit -> main Task-1 0x7fc930c18050 1935500 0x7fc93173fdf0 TNDNBTG sleep -> play TaskGroup._aexit -> TaskGroup.aexit -> album Sundowning 0x7fc930c18230 1935500 0x7fc930d32510 Levitate sleep -> play TaskGroup._aexit -> TaskGroup.aexit -> album Sundowning 0x7fc930c18230 1935500 0x7fc930d32890 DYWTYLM sleep -> play TaskGroup._aexit -> TaskGroup.aexit -> album TMBTE 0x7fc93173fa50 1935500 0x7fc93161ec30 Aqua Regia sleep -> play TaskGroup._aexit -> TaskGroup.aexit -> album TMBTE 0x7fc93173fa50
or a tree like this:
.. code-block:: bash
python -m asyncio pstree 12345
└── (T) Task-1 └── main example.py:13 └── TaskGroup.aexit Lib/asyncio/taskgroups.py:72 └── TaskGroup._aexit Lib/asyncio/taskgroups.py:121 ├── (T) Sundowning │ └── album example.py:8 │ └── TaskGroup.aexit Lib/asyncio/taskgroups.py:72 │ └── TaskGroup._aexit Lib/asyncio/taskgroups.py:121 │ ├── (T) TNDNBTG │ │ └── play example.py:4 │ │ └── sleep Lib/asyncio/tasks.py:702 │ └── (T) Levitate │ └── play example.py:4 │ └── sleep Lib/asyncio/tasks.py:702 └── (T) TMBTE └── album example.py:8 └── TaskGroup.aexit Lib/asyncio/taskgroups.py:72 └── TaskGroup._aexit Lib/asyncio/taskgroups.py:121 ├── (T) DYWTYLM │ └── play example.py:4 │ └── sleep Lib/asyncio/tasks.py:702 └── (T) Aqua Regia └── play example.py:4 └── sleep Lib/asyncio/tasks.py:702
If a cycle is detected in the async await graph (which could indicate a programming issue), the tool raises an error and lists the cycle paths that prevent tree construction:
.. code-block:: bash
python -m asyncio pstree 12345
ERROR: await-graph contains cycles - cannot print a tree!
cycle: Task-2 → Task-3 → Task-2
(Contributed by Pablo Galindo, Łukasz Langa, Yury Selivanov, and Marta
Gomez Macias in :gh:91048.)
.. _whatsnew314-concurrent-warnings-control:
The :class:warnings.catch_warnings context manager will now optionally
use a context variable for warning filters. This is enabled by setting
the :data:~sys.flags.context_aware_warnings flag, either with the -X
command-line option or an environment variable. This gives predictable
warnings control when using :class:~warnings.catch_warnings combined with
multiple threads or asynchronous tasks. The flag defaults to true for the
free-threaded build and false for the GIL-enabled build.
(Contributed by Neil Schemenauer and Kumar Aditya in :gh:130010.)
All Windows code pages are now supported as 'cpXXX' codecs on Windows.
(Contributed by Serhiy Storchaka in :gh:123803.)
Implement mixed-mode arithmetic rules combining real and complex numbers
as specified by the C standard since C99.
(Contributed by Sergey B Kirpichev in :gh:69639.)
More syntax errors are now detected regardless of optimisation and
the :option:-O command-line option.
This includes writes to __debug__, incorrect use of :keyword:await,
and asynchronous comprehensions outside asynchronous functions.
For example, python -O -c 'assert (__debug__ := 1)'
or python -O -c 'assert await 1' now produce :exc:SyntaxError\ s.
(Contributed by Irit Katriel and Jelle Zijlstra in :gh:122245 & :gh:121637.)
When subclassing a pure C type, the C slots for the new type
are no longer replaced with a wrapped version on class creation
if they are not explicitly overridden in the subclass.
(Contributed by Tomasz Pytel in :gh:132284.)
The :meth:bytes.fromhex and :meth:bytearray.fromhex methods now accept
ASCII :class:bytes and :term:bytes-like objects <bytes-like object>.
(Contributed by Daniel Pope in :gh:129349.)
Add class methods :meth:float.from_number and :meth:complex.from_number
to convert a number to :class:float or :class:complex type correspondingly.
They raise a :exc:TypeError if the argument is not a real number.
(Contributed by Serhiy Storchaka in :gh:84978.)
Support underscore and comma as thousands separators in the fractional part
for floating-point presentation types of the new-style string formatting
(with :func:format or :ref:f-strings).
(Contributed by Sergey B Kirpichev in :gh:87790.)
The :func:int function no longer delegates to :meth:~object.__trunc__.
Classes that want to support conversion to :func:!int must implement
either :meth:~object.__int__ or :meth:~object.__index__.
(Contributed by Mark Dickinson in :gh:119743.)
The :func:map function now has an optional keyword-only strict flag
like :func:zip to check that all the iterables are of equal length.
(Contributed by Wannes Boeykens in :gh:119793.)
The :class:memoryview type now supports subscription,
making it a :term:generic type.
(Contributed by Brian Schubert in :gh:126012.)
Using :data:NotImplemented in a boolean context
will now raise a :exc:TypeError.
This has raised a :exc:DeprecationWarning since Python 3.9.
(Contributed by Jelle Zijlstra in :gh:118767.)
Three-argument :func:pow now tries calling :meth:~object.__rpow__
if necessary.
Previously it was only called in two-argument :func:!pow
and the binary power operator.
(Contributed by Serhiy Storchaka in :gh:130104.)
:class:super objects are now :mod:copyable <copy> and :mod:pickleable <pickle>.
(Contributed by Serhiy Storchaka in :gh:125767.)
The import time flag can now track modules that are already loaded ('cached'),
via the new :option:-X importtime=2 <-X>.
When such a module is imported, the self and cumulative times
are replaced by the string cached.
Values above 2 for -X importtime are now reserved for future use.
(Contributed by Noah Kim and Adam Turner in :gh:118655.)
The command-line option :option:-c now automatically dedents its code
argument before execution.
(Contributed by Jon Crall and Steven Sun in :gh:103998.)
:option:!-J is no longer a reserved flag for Jython_,
and now has no special meaning.
(Contributed by Adam Turner in :gh:133336.)
.. _Jython: https://www.jython.org/
.. _whatsnew314-bracketless-except:
except and except* expressions without bracketsThe :keyword:except and :keyword:except* <except_star> expressions
now allow brackets to be omitted when there are multiple exception types
and the as clause is not used.
For example:
.. code-block:: python
try: connect_to_server() except TimeoutError, ConnectionRefusedError: print('The network has ceased to be!')
(Contributed by Pablo Galindo and Brett Cannon in :pep:758 and :gh:131831.)
.. _whatsnew314-finally-syntaxwarning:
finally blocksThe compiler now emits a :exc:SyntaxWarning when a :keyword:return,
:keyword:break, or :keyword:continue statement have the effect of
leaving a :keyword:finally block.
This change is specified in :pep:765.
In situations where this change is inconvenient (such as those where the
warnings are redundant due to code linting), the :ref:warning filter <warning-filter> can be used to turn off all syntax warnings by adding
ignore::SyntaxWarning as a filter. This can be specified in combination
with a filter that converts other warnings to errors (for example, passing
-Werror -Wignore::SyntaxWarning as CLI options, or setting
PYTHONWARNINGS=error,ignore::SyntaxWarning).
Note that applying such a filter at runtime using the :mod:warnings module
will only suppress the warning in code that is compiled after the filter is
adjusted. Code that is compiled prior to the filter adjustment (for example,
when a module is imported) will still emit the syntax warning.
(Contributed by Irit Katriel in :gh:130080.)
.. _whatsnew314-incremental-gc:
The cycle garbage collector is now incremental. This means that maximum pause times are reduced by an order of magnitude or more for larger heaps.
There are now only two generations: young and old.
When :func:gc.collect is not called directly, the
GC is invoked a little less frequently. When invoked, it
collects the young generation and an increment of the
old generation, instead of collecting one or more generations.
The behavior of :func:!gc.collect changes slightly:
gc.collect(1): Performs an increment of garbage collection,
rather than collecting generation 1.!gc.collect are unchanged.(Contributed by Mark Shannon in :gh:108362.)
.. _whatsnew314-pyrepl-highlighting:
The default :term:interactive shell now highlights Python syntax.
The feature is enabled by default, save if :envvar:PYTHON_BASIC_REPL
or any other environment variable that disables colour is set.
See :ref:using-on-controlling-color for details.
The default color theme for syntax highlighting strives for good contrast
and exclusively uses the 4-bit VGA standard ANSI color codes for maximum
compatibility. The theme can be customized using an experimental API
:func:!_colorize.set_theme.
This can be called interactively or in the :envvar:PYTHONSTARTUP script.
Note that this function has no stability guarantees,
and may change or be removed.
(Contributed by Łukasz Langa in :gh:131507.)
The default :term:interactive shell now supports import auto-completion.
This means that typing import co and pressing :kbd:<Tab> will suggest
modules starting with co. Similarly, typing from concurrent import i
will suggest submodules of concurrent starting with i.
Note that autocompletion of module attributes is not currently supported.
(Contributed by Tomas Roun in :gh:69605.)
:mod:annotationlib:
For introspecting :term:annotations <annotation>.
See :ref:PEP 749 <whatsnew314-deferred-annotations> for more details.
(Contributed by Jelle Zijlstra in :gh:119180.)
:mod:compression (including :mod:compression.zstd):
A package for compression-related modules,
including a new module to support the Zstandard compression format.
See :ref:PEP 784 <whatsnew314-zstandard> for more details.
(Contributed by Emma Harper Smith, Adam Turner, Gregory P. Smith, Tomas Roun,
Victor Stinner, and Rogdham in :gh:132983.)
:mod:concurrent.interpreters:
Support for multiple interpreters in the standard library.
See :ref:PEP 734 <whatsnew314-multiple-interpreters> for more details.
(Contributed by Eric Snow in :gh:134939.)
:mod:string.templatelib:
Support for template string literals (t-strings).
See :ref:PEP 750 <whatsnew314-template-string-literals> for more details.
(Contributed by Jim Baker, Guido van Rossum, Paul Everitt, Koudai Aono,
Lysandros Nikolaou, Dave Peck, Adam Turner, Jelle Zijlstra, Bénédikt Tran,
and Pablo Galindo Salgado in :gh:132661.)
The default value of the :ref:program name <prog> for
:class: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
:class:argparse.ArgumentParser, enabling suggestions for argument choices
and subparser names if mistyped by the user.
(Contributed by Savannah Ostrowski in :gh:124456.)
Enable color for help text, which can be disabled with the optional color
parameter to :class:argparse.ArgumentParser.
This can also be controlled by :ref:environment variables <using-on-controlling-color>.
(Contributed by Hugo van Kemenade in :gh:130645.)
Add :func:~ast.compare, a function for comparing two ASTs.
(Contributed by Batuhan Taskaya and Jeremy Hylton in :gh:60191.)
Add support for :func: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 :func:repr output for AST nodes now includes more information.
(Contributed by Tomas Roun in :gh:116022.)
When called with an AST as input, the :func:~ast.parse function
now always verifies that the root node type is appropriate.
(Contributed by Irit Katriel in :gh:130139.)
Add new options to the command-line interface:
:option:--feature-version <ast --feature-version>,
:option:--optimize <ast --optimize>, and
:option:--show-empty <ast --show-empty>.
(Contributed by Semyon Moroz in :gh:133367.)
The function and methods named :func:!create_task now take an arbitrary
list of keyword arguments. All keyword arguments are passed to the
:class:~asyncio.Task constructor or the custom task factory.
(See :meth:~asyncio.loop.set_task_factory for details.)
The name and context keyword arguments are no longer special;
the name should now be set using the name keyword argument of the factory,
and context may be None.
This affects the following function and methods:
:meth:asyncio.create_task,
:meth:asyncio.loop.create_task,
:meth:asyncio.TaskGroup.create_task.
(Contributed by Thomas Grainger in :gh:128307.)
There are two new utility functions for
introspecting and printing a program's call graph:
:func:~asyncio.capture_call_graph and :func:~asyncio.print_call_graph.
See :ref:Asyncio introspection capabilities <whatsnew314-asyncio-introspection> for more details.
(Contributed by Yury Selivanov, Pablo Galindo Salgado, and Łukasz Langa
in :gh:91048.)
.. _whatsnew314-color-calendar:
calendar's
:ref:command-line <calendar-cli> text output.
This can be controlled by :ref:environment variables <using-on-controlling-color>.
(Contributed by Hugo van Kemenade in :gh:128317.).. _whatsnew314-concurrent-futures-interp-pool:
Add a new executor class, :class:~concurrent.futures.InterpreterPoolExecutor,
which exposes multiple Python interpreters in the same process
('subinterpreters') to Python code.
This uses a pool of independent Python interpreters to execute calls
asynchronously.
This is separate from the new :mod:~concurrent.interpreters module
introduced by :ref:PEP 734 <whatsnew314-multiple-interpreters>.
(Contributed by Eric Snow in :gh:124548.)
.. _whatsnew314-concurrent-futures-start-method:
On Unix platforms other than macOS, :ref:'forkserver' <multiprocessing-start-method-forkserver> is now the default :ref:start method <multiprocessing-start-methods> for
:class:~concurrent.futures.ProcessPoolExecutor
(replacing :ref:'fork' <multiprocessing-start-method-fork>).
This change does not affect Windows or macOS, where :ref:'spawn' <multiprocessing-start-method-spawn> remains the default start method.
If the threading incompatible fork method is required, you must explicitly
request it by supplying a multiprocessing context mp_context to
:class:~concurrent.futures.ProcessPoolExecutor.
See :ref:forkserver restrictions <multiprocessing-programming-forkserver>
for information and differences with the fork method and how this change
may affect existing code with mutable global shared variables and/or shared
objects that can not be automatically :mod:pickled <pickle>.
(Contributed by Gregory P. Smith in :gh:84559.)
Add two new methods to :class:~concurrent.futures.ProcessPoolExecutor,
:meth:~concurrent.futures.ProcessPoolExecutor.terminate_workers
and :meth:~concurrent.futures.ProcessPoolExecutor.kill_workers,
as ways to terminate or kill all living worker processes in the given pool.
(Contributed by Charles Machalow in :gh:130849.)
Add the optional buffersize parameter to :meth:Executor.map <concurrent.futures.Executor.map> to limit the number of submitted
tasks whose results have not yet been yielded. If the buffer is full,
iteration over the iterables pauses until a result is yielded from the
buffer.
(Contributed by Enzo Bonnal and Josh Rosenberg in :gh:74028.)
!configparser will no longer write config files it cannot read,
to improve security.
Attempting to :meth:~configparser.ConfigParser.write keys containing
delimiters or beginning with the section header pattern will raise an
:class:~configparser.InvalidWriteError.
(Contributed by Jacob Lincoln in :gh:129270.)context manager protocol
for :class:~contextvars.Token objects.
(Contributed by Andrew Svetlov in :gh:129889.)The layout of :ref:bit fields <ctypes-bit-fields-in-structures-unions>
in :class:~ctypes.Structure and :class:~ctypes.Union objects
is now a closer match to platform defaults (GCC/Clang or MSVC).
In particular, fields no longer overlap.
(Contributed by Matthias Görgens in :gh:97702.)
The :attr:.Structure._layout_ class attribute can now be set
to help match a non-default ABI.
(Contributed by Petr Viktorin in :gh:97702.)
The class of :class:~ctypes.Structure/:class:~ctypes.Union
field descriptors is now available as :class:~ctypes.CField,
and has new attributes to aid debugging and introspection.
(Contributed by Petr Viktorin in :gh:128715.)
On Windows, the :exc:~ctypes.COMError exception is now public.
(Contributed by Jun Komoda in :gh:126686.)
On Windows, the :func:~ctypes.CopyComPointer function is now public.
(Contributed by Jun Komoda in :gh:127275.)
Add :func:~ctypes.memoryview_at, a function to create a
:class:memoryview object that refers to the supplied pointer and
length. This works like :func:ctypes.string_at except it avoids a
buffer copy, and is typically useful when implementing pure Python
callback functions that are passed dynamically-sized buffers.
(Contributed by Rian Hunter in :gh:112018.)
Complex types, :class:~ctypes.c_float_complex,
:class:~ctypes.c_double_complex, and :class:~ctypes.c_longdouble_complex,
are now available if both the compiler and the libffi library support
complex C types.
(Contributed by Sergey B Kirpichev in :gh:61103.)
Add :func:ctypes.util.dllist for listing the shared libraries
loaded by the current process.
(Contributed by Brian Ward in :gh:119349.)
Move :func:ctypes.POINTER types cache from a global internal cache
(_pointer_type_cache) to the :attr:_CData.__pointer_type__ <ctypes._CData.__pointer_type__> attribute of the corresponding
:mod:!ctypes types.
This will stop the cache from growing without limits in some situations.
(Contributed by Sergey Miryanov in :gh:100926.)
The :class:~ctypes.py_object type now supports subscription,
making it a :term:generic type.
(Contributed by Brian Schubert in :gh:132168.)
:mod:!ctypes now supports :term:free-threading builds <free threading>.
(Contributed by Kumar Aditya and Peter Bierma in :gh:127945.)
~curses.assume_default_colors function,
a refinement of the :func:~curses.use_default_colors function which
allows changing the color pair 0.
(Contributed by Serhiy Storchaka in :gh:133139.)~datetime.date.strptime method to the
:class:datetime.date and :class:datetime.time classes.
(Contributed by Wannes Boeykens in :gh:41431.)Add :meth:.Decimal.from_number as an alternative constructor for
:class:~decimal.Decimal.
(Contributed by Serhiy Storchaka in :gh:121798.)
Expose :func:~decimal.IEEEContext to support creation of contexts
corresponding to the IEEE 754 (2008) decimal interchange formats.
(Contributed by Sergey B Kirpichev in :gh:53032.)
~difflib.HtmlDiff class now support 'dark mode'.
(Contributed by Jiahao Li in :gh:129939.)Add support for rendering full source location information of
:class:instructions <dis.Instruction>, rather than only the line number.
This feature is added to the following interfaces via the show_positions
keyword argument:
dis.Bytecodedis.disdis.distbdis.disassembleThis feature is also exposed via :option:dis --show-positions.
(Contributed by Bénédikt Tran in :gh:123165.)
Add the :option:dis --specialized command-line option to
show specialized bytecode.
(Contributed by Bénédikt Tran in :gh:127413.)
~errno.EHWPOISON error code constant.
(Contributed by James Roy in :gh:126585.)support it <c-stack-compatibility> via the new
:func:~faulthandler.dump_c_stack function or via the c_stack argument
in :func:faulthandler.enable.
(Contributed by Peter Bierma in :gh:127604.)~fnmatch.filterfalse, a function to reject names
matching a given pattern.
(Contributed by Bénédikt Tran in :gh:74598.)A :class:~fractions.Fraction object may now be constructed from any
object with the :meth:!as_integer_ratio method.
(Contributed by Serhiy Storchaka in :gh:82017.)
Add :meth:.Fraction.from_number as an alternative constructor for
:class:~fractions.Fraction.
(Contributed by Serhiy Storchaka in :gh:121797.)
Add the :data:~functools.Placeholder sentinel.
This may be used with the :func:~functools.partial
or :func:~functools.partialmethod functions to reserve a place
for positional arguments in the returned :ref:partial object <partial-objects>.
(Contributed by Dominykas Grigonis in :gh:119127.)
Allow the initial parameter of :func:~functools.reduce to be passed
as a keyword argument.
(Contributed by Sayandip Dutta in :gh:125916.)
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.)
~getpass.getpass function via
the keyword-only optional argument echo_char.
Placeholder characters are rendered whenever a character is entered,
and removed when a character is deleted.
(Contributed by Semyon Moroz in :gh:77065.).TopologicalSorter.prepare to be called more than once
as long as sorting has not started.
(Contributed by Daniel Pope in :gh:130914.)The :mod:!heapq module has improved support for working with max-heaps,
via the following new functions:
~heapq.heapify_max~heapq.heappush_max~heapq.heappop_max~heapq.heapreplace_max~heapq.heappushpop_max2104) using formally verified
code from the HACL* <https://github.com/hacl-star/hacl-star/>__ project.
This implementation is used as a fallback when the OpenSSL implementation
of HMAC is not available.
(Contributed by Bénédikt Tran in :gh:99108.)Directory lists and error pages generated by the :mod:http.server
module allow the browser to apply its default dark mode.
(Contributed by Yorik Hansen in :gh:123430.)
The :mod:http.server module now supports serving over HTTPS using the
:class:http.server.HTTPSServer class. This functionality is exposed by
the command-line interface (python -m http.server) through the following
options:
--tls-cert \<path\> <http.server --tls-cert>:
Path to the TLS certificate file.--tls-key \<path\> <http.server --tls-key>:
Optional path to the private key file.--tls-password-file \<path\> <http.server --tls-password-file>:
Optional path to the password file for the private key.(Contributed by Semyon Moroz in :gh:85162.)
.IMAP4.idle, implementing the IMAP4
IDLE command as defined in :rfc:2177.
(Contributed by Forest in :gh:55454.):func:~inspect.signature takes a new argument annotation_format to control
the :class:annotationlib.Format used for representing annotations.
(Contributed by Jelle Zijlstra in :gh:101552.)
:meth:.Signature.format takes a new argument unquote_annotations.
If true, string :term:annotations <annotation> are displayed without
surrounding quotes.
(Contributed by Jelle Zijlstra in :gh:101552.)
Add function :func:~inspect.ispackage to determine whether an object is a
:term:package or not.
(Contributed by Zhikang Yan in :gh:125634.)
Reading text from a non-blocking stream with read may now raise a
:exc:BlockingIOError if the operation cannot immediately return bytes.
(Contributed by Giovanni Siragusa in :gh:109523.)
Add the :class:~io.Reader and :class:~io.Writer protocols as simpler
alternatives to the pseudo-protocols :class:typing.IO,
:class:typing.TextIO, and :class:typing.BinaryIO.
(Contributed by Sebastian Rittau in :gh:127648.)
Add exception notes for JSON serialization errors that allow
identifying the source of the error.
(Contributed by Serhiy Storchaka in :gh:122163.)
Allow using the :mod:json module as a script using the :option:-m switch:
:program:python -m json.
This is now preferred to :program:python -m json.tool,
which is :term:soft deprecated.
See the :ref:JSON command-line interface <json-commandline> documentation.
(Contributed by Trey Hunner in :gh:122873.)
By default, the output of the :ref:JSON command-line interface <json-commandline> is highlighted in color.
This can be controlled by :ref:environment variables <using-on-controlling-color>.
(Contributed by Tomas Roun in :gh:131952.)
~linecache.getline can now retrieve source code for frozen modules.
(Contributed by Tian Gao in :gh:131638.):class:~logging.handlers.QueueListener objects now support the
:term:context manager protocol.
(Contributed by Charles Machalow in :gh:132106.)
:meth:QueueListener.start <logging.handlers.QueueListener.start> now
raises a :exc:RuntimeError if the listener is already started.
(Contributed by Charles Machalow in :gh:132106.)
101410.)Add a public :ref:command-line <mimetypes-cli> for the module,
invoked via :program:python -m mimetypes.
(Contributed by Oleg Iarygin and Hugo van Kemenade in :gh:93096.)
Add several new MIME types based on RFCs and common usage:
.. rubric:: Microsoft and :rfc:8081 MIME types for fonts
application/vnd.ms-fontobjectfont/otffont/ttffont/wofffont/woff2.. rubric:: :rfc:9559 MIME types for Matroska audiovisual
data container structures
audio/matroska (.mka)video/matroska (.mkv)video/matroska-3d (.mk3d).. rubric:: Images with RFCs
1494: CCITT Group 3 (.g3)3362: Real-time Facsimile, T.38 (.t38)3745: JPEG 2000 (.jp2), extension (.jpx) and compound (.jpm)3950: Tag Image File Format Fax eXtended, TIFF-FX (.tfx)4047: Flexible Image Transport System (.fits)7903: Enhanced Metafile (.emf) and Windows Metafile (.wmf).. rubric:: Other MIME type additions and changes
2361: Change type for .avi to video/vnd.avi
and for .wav to audio/vnd.wave4337: Add MPEG-4 audio/mp4 (.m4a)5334: Add Ogg media (.oga, .ogg and .ogx)6713: Add gzip application/gzip (.gz)9639: Add FLAC audio/flac (.flac)9512 application/yaml MIME type for YAML files (.yaml
and .yml)application/x-7z-compressed (.7z)application/vnd.android.package-archive (.apk)
when not strictapplication/x-debian-package (.deb)model/gltf-binary (.glb)model/gltf+json (.gltf)video/x-m4v (.m4v)application/x-httpd-php (.php)application/vnd.rar (.rar)application/x-rpm (.rpm)model/stl (.stl)video/x-ms-wmv (.wmv)audio/webm (.weba)ECMA-376 <https://ecma-international.org/publications-and-standards/standards/ecma-376/>__:
Add .docx, .pptx and .xlsx typesOASIS <https://docs.oasis-open.org/office/v1.2/cs01/OpenDocument-v1.2-cs01-part1.html#Appendix_C>__:
Add OpenDocument .odg, .odp, .ods and .odt typesW3C <https://www.w3.org/TR/epub-33/#app-media-type>__:
Add EPUB application/epub+zip (.epub)(Contributed by Sahil Prajapati and Hugo van Kemenade in :gh:84852,
by Sasha "Nelie" Chernykh and Hugo van Kemenade in :gh:132056,
and by Hugo van Kemenade in :gh:89416, :gh:85957, and :gh:129965.)
.. _whatsnew314-multiprocessing-start-method:
On Unix platforms other than macOS, :ref:'forkserver' <multiprocessing-start-method-forkserver> is now the default :ref:start method <multiprocessing-start-methods>
(replacing :ref:'fork' <multiprocessing-start-method-fork>).
This change does not affect Windows or macOS, where :ref:'spawn' <multiprocessing-start-method-spawn> remains the default start method.
If the threading incompatible fork method is required, you must explicitly
request it via a context from :func:~multiprocessing.get_context (preferred)
or change the default via :func:~multiprocessing.set_start_method.
See :ref:forkserver restrictions <multiprocessing-programming-forkserver>
for information and differences with the fork method and how this change
may affect existing code with mutable global shared variables and/or shared
objects that can not be automatically :mod:pickled <pickle>.
(Contributed by Gregory P. Smith in :gh:84559.)
:mod:multiprocessing's 'forkserver' start method now authenticates
its control socket to avoid solely relying on filesystem permissions
to restrict what other processes could cause the forkserver to spawn workers
and run code.
(Contributed by Gregory P. Smith for :gh:97514.)
The :ref:multiprocessing proxy objects <multiprocessing-proxy_objects>
for list and dict types gain previously overlooked missing methods:
!clear and :meth:!copy for proxies of :class:list~dict.fromkeys, reversed(d), d | {}, {} | d,
d |= {'b': 2} for proxies of :class:dict(Contributed by Roy Hyunjin Han for :gh:103134.)
Add support for shared :class:set objects via
:meth:.SyncManager.set.
The :func:set in :func:~multiprocessing.Manager method is now available.
(Contributed by Mingyu Park in :gh:129949.)
Add the :meth:~multiprocessing.Process.interrupt
to :class:multiprocessing.Process objects, which terminates the child
process by sending :py:const:~signal.SIGINT. This enables
:keyword:finally clauses to print a stack trace for the terminated
process. (Contributed by Artem Pulkin in :gh:131913.)
~operator.is_none and :func:~operator.is_not_none as a pair
of functions, 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.)Add the :func:~os.reload_environ function to update :data:os.environ and
:data:os.environb with changes to the environment made by
:func:os.putenv, by :func:os.unsetenv, or made outside Python in the
same process.
(Contributed by Victor Stinner in :gh:120057.)
Add the :data:~os.SCHED_DEADLINE and :data:~os.SCHED_NORMAL constants
to the :mod:!os module.
(Contributed by James Roy in :gh:127688.)
Add the :func:~os.readinto function to read into a
:ref:buffer object <bufferobjects> from a file descriptor.
(Contributed by Cody Maloney in :gh:129205.)
~os.path.realpath accepts a new value,
:data:~os.path.ALLOW_MISSING.
If used, errors other than :exc:FileNotFoundError will be re-raised;
the resulting path can be missing but it will be free of symlinks.
(Contributed by Petr Viktorin for :cve:2025-4517.)Add methods to :class:pathlib.Path to recursively copy or move files and
directories:
~pathlib.Path.copy copies a file or directory tree to a destination.~pathlib.Path.copy_into copies into a destination directory.~pathlib.Path.move moves a file or directory tree to a destination.~pathlib.Path.move_into moves into a destination directory.(Contributed by Barney Gale in :gh:73991.)
Add the :attr:~pathlib.Path.info attribute, which stores an object
implementing the new :class:pathlib.types.PathInfo protocol. The
object supports querying the file type and internally caching
:func:~os.stat results. Path objects generated by
:meth:~pathlib.Path.iterdir are initialized with file type information
gleaned from scanning the parent directory.
(Contributed by Barney Gale in :gh:125413.)
The :mod:pdb module now supports remote attaching to a running Python process
using a new :option:-p PID <pdb --pid> command-line option:
.. code-block:: sh
python -m pdb -p 1234
This will connect to the Python process with the given PID and allow you to debug it interactively. Notice that due to how the Python interpreter works attaching to a remote process that is blocked in a system call or waiting for I/O will only work once the next bytecode instruction is executed or when the process receives a signal.
This feature uses :ref:PEP 768 <whatsnew314-remote-debugging>
and the new :func:sys.remote_exec function to attach to the remote process
and send the PDB commands to it.
(Contributed by Matt Wozniski and Pablo Galindo in :gh:131591.)
Hardcoded breakpoints (:func:breakpoint and :func:~pdb.set_trace) now
reuse the most recent :class:~pdb.Pdb instance that calls
:meth:~pdb.Pdb.set_trace, instead of creating a new one each time.
As a result, all the instance specific data like :pdbcmd:display and
:pdbcmd:commands are preserved across hardcoded breakpoints.
(Contributed by Tian Gao in :gh:121450.)
Add a new argument mode to :class:pdb.Pdb. Disable the restart
command when :mod:pdb is in inline mode.
(Contributed by Tian Gao in :gh:123757.)
A confirmation prompt will be shown when the user tries to quit :mod:pdb
in inline mode. y, Y, <Enter> or EOF will confirm
the quit and call :func:sys.exit, instead of raising :exc:bdb.BdbQuit.
(Contributed by Tian Gao in :gh:124704.)
Inline breakpoints like :func:breakpoint or :func: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 :mod: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.)
Auto-indent is introduced in :mod:pdb multi-line input. It will either
keep the indentation of the last line or insert a 4-space indentation when
it detects a new code block.
(Contributed by Tian Gao in :gh:133350.)
$_asynctask is added to access the current asyncio task if applicable.
(Contributed by Tian Gao in :gh:124367.)
:func:pdb.set_trace_async is added to support debugging asyncio
coroutines. :keyword:await statements are supported with this
function.
(Contributed by Tian Gao in :gh:132576.)
Source code displayed in :mod:pdb will be syntax-highlighted. This feature
can be controlled using the same methods as the default :term:interactive
shell, in addition to the newly added colorize argument of :class:pdb.Pdb.
(Contributed by Tian Gao and Łukasz Langa in :gh:133355.)
Set the default protocol version on the :mod:pickle module to 5.
For more details, see :ref:pickle protocols <pickle-protocols>.
Add exception notes for pickle serialization errors that allow
identifying the source of the error.
(Contributed by Serhiy Storchaka in :gh:122213.)
~platform.invalidate_caches, a function to invalidate
cached results in the :mod:!platform module.
(Contributed by Bénédikt Tran in :gh:122549.)Annotations <annotation> in help output are now usually
displayed in a format closer to that in the original source.
(Contributed by Jelle Zijlstra in :gh:101552.)Support \z as a synonym for \Z in :mod:regular expressions <re>.
It is interpreted unambiguously in many other regular expression engines,
unlike \Z, which has subtly different behavior.
(Contributed by Serhiy Storchaka in :gh:133306.)
\B in :mod:regular expression <re> now matches the empty input string,
meaning that it is now always the opposite of \b.
(Contributed by Serhiy Storchaka in :gh:124130.)
Improve and fix support for Bluetooth sockets.
132429.)~socket.BTPROTO_HCI on FreeBSD.
(Contributed by Victor Stinner in :gh:111178.)~socket.BTPROTO_SCO on FreeBSD.
(Contributed by Serhiy Storchaka in :gh:85302.)~socket.BTPROTO_L2CAP on FreeBSD.
(Contributed by Serhiy Storchaka in :gh:132429.)~socket.BTPROTO_HCI on Linux.
(Contributed by Serhiy Storchaka in :gh:70145.)~socket.BTPROTO_HCI on Linux.
(Contributed by Serhiy Storchaka in :gh:132099.)~socket.socket.getsockname for
:const:~socket.BTPROTO_L2CAP.
(Contributed by Serhiy Storchaka in :gh:132429.)132734.)~ssl.HAS_PHA Boolean whether the :mod:!ssl
module supports TLSv1.3 post-handshake client authentication (PHA).
(Contributed by Will Childs-Klein in :gh:128036.)float complex and :c:expr:double complex C types in
the :mod:struct module (formatting characters 'F' and 'D'
respectively).
(Contributed by Sergey B Kirpichev in :gh:121249.)Expose the following :class:~symtable.Symbol methods:
~symtable.Symbol.is_comp_cell~symtable.Symbol.is_comp_iter~symtable.Symbol.is_free_class(Contributed by Bénédikt Tran in :gh:120029.)
The previously undocumented special function :func:sys.getobjects,
which only exists in specialized builds of Python, may now return objects
from other interpreters than the one it's called in.
(Contributed by Eric Snow in :gh:125286.)
Add :func:sys._is_immortal for determining if an object is :term:immortal.
(Contributed by Peter Bierma in :gh:128509.)
On FreeBSD, :data:sys.platform no longer contains the major version number.
It is always 'freebsd', instead of 'freebsd13' or 'freebsd14'.
(Contributed by Michael Osipov in :gh:129393.)
Raise :exc:DeprecationWarning for :func:sys._clear_type_cache. This
function was deprecated in Python 3.13 but it didn't raise a runtime warning.
Add :func:sys.remote_exec to implement the new external debugger interface.
See :ref:PEP 768 <whatsnew314-remote-debugging> for details.
(Contributed by Pablo Galindo Salgado, Matt Wozniski, and Ivona Stojanovic
in :gh:131591.)
Add the :data:sys._jit namespace, containing utilities for introspecting
just-in-time compilation.
(Contributed by Brandt Bucher in :gh:133231.)
BRANCH_LEFT and
:monitoring-event:BRANCH_RIGHT.
These replace and deprecate the :monitoring-event:!BRANCH event.
(Contributed by Mark Shannon in :gh:122548.)ABIFLAGS key to :func:~sysconfig.get_config_vars on Windows.
(Contributed by Xuehai Pan in :gh:131799.):func:~tarfile.data_filter now normalizes symbolic link targets in order to
avoid path traversal attacks.
(Contributed by Petr Viktorin in :gh:127987 and :cve:2025-4138.)
:func:~tarfile.TarFile.extractall now skips fixing up directory attributes
when a directory was removed or replaced by another kind of file.
(Contributed by Petr Viktorin in :gh:127987 and :cve:2024-12718.)
:func:~tarfile.TarFile.extract and :func:~tarfile.TarFile.extractall
now (re-)apply the extraction filter when substituting a link (hard or
symbolic) with a copy of another archive member, and when fixing up
directory attributes.
The former raises a new exception, :exc:~tarfile.LinkFallbackError.
(Contributed by Petr Viktorin for :cve:2025-4330 and :cve:2024-12718.)
:func:~tarfile.TarFile.extract and :func:~tarfile.TarFile.extractall
no longer extract rejected members when
:func:~tarfile.TarFile.errorlevel is zero.
(Contributed by Matt Prodani and Petr Viktorin in :gh:112887
and :cve:2025-4435.)
threading.Thread.start now sets the operating system thread name
to :attr:threading.Thread.name.
(Contributed by Victor Stinner in :gh:59705.)Make :mod:tkinter widget methods :meth:!after and :meth:!after_idle
accept keyword arguments.
(Contributed by Zhikang Yan in :gh:126899.)
Add ability to specify a name for :class:!tkinter.OptionMenu and
:class:!tkinter.ttk.OptionMenu.
(Contributed by Zhikang Yan in :gh:130482.)
turtle.fill, :func:turtle.poly,
and :func:turtle.no_animation.
(Contributed by Marie Roald and Yngve Mardal Moe in :gh:126350.)types.UnionType is now an alias for :class:typing.Union.
See :ref:below <whatsnew314-typing-union> for more details.
(Contributed by Jelle Zijlstra in :gh:105499.).. _whatsnew314-typing-union:
The :class:types.UnionType and :class:typing.Union types are now
aliases for each other, meaning that both old-style unions
(created with Union[int, str]) and new-style unions (int | str)
now create instances of the same runtime type. This unifies the behavior
between the two syntaxes, but leads to some differences in behavior that
may affect users who introspect types at runtime:
Both syntaxes for creating a union now produce the same string
representation in :func:repr.
For example, repr(Union[int, str]) is now "int | str" instead of
"typing.Union[int, str]".
Unions created using the old syntax are no longer cached.
Previously, running Union[int, str] multiple times would return
the same object (Union[int, str] is Union[int, str] would be True),
but now it will return two different objects.
Use == to compare unions for equality, not is.
New-style unions have never been cached this way.
This change could increase memory usage for some programs that use
a large number of unions created by subscripting typing.Union.
However, several factors offset this cost:
unions used in annotations are no longer evaluated by default in Python
3.14 because of :pep:649; an instance of :class:types.UnionType is
itself much smaller than the object returned by Union[] was on prior
Python versions; and removing the cache also saves some space.
It is therefore unlikely that this change will cause a significant increase
in memory usage for most users.
Previously, old-style unions were implemented using the private class
typing._UnionGenericAlias.
This class is no longer needed for the implementation,
but it has been retained for backward compatibility,
with removal scheduled for Python 3.17.
Users should use documented introspection helpers like
:func:~typing.get_origin and :func:typing.get_args instead of
relying on private implementation details.
It is now possible to use :class:typing.Union itself in
:func:isinstance checks.
For example, isinstance(int | str, typing.Union) will return True;
previously this raised :exc:TypeError.
The :attr:!__args__ attribute of :class:typing.Union objects is
no longer writable.
It is no longer possible to set any attributes on :class:~typing.Union
objects.
This only ever worked for dunder attributes on previous versions, was never
documented to work, and was subtly broken in many cases.
(Contributed by Jelle Zijlstra in :gh:105499.)
:class:~typing.TypeAliasType now supports star unpacking.
.. _whatsnew314-color-unittest:
:mod:unittest output is now colored by default.
This can be controlled by :ref:environment variables <using-on-controlling-color>.
(Contributed by Hugo van Kemenade in :gh:127221.)
unittest discovery supports :term:namespace package as start
directory again. It was removed in Python 3.11.
(Contributed by Jacob Walls in :gh:80958.)
A number of new methods were added in the :class:~unittest.TestCase class
that provide more specialized tests.
~unittest.TestCase.assertHasAttr and
:meth:~unittest.TestCase.assertNotHasAttr check whether the object
has a particular attribute.~unittest.TestCase.assertIsSubclass and
:meth:~unittest.TestCase.assertNotIsSubclass check whether the object
is a subclass of a particular class, or of one of a tuple of classes.~unittest.TestCase.assertStartsWith,
:meth:~unittest.TestCase.assertNotStartsWith,
:meth:~unittest.TestCase.assertEndsWith and
:meth:~unittest.TestCase.assertNotEndsWith check whether the Unicode
or byte string starts or ends with particular strings.(Contributed by Serhiy Storchaka in :gh:71339.)
Upgrade HTTP digest authentication algorithm for :mod:urllib.request by
supporting SHA-256 digest authentication as specified in :rfc:7616.
(Contributed by Calvin Bui in :gh:128193.)
Improve ergonomics and standards compliance when parsing and emitting
file: URLs.
In :func:~urllib.request.url2pathname:
~urllib.error.URLError if a URL authority isn't local,
except on Windows where we return a UNC path as before.In :func:~urllib.request.pathname2url:
/etc/hosts is converted to the URL ///etc/hosts.On Windows, drive letters are no longer converted to uppercase, and :
characters not following a drive letter no longer cause an :exc:OSError
exception to be raised.
(Contributed by Barney Gale in :gh:125866.)
Add support for UUID versions 6, 7, and 8 via :func:~uuid.uuid6,
:func:~uuid.uuid7, and :func:~uuid.uuid8 respectively, as specified
in :rfc:9562.
(Contributed by Bénédikt Tran in :gh:89083.)
:const:~uuid.NIL and :const:~uuid.MAX are now available to represent the
Nil and Max UUID formats as defined by :rfc:9562.
(Contributed by Nick Pope in :gh:128427.)
Allow generating multiple UUIDs simultaneously on the command-line via
:option:python -m uuid --count <uuid --count>.
(Contributed by Simon Legner in :gh:131236.)
Names in the :envvar:BROWSER environment variable can now refer to already
registered browsers for the :mod:webbrowser module, instead of always
generating a new browser command.
This makes it possible to set :envvar:BROWSER to the value of one of the
supported browsers on macOS.
Added :meth:ZipInfo._for_archive <zipfile.ZipInfo._for_archive>, a method
to resolve suitable defaults for a :class:~zipfile.ZipInfo object
as used by :func:ZipFile.writestr <zipfile.ZipFile.writestr>.
(Contributed by Bénédikt Tran in :gh:123424.)
:meth:.ZipFile.writestr now respects the :envvar:SOURCE_DATE_EPOCH
environment variable in order to better support reproducible builds.
(Contributed by Jiahao Li in :gh:91279.)
.. Add improved modules above alphabetically, not here at the end.
The import time for several standard library modules has been improved,
including :mod:annotationlib, :mod:ast, :mod:asyncio, :mod:base64,
:mod:cmd, :mod:csv, :mod:gettext, :mod:importlib.util, :mod:locale,
:mod:mimetypes, :mod:optparse, :mod:pickle, :mod:pprint,
:mod:pstats, :mod:shlex, :mod:socket, :mod:string, :mod:subprocess,
:mod:threading, :mod:tomllib, :mod:types, and :mod:zipfile.
(Contributed by Adam Turner, Bénédikt Tran, Chris Markiewicz, Eli Schwartz,
Hugo van Kemenade, Jelle Zijlstra, and others in :gh:118761.)
The interpreter now avoids some reference count modifications internally
when it's safe to do so.
This can lead to different values being returned from :func:sys.getrefcount
and :c:func:Py_REFCNT compared to previous versions of Python.
See :ref:below <whatsnew314-refcount> for details.
Standard benchmark results have improved by 10-20% following the
implementation of a new per-thread doubly linked list
for :class:native tasks <asyncio.Task>,
also reducing memory usage.
This enables external introspection tools such as
:ref:python -m asyncio pstree <whatsnew314-asyncio-introspection>
to introspect the call graph of asyncio tasks running in all threads.
(Contributed by Kumar Aditya in :gh:107803.)
The module now has first class support for
:term:free-threading builds <free threading>.
This enables parallel execution of multiple event loops across
different threads, scaling linearly with the number of threads.
(Contributed by Kumar Aditya in :gh:128002.)
~base64.b16decode is now up to six times faster.
(Contributed by Bénédikt Tran, Chris Markiewicz, and Adam Turner
in :gh:118761.)sys.monitoring-based backend,
which can be selected via the passing 'monitoring'
to the :class:~bdb.Bdb class's new backend parameter.
(Contributed by Tian Gao in :gh:124533.)~difflib.IS_LINE_JUNK function is now up to twice as fast.
(Contributed by Adam Turner and Semyon Moroz in :gh:130167.)The new :ref:incremental garbage collector <whatsnew314-incremental-gc>
means that maximum pause times are reduced
by an order of magnitude or more for larger heaps.
Because of this optimization, the meaning of the results of
:meth:~gc.get_threshold and :meth:~gc.set_threshold have changed,
along with :meth:~gc.get_count and :meth:~gc.get_stats.
For backwards compatibility, :meth:~gc.get_threshold continues to return
a three-item tuple.
The first value is the threshold for young collections, as before;
the second value determines the rate at which the old collection is scanned
(the default is 10, and higher values mean that the old collection
is scanned more slowly).
The third value is now meaningless and is always zero.
:meth:~gc.set_threshold now ignores any items after the second.
:meth:~gc.get_count and :meth:~gc.get_stats continue to return
the same format of results.
The only difference is that instead of the results referring to
the young, aging and old generations,
the results refer to the young generation
and the aging and collecting spaces of the old generation.
In summary, code that attempted to manipulate the behavior of the cycle GC may not work exactly as intended, but it is very unlikely to be harmful. All other code will work just fine.
(Contributed by Mark Shannon in :gh:108362.)
120754 and :gh:90102.)Path.read_bytes <pathlib.Path.read_bytes> now uses unbuffered mode
to open files, which is between 9% and 17% faster to read in full.
(Contributed by Cody Maloney in :gh:120754.)pdb now supports two backends, based on either
:func:sys.settrace or :mod:sys.monitoring.
Using the :ref:pdb CLI <pdb-cli> or :func:breakpoint
will always use the :mod:sys.monitoring backend.
Explicitly instantiating :class:pdb.Pdb and its derived classes
will use the :func:sys.settrace backend by default, which is configurable.
(Contributed by Tian Gao in :gh:124533.)~textwrap.dedent function, improving performance by
an average of 2.4x, with larger improvements for bigger inputs,
and fix a bug with incomplete normalization of blank lines with whitespace
characters other than space and tab.:func:~uuid.uuid3 and :func:~uuid.uuid5 are now both roughly 40% faster
for 16-byte names and 20% faster for 1024-byte names.
Performance for longer names remains unchanged.
(Contributed by Bénédikt Tran in :gh:128150.)
:func:~uuid.uuid4 is now c. 30% faster.
(Contributed by Bénédikt Tran in :gh:128150.)
On Windows, zlib-ng <https://github.com/zlib-ng/zlib-ng>__
is now used as the implementation of the :mod:zlib module
in the default binaries.
There are no known incompatibilities between zlib-ng
and the previously-used zlib implementation.
This should result in better performance at all compression levels.
It is worth noting that zlib.Z_BEST_SPEED (1) may result in
significantly less compression than the previous implementation,
whilst also significantly reducing the time taken to compress.
(Contributed by Steve Dower in :gh:91349.)
Remove the type, choices, and metavar parameters
of :class:!BooleanOptionalAction.
These have been deprecated since Python 3.12.
(Contributed by Nikita Sobolev in :gh:118805.)
Calling :meth:~argparse.ArgumentParser.add_argument_group
on an argument group now raises a :exc:ValueError.
Similarly, :meth:~argparse.ArgumentParser.add_argument_group
or :meth:~argparse.ArgumentParser.add_mutually_exclusive_group
on a mutually exclusive group now both raise :exc:ValueError\ s.
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.)
Remove the following classes, which have been deprecated aliases of
:class:~ast.Constant since Python 3.8 and have emitted
deprecation warnings since Python 3.12:
!Bytes!Ellipsis!NameConstant!Num!StrAs a consequence of these removals, user-defined visit_Num, visit_Str,
visit_Bytes, visit_NameConstant and visit_Ellipsis methods
on custom :class:~ast.NodeVisitor subclasses will no longer be called
when the :class:!NodeVisitor subclass is visiting an AST.
Define a visit_Constant method instead.
(Contributed by Alex Waygood in :gh:119562.)
Remove the following deprecated properties on :class:ast.Constant,
which were present for compatibility with the now-removed AST classes:
!Constant.n!Constant.sUse :attr:!Constant.value instead.
(Contributed by Alex Waygood in :gh:119562.)
Remove the following classes, methods, and functions, which have been deprecated since Python 3.12:
!AbstractChildWatcher!FastChildWatcher!MultiLoopChildWatcher!PidfdChildWatcher!SafeChildWatcher!ThreadedChildWatcher!AbstractEventLoopPolicy.get_child_watcher!AbstractEventLoopPolicy.set_child_watcher!get_child_watcher!set_child_watcher(Contributed by Kumar Aditya in :gh:120804.)
:func:asyncio.get_event_loop now raises a :exc:RuntimeError
if there is no current event loop,
and no longer implicitly creates an event loop.
(Contributed by Kumar Aditya in :gh:126353.)
.. TODO: move these patterns to the asyncio docs? quite long for What's New
There's a few patterns that use :func:asyncio.get_event_loop, most
of them can be replaced with :func:asyncio.run.
If you're running an async function, simply use :func:asyncio.run.
Before:
.. code:: python
async def main(): ...
loop = asyncio.get_event_loop() try: loop.run_until_complete(main()) finally: loop.close()
After:
.. code:: python
async def main(): ...
asyncio.run(main())
If you need to start something, for example, a server listening on a socket
and then run forever, use :func:asyncio.run and an
:class:asyncio.Event.
Before:
.. code:: python
def start_server(loop): ...
loop = asyncio.get_event_loop() try: start_server(loop) loop.run_forever() finally: loop.close()
After:
.. code:: python
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 :class:asyncio.Runner.
Before:
.. code:: python
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:
.. code:: python
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())
email.utils.localtime's isdst parameter,
which was deprecated in and has been ignored since Python 3.12.
(Contributed by Hugo van Kemenade in :gh:118798.)Remove deprecated :mod:importlib.abc classes:
!ResourceReader
(use :class:~importlib.resources.abc.TraversableResources)!Traversable
(use :class:~importlib.resources.abc.Traversable)!TraversableResources
(use :class:~importlib.resources.abc.TraversableResources)(Contributed by Jason R. Coombs and Hugo van Kemenade in :gh:93963.)
itertools iterators.
These have emitted a :exc:DeprecationWarning since Python 3.12.
(Contributed by Raymond Hettinger in :gh:101588.)Remove support for passing additional keyword arguments
to :class:~pathlib.Path.
In previous versions, any such arguments are ignored.
(Contributed by Barney Gale in :gh:74033.)
Remove support for passing additional positional arguments to
:meth:.PurePath.relative_to and :meth:~pathlib.PurePath.is_relative_to.
In previous versions, any such arguments are joined onto other.
(Contributed by Barney Gale in :gh:78707.)
!get_loader and :func:!find_loader functions,
which have been deprecated since Python 3.12.
(Contributed by Bénédikt Tran in :gh:97850.)!master_open and :func:!slave_open functions,
which have been deprecated since Python 3.12.
Use :func:pty.openpty instead.
(Contributed by Nikita Sobolev in :gh:118824.)Remove :data:!version and :data:!version_info from
the :mod:sqlite3 module;
use :data:~sqlite3.sqlite_version and :data:~sqlite3.sqlite_version_info
for the actual version number of the runtime SQLite library.
(Contributed by Hugo van Kemenade in :gh:118924.)
Using a sequence of parameters with named placeholders now
raises a :exc:~sqlite3.ProgrammingError,
having been deprecated since Python 3.12.
(Contributed by Erlend E. Aasland in :gh:118928 and :gh:101693.)
Remove the :class:!Quoter class from :mod:urllib.parse,
which has been deprecated since Python 3.11.
(Contributed by Nikita Sobolev in :gh:118827.)
Remove the :class:!URLopener and :class:!FancyURLopener classes
from :mod:urllib.request,
which have been deprecated since Python 3.3.
myopener.open() can be replaced with :func:~urllib.request.urlopen.
myopener.retrieve() can be replaced with
:func:~urllib.request.urlretrieve.
Customisations to the opener classes can be replaced by passing
customized handlers to :func:~urllib.request.build_opener.
(Contributed by Barney Gale in :gh:84850.)
Passing a complex number as the real or imag argument in the
:func:complex constructor is now deprecated;
complex numbers should only be passed as a single positional argument.
(Contributed by Serhiy Storchaka in :gh:109218.)
:mod:argparse:
Passing the undocumented keyword argument prefix_chars to the
:meth:~argparse.ArgumentParser.add_argument_group method is now deprecated.
(Contributed by Savannah Ostrowski in :gh:125563.)
Deprecated the :class:argparse.FileType type converter.
Anything relating to resource management should be handled
downstream, after the arguments have been parsed.
(Contributed by Serhiy Storchaka in :gh:58032.)
:mod:asyncio:
The :func:!asyncio.iscoroutinefunction is now deprecated
and will be removed in Python 3.16;
use :func:inspect.iscoroutinefunction instead.
(Contributed by Jiahao Li and Kumar Aditya in :gh:122875.)
The :mod:asyncio policy system is deprecated
and will be removed in Python 3.16.
In particular, the following classes and functions are deprecated:
asyncio.AbstractEventLoopPolicyasyncio.DefaultEventLoopPolicyasyncio.WindowsSelectorEventLoopPolicyasyncio.WindowsProactorEventLoopPolicyasyncio.get_event_loop_policyasyncio.set_event_loop_policyUsers should use :func:asyncio.run or :class:asyncio.Runner with
the loop_factory argument to use the desired event loop implementation.
For example, to use :class:asyncio.SelectorEventLoop on Windows:
.. code-block:: python
import asyncio
async def main(): ...
asyncio.run(main(), loop_factory=asyncio.SelectorEventLoop)
(Contributed by Kumar Aditya in :gh:127949.)
:mod:codecs:
The :func:codecs.open function is now deprecated,
and will be removed in a future version of Python.
Use :func:open instead.
(Contributed by Inada Naoki in :gh:133036.)
:mod:ctypes:
On non-Windows platforms, setting :attr:.Structure._pack_ to use a
MSVC-compatible default memory layout is now deprecated in favor of setting
:attr:.Structure._layout_ to 'ms', and will be removed in Python 3.19.
(Contributed by Petr Viktorin in :gh:131747.)
Calling :func:ctypes.POINTER on a string is now deprecated.
Use :ref:incomplete types <ctypes-incomplete-types>
for self-referential structures.
Also, the internal ctypes._pointer_type_cache is deprecated.
See :func:ctypes.POINTER for updated implementation details.
(Contributed by Sergey Myrianov in :gh:100926.)
:mod:functools:
Calling the Python implementation of :func:functools.reduce with function
or sequence as keyword arguments is now deprecated;
the parameters will be made positional-only in Python 3.16.
(Contributed by Kirill Podoprigora in :gh:121676.)
:mod:logging:
Support for custom logging handlers with the strm argument
is now deprecated and scheduled for removal in Python 3.16.
Define handlers with the stream argument instead.
(Contributed by Mariusz Felisiak in :gh:115032.)
:mod:mimetypes:
Valid extensions are either empty or must start with '.' for
:meth:mimetypes.MimeTypes.add_type.
Undotted extensions are deprecated and will
raise a :exc:ValueError in Python 3.16.
(Contributed by Hugo van Kemenade in :gh:75223.)
:mod:!nturl2path:
This module is now deprecated. Call :func:urllib.request.url2pathname
and :func:~urllib.request.pathname2url instead.
(Contributed by Barney Gale in :gh:125866.)
:mod:os:
The :func:os.popen and :func:os.spawn* <os.spawnl> functions
are now :term:soft deprecated.
They should no longer be used to write new code.
The :mod:subprocess module is recommended instead.
(Contributed by Victor Stinner in :gh:120743.)
:mod:pathlib:
:meth:!pathlib.PurePath.as_uri is now deprecated
and scheduled for removal in Python 3.19.
Use :meth:pathlib.Path.as_uri instead.
(Contributed by Barney Gale in :gh:123599.)
:mod:pdb:
The undocumented pdb.Pdb.curframe_locals attribute is now a deprecated
read-only property, which will be removed in a future version of Python.
The low overhead dynamic frame locals access added in Python 3.13 by :pep:667
means the frame locals cache reference previously stored in this attribute
is no longer needed. Derived debuggers should access
pdb.Pdb.curframe.f_locals directly in Python 3.13 and later versions.
(Contributed by Tian Gao in :gh:124369 and :gh:125951.)
:mod:symtable:
Deprecate :meth:symtable.Class.get_methods due to the lack of interest,
scheduled for removal in Python 3.16.
(Contributed by Bénédikt Tran in :gh:119698.)
:mod:tkinter:
The :class:!tkinter.Variable methods :meth:!trace_variable,
:meth:!trace_vdelete and :meth:!trace_vinfo are now deprecated.
Use :meth:!trace_add, :meth:!trace_remove and :meth:!trace_info instead.
(Contributed by Serhiy Storchaka in :gh:120220.)
:mod:urllib.parse:
Accepting objects with false values (like 0 and []) except empty
strings, bytes-like objects and None in :func:~urllib.parse.parse_qsl
and :func:~urllib.parse.parse_qs is now deprecated.
(Contributed by Serhiy Storchaka in :gh:116897.)
.. Add deprecations above alphabetically, not here at the end.
.. include:: ../deprecations/pending-removal-in-3.15.rst
.. include:: ../deprecations/pending-removal-in-3.16.rst
.. include:: ../deprecations/pending-removal-in-3.17.rst
.. include:: ../deprecations/pending-removal-in-3.18.rst
.. include:: ../deprecations/pending-removal-in-3.19.rst
.. include:: ../deprecations/pending-removal-in-3.20.rst
.. include:: ../deprecations/pending-removal-in-future.rst
Replaced the opcode :opcode:!BINARY_SUBSCR by the :opcode:BINARY_OP
opcode with the NB_SUBSCR oparg.
(Contributed by Irit Katriel in :gh:100239.)
Add the :opcode:BUILD_INTERPOLATION and :opcode:BUILD_TEMPLATE
opcodes to construct new :class:~string.templatelib.Interpolation
and :class:~string.templatelib.Template instances, respectively.
(Contributed by Lysandros Nikolaou and others in :gh:132661;
see also :ref:PEP 750: Template strings <whatsnew314-template-string-literals>).
Remove the :opcode:!BUILD_CONST_KEY_MAP opcode.
Use :opcode:BUILD_MAP instead.
(Contributed by Mark Shannon in :gh:122160.)
Replace the :opcode:!LOAD_ASSERTION_ERROR opcode with
:opcode:LOAD_COMMON_CONSTANT and add support for loading
:exc:NotImplementedError.
Add the :opcode:LOAD_FAST_BORROW and :opcode:LOAD_FAST_BORROW_LOAD_FAST_BORROW
opcodes to reduce reference counting overhead when the interpreter can prove
that the reference in the frame outlives the reference loaded onto the stack.
(Contributed by Matt Page in :gh:130704.)
Add the :opcode:LOAD_SMALL_INT opcode, which pushes a small integer
equal to the oparg to the stack.
The :opcode:!RETURN_CONST opcode is removed as it is no longer used.
(Contributed by Mark Shannon in :gh:125837.)
Add the new :opcode:LOAD_SPECIAL instruction.
Generate code for :keyword:with and :keyword:async with statements
using the new instruction.
Removed the :opcode:!BEFORE_WITH and :opcode:!BEFORE_ASYNC_WITH instructions.
(Contributed by Mark Shannon in :gh:120507.)
Add the :opcode:POP_ITER opcode to support 'virtual' iterators.
(Contributed by Mark Shannon in :gh:132554.)
Add the :opcode:!ANNOTATIONS_PLACEHOLDER pseudo instruction
to support partially executed module-level annotations with
:ref:deferred evaluation of annotations <whatsnew314-deferred-annotations>.
(Contributed by Jelle Zijlstra in :gh:130907.)
Add the :opcode:!BINARY_OP_EXTEND pseudo instruction,
which executes a pair of functions (guard and specialization functions)
accessed from the inline cache.
(Contributed by Irit Katriel in :gh:100239.)
Add three specializations for :opcode:CALL_KW;
:opcode:!CALL_KW_PY for calls to Python functions,
:opcode:!CALL_KW_BOUND_METHOD for calls to bound methods, and
:opcode:!CALL_KW_NON_PY for all other calls.
(Contributed by Mark Shannon in :gh:118093.)
Add the :opcode:JUMP_IF_TRUE and :opcode:JUMP_IF_FALSE pseudo instructions,
conditional jumps which do not impact the stack.
Replaced by the sequence COPY 1, TO_BOOL, POP_JUMP_IF_TRUE/FALSE.
(Contributed by Irit Katriel in :gh:124285.)
Add the :opcode:!LOAD_CONST_MORTAL pseudo instruction.
(Contributed by Mark Shannon in :gh:128685.)
Add the :opcode:!LOAD_CONST_IMMORTAL pseudo instruction,
which does the same as :opcode:!LOAD_CONST, but is more efficient
for immortal objects.
(Contributed by Mark Shannon in :gh:125837.)
Add the :opcode:NOT_TAKEN pseudo instruction, used by :mod:sys.monitoring
to record branch events (such as :monitoring-event:BRANCH_LEFT).
(Contributed by Mark Shannon in :gh:122548.)
.. _whatsnew314-capi-config:
Add a :ref:PyInitConfig C API <pyinitconfig_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 :ref:PyConfig C API <pyconfig_api> by adding
:c:func:PyInitConfig_AddModule which can be used to add a built-in extension
module; a feature previously referred to as the "inittab".
Add :c:func:PyConfig_Get and :c:func:PyConfig_Set functions to get and set
the current runtime configuration.
:pep:587 'Python Initialization Configuration' unified all the ways
to configure Python's initialization. This PEP also unifies the configuration
of Python's preinitialization and 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 further simplify the API.
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.)
.. seealso:: :pep:741 and :pep:587
Add :c:func:Py_PACK_VERSION and :c:func:Py_PACK_FULL_VERSION,
two new macros for bit-packing Python version numbers.
This is useful for comparisons with :c:var:Py_Version
or :c:macro:PY_VERSION_HEX.
(Contributed by Petr Viktorin in :gh:128629.)
Add :c:func:PyBytes_Join(sep, iterable) <PyBytes_Join> function,
similar to sep.join(iterable) in Python.
(Contributed by Victor Stinner in :gh:121645.)
Add functions to manipulate the configuration of the current
runtime Python interpreter
(:ref:PEP 741: Python configuration C API <whatsnew314-capi-config>):
PyConfig_GetPyConfig_GetIntPyConfig_SetPyConfig_Names(Contributed by Victor Stinner in :gh:107954.)
Add functions to configure Python initialization
(:ref:PEP 741: Python configuration C API <whatsnew314-capi-config>):
Py_InitializeFromInitConfigPyInitConfig_AddModulePyInitConfig_CreatePyInitConfig_FreePyInitConfig_FreeStrListPyInitConfig_GetErrorPyInitConfig_GetExitCodePyInitConfig_GetIntPyInitConfig_GetStrPyInitConfig_GetStrListPyInitConfig_HasOptionPyInitConfig_SetIntPyInitConfig_SetStrPyInitConfig_SetStrList(Contributed by Victor Stinner in :gh:107954.)
Add :c:func:Py_fopen function to open a file.
This works similarly to the standard C :c:func:!fopen function,
instead accepting a Python object for the path parameter
and setting an exception on error.
The corresponding new :c:func:Py_fclose function should be used
to close a file.
(Contributed by Victor Stinner in :gh:127350.)
Add :c:func:Py_HashBuffer to compute and return the hash value of a buffer.
(Contributed by Antoine Pitrou and Victor Stinner in :gh:122854.)
Add :c:func:PyImport_ImportModuleAttr and
:c:func:PyImport_ImportModuleAttrString helper functions to import a module
and get an attribute of the module.
(Contributed by Victor Stinner in :gh:128911.)
Add :c:func:PyIter_NextItem to replace :c:func:PyIter_Next,
which has an ambiguous return value.
(Contributed by Irit Katriel and Erlend Aasland in :gh:105201.)
Add :c:func:PyLong_GetSign function to get the sign of :class:int objects.
(Contributed by Sergey B Kirpichev in :gh:116560.)
Add :c:func:PyLong_IsPositive, :c:func:PyLong_IsNegative
and :c:func:PyLong_IsZero for checking if :c:type:PyLongObject
is positive, negative, or zero, respectively.
(Contributed by James Roy and Sergey B Kirpichev in :gh:126061.)
Add new functions to convert C <stdint.h> numbers to/from
Python :class:int objects:
PyLong_AsInt32PyLong_AsInt64PyLong_AsUInt32PyLong_AsUInt64PyLong_FromInt32PyLong_FromInt64PyLong_FromUInt32PyLong_FromUInt64(Contributed by Victor Stinner in :gh:120389.)
Add a new import and export API for Python :class:int objects
(:pep:757):
PyLong_GetNativeLayoutPyLong_ExportPyLong_FreeExportPyLongWriter_CreatePyLongWriter_FinishPyLongWriter_Discard(Contributed by Sergey B Kirpichev and Victor Stinner in :gh:102471.)
Add :c:func:PyMonitoring_FireBranchLeftEvent and
:c:func:PyMonitoring_FireBranchRightEvent for generating
:monitoring-event:BRANCH_LEFT and :monitoring-event:BRANCH_RIGHT
events, respectively.
(Contributed by Mark Shannon in :gh:122548.)
Add :c:func:PyType_Freeze function to make a type immutable.
(Contributed by Victor Stinner in :gh:121654.)
Add :c:func:PyType_GetBaseByToken and :c:data:Py_tp_token slot
for easier superclass identification, which attempts to resolve the
type checking issue mentioned in :pep:PEP 630 <630#type-checking>.
(Contributed in :gh:124153.)
Add a new :c:func:PyUnicode_Equal function to test if two
strings are equal.
The function is also added to the Limited C API.
(Contributed by Victor Stinner in :gh:124502.)
Add a new :c:type:PyUnicodeWriter API to create a Python :class:str
object, with the following functions:
PyUnicodeWriter_CreatePyUnicodeWriter_DecodeUTF8StatefulPyUnicodeWriter_DiscardPyUnicodeWriter_FinishPyUnicodeWriter_FormatPyUnicodeWriter_WriteASCIIPyUnicodeWriter_WriteCharPyUnicodeWriter_WriteReprPyUnicodeWriter_WriteStrPyUnicodeWriter_WriteSubstringPyUnicodeWriter_WriteUCS4PyUnicodeWriter_WriteUTF8PyUnicodeWriter_WriteWideChar(Contributed by Victor Stinner in :gh:119182.)
The k and K formats in :c:func:PyArg_ParseTuple and
similar functions now use :meth:~object.__index__ if available,
like all other integer formats.
(Contributed by Serhiy Storchaka in :gh:112068.)
Add support for a new p format unit in :c:func:Py_BuildValue
that produces a Python :class:bool object from a C integer.
(Contributed by Pablo Galindo in :issue:45325.)
Add :c:func:PyUnstable_IsImmortal for determining if
an object is :term:immortal, for debugging purposes.
(Contributed by Peter Bierma in :gh:128509.)
Add :c:func:PyUnstable_Object_EnableDeferredRefcount for enabling
deferred reference counting, as outlined in :pep:703.
Add :c:func:PyUnstable_Object_IsUniquelyReferenced as
a replacement for Py_REFCNT(op) == 1 on :term:free threaded <free threading> builds.
(Contributed by Peter Bierma in :gh:133140.)
Add :c:func:PyUnstable_Object_IsUniqueReferencedTemporary to
determine if an object is a unique temporary object on the
interpreter's operand stack.
This can be used in some cases as a replacement for checking
if :c:func:Py_REFCNT is 1 for Python objects passed
as arguments to C API functions.
(Contributed by Sam Gross in :gh:133164.)
In the limited C API version 3.14 and newer, :c:func:Py_TYPE and
:c:func:Py_REFCNT are now implemented as an opaque function call
to hide implementation details.
(Contributed by Victor Stinner in :gh:120600 and :gh:124127.)
Remove the :c:macro:PySequence_Fast_GET_SIZE,
:c:macro:PySequence_Fast_GET_ITEM,
and :c:macro:PySequence_Fast_ITEMS
macros from the limited C API, since they have always been broken
in the limited C API.
(Contributed by Victor Stinner in :gh:91417.)
.. _whatsnew314-c-api-removed:
Creating :c:data:immutable types <Py_TPFLAGS_IMMUTABLETYPE> with
mutable bases was deprecated in Python 3.12,
and now raises a :exc:TypeError.
(Contributed by Nikita Sobolev in :gh:119775.)
Remove PyDictObject.ma_version_tag member, which was deprecated
in Python 3.12.
Use the :c:func:PyDict_AddWatcher API instead.
(Contributed by Sam Gross in :gh:124296.)
Remove the private _Py_InitializeMain() function.
It was a :term:provisional API added to Python 3.8 by :pep:587.
(Contributed by Victor Stinner in :gh:129033.)
Remove the undocumented APIs :c:macro:!Py_C_RECURSION_LIMIT
and :c:member:!PyThreadState.c_recursion_remaining.
These were added in 3.13 and have been removed without deprecation.
Use :c:func:Py_EnterRecursiveCall to guard against runaway
recursion in C code.
(Removed by Petr Viktorin in :gh:133079, see also :gh:130396.)
.. _whatsnew314-c-api-deprecated:
The :c:macro:!Py_HUGE_VAL macro is now :term:soft deprecated.
Use :c:macro:!INFINITY instead.
(Contributed by Sergey B Kirpichev in :gh:120026.)
The :c:macro:!Py_IS_NAN, :c:macro:!Py_IS_INFINITY,
and :c:macro:!Py_IS_FINITE macros are now :term:soft deprecated.
Use :c:macro:!isnan, :c:macro:!isinf and :c:macro:!isfinite
instead, available from :file:math.h since C99.
(Contributed by Sergey B Kirpichev in :gh:119613.)
Non-tuple sequences are now deprecated as argument for the (items)
format unit in :c:func:PyArg_ParseTuple and other :ref:argument parsing <arg-parsing> functions if items contains format units
which store a :ref:borrowed buffer <c-arg-borrowed-buffer> or a
:term:borrowed reference.
(Contributed by Serhiy Storchaka in :gh:50333.)
The _PyMonitoring_FireBranchEvent function is now deprecated
and should be replaced with calls to
:c:func:PyMonitoring_FireBranchLeftEvent and
:c:func:PyMonitoring_FireBranchRightEvent.
The previously undocumented function :c:func:PySequence_In is
now :term:soft deprecated.
Use :c:func:PySequence_Contains instead.
(Contributed by Yuki Kobayashi in :gh:127896.)
.. Add C API deprecations above alphabetically, not here at the end.
.. include:: ../deprecations/c-api-pending-removal-in-3.15.rst
.. include:: ../deprecations/c-api-pending-removal-in-3.16.rst
.. include:: ../deprecations/c-api-pending-removal-in-3.18.rst
.. include:: ../deprecations/c-api-pending-removal-in-future.rst
.. _whatsnew314-build-changes:
:pep:776: Emscripten is now an officially supported platform at
:pep:tier 3 <11#tier-3>. As a part of this effort, more than 25 bugs in
Emscripten libc__ were fixed. Emscripten now includes support
for :mod:ctypes, :mod:termios, and :mod:fcntl, as well as
experimental support for the new :ref:default interactive shell <tut-interactive>.
(Contributed by R. Hood Chatham in :gh:127146, :gh:127683, and :gh:136931.)
__ https://emscripten.org/docs/porting/emscripten-runtime-environment.html
Official Android binary releases are now provided on python.org__.
GNU Autoconf 2.72 is now required to generate :file:configure.
(Contributed by Erlend Aasland in :gh:115765.)
wasm32-unknown-emscripten is now a :pep:11 tier 3 platform.
(Contributed by R. Hood Chatham in :gh:127146, :gh:127683, and :gh:136931.)
#pragma-based linking with python3*.lib can now be switched off
with :c:expr:Py_NO_LINK_LIB.
(Contributed by Jean-Christophe Fillion-Robin in :gh:82909.)
CPython now enables a set of recommended compiler options by default
for improved security.
Use the :option:--disable-safety :file:configure option to disable them,
or the :option:--enable-slower-safety option for a larger set
of compiler options, albeit with a performance cost.
The WITH_FREELISTS macro and --without-freelists :file:configure
option have been removed.
The new :file:configure option :option:--with-tail-call-interp
may be used to enable the experimental tail call interpreter.
See :ref:whatsnew314-tail-call-interpreter for further details.
To disable the new remote debugging support, use the
:option:--without-remote-debug :file:configure option.
This may be useful for security reasons.
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.)
.. _whatsnew314-build_details:
build-details.jsonInstallations of Python now contain a new file, :file:build-details.json.
This is a static JSON document containing build details for CPython,
to allow for introspection without needing to run code.
This is helpful for use-cases such as Python launchers, cross-compilation,
and so on.
:file:build-details.json must be installed in the platform-independent
standard library directory. This corresponds to the :ref:'stdlib' <installation_paths> :mod:sysconfig installation path,
which can be found by running sysconfig.get_path('stdlib').
.. seealso::
:pep:739 -- build-details.json 1.0 -- a static description file
for Python build details
.. _whatsnew314-no-more-pgp:
PGP (Pretty Good Privacy) signatures will not be provided
for releases of Python 3.14 or future versions.
To verify CPython artifacts, users must use Sigstore verification materials <https://www.python.org/downloads/metadata/sigstore/>__.
Releases have been signed using Sigstore_ since Python 3.11.
This change in release process was specified in :pep:761.
.. _Sigstore: https://www.sigstore.dev/
.. _whatsnew314-free-threaded-now-supported:
The free-threaded build of Python is now supported and no longer experimental.
This is the start of phase II <https://discuss.python.org/t/37075>__ where
free-threaded Python is officially supported but still optional.
The free-threading team are confident that the project is on the right path, and appreciate the continued dedication from everyone working to make free-threading ready for broader adoption across the Python community.
With these recommendations and the acceptance of this PEP, the Python developer community should broadly advertise that free-threading is a supported Python build option now and into the future, and that it will not be removed without a proper deprecation schedule.
Any decision to transition to phase III <https://discuss.python.org/t/37075>__,
with free-threading as the default or sole build of Python is still undecided,
and dependent on many factors both within CPython itself and the community.
This decision is for the future.
.. seealso::
:pep:779
PEP 779's acceptance <https://discuss.python.org/t/84319/123>__
.. _whatsnew314-jit-compiler:
The official macOS and Windows release binaries now include an experimental
just-in-time (JIT) compiler. Although it is not recommended for production
use, it can be tested by setting :envvar:PYTHON_JIT=1 <PYTHON_JIT> as an
environment variable. Downstream source builds and redistributors can use the
:option:--enable-experimental-jit=yes-off configuration option for similar
behavior.
The JIT is at an early stage and still in active development. As such, the
typical performance impact of enabling it can range from 10% slower to 20%
faster, depending on workload. To aid in testing and evaluation, a set of
introspection functions has been provided in the :data:sys._jit namespace.
:func:sys._jit.is_available can be used to determine if the current executable
supports JIT compilation, while :func:sys._jit.is_enabled can be used to tell
if JIT compilation has been enabled for the current process.
Currently, the most significant missing functionality is that native debuggers
and profilers like gdb and perf are unable to unwind through JIT frames
(Python debuggers and profilers, like :mod:pdb or :mod:profile, continue to
work without modification). Free-threaded builds do not support JIT compilation.
Please report any bugs or major performance regressions that you encounter!
.. seealso:: :pep:744
This section lists previously described changes and other bugfixes that may require changes to your code.
On Unix platforms other than macOS, forkserver is now the default
:ref:start method <multiprocessing-start-methods> for :mod:multiprocessing
and :class:~concurrent.futures.ProcessPoolExecutor, instead of fork.
See :ref:(1) <whatsnew314-concurrent-futures-start-method> and
:ref:(2) <whatsnew314-multiprocessing-start-method> for details.
If you encounter :exc:NameError\s or pickling errors coming out of
:mod:multiprocessing or :mod:concurrent.futures, see the
:ref:forkserver restrictions <multiprocessing-programming-forkserver>.
This change does not affect Windows or macOS, where :ref:'spawn' <multiprocessing-start-method-spawn> remains the default start method.
:class:functools.partial is now a method descriptor.
Wrap it in :func:staticmethod if you want to preserve the old behavior.
(Contributed by Serhiy Storchaka and Dominykas Grigonis in :gh:121027.)
The :ref:garbage collector is now incremental <whatsnew314-incremental-gc>,
which means that the behavior of :func:gc.collect changes slightly:
gc.collect(1): Performs an increment of garbage collection,
rather than collecting generation 1.!gc.collect are unchanged.The :func:locale.nl_langinfo function now temporarily sets the LC_CTYPE
locale in some cases.
This temporary change affects other threads.
(Contributed by Serhiy Storchaka in :gh:69998.)
:class:types.UnionType is now an alias for :class:typing.Union,
causing changes in some behaviors.
See :ref:above <whatsnew314-typing-union> for more details.
(Contributed by Jelle Zijlstra in :gh:105499.)
The runtime behavior of annotations has changed in various ways; see
:ref:above <whatsnew314-deferred-annotations> for details. While most code that interacts
with annotations should continue to work, some undocumented details may behave
differently.
As part of making the :mod:mimetypes CLI public,
it now exits with 1 on failure instead of 0
and 2 on incorrect command-line parameters instead of 1.
Error messages are now printed to stderr.
The \B pattern in regular expression now matches the empty string
when given as the entire pattern, which may cause behavioural changes.
On FreeBSD, :data:sys.platform no longer contains the major version number.
.. _whatsnew314-porting-annotations:
649 and :pep:749)This section contains guidance on changes that may be needed to annotations
or Python code that interacts with or introspects annotations,
due to the changes related to :ref:deferred evaluation of annotations <whatsnew314-deferred-annotations>.
In the majority of cases, working code from older versions of Python will not require any changes.
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 once you support only Python 3.14 and newer.
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 :attr:~object.__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 :func:annotationlib.get_annotations with
the :attr:~annotationlib.Format.FORWARDREF format,
as the :mod:dataclasses module now does.
The external :pypi:typing_extensions package provides partial backports
of some of the functionality of the :mod:annotationlib module,
such as the :class:~annotationlib.Format enum and
the :func:~annotationlib.get_annotations function.
These can be used to write cross-version code that takes advantage of
the new behavior in Python 3.14.
Related changes ^^^^^^^^^^^^^^^
The changes in Python 3.14 are designed to rework how :attr:!__annotations__
works at runtime while minimizing breakage to code that contains
annotations in source code and to code that reads :attr:!__annotations__.
However, if you rely on undocumented details of the annotation behavior
or on private functions in the standard library, there are many ways in which
your code may not work in Python 3.14.
To safeguard your code against future changes, only use the documented
functionality of the :mod:annotationlib module.
In particular, do not read annotations directly from the namespace dictionary
attribute of type objects.
Use :func:annotationlib.get_annotate_from_class_namespace during class
construction and :func:annotationlib.get_annotations afterwards.
In previous releases, it was sometimes possible to access class annotations from an instance of an annotated class. This behavior was undocumented and accidental, and will no longer work in Python 3.14.
from __future__ import annotations
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
In Python 3.7, :pep:563 introduced the from __future__ import annotations
:ref:future statement <future>, which turns all annotations into strings.
However, this statement is now deprecated and it is expected to be removed in a future version of Python. This removal will not happen until after Python 3.13 reaches its end of life in 2029, being the last version of Python without support for deferred evaluation of annotations.
In Python 3.14, the behavior of code using from __future__ import annotations
is unchanged.
:c:func:Py_Finalize now deletes all interned strings. This
is backwards incompatible to any C extension that holds onto an interned
string after a call to :c:func:Py_Finalize and is then reused after a
call to :c:func:Py_Initialize. Any issues arising from this behavior will
normally result in crashes during the execution of the subsequent call to
:c:func:Py_Initialize from accessing uninitialized memory. To fix, use
an address sanitizer to identify any use-after-free coming from
an interned string and deallocate it during module shutdown.
(Contributed by Eddie Elizondo in :gh:113601.)
The :ref:Unicode Exception Objects <unicodeexceptions> C API
now raises a :exc:TypeError if its exception argument is not
a :exc:UnicodeError object.
(Contributed by Bénédikt Tran in :gh:127691.)
.. _whatsnew314-refcount:
The interpreter internally avoids some reference count modifications when
loading objects onto the operands stack by :term:borrowing <borrowed reference>
references when possible. This can lead to smaller reference count values
compared to previous Python versions. C API extensions that checked
:c:func:Py_REFCNT of 1 to determine if an function argument is not
referenced by any other code should instead use
:c:func:PyUnstable_Object_IsUniqueReferencedTemporary as a safer replacement.
Private functions promoted to public C APIs:
_PyBytes_Join(): :c:func:PyBytes_Join_PyLong_IsNegative(): :c:func:PyLong_IsNegative_PyLong_IsPositive(): :c:func:PyLong_IsPositive_PyLong_IsZero(): :c:func:PyLong_IsZero_PyLong_Sign(): :c:func:PyLong_GetSign_PyUnicodeWriter_Dealloc(): :c:func:PyUnicodeWriter_Discard_PyUnicodeWriter_Finish(): :c:func:PyUnicodeWriter_Finish_PyUnicodeWriter_Init(): use :c:func:PyUnicodeWriter_Create_PyUnicodeWriter_Prepare(): (no replacement)_PyUnicodeWriter_PrepareKind(): (no replacement)_PyUnicodeWriter_WriteChar(): :c:func:PyUnicodeWriter_WriteChar_PyUnicodeWriter_WriteStr(): :c:func:PyUnicodeWriter_WriteStr_PyUnicodeWriter_WriteSubstring(): :c:func:PyUnicodeWriter_WriteSubstring_PyUnicode_EQ(): :c:func:PyUnicode_Equal_PyUnicode_Equal(): :c:func:PyUnicode_Equal_Py_GetConfig(): :c:func:PyConfig_Get and :c:func:PyConfig_GetInt_Py_HashBytes(): :c:func:Py_HashBuffer_Py_fopen_obj(): :c:func:Py_fopenPyMutex_IsLocked() : :c:func:PyMutex_IsLockedThe pythoncapi-compat project_ can be used to get most of these new
functions on Python 3.13 and older.
.. _pythoncapi-compat project: https://github.com/python/pythoncapi-compat/