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What's new in Python 3.14

Editors : Adam Turner and Hugo van Kemenade

* 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 12345{.interpreted-text role="gh"}.)

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 changelog <changelog>{.interpreted-text role="ref"}.

::: seealso 745{.interpreted-text role="pep"} -- Python 3.14 release schedule :::

Summary -- Release highlights

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 template string literals <whatsnew314-template-string-literals>{.interpreted-text role="ref"}, deferred evaluation of annotations <whatsnew314-deferred-annotations>{.interpreted-text role="ref"}, and support for subinterpreters <whatsnew314-multiple-interpreters>{.interpreted-text role="ref"} in the standard library.

The library changes include significantly improved capabilities for introspection in asyncio <whatsnew314-asyncio-introspection>{.interpreted-text role="ref"}, support for Zstandard <whatsnew314-zstandard>{.interpreted-text role="ref"} via a new compression.zstd{.interpreted-text role="mod"} 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 Library Reference <library-index>{.interpreted-text role="ref"} and Language Reference <reference-index>{.interpreted-text role="ref"}. 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.

Interpreter improvements:

649{.interpreted-text role="pep"} and 749{.interpreted-text role="pep"}: Deferred evaluation of annotations <whatsnew314-deferred-annotations>{.interpreted-text role="ref"}
734{.interpreted-text role="pep"}: Multiple interpreters in the standard library <whatsnew314-multiple-interpreters>{.interpreted-text role="ref"}
750{.interpreted-text role="pep"}: Template strings <whatsnew314-template-string-literals>{.interpreted-text role="ref"}
758{.interpreted-text role="pep"}: Allow except and except* expressions without brackets <whatsnew314-bracketless-except>{.interpreted-text role="ref"}
765{.interpreted-text role="pep"}: Control flow in finally blocks <whatsnew314-finally-syntaxwarning>{.interpreted-text role="ref"}
768{.interpreted-text role="pep"}: Safe external debugger interface for CPython <whatsnew314-remote-debugging>{.interpreted-text role="ref"}
A new type of interpreter <whatsnew314-tail-call-interpreter>{.interpreted-text role="ref"}
Free-threaded mode improvements <whatsnew314-free-threaded-cpython>{.interpreted-text role="ref"}
Improved error messages <whatsnew314-improved-error-messages>{.interpreted-text role="ref"}
Incremental garbage collection <whatsnew314-incremental-gc>{.interpreted-text role="ref"}

Significant improvements in the standard library:

784{.interpreted-text role="pep"}: Zstandard support in the standard library <whatsnew314-zstandard>{.interpreted-text role="ref"}
whatsnew314-asyncio-introspection{.interpreted-text role="ref"}
whatsnew314-concurrent-warnings-control{.interpreted-text role="ref"}
Syntax highlighting in the default interactive shell <whatsnew314-pyrepl-highlighting>{.interpreted-text role="ref"}, and color output in several standard library CLIs

C API improvements:

741{.interpreted-text role="pep"}: Python configuration C API <whatsnew314-capi-config>{.interpreted-text role="ref"}

Platform support:

776{.interpreted-text role="pep"}: Emscripten is now an officially supported platform <whatsnew314-build-changes>{.interpreted-text role="ref"}, at tier 3 <11#tier-3>{.interpreted-text role="pep"}.

Release changes:

779{.interpreted-text role="pep"}: Free-threaded Python is officially supported <whatsnew314-free-threaded-now-supported>{.interpreted-text role="ref"}
761{.interpreted-text role="pep"}: PGP signatures have been discontinued for official releases <whatsnew314-no-more-pgp>{.interpreted-text role="ref"}
Windows and macOS binary releases now support the experimental just-in-time compiler <whatsnew314-jit-compiler>{.interpreted-text role="ref"}
Binary releases for Android are now provided <whatsnew314-build-changes>{.interpreted-text role="ref"}

New features

`649`{.interpreted-text role="pep"} & `749`{.interpreted-text role="pep"}: Deferred evaluation of annotations {#whatsnew314-deferred-annotations}

The annotations <annotation>{.interpreted-text role="term"} on functions, classes, and modules are no longer evaluated eagerly. Instead, annotations are stored in special-purpose annotate functions <annotate function>{.interpreted-text role="term"} 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 annotationlib{.interpreted-text role="mod"} module provides tools for inspecting deferred annotations. Annotations may be evaluated in the ~annotationlib.Format.VALUE{.interpreted-text role="attr"} format (which evaluates annotations to runtime values, similar to the behavior in earlier Python versions), the ~annotationlib.Format.FORWARDREF{.interpreted-text role="attr"} format (which replaces undefined names with special markers), and the ~annotationlib.Format.STRING{.interpreted-text role="attr"} 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 porting <whatsnew314-porting-annotations>{.interpreted-text role="ref"} 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 749{.interpreted-text role="pep"} and 119180{.interpreted-text role="gh"}; 649{.interpreted-text role="pep"} was written by Larry Hastings.)

::: seealso

649{.interpreted-text role="pep"}

: Deferred Evaluation Of Annotations Using Descriptors

749{.interpreted-text role="pep"}

: Implementing PEP 649 :::

`734`{.interpreted-text role="pep"}: Multiple interpreters in the standard library {#whatsnew314-multiple-interpreters}

The 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 C-API <sub-interpreter-support>{.interpreted-text role="ref"}.

That limitation is removed in Python 3.14, with the new concurrent.interpreters{.interpreted-text role="mod"} module.

There are at least two notable reasons why using multiple interpreters has significant benefits:

they support a new (to Python), human-friendly concurrency model
true multi-core parallelism

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, threading{.interpreted-text role="mod"}), 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 684{.interpreted-text role="pep"}). This unlocks a variety of CPU-intensive use cases for Python that were limited by the GIL{.interpreted-text role="term"}.

Using multiple interpreters is similar in many ways to multiprocessing{.interpreted-text role="mod"}, 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.

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:

starting each interpreter has not been optimized yet
each interpreter uses more memory than necessary (work continues on extensive internal sharing between interpreters)
there aren't many options yet for truly sharing objects or other data between interpreters (other than memoryview{.interpreted-text role="type"})
many third-party extension modules on PyPI are not yet compatible with multiple interpreters (all standard library extension modules are compatible)
the approach to writing applications that use multiple isolated interpreters is mostly unfamiliar to Python users, for now

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 GIL{.interpreted-text role="term"}. 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 isolating-extensions-howto{.interpreted-text role="ref"}. Isolating a module has a lot of overlap with what is required to support free-threading <whatsnew314-free-threaded-cpython>{.interpreted-text role="ref"}, so the ongoing work in the community in that area will help accelerate support for multiple interpreters.

Also added in 3.14: concurrent.futures.InterpreterPoolExecutor <whatsnew314-concurrent-futures-interp-pool>{.interpreted-text role="ref"}.

(Contributed by Eric Snow in 134939{.interpreted-text role="gh"}.)

::: seealso 734{.interpreted-text role="pep"} :::

`750`{.interpreted-text role="pep"}: Template string literals {#whatsnew314-template-string-literals}

Template 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 str{.interpreted-text role="class"}.

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'> :::

~string.templatelib.Template{.interpreted-text role="class"} objects provide access to the static and interpolated (in curly braces) parts of a string before they are combined. Iterate over !Template{.interpreted-text role="class"} 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 !Template{.interpreted-text role="class"} instances. For example, here's a function that renders static parts lowercase and ~string.templatelib.Interpolation{.interpreted-text role="class"} instances uppercase:

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 !Template{.interpreted-text role="class"} instances distinguish between static strings and interpolations at runtime, they can be useful for sanitising user input. Writing a !html{.interpreted-text role="func"} 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 !html{.interpreted-text role="func"} function could accept a !dict{.interpreted-text role="class"} of HTML attributes directly in the template:

attributes = {'src': 'limburger.jpg', 'alt': 'lovely cheese'}
template = t'<img {attributes}>'
assert html(template) == '<img src="/spaces/ITookAPill/PyComp/resolve/main/python_doc_md/Beginner/whatsnew/limburger.jpg" alt="lovely cheese" />'

Of course, template processing code does not need to return a string-like result. An even more advanced !html{.interpreted-text role="func"} 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 132661{.interpreted-text role="gh"}.)

::: seealso 750{.interpreted-text role="pep"}. :::

`768`{.interpreted-text role="pep"}: Safe external debugger interface {#whatsnew314-remote-debugging}

Python 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 sys.remote_exec{.interpreted-text role="func"} function. For example:

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()})')

# Execute in process with PID 1234
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:

A PYTHON_DISABLE_REMOTE_DEBUG{.interpreted-text role="envvar"} environment variable.
A -X disable-remote-debug{.interpreted-text role="option"} command-line option.
A --without-remote-debug{.interpreted-text role="option"} configure flag to completely disable the feature at build time.

(Contributed by Pablo Galindo Salgado, Matt Wozniski, and Ivona Stojanovic in 131591{.interpreted-text role="gh"}.)

::: seealso 768{.interpreted-text role="pep"}. :::

A new type of interpreter {#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 recommendeded when using the new interpreter as it is the only configuration that has been tested and validated for improved performance. For further information, see --with-tail-call-interp{.interpreted-text role="option"}.

:::: note ::: title 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. ::::

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

Free-threaded mode improvements {#whatsnew314-free-threaded-cpython}

CPython's free-threaded mode (703{.interpreted-text role="pep"}), 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 (659{.interpreted-text role="pep"}) 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 sysconfig.get_config_var{.interpreted-text role="func"}.

The new -X context_aware_warnings <-X>{.interpreted-text role="option"} flag controls if concurrent safe warnings control <whatsnew314-concurrent-warnings-control>{.interpreted-text role="ref"} is enabled. The flag defaults to true for the free-threaded build and false for the GIL-enabled build.

A new ~sys.flags.thread_inherit_context{.interpreted-text role="data"} flag has been added, which if enabled means that threads created with threading.Thread{.interpreted-text role="class"} start with a copy of the ~contextvars.Context(){.interpreted-text role="class"} of the caller of ~threading.Thread.start{.interpreted-text role="meth"}. Most significantly, this makes the warning filtering context established by ~warnings.catch_warnings{.interpreted-text role="class"} be "inherited" by threads (or asyncio tasks) started within that context. It also affects other modules that use context variables, such as the decimal{.interpreted-text role="mod"} 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.)

Improved error messages {#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:
```
>>> 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 132449{.interpreted-text role="gh"}.)

elif{.interpreted-text role="keyword"} statements that follow an else{.interpreted-text role="keyword"} block now have a specific error message. (Contributed by Steele Farnsworth in 129902{.interpreted-text role="gh"}.)

>>> 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 if_expr{.interpreted-text role="ref"} after else{.interpreted-text role="keyword"}, or one of pass{.interpreted-text role="keyword"}, break{.interpreted-text role="keyword"}, or continue{.interpreted-text role="keyword"} is passed before if{.interpreted-text role="keyword"}, then the error message highlights where the ~python-grammar:expression{.interpreted-text role="token"} is required. (Contributed by Sergey Miryanov in 129515{.interpreted-text role="gh"}.)
```
>>> 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 88535{.interpreted-text role="gh"}.)
```
>>> "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 133197{.interpreted-text role="gh"}.)
```
>>> 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:
- Imports: import ... as ...
- From imports: from ... import ... as ...
- Except handlers: except ... as ...
- Pattern-match cases: case ... as ...
(Contributed by Nikita Sobolev in 123539{.interpreted-text role="gh"}, 123562{.interpreted-text role="gh"}, and 123440{.interpreted-text role="gh"}.)

Improved error message when trying to add an instance of an unhashable type to a dict{.interpreted-text role="class"} or set{.interpreted-text role="class"}. (Contributed by CF Bolz-Tereick and Victor Stinner in 132828{.interpreted-text role="gh"}.)

>>> 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 async with{.interpreted-text role="keyword"} instead of with{.interpreted-text role="keyword"}, and vice versa for the asynchronous context manager protocol. (Contributed by Bénédikt Tran in 128398{.interpreted-text role="gh"}.)

`784`{.interpreted-text role="pep"}: Zstandard support in the standard library {#whatsnew314-zstandard}

The new !compression{.interpreted-text role="mod"} package contains modules !compression.lzma{.interpreted-text role="mod"}, !compression.bz2{.interpreted-text role="mod"}, !compression.gzip{.interpreted-text role="mod"} and !compression.zlib{.interpreted-text role="mod"} which re-export the lzma{.interpreted-text role="mod"}, bz2{.interpreted-text role="mod"}, gzip{.interpreted-text role="mod"} and zlib{.interpreted-text role="mod"} modules respectively. The new import names under !compression{.interpreted-text role="mod"} 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 !compression.zstd{.interpreted-text role="mod"} module provides compression and decompression APIs for the Zstandard format via bindings to Meta's zstd library. Zstandard is a widely adopted, highly efficient, and fast compression format. In addition to the APIs introduced in !compression.zstd{.interpreted-text role="mod"}, support for reading and writing Zstandard compressed archives has been added to the tarfile{.interpreted-text role="mod"}, zipfile{.interpreted-text role="mod"}, and shutil{.interpreted-text role="mod"} modules.

Here's an example of using the new module to compress some data:

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 !lzma{.interpreted-text role="mod"} and !bz2{.interpreted-text role="mod"} modules.

(Contributed by Emma Harper Smith, Adam Turner, Gregory P. Smith, Tomas Roun, Victor Stinner, and Rogdham in 132983{.interpreted-text role="gh"}.)

::: seealso 784{.interpreted-text role="pep"}. :::

Asyncio introspection capabilities {#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:

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:

python -m asyncio ps 12345

tid        task id              task name            coroutine stack                                    awaiter chain                                      awaiter name    awaiter id
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
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:

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:

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 91048{.interpreted-text role="gh"}.)

Concurrent safe warnings control {#whatsnew314-concurrent-warnings-control}

The warnings.catch_warnings{.interpreted-text role="class"} context manager will now optionally use a context variable for warning filters. This is enabled by setting the ~sys.flags.context_aware_warnings{.interpreted-text role="data"} flag, either with the -X command-line option or an environment variable. This gives predictable warnings control when using ~warnings.catch_warnings{.interpreted-text role="class"} 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 130010{.interpreted-text role="gh"}.)

Other language changes

All Windows code pages are now supported as 'cpXXX' codecs on Windows. (Contributed by Serhiy Storchaka in 123803{.interpreted-text role="gh"}.)
Implement mixed-mode arithmetic rules combining real and complex numbers as specified by the C standard since C99. (Contributed by Sergey B Kirpichev in 69639{.interpreted-text role="gh"}.)
More syntax errors are now detected regardless of optimisation and the -O{.interpreted-text role="option"} command-line option. This includes writes to __debug__, incorrect use of await{.interpreted-text role="keyword"}, and asynchronous comprehensions outside asynchronous functions. For example, python -O -c 'assert (__debug__ := 1)' or python -O -c 'assert await 1' now produce SyntaxError{.interpreted-text role="exc"}s. (Contributed by Irit Katriel and Jelle Zijlstra in 122245{.interpreted-text role="gh"} & 121637{.interpreted-text role="gh"}.)
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 132284{.interpreted-text role="gh"}.)

Built-ins

The bytes.fromhex{.interpreted-text role="meth"} and bytearray.fromhex{.interpreted-text role="meth"} methods now accept ASCII bytes{.interpreted-text role="class"} and bytes-like objects <bytes-like object>{.interpreted-text role="term"}. (Contributed by Daniel Pope in 129349{.interpreted-text role="gh"}.)
Add class methods float.from_number{.interpreted-text role="meth"} and complex.from_number{.interpreted-text role="meth"} to convert a number to float{.interpreted-text role="class"} or complex{.interpreted-text role="class"} type correspondingly. They raise a TypeError{.interpreted-text role="exc"} if the argument is not a real number. (Contributed by Serhiy Storchaka in 84978{.interpreted-text role="gh"}.)
Support underscore and comma as thousands separators in the fractional part for floating-point presentation types of the new-style string formatting (with format{.interpreted-text role="func"} or f-strings{.interpreted-text role="ref"}). (Contributed by Sergey B Kirpichev in 87790{.interpreted-text role="gh"}.)
The int{.interpreted-text role="func"} function no longer delegates to ~object.__trunc__{.interpreted-text role="meth"}. Classes that want to support conversion to !int{.interpreted-text role="func"} must implement either ~object.__int__{.interpreted-text role="meth"} or ~object.__index__{.interpreted-text role="meth"}. (Contributed by Mark Dickinson in 119743{.interpreted-text role="gh"}.)
The map{.interpreted-text role="func"} function now has an optional keyword-only strict flag like zip{.interpreted-text role="func"} to check that all the iterables are of equal length. (Contributed by Wannes Boeykens in 119793{.interpreted-text role="gh"}.)
The memoryview{.interpreted-text role="class"} type now supports subscription, making it a generic type{.interpreted-text role="term"}. (Contributed by Brian Schubert in 126012{.interpreted-text role="gh"}.)
Using NotImplemented{.interpreted-text role="data"} in a boolean context will now raise a TypeError{.interpreted-text role="exc"}. This has raised a DeprecationWarning{.interpreted-text role="exc"} since Python 3.9. (Contributed by Jelle Zijlstra in 118767{.interpreted-text role="gh"}.)
Three-argument pow{.interpreted-text role="func"} now tries calling ~object.__rpow__{.interpreted-text role="meth"} if necessary. Previously it was only called in two-argument !pow{.interpreted-text role="func"} and the binary power operator. (Contributed by Serhiy Storchaka in 130104{.interpreted-text role="gh"}.)
super{.interpreted-text role="class"} objects are now copyable <copy>{.interpreted-text role="mod"} and pickleable <pickle>{.interpreted-text role="mod"}. (Contributed by Serhiy Storchaka in 125767{.interpreted-text role="gh"}.)

Command line and environment

The import time flag can now track modules that are already loaded ('cached'), via the new -X importtime=2 <-X>{.interpreted-text role="option"}. 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 118655{.interpreted-text role="gh"}.)
The command-line option -c{.interpreted-text role="option"} now automatically dedents its code argument before execution. The auto-dedentation behavior mirrors textwrap.dedent{.interpreted-text role="func"}. (Contributed by Jon Crall and Steven Sun in 103998{.interpreted-text role="gh"}.)
!-J{.interpreted-text role="option"} is no longer a reserved flag for Jython, and now has no special meaning. (Contributed by Adam Turner in 133336{.interpreted-text role="gh"}.)

PEP 758: Allow `except` and `except*` expressions without brackets {#whatsnew314-bracketless-except}

The except{.interpreted-text role="keyword"} and except* <except_star>{.interpreted-text role="keyword"} expressions now allow brackets to be omitted when there are multiple exception types and the as clause is not used. For example:

try:
    connect_to_server()
except TimeoutError, ConnectionRefusedError:
    print('The network has ceased to be!')

(Contributed by Pablo Galindo and Brett Cannon in 758{.interpreted-text role="pep"} and 131831{.interpreted-text role="gh"}.)

PEP 765: Control flow in `finally`{.interpreted-text role="keyword"} blocks {#whatsnew314-finally-syntaxwarning}

The compiler now emits a SyntaxWarning{.interpreted-text role="exc"} when a return{.interpreted-text role="keyword"}, break{.interpreted-text role="keyword"}, or continue{.interpreted-text role="keyword"} statement have the effect of leaving a finally{.interpreted-text role="keyword"} block. This change is specified in 765{.interpreted-text role="pep"}.

In situations where this change is inconvenient (such as those where the warnings are redundant due to code linting), the warning filter <warning-filter>{.interpreted-text role="ref"} 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 warnings{.interpreted-text role="mod"} 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 130080{.interpreted-text role="gh"}.)

Incremental garbage collection {#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 gc.collect{.interpreted-text role="func"} 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 !gc.collect{.interpreted-text role="func"} changes slightly:

gc.collect(1): Performs an increment of garbage collection, rather than collecting generation 1.
Other calls to !gc.collect{.interpreted-text role="func"} are unchanged.

(Contributed by Mark Shannon in 108362{.interpreted-text role="gh"}.)

Default interactive shell

::: {#whatsnew314-pyrepl-highlighting}

The default interactive{.interpreted-text role="term"} shell now highlights Python syntax. The feature is enabled by default, save if PYTHON_BASIC_REPL{.interpreted-text role="envvar"} or any other environment variable that disables colour is set. See using-on-controlling-color{.interpreted-text role="ref"} 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 !_colorize.set_theme{.interpreted-text role="func"}. This can be called interactively or in the PYTHONSTARTUP{.interpreted-text role="envvar"} script. Note that this function has no stability guarantees, and may change or be removed.

(Contributed by Łukasz Langa in 131507{.interpreted-text role="gh"}.)
The default interactive{.interpreted-text role="term"} shell now supports import auto-completion. This means that typing import co and pressing <Tab>{.interpreted-text role="kbd"} 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 69605{.interpreted-text role="gh"}.) :::

New modules

annotationlib{.interpreted-text role="mod"}: For introspecting annotations <annotation>{.interpreted-text role="term"}. See PEP 749 <whatsnew314-deferred-annotations>{.interpreted-text role="ref"} for more details. (Contributed by Jelle Zijlstra in 119180{.interpreted-text role="gh"}.)
compression{.interpreted-text role="mod"} (including compression.zstd{.interpreted-text role="mod"}): A package for compression-related modules, including a new module to support the Zstandard compression format. See PEP 784 <whatsnew314-zstandard>{.interpreted-text role="ref"} for more details. (Contributed by Emma Harper Smith, Adam Turner, Gregory P. Smith, Tomas Roun, Victor Stinner, and Rogdham in 132983{.interpreted-text role="gh"}.)
concurrent.interpreters{.interpreted-text role="mod"}: Support for multiple interpreters in the standard library. See PEP 734 <whatsnew314-multiple-interpreters>{.interpreted-text role="ref"} for more details. (Contributed by Eric Snow in 134939{.interpreted-text role="gh"}.)
string.templatelib{.interpreted-text role="mod"}: Support for template string literals (t-strings). See PEP 750 <whatsnew314-template-string-literals>{.interpreted-text role="ref"} 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 132661{.interpreted-text role="gh"}.)

Improved modules

argparse

The default value of the program name <prog>{.interpreted-text role="ref"} for argparse.ArgumentParser{.interpreted-text role="class"} now reflects the way the Python interpreter was instructed to find the __main__ module code. (Contributed by Serhiy Storchaka and Alyssa Coghlan in 66436{.interpreted-text role="gh"}.)
Introduced the optional suggest_on_error parameter to argparse.ArgumentParser{.interpreted-text role="class"}, enabling suggestions for argument choices and subparser names if mistyped by the user. (Contributed by Savannah Ostrowski in 124456{.interpreted-text role="gh"}.)
Enable color for help text, which can be disabled with the optional color parameter to argparse.ArgumentParser{.interpreted-text role="class"}. This can also be controlled by environment variables <using-on-controlling-color>{.interpreted-text role="ref"}. (Contributed by Hugo van Kemenade in 130645{.interpreted-text role="gh"}.)

ast

Add ~ast.compare{.interpreted-text role="func"}, a function for comparing two ASTs. (Contributed by Batuhan Taskaya and Jeremy Hylton in 60191{.interpreted-text role="gh"}.)
Add support for copy.replace{.interpreted-text role="func"} for AST nodes. (Contributed by Bénédikt Tran in 121141{.interpreted-text role="gh"}.)
Docstrings are now removed from an optimized AST in optimization level 2. (Contributed by Irit Katriel in 123958{.interpreted-text role="gh"}.)
The repr{.interpreted-text role="func"} output for AST nodes now includes more information. (Contributed by Tomas Roun in 116022{.interpreted-text role="gh"}.)
When called with an AST as input, the ~ast.parse{.interpreted-text role="func"} function now always verifies that the root node type is appropriate. (Contributed by Irit Katriel in 130139{.interpreted-text role="gh"}.)
Add new options to the command-line interface: --feature-version <ast --feature-version>{.interpreted-text role="option"}, --optimize <ast --optimize>{.interpreted-text role="option"}, and --show-empty <ast --show-empty>{.interpreted-text role="option"}. (Contributed by Semyon Moroz in 133367{.interpreted-text role="gh"}.)

asyncio

The function and methods named !create_task{.interpreted-text role="func"} now take an arbitrary list of keyword arguments. All keyword arguments are passed to the ~asyncio.Task{.interpreted-text role="class"} constructor or the custom task factory. (See ~asyncio.loop.set_task_factory{.interpreted-text role="meth"} 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: asyncio.create_task{.interpreted-text role="meth"}, asyncio.loop.create_task{.interpreted-text role="meth"}, asyncio.TaskGroup.create_task{.interpreted-text role="meth"}.

(Contributed by Thomas Grainger in 128307{.interpreted-text role="gh"}.)
There are two new utility functions for introspecting and printing a program's call graph: ~asyncio.capture_call_graph{.interpreted-text role="func"} and ~asyncio.print_call_graph{.interpreted-text role="func"}. See Asyncio introspection capabilities <whatsnew314-asyncio-introspection>{.interpreted-text role="ref"} for more details. (Contributed by Yury Selivanov, Pablo Galindo Salgado, and Łukasz Langa in 91048{.interpreted-text role="gh"}.)

calendar

::: {#whatsnew314-color-calendar}

By default, today's date is highlighted in color in calendar{.interpreted-text role="mod"}'s command-line <calendar-cli>{.interpreted-text role="ref"} text output. This can be controlled by environment variables <using-on-controlling-color>{.interpreted-text role="ref"}. (Contributed by Hugo van Kemenade in 128317{.interpreted-text role="gh"}.) :::

concurrent.futures

::: {#whatsnew314-concurrent-futures-interp-pool}

Add a new executor class, ~concurrent.futures.InterpreterPoolExecutor{.interpreted-text role="class"}, 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 ~concurrent.interpreters{.interpreted-text role="mod"} module introduced by PEP 734 <whatsnew314-multiple-interpreters>{.interpreted-text role="ref"}. (Contributed by Eric Snow in 124548{.interpreted-text role="gh"}.)

:::

::: {#whatsnew314-concurrent-futures-start-method}

On Unix platforms other than macOS, 'forkserver' <multiprocessing-start-method-forkserver>{.interpreted-text role="ref"} is now the default start method <multiprocessing-start-methods>{.interpreted-text role="ref"} for ~concurrent.futures.ProcessPoolExecutor{.interpreted-text role="class"} (replacing 'fork' <multiprocessing-start-method-fork>{.interpreted-text role="ref"}). This change does not affect Windows or macOS, where 'spawn' <multiprocessing-start-method-spawn>{.interpreted-text role="ref"} 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 ~concurrent.futures.ProcessPoolExecutor{.interpreted-text role="class"}.

See forkserver restrictions <multiprocessing-programming-forkserver>{.interpreted-text role="ref"} 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 pickled <pickle>{.interpreted-text role="mod"}.

(Contributed by Gregory P. Smith in 84559{.interpreted-text role="gh"}.)
Add two new methods to ~concurrent.futures.ProcessPoolExecutor{.interpreted-text role="class"}, ~concurrent.futures.ProcessPoolExecutor.terminate_workers{.interpreted-text role="meth"} and ~concurrent.futures.ProcessPoolExecutor.kill_workers{.interpreted-text role="meth"}, as ways to terminate or kill all living worker processes in the given pool. (Contributed by Charles Machalow in 130849{.interpreted-text role="gh"}.)
Add the optional buffersize parameter to Executor.map <concurrent.futures.Executor.map>{.interpreted-text role="meth"} 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 74028{.interpreted-text role="gh"}.) :::

configparser

!configparser{.interpreted-text role="mod"} will no longer write config files it cannot read, to improve security. Attempting to ~configparser.ConfigParser.write{.interpreted-text role="meth"} keys containing delimiters or beginning with the section header pattern will raise an ~configparser.InvalidWriteError{.interpreted-text role="class"}. (Contributed by Jacob Lincoln in 129270{.interpreted-text role="gh"}.)

contextvars

Support the context manager{.interpreted-text role="term"} protocol for ~contextvars.Token{.interpreted-text role="class"} objects. (Contributed by Andrew Svetlov in 129889{.interpreted-text role="gh"}.)

ctypes

The layout of bit fields <ctypes-bit-fields-in-structures-unions>{.interpreted-text role="ref"} in ~ctypes.Structure{.interpreted-text role="class"} and ~ctypes.Union{.interpreted-text role="class"} objects is now a closer match to platform defaults (GCC/Clang or MSVC). In particular, fields no longer overlap. (Contributed by Matthias Görgens in 97702{.interpreted-text role="gh"}.)
The .Structure._layout_{.interpreted-text role="attr"} class attribute can now be set to help match a non-default ABI. (Contributed by Petr Viktorin in 97702{.interpreted-text role="gh"}.)
The class of ~ctypes.Structure{.interpreted-text role="class"}/~ctypes.Union{.interpreted-text role="class"} field descriptors is now available as ~ctypes.CField{.interpreted-text role="class"}, and has new attributes to aid debugging and introspection. (Contributed by Petr Viktorin in 128715{.interpreted-text role="gh"}.)
On Windows, the ~ctypes.COMError{.interpreted-text role="exc"} exception is now public. (Contributed by Jun Komoda in 126686{.interpreted-text role="gh"}.)
On Windows, the ~ctypes.CopyComPointer{.interpreted-text role="func"} function is now public. (Contributed by Jun Komoda in 127275{.interpreted-text role="gh"}.)
Add ~ctypes.memoryview_at{.interpreted-text role="func"}, a function to create a memoryview{.interpreted-text role="class"} object that refers to the supplied pointer and length. This works like ctypes.string_at{.interpreted-text role="func"} 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 112018{.interpreted-text role="gh"}.)
Complex types, ~ctypes.c_float_complex{.interpreted-text role="class"}, ~ctypes.c_double_complex{.interpreted-text role="class"}, and ~ctypes.c_longdouble_complex{.interpreted-text role="class"}, are now available if both the compiler and the libffi library support complex C types. (Contributed by Sergey B Kirpichev in 61103{.interpreted-text role="gh"}.)
Add ctypes.util.dllist{.interpreted-text role="func"} for listing the shared libraries loaded by the current process. (Contributed by Brian Ward in 119349{.interpreted-text role="gh"}.)
Move ctypes.POINTER{.interpreted-text role="func"} types cache from a global internal cache (_pointer_type_cache) to the _CData.__pointer_type__ <ctypes._CData.__pointer_type__>{.interpreted-text role="attr"} attribute of the corresponding !ctypes{.interpreted-text role="mod"} types. This will stop the cache from growing without limits in some situations. (Contributed by Sergey Miryanov in 100926{.interpreted-text role="gh"}.)
The ~ctypes.py_object{.interpreted-text role="class"} type now supports subscription, making it a generic type{.interpreted-text role="term"}. (Contributed by Brian Schubert in 132168{.interpreted-text role="gh"}.)
!ctypes{.interpreted-text role="mod"} now supports free-threading builds <free threading>{.interpreted-text role="term"}. (Contributed by Kumar Aditya and Peter Bierma in 127945{.interpreted-text role="gh"}.)

curses

Add the ~curses.assume_default_colors{.interpreted-text role="func"} function, a refinement of the ~curses.use_default_colors{.interpreted-text role="func"} function which allows changing the color pair 0. (Contributed by Serhiy Storchaka in 133139{.interpreted-text role="gh"}.)

datetime

Add the ~datetime.date.strptime{.interpreted-text role="meth"} method to the datetime.date{.interpreted-text role="class"} and datetime.time{.interpreted-text role="class"} classes. (Contributed by Wannes Boeykens in 41431{.interpreted-text role="gh"}.)

decimal

Add .Decimal.from_number{.interpreted-text role="meth"} as an alternative constructor for ~decimal.Decimal{.interpreted-text role="class"}. (Contributed by Serhiy Storchaka in 121798{.interpreted-text role="gh"}.)
Expose ~decimal.IEEEContext{.interpreted-text role="func"} to support creation of contexts corresponding to the IEEE 754 (2008) decimal interchange formats. (Contributed by Sergey B Kirpichev in 53032{.interpreted-text role="gh"}.)

difflib

Comparison pages with highlighted changes generated by the ~difflib.HtmlDiff{.interpreted-text role="class"} class now support 'dark mode'. (Contributed by Jiahao Li in 129939{.interpreted-text role="gh"}.)

dis

Add support for rendering full source location information of instructions <dis.Instruction>{.interpreted-text role="class"}, rather than only the line number. This feature is added to the following interfaces via the show_positions keyword argument:
- dis.Bytecode{.interpreted-text role="class"}
- dis.dis{.interpreted-text role="func"}
- dis.distb{.interpreted-text role="func"}
- dis.disassemble{.interpreted-text role="func"}
This feature is also exposed via dis --show-positions{.interpreted-text role="option"}. (Contributed by Bénédikt Tran in 123165{.interpreted-text role="gh"}.)
Add the dis --specialized{.interpreted-text role="option"} command-line option to show specialized bytecode. (Contributed by Bénédikt Tran in 127413{.interpreted-text role="gh"}.)

errno

Add the ~errno.EHWPOISON{.interpreted-text role="data"} error code constant. (Contributed by James Roy in 126585{.interpreted-text role="gh"}.)

faulthandler

Add support for printing the C stack trace on systems that support it <c-stack-compatibility>{.interpreted-text role="ref"} via the new ~faulthandler.dump_c_stack{.interpreted-text role="func"} function or via the c_stack argument in faulthandler.enable{.interpreted-text role="func"}. (Contributed by Peter Bierma in 127604{.interpreted-text role="gh"}.)

fnmatch

Add ~fnmatch.filterfalse{.interpreted-text role="func"}, a function to reject names matching a given pattern. (Contributed by Bénédikt Tran in 74598{.interpreted-text role="gh"}.)

fractions

A ~fractions.Fraction{.interpreted-text role="class"} object may now be constructed from any object with the !as_integer_ratio{.interpreted-text role="meth"} method. (Contributed by Serhiy Storchaka in 82017{.interpreted-text role="gh"}.)
Add .Fraction.from_number{.interpreted-text role="meth"} as an alternative constructor for ~fractions.Fraction{.interpreted-text role="class"}. (Contributed by Serhiy Storchaka in 121797{.interpreted-text role="gh"}.)

functools

Add the ~functools.Placeholder{.interpreted-text role="data"} sentinel. This may be used with the ~functools.partial{.interpreted-text role="func"} or ~functools.partialmethod{.interpreted-text role="func"} functions to reserve a place for positional arguments in the returned partial object <partial-objects>{.interpreted-text role="ref"}. (Contributed by Dominykas Grigonis in 119127{.interpreted-text role="gh"}.)
Allow the initial parameter of ~functools.reduce{.interpreted-text role="func"} to be passed as a keyword argument. (Contributed by Sayandip Dutta in 125916{.interpreted-text role="gh"}.)

getopt

Add support for options with optional arguments. (Contributed by Serhiy Storchaka in 126374{.interpreted-text role="gh"}.)
Add support for returning intermixed options and non-option arguments in order. (Contributed by Serhiy Storchaka in 126390{.interpreted-text role="gh"}.)

getpass

Support keyboard feedback in the ~getpass.getpass{.interpreted-text role="func"} 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 77065{.interpreted-text role="gh"}.)

graphlib

Allow .TopologicalSorter.prepare{.interpreted-text role="meth"} to be called more than once as long as sorting has not started. (Contributed by Daniel Pope in 130914{.interpreted-text role="gh"}.)

heapq

The !heapq{.interpreted-text role="mod"} module has improved support for working with max-heaps, via the following new functions:
- ~heapq.heapify_max{.interpreted-text role="func"}
- ~heapq.heappush_max{.interpreted-text role="func"}
- ~heapq.heappop_max{.interpreted-text role="func"}
- ~heapq.heapreplace_max{.interpreted-text role="func"}
- ~heapq.heappushpop_max{.interpreted-text role="func"}

hmac

Add a built-in implementation for HMAC (2104{.interpreted-text role="rfc"}) using formally verified code from the HACL* project. This implementation is used as a fallback when the OpenSSL implementation of HMAC is not available. (Contributed by Bénédikt Tran in 99108{.interpreted-text role="gh"}.)

http

Directory lists and error pages generated by the http.server{.interpreted-text role="mod"} module allow the browser to apply its default dark mode. (Contributed by Yorik Hansen in 123430{.interpreted-text role="gh"}.)
The http.server{.interpreted-text role="mod"} module now supports serving over HTTPS using the http.server.HTTPSServer{.interpreted-text role="class"} 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>{.interpreted-text role="option"}: Path to the TLS certificate file.
- --tls-key \<path\> <http.server --tls-key>{.interpreted-text role="option"}: Optional path to the private key file.
- --tls-password-file \<path\> <http.server --tls-password-file>{.interpreted-text role="option"}: Optional path to the password file for the private key.
(Contributed by Semyon Moroz in 85162{.interpreted-text role="gh"}.)

imaplib

Add .IMAP4.idle{.interpreted-text role="meth"}, implementing the IMAP4 IDLE command as defined in 2177{.interpreted-text role="rfc"}. (Contributed by Forest in 55454{.interpreted-text role="gh"}.)

inspect

~inspect.signature{.interpreted-text role="func"} takes a new argument annotation_format to control the annotationlib.Format{.interpreted-text role="class"} used for representing annotations. (Contributed by Jelle Zijlstra in 101552{.interpreted-text role="gh"}.)
.Signature.format{.interpreted-text role="meth"} takes a new argument unquote_annotations. If true, string annotations <annotation>{.interpreted-text role="term"} are displayed without surrounding quotes. (Contributed by Jelle Zijlstra in 101552{.interpreted-text role="gh"}.)
Add function ~inspect.ispackage{.interpreted-text role="func"} to determine whether an object is a package{.interpreted-text role="term"} or not. (Contributed by Zhikang Yan in 125634{.interpreted-text role="gh"}.)

io

Reading text from a non-blocking stream with read may now raise a BlockingIOError{.interpreted-text role="exc"} if the operation cannot immediately return bytes. (Contributed by Giovanni Siragusa in 109523{.interpreted-text role="gh"}.)
Add the ~io.Reader{.interpreted-text role="class"} and ~io.Writer{.interpreted-text role="class"} protocols as simpler alternatives to the pseudo-protocols typing.IO{.interpreted-text role="class"}, typing.TextIO{.interpreted-text role="class"}, and typing.BinaryIO{.interpreted-text role="class"}. (Contributed by Sebastian Rittau in 127648{.interpreted-text role="gh"}.)

json

Add exception notes for JSON serialization errors that allow identifying the source of the error. (Contributed by Serhiy Storchaka in 122163{.interpreted-text role="gh"}.)
Allow using the json{.interpreted-text role="mod"} module as a script using the -m{.interpreted-text role="option"} switch: python -m json{.interpreted-text role="program"}. This is now preferred to python -m json.tool{.interpreted-text role="program"}, which is soft deprecated{.interpreted-text role="term"}. See the JSON command-line interface <json-commandline>{.interpreted-text role="ref"} documentation. (Contributed by Trey Hunner in 122873{.interpreted-text role="gh"}.)
By default, the output of the JSON command-line interface <json-commandline>{.interpreted-text role="ref"} is highlighted in color. This can be controlled by environment variables <using-on-controlling-color>{.interpreted-text role="ref"}. (Contributed by Tomas Roun in 131952{.interpreted-text role="gh"}.)

linecache

~linecache.getline{.interpreted-text role="func"} can now retrieve source code for frozen modules. (Contributed by Tian Gao in 131638{.interpreted-text role="gh"}.)

logging.handlers

~logging.handlers.QueueListener{.interpreted-text role="class"} objects now support the context manager{.interpreted-text role="term"} protocol. (Contributed by Charles Machalow in 132106{.interpreted-text role="gh"}.)
QueueListener.start <logging.handlers.QueueListener.start>{.interpreted-text role="meth"} now raises a RuntimeError{.interpreted-text role="exc"} if the listener is already started. (Contributed by Charles Machalow in 132106{.interpreted-text role="gh"}.)

math

Added more detailed error messages for domain errors in the module. (Contributed by Charlie Zhao and Sergey B Kirpichev in 101410{.interpreted-text role="gh"}.)

mimetypes

Add a public command-line <mimetypes-cli>{.interpreted-text role="ref"} for the module, invoked via python -m mimetypes{.interpreted-text role="program"}. (Contributed by Oleg Iarygin and Hugo van Kemenade in 93096{.interpreted-text role="gh"}.)
Add several new MIME types based on RFCs and common usage:

Microsoft and 8081{.interpreted-text role="rfc"} MIME types for fonts
- Embedded OpenType: application/vnd.ms-fontobject
- OpenType Layout (OTF) font/otf
- TrueType: font/ttf
- WOFF 1.0 font/woff
- WOFF 2.0 font/woff2
9559{.interpreted-text role="rfc"} MIME types for Matroska audiovisual data container structures
- audio with no video: audio/matroska (.mka)
- video: video/matroska (.mkv)
- stereoscopic video: video/matroska-3d (.mk3d)
Images with RFCs
- 1494{.interpreted-text role="rfc"}: CCITT Group 3 (.g3)
- 3362{.interpreted-text role="rfc"}: Real-time Facsimile, T.38 (.t38)
- 3745{.interpreted-text role="rfc"}: JPEG 2000 (.jp2), extension (.jpx) and compound (.jpm)
- 3950{.interpreted-text role="rfc"}: Tag Image File Format Fax eXtended, TIFF-FX (.tfx)
- 4047{.interpreted-text role="rfc"}: Flexible Image Transport System (.fits)
- 7903{.interpreted-text role="rfc"}: Enhanced Metafile (.emf) and Windows Metafile (.wmf)
Other MIME type additions and changes
- 2361{.interpreted-text role="rfc"}: Change type for .avi to video/vnd.avi and for .wav to audio/vnd.wave
- 4337{.interpreted-text role="rfc"}: Add MPEG-4 audio/mp4 (.m4a)
- 5334{.interpreted-text role="rfc"}: Add Ogg media (.oga, .ogg and .ogx)
- 6713{.interpreted-text role="rfc"}: Add gzip application/gzip (.gz)
- 9639{.interpreted-text role="rfc"}: Add FLAC audio/flac (.flac)
- 9512{.interpreted-text role="rfc"} application/yaml MIME type for YAML files (.yaml and .yml)
- Add 7z application/x-7z-compressed (.7z)
- Add Android Package application/vnd.android.package-archive (.apk) when not strict
- Add deb application/x-debian-package (.deb)
- Add glTF binary model/gltf-binary (.glb)
- Add glTF JSON/ASCII model/gltf+json (.gltf)
- Add M4V video/x-m4v (.m4v)
- Add PHP application/x-httpd-php (.php)
- Add RAR application/vnd.rar (.rar)
- Add RPM application/x-rpm (.rpm)
- Add STL model/stl (.stl)
- Add Windows Media Video video/x-ms-wmv (.wmv)
- De facto: Add WebM audio/webm (.weba)
- ECMA-376: Add .docx, .pptx and .xlsx types
- OASIS: Add OpenDocument .odg, .odp, .ods and .odt types
- W3C: Add EPUB application/epub+zip (.epub)
(Contributed by Sahil Prajapati and Hugo van Kemenade in 84852{.interpreted-text role="gh"}, by Sasha "Nelie" Chernykh and Hugo van Kemenade in 132056{.interpreted-text role="gh"}, and by Hugo van Kemenade in 89416{.interpreted-text role="gh"}, 85957{.interpreted-text role="gh"}, and 129965{.interpreted-text role="gh"}.)

multiprocessing

::: {#whatsnew314-multiprocessing-start-method}

On Unix platforms other than macOS, 'forkserver' <multiprocessing-start-method-forkserver>{.interpreted-text role="ref"} is now the default start method <multiprocessing-start-methods>{.interpreted-text role="ref"} (replacing 'fork' <multiprocessing-start-method-fork>{.interpreted-text role="ref"}). This change does not affect Windows or macOS, where 'spawn' <multiprocessing-start-method-spawn>{.interpreted-text role="ref"} remains the default start method.

If the threading incompatible fork method is required, you must explicitly request it via a context from ~multiprocessing.get_context{.interpreted-text role="func"} (preferred) or change the default via ~multiprocessing.set_start_method{.interpreted-text role="func"}.

See forkserver restrictions <multiprocessing-programming-forkserver>{.interpreted-text role="ref"} 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 pickled <pickle>{.interpreted-text role="mod"}.

(Contributed by Gregory P. Smith in 84559{.interpreted-text role="gh"}.)
multiprocessing{.interpreted-text role="mod"}'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 97514{.interpreted-text role="gh"}.)
The multiprocessing proxy objects <multiprocessing-proxy_objects>{.interpreted-text role="ref"} for list and dict types gain previously overlooked missing methods:
- !clear{.interpreted-text role="meth"} and !copy{.interpreted-text role="meth"} for proxies of list{.interpreted-text role="class"}
- ~dict.fromkeys{.interpreted-text role="meth"}, reversed(d), d | {}, {} | d, d |= {'b': 2} for proxies of dict{.interpreted-text role="class"}
(Contributed by Roy Hyunjin Han for 103134{.interpreted-text role="gh"}.)
Add support for shared set{.interpreted-text role="class"} objects via .SyncManager.set{.interpreted-text role="meth"}. The set{.interpreted-text role="func"} in ~multiprocessing.Manager{.interpreted-text role="func"} method is now available. (Contributed by Mingyu Park in 129949{.interpreted-text role="gh"}.)
Add the ~multiprocessing.Process.interrupt{.interpreted-text role="meth"} to multiprocessing.Process{.interpreted-text role="class"} objects, which terminates the child process by sending ~signal.SIGINT{.interpreted-text role="py:const"}. This enables finally{.interpreted-text role="keyword"} clauses to print a stack trace for the terminated process. (Contributed by Artem Pulkin in 131913{.interpreted-text role="gh"}.) :::

operator

Add ~operator.is_none{.interpreted-text role="func"} and ~operator.is_not_none{.interpreted-text role="func"} 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 115808{.interpreted-text role="gh"}.)

os

Add the ~os.reload_environ{.interpreted-text role="func"} function to update os.environ{.interpreted-text role="data"} and os.environb{.interpreted-text role="data"} with changes to the environment made by os.putenv{.interpreted-text role="func"}, by os.unsetenv{.interpreted-text role="func"}, or made outside Python in the same process. (Contributed by Victor Stinner in 120057{.interpreted-text role="gh"}.)
Add the ~os.SCHED_DEADLINE{.interpreted-text role="data"} and ~os.SCHED_NORMAL{.interpreted-text role="data"} constants to the !os{.interpreted-text role="mod"} module. (Contributed by James Roy in 127688{.interpreted-text role="gh"}.)
Add the ~os.readinto{.interpreted-text role="func"} function to read into a buffer object <bufferobjects>{.interpreted-text role="ref"} from a file descriptor. (Contributed by Cody Maloney in 129205{.interpreted-text role="gh"}.)

os.path

The strict parameter to ~os.path.realpath{.interpreted-text role="func"} accepts a new value, ~os.path.ALLOW_MISSING{.interpreted-text role="data"}. If used, errors other than FileNotFoundError{.interpreted-text role="exc"} will be re-raised; the resulting path can be missing but it will be free of symlinks. (Contributed by Petr Viktorin for 2025-4517{.interpreted-text role="cve"}.)

pathlib

Add methods to pathlib.Path{.interpreted-text role="class"} to recursively copy or move files and directories:
- ~pathlib.Path.copy{.interpreted-text role="meth"} copies a file or directory tree to a destination.
- ~pathlib.Path.copy_into{.interpreted-text role="meth"} copies into a destination directory.
- ~pathlib.Path.move{.interpreted-text role="meth"} moves a file or directory tree to a destination.
- ~pathlib.Path.move_into{.interpreted-text role="meth"} moves into a destination directory.
(Contributed by Barney Gale in 73991{.interpreted-text role="gh"}.)
Add the ~pathlib.Path.info{.interpreted-text role="attr"} attribute, which stores an object implementing the new pathlib.types.PathInfo{.interpreted-text role="class"} protocol. The object supports querying the file type and internally caching ~os.stat{.interpreted-text role="func"} results. Path objects generated by ~pathlib.Path.iterdir{.interpreted-text role="meth"} are initialized with file type information gleaned from scanning the parent directory. (Contributed by Barney Gale in 125413{.interpreted-text role="gh"}.)

pdb

The pdb{.interpreted-text role="mod"} module now supports remote attaching to a running Python process using a new -p PID <pdb --pid>{.interpreted-text role="option"} command-line option:
```
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 PEP 768 <whatsnew314-remote-debugging>{.interpreted-text role="ref"} and the new sys.remote_exec{.interpreted-text role="func"} function to attach to the remote process and send the PDB commands to it.

(Contributed by Matt Wozniski and Pablo Galindo in 131591{.interpreted-text role="gh"}.)
Hardcoded breakpoints (breakpoint{.interpreted-text role="func"} and ~pdb.set_trace{.interpreted-text role="func"}) now reuse the most recent ~pdb.Pdb{.interpreted-text role="class"} instance that calls ~pdb.Pdb.set_trace{.interpreted-text role="meth"}, instead of creating a new one each time. As a result, all the instance specific data like display{.interpreted-text role="pdbcmd"} and commands{.interpreted-text role="pdbcmd"} are preserved across hardcoded breakpoints. (Contributed by Tian Gao in 121450{.interpreted-text role="gh"}.)
Add a new argument mode to pdb.Pdb{.interpreted-text role="class"}. Disable the restart command when pdb{.interpreted-text role="mod"} is in inline mode. (Contributed by Tian Gao in 123757{.interpreted-text role="gh"}.)
A confirmation prompt will be shown when the user tries to quit pdb{.interpreted-text role="mod"} in inline mode. y, Y, <Enter> or EOF will confirm the quit and call sys.exit{.interpreted-text role="func"}, instead of raising bdb.BdbQuit{.interpreted-text role="exc"}. (Contributed by Tian Gao in 124704{.interpreted-text role="gh"}.)
Inline breakpoints like breakpoint{.interpreted-text role="func"} or pdb.set_trace{.interpreted-text role="func"} will always stop the program at calling frame, ignoring the skip pattern (if any). (Contributed by Tian Gao in 130493{.interpreted-text role="gh"}.)
<tab> at the beginning of the line in pdb{.interpreted-text role="mod"} multi-line input will fill in a 4-space indentation now, instead of inserting a \t character. (Contributed by Tian Gao in 130471{.interpreted-text role="gh"}.)
Auto-indent is introduced in pdb{.interpreted-text role="mod"} 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 133350{.interpreted-text role="gh"}.)
$_asynctask is added to access the current asyncio task if applicable. (Contributed by Tian Gao in 124367{.interpreted-text role="gh"}.)
pdb.set_trace_async{.interpreted-text role="func"} is added to support debugging asyncio coroutines. await{.interpreted-text role="keyword"} statements are supported with this function. (Contributed by Tian Gao in 132576{.interpreted-text role="gh"}.)
Source code displayed in pdb{.interpreted-text role="mod"} will be syntax-highlighted. This feature can be controlled using the same methods as the default interactive{.interpreted-text role="term"} shell, in addition to the newly added colorize argument of pdb.Pdb{.interpreted-text role="class"}. (Contributed by Tian Gao and Łukasz Langa in 133355{.interpreted-text role="gh"}.)

pickle

Set the default protocol version on the pickle{.interpreted-text role="mod"} module to 5. For more details, see pickle protocols <pickle-protocols>{.interpreted-text role="ref"}.
Add exception notes for pickle serialization errors that allow identifying the source of the error. (Contributed by Serhiy Storchaka in 122213{.interpreted-text role="gh"}.)

platform

Add ~platform.invalidate_caches{.interpreted-text role="func"}, a function to invalidate cached results in the !platform{.interpreted-text role="mod"} module. (Contributed by Bénédikt Tran in 122549{.interpreted-text role="gh"}.)

pydoc

Annotations <annotation>{.interpreted-text role="term"} in help output are now usually displayed in a format closer to that in the original source. (Contributed by Jelle Zijlstra in 101552{.interpreted-text role="gh"}.)

re

Support \z as a synonym for \Z in regular expressions <re>{.interpreted-text role="mod"}. It is interpreted unambiguously in many other regular expression engines, unlike \Z, which has subtly different behavior. (Contributed by Serhiy Storchaka in 133306{.interpreted-text role="gh"}.)
\B in regular expression <re>{.interpreted-text role="mod"} now matches the empty input string, meaning that it is now always the opposite of \b. (Contributed by Serhiy Storchaka in 124130{.interpreted-text role="gh"}.)

socket

Improve and fix support for Bluetooth sockets.
- Fix support of Bluetooth sockets on NetBSD and DragonFly BSD. (Contributed by Serhiy Storchaka in 132429{.interpreted-text role="gh"}.)
- Fix support for ~socket.BTPROTO_HCI{.interpreted-text role="const"} on FreeBSD. (Contributed by Victor Stinner in 111178{.interpreted-text role="gh"}.)
- Add support for ~socket.BTPROTO_SCO{.interpreted-text role="const"} on FreeBSD. (Contributed by Serhiy Storchaka in 85302{.interpreted-text role="gh"}.)
- Add support for cid and bdaddr_type in the address for ~socket.BTPROTO_L2CAP{.interpreted-text role="const"} on FreeBSD. (Contributed by Serhiy Storchaka in 132429{.interpreted-text role="gh"}.)
- Add support for channel in the address for ~socket.BTPROTO_HCI{.interpreted-text role="const"} on Linux. (Contributed by Serhiy Storchaka in 70145{.interpreted-text role="gh"}.)
- Accept an integer as the address for ~socket.BTPROTO_HCI{.interpreted-text role="const"} on Linux. (Contributed by Serhiy Storchaka in 132099{.interpreted-text role="gh"}.)
- Return cid in ~socket.socket.getsockname{.interpreted-text role="meth"} for ~socket.BTPROTO_L2CAP{.interpreted-text role="const"}. (Contributed by Serhiy Storchaka in 132429{.interpreted-text role="gh"}.)
- Add many new constants. (Contributed by Serhiy Storchaka in 132734{.interpreted-text role="gh"}.)

ssl

Indicate through the ~ssl.HAS_PHA{.interpreted-text role="data"} Boolean whether the !ssl{.interpreted-text role="mod"} module supports TLSv1.3 post-handshake client authentication (PHA). (Contributed by Will Childs-Klein in 128036{.interpreted-text role="gh"}.)

struct

Support the float complex{.interpreted-text role="c:expr"} and double complex{.interpreted-text role="c:expr"} C types in the struct{.interpreted-text role="mod"} module (formatting characters 'F' and 'D' respectively). (Contributed by Sergey B Kirpichev in 121249{.interpreted-text role="gh"}.)

symtable

Expose the following ~symtable.Symbol{.interpreted-text role="class"} methods:
- ~symtable.Symbol.is_comp_cell{.interpreted-text role="meth"}
- ~symtable.Symbol.is_comp_iter{.interpreted-text role="meth"}
- ~symtable.Symbol.is_free_class{.interpreted-text role="meth"}
(Contributed by Bénédikt Tran in 120029{.interpreted-text role="gh"}.)

sys

The previously undocumented special function sys.getobjects{.interpreted-text role="func"}, 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 125286{.interpreted-text role="gh"}.)
Add sys._is_immortal{.interpreted-text role="func"} for determining if an object is immortal{.interpreted-text role="term"}. (Contributed by Peter Bierma in 128509{.interpreted-text role="gh"}.)
On FreeBSD, sys.platform{.interpreted-text role="data"} no longer contains the major version number. It is always 'freebsd', instead of 'freebsd13' or 'freebsd14'. (Contributed by Michael Osipov in 129393{.interpreted-text role="gh"}.)
Raise DeprecationWarning{.interpreted-text role="exc"} for sys._clear_type_cache{.interpreted-text role="func"}. This function was deprecated in Python 3.13 but it didn't raise a runtime warning.
Add sys.remote_exec{.interpreted-text role="func"} to implement the new external debugger interface. See PEP 768 <whatsnew314-remote-debugging>{.interpreted-text role="ref"} for details. (Contributed by Pablo Galindo Salgado, Matt Wozniski, and Ivona Stojanovic in 131591{.interpreted-text role="gh"}.)
Add the sys._jit{.interpreted-text role="data"} namespace, containing utilities for introspecting just-in-time compilation. (Contributed by Brandt Bucher in 133231{.interpreted-text role="gh"}.)

sys.monitoring

Add two new monitoring events, BRANCH_LEFT{.interpreted-text role="monitoring-event"} and BRANCH_RIGHT{.interpreted-text role="monitoring-event"}. These replace and deprecate the !BRANCH{.interpreted-text role="monitoring-event"} event. (Contributed by Mark Shannon in 122548{.interpreted-text role="gh"}.)

sysconfig

Add ABIFLAGS key to ~sysconfig.get_config_vars{.interpreted-text role="func"} on Windows. (Contributed by Xuehai Pan in 131799{.interpreted-text role="gh"}.)

tarfile

~tarfile.data_filter{.interpreted-text role="func"} now normalizes symbolic link targets in order to avoid path traversal attacks. (Contributed by Petr Viktorin in 127987{.interpreted-text role="gh"} and 2025-4138{.interpreted-text role="cve"}.)
~tarfile.TarFile.extractall{.interpreted-text role="func"} now skips fixing up directory attributes when a directory was removed or replaced by another kind of file. (Contributed by Petr Viktorin in 127987{.interpreted-text role="gh"} and 2024-12718{.interpreted-text role="cve"}.)
~tarfile.TarFile.extract{.interpreted-text role="func"} and ~tarfile.TarFile.extractall{.interpreted-text role="func"} 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, ~tarfile.LinkFallbackError{.interpreted-text role="exc"}. (Contributed by Petr Viktorin for 2025-4330{.interpreted-text role="cve"} and 2024-12718{.interpreted-text role="cve"}.)
~tarfile.TarFile.extract{.interpreted-text role="func"} and ~tarfile.TarFile.extractall{.interpreted-text role="func"} no longer extract rejected members when ~tarfile.TarFile.errorlevel{.interpreted-text role="func"} is zero. (Contributed by Matt Prodani and Petr Viktorin in 112887{.interpreted-text role="gh"} and 2025-4435{.interpreted-text role="cve"}.)

threading

threading.Thread.start{.interpreted-text role="meth"} now sets the operating system thread name to threading.Thread.name{.interpreted-text role="attr"}. (Contributed by Victor Stinner in 59705{.interpreted-text role="gh"}.)

tkinter

Make tkinter{.interpreted-text role="mod"} widget methods !after{.interpreted-text role="meth"} and !after_idle{.interpreted-text role="meth"} accept keyword arguments. (Contributed by Zhikang Yan in 126899{.interpreted-text role="gh"}.)
Add ability to specify a name for !tkinter.OptionMenu{.interpreted-text role="class"} and !tkinter.ttk.OptionMenu{.interpreted-text role="class"}. (Contributed by Zhikang Yan in 130482{.interpreted-text role="gh"}.)

turtle

Add context managers for turtle.fill{.interpreted-text role="func"}, turtle.poly{.interpreted-text role="func"}, and turtle.no_animation{.interpreted-text role="func"}. (Contributed by Marie Roald and Yngve Mardal Moe in 126350{.interpreted-text role="gh"}.)

types

types.UnionType{.interpreted-text role="class"} is now an alias for typing.Union{.interpreted-text role="class"}. See below <whatsnew314-typing-union>{.interpreted-text role="ref"} for more details. (Contributed by Jelle Zijlstra in 105499{.interpreted-text role="gh"}.)

typing

::: {#whatsnew314-typing-union}

The types.UnionType{.interpreted-text role="class"} and typing.Union{.interpreted-text role="class"} 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 repr{.interpreted-text role="func"}. 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 649{.interpreted-text role="pep"}; an instance of types.UnionType{.interpreted-text role="class"} 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 ~typing.get_origin{.interpreted-text role="func"} and typing.get_args{.interpreted-text role="func"} instead of relying on private implementation details.
- It is now possible to use typing.Union{.interpreted-text role="class"} itself in isinstance{.interpreted-text role="func"} checks. For example, isinstance(int | str, typing.Union) will return True; previously this raised TypeError{.interpreted-text role="exc"}.
- The !__args__{.interpreted-text role="attr"} attribute of typing.Union{.interpreted-text role="class"} objects is no longer writable.
- It is no longer possible to set any attributes on ~typing.Union{.interpreted-text role="class"} 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 105499{.interpreted-text role="gh"}.)
~typing.TypeAliasType{.interpreted-text role="class"} now supports star unpacking. :::

unicodedata

The Unicode database has been updated to Unicode 16.0.0.

unittest

::: {#whatsnew314-color-unittest}

unittest{.interpreted-text role="mod"} output is now colored by default. This can be controlled by environment variables <using-on-controlling-color>{.interpreted-text role="ref"}. (Contributed by Hugo van Kemenade in 127221{.interpreted-text role="gh"}.)
unittest discovery supports namespace package{.interpreted-text role="term"} as start directory again. It was removed in Python 3.11. (Contributed by Jacob Walls in 80958{.interpreted-text role="gh"}.)
A number of new methods were added in the ~unittest.TestCase{.interpreted-text role="class"} class that provide more specialized tests.
- ~unittest.TestCase.assertHasAttr{.interpreted-text role="meth"} and ~unittest.TestCase.assertNotHasAttr{.interpreted-text role="meth"} check whether the object has a particular attribute.
- ~unittest.TestCase.assertIsSubclass{.interpreted-text role="meth"} and ~unittest.TestCase.assertNotIsSubclass{.interpreted-text role="meth"} check whether the object is a subclass of a particular class, or of one of a tuple of classes.
- ~unittest.TestCase.assertStartsWith{.interpreted-text role="meth"}, ~unittest.TestCase.assertNotStartsWith{.interpreted-text role="meth"}, ~unittest.TestCase.assertEndsWith{.interpreted-text role="meth"} and ~unittest.TestCase.assertNotEndsWith{.interpreted-text role="meth"} check whether the Unicode or byte string starts or ends with particular strings.
(Contributed by Serhiy Storchaka in 71339{.interpreted-text role="gh"}.)

:::

urllib

Upgrade HTTP digest authentication algorithm for urllib.request{.interpreted-text role="mod"} by supporting SHA-256 digest authentication as specified in 7616{.interpreted-text role="rfc"}. (Contributed by Calvin Bui in 128193{.interpreted-text role="gh"}.)
Improve ergonomics and standards compliance when parsing and emitting file: URLs.

In ~urllib.request.url2pathname{.interpreted-text role="func"}:
- Accept a complete URL when the new require_scheme argument is set to true.
- Discard URL authority if it matches the local hostname.
- Discard URL authority if it resolves to a local IP address when the new resolve_host argument is set to true.
- Discard URL query and fragment components.
- Raise ~urllib.error.URLError{.interpreted-text role="exc"} if a URL authority isn't local, except on Windows where we return a UNC path as before.
In ~urllib.request.pathname2url{.interpreted-text role="func"}:
- Return a complete URL when the new add_scheme argument is set to true.
- Include an empty URL authority when a path begins with a slash. For example, the path /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 OSError{.interpreted-text role="exc"} exception to be raised.

(Contributed by Barney Gale in 125866{.interpreted-text role="gh"}.)

uuid

Add support for UUID versions 6, 7, and 8 via ~uuid.uuid6{.interpreted-text role="func"}, ~uuid.uuid7{.interpreted-text role="func"}, and ~uuid.uuid8{.interpreted-text role="func"} respectively, as specified in 9562{.interpreted-text role="rfc"}. (Contributed by Bénédikt Tran in 89083{.interpreted-text role="gh"}.)
~uuid.NIL{.interpreted-text role="const"} and ~uuid.MAX{.interpreted-text role="const"} are now available to represent the Nil and Max UUID formats as defined by 9562{.interpreted-text role="rfc"}. (Contributed by Nick Pope in 128427{.interpreted-text role="gh"}.)
Allow generating multiple UUIDs simultaneously on the command-line via python -m uuid --count <uuid --count>{.interpreted-text role="option"}. (Contributed by Simon Legner in 131236{.interpreted-text role="gh"}.)

webbrowser

Names in the BROWSER{.interpreted-text role="envvar"} environment variable can now refer to already registered browsers for the webbrowser{.interpreted-text role="mod"} module, instead of always generating a new browser command.

This makes it possible to set BROWSER{.interpreted-text role="envvar"} to the value of one of the supported browsers on macOS.

zipfile

Added ZipInfo._for_archive <zipfile.ZipInfo._for_archive>{.interpreted-text role="meth"}, a method to resolve suitable defaults for a ~zipfile.ZipInfo{.interpreted-text role="class"} object as used by ZipFile.writestr <zipfile.ZipFile.writestr>{.interpreted-text role="func"}. (Contributed by Bénédikt Tran in 123424{.interpreted-text role="gh"}.)
.ZipFile.writestr{.interpreted-text role="meth"} now respects the SOURCE_DATE_EPOCH{.interpreted-text role="envvar"} environment variable in order to better support reproducible builds. (Contributed by Jiahao Li in 91279{.interpreted-text role="gh"}.)

Optimizations

The import time for several standard library modules has been improved, including annotationlib{.interpreted-text role="mod"}, ast{.interpreted-text role="mod"}, asyncio{.interpreted-text role="mod"}, base64{.interpreted-text role="mod"}, cmd{.interpreted-text role="mod"}, csv{.interpreted-text role="mod"}, gettext{.interpreted-text role="mod"}, importlib.util{.interpreted-text role="mod"}, locale{.interpreted-text role="mod"}, mimetypes{.interpreted-text role="mod"}, optparse{.interpreted-text role="mod"}, pickle{.interpreted-text role="mod"}, pprint{.interpreted-text role="mod"}, pstats{.interpreted-text role="mod"}, shlex{.interpreted-text role="mod"}, socket{.interpreted-text role="mod"}, string{.interpreted-text role="mod"}, subprocess{.interpreted-text role="mod"}, threading{.interpreted-text role="mod"}, tomllib{.interpreted-text role="mod"}, types{.interpreted-text role="mod"}, and zipfile{.interpreted-text role="mod"}.

(Contributed by Adam Turner, Bénédikt Tran, Chris Markiewicz, Eli Schwartz, Hugo van Kemenade, Jelle Zijlstra, and others in 118761{.interpreted-text role="gh"}.)
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 sys.getrefcount{.interpreted-text role="func"} and Py_REFCNT{.interpreted-text role="c:func"} compared to previous versions of Python. See below <whatsnew314-refcount>{.interpreted-text role="ref"} for details.

asyncio

Standard benchmark results have improved by 10-20% following the implementation of a new per-thread doubly linked list for native tasks <asyncio.Task>{.interpreted-text role="class"}, also reducing memory usage. This enables external introspection tools such as python -m asyncio pstree <whatsnew314-asyncio-introspection>{.interpreted-text role="ref"} to introspect the call graph of asyncio tasks running in all threads. (Contributed by Kumar Aditya in 107803{.interpreted-text role="gh"}.)
The module now has first class support for free-threading builds <free threading>{.interpreted-text role="term"}. This enables parallel execution of multiple event loops across different threads, scaling linearly with the number of threads. (Contributed by Kumar Aditya in 128002{.interpreted-text role="gh"}.)

base64

~base64.b16decode{.interpreted-text role="func"} is now up to six times faster. (Contributed by Bénédikt Tran, Chris Markiewicz, and Adam Turner in 118761{.interpreted-text role="gh"}.)

bdb

The basic debugger now has a sys.monitoring{.interpreted-text role="mod"}-based backend, which can be selected via the passing 'monitoring' to the ~bdb.Bdb{.interpreted-text role="class"} class's new backend parameter. (Contributed by Tian Gao in 124533{.interpreted-text role="gh"}.)

difflib

The ~difflib.IS_LINE_JUNK{.interpreted-text role="func"} function is now up to twice as fast. (Contributed by Adam Turner and Semyon Moroz in 130167{.interpreted-text role="gh"}.)

gc

The new incremental garbage collector <whatsnew314-incremental-gc>{.interpreted-text role="ref"} 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 ~gc.get_threshold{.interpreted-text role="meth"} and ~gc.set_threshold{.interpreted-text role="meth"} have changed, along with ~gc.get_count{.interpreted-text role="meth"} and ~gc.get_stats{.interpreted-text role="meth"}.
- For backwards compatibility, ~gc.get_threshold{.interpreted-text role="meth"} 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.
- ~gc.set_threshold{.interpreted-text role="meth"} now ignores any items after the second.
- ~gc.get_count{.interpreted-text role="meth"} and ~gc.get_stats{.interpreted-text role="meth"} 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 108362{.interpreted-text role="gh"}.)

io

Opening and reading files now executes fewer system calls. Reading a small operating system cached file in full is up to 15% faster. (Contributed by Cody Maloney and Victor Stinner in 120754{.interpreted-text role="gh"} and 90102{.interpreted-text role="gh"}.)

pathlib

Path.read_bytes <pathlib.Path.read_bytes>{.interpreted-text role="func"} now uses unbuffered mode to open files, which is between 9% and 17% faster to read in full. (Contributed by Cody Maloney in 120754{.interpreted-text role="gh"}.)

pdb

pdb{.interpreted-text role="mod"} now supports two backends, based on either sys.settrace{.interpreted-text role="func"} or sys.monitoring{.interpreted-text role="mod"}. Using the pdb CLI <pdb-cli>{.interpreted-text role="ref"} or breakpoint{.interpreted-text role="func"} will always use the sys.monitoring{.interpreted-text role="mod"} backend. Explicitly instantiating pdb.Pdb{.interpreted-text role="class"} and its derived classes will use the sys.settrace{.interpreted-text role="func"} backend by default, which is configurable. (Contributed by Tian Gao in 124533{.interpreted-text role="gh"}.)

textwrap

Optimize the ~textwrap.dedent{.interpreted-text role="func"} 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.

uuid

~uuid.uuid3{.interpreted-text role="func"} and ~uuid.uuid5{.interpreted-text role="func"} 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 128150{.interpreted-text role="gh"}.)
~uuid.uuid4{.interpreted-text role="func"} is now c. 30% faster. (Contributed by Bénédikt Tran in 128150{.interpreted-text role="gh"}.)

zlib

On Windows, zlib-ng is now used as the implementation of the zlib{.interpreted-text role="mod"} 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 91349{.interpreted-text role="gh"}.)

Removed

argparse

Remove the type, choices, and metavar parameters of !BooleanOptionalAction{.interpreted-text role="class"}. These have been deprecated since Python 3.12. (Contributed by Nikita Sobolev in 118805{.interpreted-text role="gh"}.)
Calling ~argparse.ArgumentParser.add_argument_group{.interpreted-text role="meth"} on an argument group now raises a ValueError{.interpreted-text role="exc"}. Similarly, ~argparse.ArgumentParser.add_argument_group{.interpreted-text role="meth"} or ~argparse.ArgumentParser.add_mutually_exclusive_group{.interpreted-text role="meth"} on a mutually exclusive group now both raise ValueError{.interpreted-text role="exc"}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 127186{.interpreted-text role="gh"}.)

ast

Remove the following classes, which have been deprecated aliases of ~ast.Constant{.interpreted-text role="class"} since Python 3.8 and have emitted deprecation warnings since Python 3.12:
- !Bytes{.interpreted-text role="class"}
- !Ellipsis{.interpreted-text role="class"}
- !NameConstant{.interpreted-text role="class"}
- !Num{.interpreted-text role="class"}
- !Str{.interpreted-text role="class"}
As a consequence of these removals, user-defined visit_Num, visit_Str, visit_Bytes, visit_NameConstant and visit_Ellipsis methods on custom ~ast.NodeVisitor{.interpreted-text role="class"} subclasses will no longer be called when the !NodeVisitor{.interpreted-text role="class"} subclass is visiting an AST. Define a visit_Constant method instead.

(Contributed by Alex Waygood in 119562{.interpreted-text role="gh"}.)
Remove the following deprecated properties on ast.Constant{.interpreted-text role="class"}, which were present for compatibility with the now-removed AST classes:
- !Constant.n{.interpreted-text role="attr"}
- !Constant.s{.interpreted-text role="attr"}
Use !Constant.value{.interpreted-text role="attr"} instead. (Contributed by Alex Waygood in 119562{.interpreted-text role="gh"}.)

asyncio

Remove the following classes, methods, and functions, which have been deprecated since Python 3.12:
- !AbstractChildWatcher{.interpreted-text role="class"}
- !FastChildWatcher{.interpreted-text role="class"}
- !MultiLoopChildWatcher{.interpreted-text role="class"}
- !PidfdChildWatcher{.interpreted-text role="class"}
- !SafeChildWatcher{.interpreted-text role="class"}
- !ThreadedChildWatcher{.interpreted-text role="class"}
- !AbstractEventLoopPolicy.get_child_watcher{.interpreted-text role="meth"}
- !AbstractEventLoopPolicy.set_child_watcher{.interpreted-text role="meth"}
- !get_child_watcher{.interpreted-text role="func"}
- !set_child_watcher{.interpreted-text role="func"}
(Contributed by Kumar Aditya in 120804{.interpreted-text role="gh"}.)

asyncio.get_event_loop{.interpreted-text role="func"} now raises a RuntimeError{.interpreted-text role="exc"} if there is no current event loop, and no longer implicitly creates an event loop.

(Contributed by Kumar Aditya in 126353{.interpreted-text role="gh"}.)

There's a few patterns that use asyncio.get_event_loop{.interpreted-text role="func"}, most of them can be replaced with asyncio.run{.interpreted-text role="func"}.

If you're running an async function, simply use asyncio.run{.interpreted-text role="func"}.

Before:

async def main():
    ...


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

After:

async def main():
    ...

asyncio.run(main())

If you need to start something, for example, a server listening on a socket and then run forever, use asyncio.run{.interpreted-text role="func"} and an asyncio.Event{.interpreted-text role="class"}.

Before:

def start_server(loop): ...

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

After:

def start_server(loop): ...

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

asyncio.run(main())

If you need to run something in an event loop, then run some blocking code around it, use asyncio.Runner{.interpreted-text role="class"}.

Before:

async def operation_one(): ...
def blocking_code(): ...
async def operation_two(): ...

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

After:

async def operation_one(): ...
def blocking_code(): ...
async def operation_two(): ...

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

email

Remove email.utils.localtime{.interpreted-text role="func"}'s isdst parameter, which was deprecated in and has been ignored since Python 3.12. (Contributed by Hugo van Kemenade in 118798{.interpreted-text role="gh"}.)

importlib.abc

Remove deprecated importlib.abc{.interpreted-text role="mod"} classes:
- !ResourceReader{.interpreted-text role="class"} (use ~importlib.resources.abc.TraversableResources{.interpreted-text role="class"})
- !Traversable{.interpreted-text role="class"} (use ~importlib.resources.abc.Traversable{.interpreted-text role="class"})
- !TraversableResources{.interpreted-text role="class"} (use ~importlib.resources.abc.TraversableResources{.interpreted-text role="class"})
(Contributed by Jason R. Coombs and Hugo van Kemenade in 93963{.interpreted-text role="gh"}.)

itertools

Remove support for copy, deepcopy, and pickle operations from itertools{.interpreted-text role="mod"} iterators. These have emitted a DeprecationWarning{.interpreted-text role="exc"} since Python 3.12. (Contributed by Raymond Hettinger in 101588{.interpreted-text role="gh"}.)

pathlib

Remove support for passing additional keyword arguments to ~pathlib.Path{.interpreted-text role="class"}. In previous versions, any such arguments are ignored. (Contributed by Barney Gale in 74033{.interpreted-text role="gh"}.)
Remove support for passing additional positional arguments to .PurePath.relative_to{.interpreted-text role="meth"} and ~pathlib.PurePath.is_relative_to{.interpreted-text role="meth"}. In previous versions, any such arguments are joined onto other. (Contributed by Barney Gale in 78707{.interpreted-text role="gh"}.)

pkgutil

Remove the !get_loader{.interpreted-text role="func"} and !find_loader{.interpreted-text role="func"} functions, which have been deprecated since Python 3.12. (Contributed by Bénédikt Tran in 97850{.interpreted-text role="gh"}.)

pty

Remove the !master_open{.interpreted-text role="func"} and !slave_open{.interpreted-text role="func"} functions, which have been deprecated since Python 3.12. Use pty.openpty{.interpreted-text role="func"} instead. (Contributed by Nikita Sobolev in 118824{.interpreted-text role="gh"}.)

sqlite3

Remove !version{.interpreted-text role="data"} and !version_info{.interpreted-text role="data"} from the sqlite3{.interpreted-text role="mod"} module; use ~sqlite3.sqlite_version{.interpreted-text role="data"} and ~sqlite3.sqlite_version_info{.interpreted-text role="data"} for the actual version number of the runtime SQLite library. (Contributed by Hugo van Kemenade in 118924{.interpreted-text role="gh"}.)
Using a sequence of parameters with named placeholders now raises a ~sqlite3.ProgrammingError{.interpreted-text role="exc"}, having been deprecated since Python 3.12. (Contributed by Erlend E. Aasland in 118928{.interpreted-text role="gh"} and 101693{.interpreted-text role="gh"}.)

urllib

Remove the !Quoter{.interpreted-text role="class"} class from urllib.parse{.interpreted-text role="mod"}, which has been deprecated since Python 3.11. (Contributed by Nikita Sobolev in 118827{.interpreted-text role="gh"}.)
Remove the !URLopener{.interpreted-text role="class"} and !FancyURLopener{.interpreted-text role="class"} classes from urllib.request{.interpreted-text role="mod"}, which have been deprecated since Python 3.3.

myopener.open() can be replaced with ~urllib.request.urlopen{.interpreted-text role="func"}. myopener.retrieve() can be replaced with ~urllib.request.urlretrieve{.interpreted-text role="func"}. Customisations to the opener classes can be replaced by passing customized handlers to ~urllib.request.build_opener{.interpreted-text role="func"}. (Contributed by Barney Gale in 84850{.interpreted-text role="gh"}.)

Deprecated

New deprecations

Passing a complex number as the real or imag argument in the complex{.interpreted-text role="func"} constructor is now deprecated; complex numbers should only be passed as a single positional argument. (Contributed by Serhiy Storchaka in 109218{.interpreted-text role="gh"}.)
argparse{.interpreted-text role="mod"}:
- Passing the undocumented keyword argument prefix_chars to the ~argparse.ArgumentParser.add_argument_group{.interpreted-text role="meth"} method is now deprecated. (Contributed by Savannah Ostrowski in 125563{.interpreted-text role="gh"}.)
- Deprecated the argparse.FileType{.interpreted-text role="class"} type converter. Anything relating to resource management should be handled downstream, after the arguments have been parsed. (Contributed by Serhiy Storchaka in 58032{.interpreted-text role="gh"}.)
asyncio{.interpreted-text role="mod"}:
- The !asyncio.iscoroutinefunction{.interpreted-text role="func"} is now deprecated and will be removed in Python 3.16; use inspect.iscoroutinefunction{.interpreted-text role="func"} instead. (Contributed by Jiahao Li and Kumar Aditya in 122875{.interpreted-text role="gh"}.)
- The asyncio{.interpreted-text role="mod"} policy system is deprecated and will be removed in Python 3.16. In particular, the following classes and functions are deprecated:
  - asyncio.AbstractEventLoopPolicy{.interpreted-text role="class"}
  - asyncio.DefaultEventLoopPolicy{.interpreted-text role="class"}
  - asyncio.WindowsSelectorEventLoopPolicy{.interpreted-text role="class"}
  - asyncio.WindowsProactorEventLoopPolicy{.interpreted-text role="class"}
  - asyncio.get_event_loop_policy{.interpreted-text role="func"}
  - asyncio.set_event_loop_policy{.interpreted-text role="func"}
  Users should use asyncio.run{.interpreted-text role="func"} or asyncio.Runner{.interpreted-text role="class"} with the loop_factory argument to use the desired event loop implementation.
  
  For example, to use asyncio.SelectorEventLoop{.interpreted-text role="class"} on Windows:
```
import asyncio

async def main():
    ...

asyncio.run(main(), loop_factory=asyncio.SelectorEventLoop)
```
  (Contributed by Kumar Aditya in 127949{.interpreted-text role="gh"}.)
codecs{.interpreted-text role="mod"}: The codecs.open{.interpreted-text role="func"} function is now deprecated, and will be removed in a future version of Python. Use open{.interpreted-text role="func"} instead. (Contributed by Inada Naoki in 133036{.interpreted-text role="gh"}.)
ctypes{.interpreted-text role="mod"}:
- On non-Windows platforms, setting .Structure._pack_{.interpreted-text role="attr"} to use a MSVC-compatible default memory layout is now deprecated in favor of setting .Structure._layout_{.interpreted-text role="attr"} to 'ms', and will be removed in Python 3.19. (Contributed by Petr Viktorin in 131747{.interpreted-text role="gh"}.)
- Calling ctypes.POINTER{.interpreted-text role="func"} on a string is now deprecated. Use incomplete types <ctypes-incomplete-types>{.interpreted-text role="ref"} for self-referential structures. Also, the internal ctypes._pointer_type_cache is deprecated. See ctypes.POINTER{.interpreted-text role="func"} for updated implementation details. (Contributed by Sergey Myrianov in 100926{.interpreted-text role="gh"}.)
functools{.interpreted-text role="mod"}: Calling the Python implementation of functools.reduce{.interpreted-text role="func"} 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 121676{.interpreted-text role="gh"}.)
logging{.interpreted-text role="mod"}: 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 115032{.interpreted-text role="gh"}.)
mimetypes{.interpreted-text role="mod"}: Valid extensions are either empty or must start with '.' for mimetypes.MimeTypes.add_type{.interpreted-text role="meth"}. Undotted extensions are deprecated and will raise a ValueError{.interpreted-text role="exc"} in Python 3.16. (Contributed by Hugo van Kemenade in 75223{.interpreted-text role="gh"}.)
!nturl2path{.interpreted-text role="mod"}: This module is now deprecated. Call urllib.request.url2pathname{.interpreted-text role="func"} and ~urllib.request.pathname2url{.interpreted-text role="func"} instead. (Contributed by Barney Gale in 125866{.interpreted-text role="gh"}.)
os{.interpreted-text role="mod"}: The os.popen{.interpreted-text role="func"} and os.spawn* <os.spawnl>{.interpreted-text role="func"} functions are now soft deprecated{.interpreted-text role="term"}. They should no longer be used to write new code. The subprocess{.interpreted-text role="mod"} module is recommended instead. (Contributed by Victor Stinner in 120743{.interpreted-text role="gh"}.)
pathlib{.interpreted-text role="mod"}: !pathlib.PurePath.as_uri{.interpreted-text role="meth"} is now deprecated and scheduled for removal in Python 3.19. Use pathlib.Path.as_uri{.interpreted-text role="meth"} instead. (Contributed by Barney Gale in 123599{.interpreted-text role="gh"}.)
pdb{.interpreted-text role="mod"}: 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 667{.interpreted-text role="pep"} 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 124369{.interpreted-text role="gh"} and 125951{.interpreted-text role="gh"}.)
symtable{.interpreted-text role="mod"}: Deprecate symtable.Class.get_methods{.interpreted-text role="meth"} due to the lack of interest, scheduled for removal in Python 3.16. (Contributed by Bénédikt Tran in 119698{.interpreted-text role="gh"}.)
tkinter{.interpreted-text role="mod"}: The !tkinter.Variable{.interpreted-text role="class"} methods !trace_variable{.interpreted-text role="meth"}, !trace_vdelete{.interpreted-text role="meth"} and !trace_vinfo{.interpreted-text role="meth"} are now deprecated. Use !trace_add{.interpreted-text role="meth"}, !trace_remove{.interpreted-text role="meth"} and !trace_info{.interpreted-text role="meth"} instead. (Contributed by Serhiy Storchaka in 120220{.interpreted-text role="gh"}.)
urllib.parse{.interpreted-text role="mod"}: Accepting objects with false values (like 0 and []) except empty strings, bytes-like objects and None in ~urllib.parse.parse_qsl{.interpreted-text role="func"} and ~urllib.parse.parse_qs{.interpreted-text role="func"} is now deprecated. (Contributed by Serhiy Storchaka in 116897{.interpreted-text role="gh"}.)

Pending removal in Python 3.15

The import system:
- Setting __cached__ on a module while failing to set __spec__.cached <importlib.machinery.ModuleSpec.cached>{.interpreted-text role="attr"} is deprecated. In Python 3.15, __cached__ will cease to be set or take into consideration by the import system or standard library. (97879{.interpreted-text role="gh"})
- Setting ~module.__package__{.interpreted-text role="attr"} on a module while failing to set __spec__.parent <importlib.machinery.ModuleSpec.parent>{.interpreted-text role="attr"} is deprecated. In Python 3.15, !__package__{.interpreted-text role="attr"} will cease to be set or take into consideration by the import system or standard library. (97879{.interpreted-text role="gh"})
ctypes{.interpreted-text role="mod"}:
- The undocumented !ctypes.SetPointerType{.interpreted-text role="func"} function has been deprecated since Python 3.13.
http.server{.interpreted-text role="mod"}:
- The obsolete and rarely used !CGIHTTPRequestHandler{.interpreted-text role="class"} has been deprecated since Python 3.13. No direct replacement exists. Anything is better than CGI to interface a web server with a request handler.
- The !--cgi{.interpreted-text role="option"} flag to the python -m http.server{.interpreted-text role="program"} command-line interface has been deprecated since Python 3.13.
importlib{.interpreted-text role="mod"}:
- load_module() method: use exec_module() instead.
pathlib{.interpreted-text role="mod"}:
- !.PurePath.is_reserved{.interpreted-text role="meth"} has been deprecated since Python 3.13. Use os.path.isreserved{.interpreted-text role="func"} to detect reserved paths on Windows.
platform{.interpreted-text role="mod"}:
- !platform.java_ver{.interpreted-text role="func"} has been deprecated since Python 3.13. This function is only useful for Jython support, has a confusing API, and is largely untested.
sysconfig{.interpreted-text role="mod"}:
- The check_home argument of sysconfig.is_python_build{.interpreted-text role="func"} has been deprecated since Python 3.12.
threading{.interpreted-text role="mod"}:
- ~threading.RLock{.interpreted-text role="func"} will take no arguments in Python 3.15. Passing any arguments has been deprecated since Python 3.14, as the Python version does not permit any arguments, but the C version allows any number of positional or keyword arguments, ignoring every argument.
types{.interpreted-text role="mod"}:
- types.CodeType{.interpreted-text role="class"}: Accessing ~codeobject.co_lnotab{.interpreted-text role="attr"} was deprecated in 626{.interpreted-text role="pep"} since 3.10 and was planned to be removed in 3.12, but it only got a proper DeprecationWarning{.interpreted-text role="exc"} in 3.12. May be removed in 3.15. (Contributed by Nikita Sobolev in 101866{.interpreted-text role="gh"}.)
typing{.interpreted-text role="mod"}:
- The undocumented keyword argument syntax for creating ~typing.NamedTuple{.interpreted-text role="class"} classes (for example, Point = NamedTuple("Point", x=int, y=int)) has been deprecated since Python 3.13. Use the class-based syntax or the functional syntax instead.
- When using the functional syntax of ~typing.TypedDict{.interpreted-text role="class"}s, failing to pass a value to the fields parameter (TD = TypedDict("TD")) or passing None (TD = TypedDict("TD", None)) has been deprecated since Python 3.13. Use class TD(TypedDict): pass or TD = TypedDict("TD", {}) to create a TypedDict with zero field.
- The !typing.no_type_check_decorator{.interpreted-text role="func"} decorator function has been deprecated since Python 3.13. After eight years in the typing{.interpreted-text role="mod"} module, it has yet to be supported by any major type checker.
!sre_compile{.interpreted-text role="mod"}, !sre_constants{.interpreted-text role="mod"} and !sre_parse{.interpreted-text role="mod"} modules.
wave{.interpreted-text role="mod"}:
- The getmark(), setmark() and getmarkers() methods of the ~wave.Wave_read{.interpreted-text role="class"} and ~wave.Wave_write{.interpreted-text role="class"} classes have been deprecated since Python 3.13.
zipimport{.interpreted-text role="mod"}:
- !zipimport.zipimporter.load_module{.interpreted-text role="meth"} has been deprecated since Python 3.10. Use ~zipimport.zipimporter.exec_module{.interpreted-text role="meth"} instead. (125746{.interpreted-text role="gh"}.)

Pending removal in Python 3.16

The import system:
- Setting ~module.__loader__{.interpreted-text role="attr"} on a module while failing to set __spec__.loader <importlib.machinery.ModuleSpec.loader>{.interpreted-text role="attr"} is deprecated. In Python 3.16, !__loader__{.interpreted-text role="attr"} will cease to be set or taken into consideration by the import system or the standard library.
array{.interpreted-text role="mod"}:
- The 'u' format code (wchar_t{.interpreted-text role="c:type"}) has been deprecated in documentation since Python 3.3 and at runtime since Python 3.13. Use the 'w' format code (Py_UCS4{.interpreted-text role="c:type"}) for Unicode characters instead.
asyncio{.interpreted-text role="mod"}:
- !asyncio.iscoroutinefunction{.interpreted-text role="func"} is deprecated and will be removed in Python 3.16; use inspect.iscoroutinefunction{.interpreted-text role="func"} instead. (Contributed by Jiahao Li and Kumar Aditya in 122875{.interpreted-text role="gh"}.)
- asyncio{.interpreted-text role="mod"} policy system is deprecated and will be removed in Python 3.16. In particular, the following classes and functions are deprecated:
  - asyncio.AbstractEventLoopPolicy{.interpreted-text role="class"}
  - asyncio.DefaultEventLoopPolicy{.interpreted-text role="class"}
  - asyncio.WindowsSelectorEventLoopPolicy{.interpreted-text role="class"}
  - asyncio.WindowsProactorEventLoopPolicy{.interpreted-text role="class"}
  - asyncio.get_event_loop_policy{.interpreted-text role="func"}
  - asyncio.set_event_loop_policy{.interpreted-text role="func"}
  Users should use asyncio.run{.interpreted-text role="func"} or asyncio.Runner{.interpreted-text role="class"} with loop_factory to use the desired event loop implementation.
  
  For example, to use asyncio.SelectorEventLoop{.interpreted-text role="class"} on Windows:
```
import asyncio

async def main():
    ...

asyncio.run(main(), loop_factory=asyncio.SelectorEventLoop)
```
  (Contributed by Kumar Aditya in 127949{.interpreted-text role="gh"}.)
builtins{.interpreted-text role="mod"}:
- Bitwise inversion on boolean types, ~True or ~False has been deprecated since Python 3.12, as it produces surprising and unintuitive results (-2 and -1). Use not x instead for the logical negation of a Boolean. In the rare case that you need the bitwise inversion of the underlying integer, convert to int explicitly (~int(x)).
functools{.interpreted-text role="mod"}:
- Calling the Python implementation of functools.reduce{.interpreted-text role="func"} with function or sequence as keyword arguments has been deprecated since Python 3.14.
logging{.interpreted-text role="mod"}:
- Support for custom logging handlers with the strm argument is deprecated and scheduled for removal in Python 3.16. Define handlers with the stream argument instead. (Contributed by Mariusz Felisiak in 115032{.interpreted-text role="gh"}.)
mimetypes{.interpreted-text role="mod"}:
- Valid extensions start with a '.' or are empty for mimetypes.MimeTypes.add_type{.interpreted-text role="meth"}. Undotted extensions are deprecated and will raise a ValueError{.interpreted-text role="exc"} in Python 3.16. (Contributed by Hugo van Kemenade in 75223{.interpreted-text role="gh"}.)
shutil{.interpreted-text role="mod"}:
- The !ExecError{.interpreted-text role="class"} exception has been deprecated since Python 3.14. It has not been used by any function in !shutil{.interpreted-text role="mod"} since Python 3.4, and is now an alias of RuntimeError{.interpreted-text role="exc"}.
symtable{.interpreted-text role="mod"}:
- The Class.get_methods <symtable.Class.get_methods>{.interpreted-text role="meth"} method has been deprecated since Python 3.14.
sys{.interpreted-text role="mod"}:
- The ~sys._enablelegacywindowsfsencoding{.interpreted-text role="func"} function has been deprecated since Python 3.13. Use the PYTHONLEGACYWINDOWSFSENCODING{.interpreted-text role="envvar"} environment variable instead.
sysconfig{.interpreted-text role="mod"}:
- The !sysconfig.expand_makefile_vars{.interpreted-text role="func"} function has been deprecated since Python 3.14. Use the vars argument of sysconfig.get_paths{.interpreted-text role="func"} instead.
tarfile{.interpreted-text role="mod"}:
- The undocumented and unused !TarFile.tarfile{.interpreted-text role="attr"} attribute has been deprecated since Python 3.13.

Pending removal in Python 3.17

collections.abc{.interpreted-text role="mod"}:
- collections.abc.ByteString{.interpreted-text role="class"} is scheduled for removal in Python 3.17.
  
  Use isinstance(obj, collections.abc.Buffer) to test if obj implements the buffer protocol <bufferobjects>{.interpreted-text role="ref"} at runtime. For use in type annotations, either use ~collections.abc.Buffer{.interpreted-text role="class"} or a union that explicitly specifies the types your code supports (e.g., bytes | bytearray | memoryview).
  
  !ByteString{.interpreted-text role="class"} was originally intended to be an abstract class that would serve as a supertype of both bytes{.interpreted-text role="class"} and bytearray{.interpreted-text role="class"}. However, since the ABC never had any methods, knowing that an object was an instance of !ByteString{.interpreted-text role="class"} never actually told you anything useful about the object. Other common buffer types such as memoryview{.interpreted-text role="class"} were also never understood as subtypes of !ByteString{.interpreted-text role="class"} (either at runtime or by static type checkers).
  
  See PEP 688 <688#current-options>{.interpreted-text role="pep"} for more details. (Contributed by Shantanu Jain in 91896{.interpreted-text role="gh"}.)
encodings{.interpreted-text role="mod"}:
- Passing non-ascii encoding names to encodings.normalize_encoding{.interpreted-text role="func"} is deprecated and scheduled for removal in Python 3.17. (Contributed by Stan Ulbrych in 136702{.interpreted-text role="gh"})
typing{.interpreted-text role="mod"}:
- Before Python 3.14, 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 typing.get_origin{.interpreted-text role="func"} and typing.get_args{.interpreted-text role="func"} instead of relying on private implementation details.
- typing.ByteString{.interpreted-text role="class"}, deprecated since Python 3.9, is scheduled for removal in Python 3.17.
  
  Use isinstance(obj, collections.abc.Buffer) to test if obj implements the buffer protocol <bufferobjects>{.interpreted-text role="ref"} at runtime. For use in type annotations, either use ~collections.abc.Buffer{.interpreted-text role="class"} or a union that explicitly specifies the types your code supports (e.g., bytes | bytearray | memoryview).
  
  !ByteString{.interpreted-text role="class"} was originally intended to be an abstract class that would serve as a supertype of both bytes{.interpreted-text role="class"} and bytearray{.interpreted-text role="class"}. However, since the ABC never had any methods, knowing that an object was an instance of !ByteString{.interpreted-text role="class"} never actually told you anything useful about the object. Other common buffer types such as memoryview{.interpreted-text role="class"} were also never understood as subtypes of !ByteString{.interpreted-text role="class"} (either at runtime or by static type checkers).
  
  See PEP 688 <688#current-options>{.interpreted-text role="pep"} for more details. (Contributed by Shantanu Jain in 91896{.interpreted-text role="gh"}.)

Pending removal in Python 3.18

decimal{.interpreted-text role="mod"}:
- The non-standard and undocumented ~decimal.Decimal{.interpreted-text role="class"} format specifier 'N', which is only supported in the !decimal{.interpreted-text role="mod"} module's C implementation, has been deprecated since Python 3.13. (Contributed by Serhiy Storchaka in 89902{.interpreted-text role="gh"}.)

Pending removal in Python 3.19

ctypes{.interpreted-text role="mod"}:
- Implicitly switching to the MSVC-compatible struct layout by setting ~ctypes.Structure._pack_{.interpreted-text role="attr"} but not ~ctypes.Structure._layout_{.interpreted-text role="attr"} on non-Windows platforms.
hashlib{.interpreted-text role="mod"}:
- In hash function constructors such as ~hashlib.new{.interpreted-text role="func"} or the direct hash-named constructors such as ~hashlib.md5{.interpreted-text role="func"} and ~hashlib.sha256{.interpreted-text role="func"}, their optional initial data parameter could also be passed a keyword argument named data= or string= in various !hashlib{.interpreted-text role="mod"} implementations.
  
  Support for the string keyword argument name is now deprecated and slated for removal in Python 3.19.
  
  Before Python 3.13, the string keyword parameter was not correctly supported depending on the backend implementation of hash functions. Prefer passing the initial data as a positional argument for maximum backwards compatibility.

Pending removal in Python 3.20

The __version__, version and VERSION attributes have been deprecated in these standard library modules and will be removed in Python 3.20. Use sys.version_info{.interpreted-text role="py:data"} instead.
- argparse{.interpreted-text role="mod"}
- csv{.interpreted-text role="mod"}
- ctypes{.interpreted-text role="mod"}
- !ctypes.macholib{.interpreted-text role="mod"}
- decimal{.interpreted-text role="mod"} (use decimal.SPEC_VERSION{.interpreted-text role="data"} instead)
- http.server{.interpreted-text role="mod"}
- imaplib{.interpreted-text role="mod"}
- ipaddress{.interpreted-text role="mod"}
- json{.interpreted-text role="mod"}
- logging{.interpreted-text role="mod"} (__date__ also deprecated)
- optparse{.interpreted-text role="mod"}
- pickle{.interpreted-text role="mod"}
- platform{.interpreted-text role="mod"}
- re{.interpreted-text role="mod"}
- socketserver{.interpreted-text role="mod"}
- tabnanny{.interpreted-text role="mod"}
- tkinter.font{.interpreted-text role="mod"}
- tkinter.ttk{.interpreted-text role="mod"}
- wsgiref.simple_server{.interpreted-text role="mod"}
- xml.etree.ElementTree{.interpreted-text role="mod"}
- !xml.sax.expatreader{.interpreted-text role="mod"}
- xml.sax.handler{.interpreted-text role="mod"}
- zlib{.interpreted-text role="mod"}
(Contributed by Hugo van Kemenade and Stan Ulbrych in 76007{.interpreted-text role="gh"}.)

Pending removal in future versions

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

argparse{.interpreted-text role="mod"}:
- Nesting argument groups and nesting mutually exclusive groups are deprecated.
- Passing the undocumented keyword argument prefix_chars to ~argparse.ArgumentParser.add_argument_group{.interpreted-text role="meth"} is now deprecated.
- The argparse.FileType{.interpreted-text role="class"} type converter is deprecated.
builtins{.interpreted-text role="mod"}:
- Generators: throw(type, exc, tb) and athrow(type, exc, tb) signature is deprecated: use throw(exc) and athrow(exc) instead, the single argument signature.
- Currently Python accepts numeric literals immediately followed by keywords, for example 0in x, 1or x, 0if 1else 2. It allows confusing and ambiguous expressions like [0x1for x in y] (which can be interpreted as [0x1 for x in y] or [0x1f or x in y]). A syntax warning is raised if the numeric literal is immediately followed by one of keywords and{.interpreted-text role="keyword"}, else{.interpreted-text role="keyword"}, for{.interpreted-text role="keyword"}, if{.interpreted-text role="keyword"}, in{.interpreted-text role="keyword"}, is{.interpreted-text role="keyword"} and or{.interpreted-text role="keyword"}. In a future release it will be changed to a syntax error. (87999{.interpreted-text role="gh"})
- Support for __index__() and __int__() method returning non-int type: these methods will be required to return an instance of a strict subclass of int{.interpreted-text role="class"}.
- Support for __float__() method returning a strict subclass of float{.interpreted-text role="class"}: these methods will be required to return an instance of float{.interpreted-text role="class"}.
- Support for __complex__() method returning a strict subclass of complex{.interpreted-text role="class"}: these methods will be required to return an instance of complex{.interpreted-text role="class"}.
- Passing a complex number as the real or imag argument in the complex{.interpreted-text role="func"} constructor is now deprecated; it should only be passed as a single positional argument. (Contributed by Serhiy Storchaka in 109218{.interpreted-text role="gh"}.)
calendar{.interpreted-text role="mod"}: calendar.January and calendar.February constants are deprecated and replaced by calendar.JANUARY{.interpreted-text role="data"} and calendar.FEBRUARY{.interpreted-text role="data"}. (Contributed by Prince Roshan in 103636{.interpreted-text role="gh"}.)
codecs{.interpreted-text role="mod"}: use open{.interpreted-text role="func"} instead of codecs.open{.interpreted-text role="func"}. (133038{.interpreted-text role="gh"})
codeobject.co_lnotab{.interpreted-text role="attr"}: use the codeobject.co_lines{.interpreted-text role="meth"} method instead.
datetime{.interpreted-text role="mod"}:
- ~datetime.datetime.utcnow{.interpreted-text role="meth"}: use datetime.datetime.now(tz=datetime.UTC).
- ~datetime.datetime.utcfromtimestamp{.interpreted-text role="meth"}: use datetime.datetime.fromtimestamp(timestamp, tz=datetime.UTC).
gettext{.interpreted-text role="mod"}: Plural value must be an integer.
importlib{.interpreted-text role="mod"}:
- ~importlib.util.cache_from_source{.interpreted-text role="func"} debug_override parameter is deprecated: use the optimization parameter instead.
importlib.metadata{.interpreted-text role="mod"}:
- EntryPoints tuple interface.
- Implicit None on return values.
logging{.interpreted-text role="mod"}: the warn() method has been deprecated since Python 3.3, use ~logging.warning{.interpreted-text role="meth"} instead.
mailbox{.interpreted-text role="mod"}: Use of StringIO input and text mode is deprecated, use BytesIO and binary mode instead.
os{.interpreted-text role="mod"}: Calling os.register_at_fork{.interpreted-text role="func"} in a multi-threaded process.
os.path{.interpreted-text role="mod"}: os.path.commonprefix{.interpreted-text role="func"} is deprecated, use os.path.commonpath{.interpreted-text role="func"} for path prefixes. The os.path.commonprefix{.interpreted-text role="func"} function is being deprecated due to having a misleading name and module. The function is not safe to use for path prefixes despite being included in a module about path manipulation, meaning it is easy to accidentally introduce path traversal vulnerabilities into Python programs by using this function.
!pydoc.ErrorDuringImport{.interpreted-text role="class"}: A tuple value for exc_info parameter is deprecated, use an exception instance.
re{.interpreted-text role="mod"}: More strict rules are now applied for numerical group references and group names in regular expressions. Only sequence of ASCII digits is now accepted as a numerical reference. The group name in bytes patterns and replacement strings can now only contain ASCII letters and digits and underscore. (Contributed by Serhiy Storchaka in 91760{.interpreted-text role="gh"}.)
shutil{.interpreted-text role="mod"}: ~shutil.rmtree{.interpreted-text role="func"}'s onerror parameter is deprecated in Python 3.12; use the onexc parameter instead.
ssl{.interpreted-text role="mod"} options and protocols:
- ssl.SSLContext{.interpreted-text role="class"} without protocol argument is deprecated.
- ssl.SSLContext{.interpreted-text role="class"}: ~ssl.SSLContext.set_npn_protocols{.interpreted-text role="meth"} and !selected_npn_protocol{.interpreted-text role="meth"} are deprecated: use ALPN instead.
- ssl.OP_NO_SSL* options
- ssl.OP_NO_TLS* options
- ssl.PROTOCOL_SSLv3
- ssl.PROTOCOL_TLS
- ssl.PROTOCOL_TLSv1
- ssl.PROTOCOL_TLSv1_1
- ssl.PROTOCOL_TLSv1_2
- ssl.TLSVersion.SSLv3
- ssl.TLSVersion.TLSv1
- ssl.TLSVersion.TLSv1_1
threading{.interpreted-text role="mod"} methods:
- !threading.Condition.notifyAll{.interpreted-text role="meth"}: use ~threading.Condition.notify_all{.interpreted-text role="meth"}.
- !threading.Event.isSet{.interpreted-text role="meth"}: use ~threading.Event.is_set{.interpreted-text role="meth"}.
- !threading.Thread.isDaemon{.interpreted-text role="meth"}, threading.Thread.setDaemon{.interpreted-text role="meth"}: use threading.Thread.daemon{.interpreted-text role="attr"} attribute.
- !threading.Thread.getName{.interpreted-text role="meth"}, threading.Thread.setName{.interpreted-text role="meth"}: use threading.Thread.name{.interpreted-text role="attr"} attribute.
- !threading.currentThread{.interpreted-text role="meth"}: use threading.current_thread{.interpreted-text role="meth"}.
- !threading.activeCount{.interpreted-text role="meth"}: use threading.active_count{.interpreted-text role="meth"}.
typing.Text{.interpreted-text role="class"} (92332{.interpreted-text role="gh"}).
The internal class typing._UnionGenericAlias is no longer used to implement typing.Union{.interpreted-text role="class"}. To preserve compatibility with users using this private class, a compatibility shim will be provided until at least Python 3.17. (Contributed by Jelle Zijlstra in 105499{.interpreted-text role="gh"}.)
unittest.IsolatedAsyncioTestCase{.interpreted-text role="class"}: it is deprecated to return a value that is not None from a test case.
urllib.parse{.interpreted-text role="mod"} deprecated functions: ~urllib.parse.urlparse{.interpreted-text role="func"} instead
- splitattr()
- splithost()
- splitnport()
- splitpasswd()
- splitport()
- splitquery()
- splittag()
- splittype()
- splituser()
- splitvalue()
- to_bytes()
wsgiref{.interpreted-text role="mod"}: SimpleHandler.stdout.write() should not do partial writes.
xml.etree.ElementTree{.interpreted-text role="mod"}: Testing the truth value of an ~xml.etree.ElementTree.Element{.interpreted-text role="class"} is deprecated. In a future release it will always return True. Prefer explicit len(elem) or elem is not None tests instead.
sys._clear_type_cache{.interpreted-text role="func"} is deprecated: use sys._clear_internal_caches{.interpreted-text role="func"} instead.

CPython bytecode changes

Replaced the opcode !BINARY_SUBSCR{.interpreted-text role="opcode"} by the BINARY_OP{.interpreted-text role="opcode"} opcode with the NB_SUBSCR oparg. (Contributed by Irit Katriel in 100239{.interpreted-text role="gh"}.)
Add the BUILD_INTERPOLATION{.interpreted-text role="opcode"} and BUILD_TEMPLATE{.interpreted-text role="opcode"} opcodes to construct new ~string.templatelib.Interpolation{.interpreted-text role="class"} and ~string.templatelib.Template{.interpreted-text role="class"} instances, respectively. (Contributed by Lysandros Nikolaou and others in 132661{.interpreted-text role="gh"}; see also PEP 750: Template strings <whatsnew314-template-string-literals>{.interpreted-text role="ref"}).
Remove the !BUILD_CONST_KEY_MAP{.interpreted-text role="opcode"} opcode. Use BUILD_MAP{.interpreted-text role="opcode"} instead. (Contributed by Mark Shannon in 122160{.interpreted-text role="gh"}.)
Replace the !LOAD_ASSERTION_ERROR{.interpreted-text role="opcode"} opcode with LOAD_COMMON_CONSTANT{.interpreted-text role="opcode"} and add support for loading NotImplementedError{.interpreted-text role="exc"}.
Add the LOAD_FAST_BORROW{.interpreted-text role="opcode"} and LOAD_FAST_BORROW_LOAD_FAST_BORROW{.interpreted-text role="opcode"} 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 130704{.interpreted-text role="gh"}.)
Add the LOAD_SMALL_INT{.interpreted-text role="opcode"} opcode, which pushes a small integer equal to the oparg to the stack. The !RETURN_CONST{.interpreted-text role="opcode"} opcode is removed as it is no longer used. (Contributed by Mark Shannon in 125837{.interpreted-text role="gh"}.)
Add the new LOAD_SPECIAL{.interpreted-text role="opcode"} instruction. Generate code for with{.interpreted-text role="keyword"} and async with{.interpreted-text role="keyword"} statements using the new instruction. Removed the !BEFORE_WITH{.interpreted-text role="opcode"} and !BEFORE_ASYNC_WITH{.interpreted-text role="opcode"} instructions. (Contributed by Mark Shannon in 120507{.interpreted-text role="gh"}.)
Add the POP_ITER{.interpreted-text role="opcode"} opcode to support 'virtual' iterators. (Contributed by Mark Shannon in 132554{.interpreted-text role="gh"}.)

Pseudo-instructions

Add the !ANNOTATIONS_PLACEHOLDER{.interpreted-text role="opcode"} pseudo instruction to support partially executed module-level annotations with deferred evaluation of annotations <whatsnew314-deferred-annotations>{.interpreted-text role="ref"}. (Contributed by Jelle Zijlstra in 130907{.interpreted-text role="gh"}.)
Add the !BINARY_OP_EXTEND{.interpreted-text role="opcode"} pseudo instruction, which executes a pair of functions (guard and specialization functions) accessed from the inline cache. (Contributed by Irit Katriel in 100239{.interpreted-text role="gh"}.)
Add three specializations for CALL_KW{.interpreted-text role="opcode"}; !CALL_KW_PY{.interpreted-text role="opcode"} for calls to Python functions, !CALL_KW_BOUND_METHOD{.interpreted-text role="opcode"} for calls to bound methods, and !CALL_KW_NON_PY{.interpreted-text role="opcode"} for all other calls. (Contributed by Mark Shannon in 118093{.interpreted-text role="gh"}.)
Add the JUMP_IF_TRUE{.interpreted-text role="opcode"} and JUMP_IF_FALSE{.interpreted-text role="opcode"} 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 124285{.interpreted-text role="gh"}.)
Add the !LOAD_CONST_MORTAL{.interpreted-text role="opcode"} pseudo instruction. (Contributed by Mark Shannon in 128685{.interpreted-text role="gh"}.)
Add the !LOAD_CONST_IMMORTAL{.interpreted-text role="opcode"} pseudo instruction, which does the same as !LOAD_CONST{.interpreted-text role="opcode"}, but is more efficient for immortal objects. (Contributed by Mark Shannon in 125837{.interpreted-text role="gh"}.)
Add the NOT_TAKEN{.interpreted-text role="opcode"} pseudo instruction, used by sys.monitoring{.interpreted-text role="mod"} to record branch events (such as BRANCH_LEFT{.interpreted-text role="monitoring-event"}). (Contributed by Mark Shannon in 122548{.interpreted-text role="gh"}.)

C API changes

Python configuration C API {#whatsnew314-capi-config}

Add a PyInitConfig C API <pyinitconfig_api>{.interpreted-text role="ref"} to configure the Python initialization without relying on C structures and the ability to make ABI-compatible changes in the future.

Complete the 587{.interpreted-text role="pep"} PyConfig C API <pyconfig_api>{.interpreted-text role="ref"} by adding PyInitConfig_AddModule{.interpreted-text role="c:func"} which can be used to add a built-in extension module; a feature previously referred to as the "inittab".

Add PyConfig_Get{.interpreted-text role="c:func"} and PyConfig_Set{.interpreted-text role="c:func"} functions to get and set the current runtime configuration.

587{.interpreted-text role="pep"} '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 107954{.interpreted-text role="gh"}.)

::: seealso 741{.interpreted-text role="pep"} and 587{.interpreted-text role="pep"} :::

New features in the C API

Add Py_PACK_VERSION{.interpreted-text role="c:func"} and Py_PACK_FULL_VERSION{.interpreted-text role="c:func"}, two new macros for bit-packing Python version numbers. This is useful for comparisons with Py_Version{.interpreted-text role="c:var"} or PY_VERSION_HEX{.interpreted-text role="c:macro"}. (Contributed by Petr Viktorin in 128629{.interpreted-text role="gh"}.)
Add PyBytes_Join(sep, iterable) <PyBytes_Join>{.interpreted-text role="c:func"} function, similar to sep.join(iterable) in Python. (Contributed by Victor Stinner in 121645{.interpreted-text role="gh"}.)
Add functions to manipulate the configuration of the current runtime Python interpreter (PEP 741: Python configuration C API <whatsnew314-capi-config>{.interpreted-text role="ref"}):
- PyConfig_Get{.interpreted-text role="c:func"}
- PyConfig_GetInt{.interpreted-text role="c:func"}
- PyConfig_Set{.interpreted-text role="c:func"}
- PyConfig_Names{.interpreted-text role="c:func"}
(Contributed by Victor Stinner in 107954{.interpreted-text role="gh"}.)
Add functions to configure Python initialization (PEP 741: Python configuration C API <whatsnew314-capi-config>{.interpreted-text role="ref"}):
- Py_InitializeFromInitConfig{.interpreted-text role="c:func"}
- PyInitConfig_AddModule{.interpreted-text role="c:func"}
- PyInitConfig_Create{.interpreted-text role="c:func"}
- PyInitConfig_Free{.interpreted-text role="c:func"}
- PyInitConfig_FreeStrList{.interpreted-text role="c:func"}
- PyInitConfig_GetError{.interpreted-text role="c:func"}
- PyInitConfig_GetExitCode{.interpreted-text role="c:func"}
- PyInitConfig_GetInt{.interpreted-text role="c:func"}
- PyInitConfig_GetStr{.interpreted-text role="c:func"}
- PyInitConfig_GetStrList{.interpreted-text role="c:func"}
- PyInitConfig_HasOption{.interpreted-text role="c:func"}
- PyInitConfig_SetInt{.interpreted-text role="c:func"}
- PyInitConfig_SetStr{.interpreted-text role="c:func"}
- PyInitConfig_SetStrList{.interpreted-text role="c:func"}
(Contributed by Victor Stinner in 107954{.interpreted-text role="gh"}.)
Add Py_fopen{.interpreted-text role="c:func"} function to open a file. This works similarly to the standard C !fopen{.interpreted-text role="c:func"} function, instead accepting a Python object for the path parameter and setting an exception on error. The corresponding new Py_fclose{.interpreted-text role="c:func"} function should be used to close a file. (Contributed by Victor Stinner in 127350{.interpreted-text role="gh"}.)
Add Py_HashBuffer{.interpreted-text role="c:func"} to compute and return the hash value of a buffer. (Contributed by Antoine Pitrou and Victor Stinner in 122854{.interpreted-text role="gh"}.)
Add PyImport_ImportModuleAttr{.interpreted-text role="c:func"} and PyImport_ImportModuleAttrString{.interpreted-text role="c:func"} helper functions to import a module and get an attribute of the module. (Contributed by Victor Stinner in 128911{.interpreted-text role="gh"}.)
Add PyIter_NextItem{.interpreted-text role="c:func"} to replace PyIter_Next{.interpreted-text role="c:func"}, which has an ambiguous return value. (Contributed by Irit Katriel and Erlend Aasland in 105201{.interpreted-text role="gh"}.)
Add PyLong_GetSign{.interpreted-text role="c:func"} function to get the sign of int{.interpreted-text role="class"} objects. (Contributed by Sergey B Kirpichev in 116560{.interpreted-text role="gh"}.)
Add PyLong_IsPositive{.interpreted-text role="c:func"}, PyLong_IsNegative{.interpreted-text role="c:func"} and PyLong_IsZero{.interpreted-text role="c:func"} for checking if PyLongObject{.interpreted-text role="c:type"} is positive, negative, or zero, respectively. (Contributed by James Roy and Sergey B Kirpichev in 126061{.interpreted-text role="gh"}.)
Add new functions to convert C <stdint.h> numbers to/from Python int{.interpreted-text role="class"} objects:
- PyLong_AsInt32{.interpreted-text role="c:func"}
- PyLong_AsInt64{.interpreted-text role="c:func"}
- PyLong_AsUInt32{.interpreted-text role="c:func"}
- PyLong_AsUInt64{.interpreted-text role="c:func"}
- PyLong_FromInt32{.interpreted-text role="c:func"}
- PyLong_FromInt64{.interpreted-text role="c:func"}
- PyLong_FromUInt32{.interpreted-text role="c:func"}
- PyLong_FromUInt64{.interpreted-text role="c:func"}
(Contributed by Victor Stinner in 120389{.interpreted-text role="gh"}.)
Add a new import and export API for Python int{.interpreted-text role="class"} objects (757{.interpreted-text role="pep"}):
- PyLong_GetNativeLayout{.interpreted-text role="c:func"}
- PyLong_Export{.interpreted-text role="c:func"}
- PyLong_FreeExport{.interpreted-text role="c:func"}
- PyLongWriter_Create{.interpreted-text role="c:func"}
- PyLongWriter_Finish{.interpreted-text role="c:func"}
- PyLongWriter_Discard{.interpreted-text role="c:func"}
(Contributed by Sergey B Kirpichev and Victor Stinner in 102471{.interpreted-text role="gh"}.)
Add PyMonitoring_FireBranchLeftEvent{.interpreted-text role="c:func"} and PyMonitoring_FireBranchRightEvent{.interpreted-text role="c:func"} for generating BRANCH_LEFT{.interpreted-text role="monitoring-event"} and BRANCH_RIGHT{.interpreted-text role="monitoring-event"} events, respectively. (Contributed by Mark Shannon in 122548{.interpreted-text role="gh"}.)
Add PyType_Freeze{.interpreted-text role="c:func"} function to make a type immutable. (Contributed by Victor Stinner in 121654{.interpreted-text role="gh"}.)
Add PyType_GetBaseByToken{.interpreted-text role="c:func"} and Py_tp_token{.interpreted-text role="c:data"} slot for easier superclass identification, which attempts to resolve the type checking issue mentioned in PEP 630 <630#type-checking>{.interpreted-text role="pep"}. (Contributed in 124153{.interpreted-text role="gh"}.)
Add a new PyUnicode_Equal{.interpreted-text role="c:func"} function to test if two strings are equal. The function is also added to the Limited C API. (Contributed by Victor Stinner in 124502{.interpreted-text role="gh"}.)
Add a new PyUnicodeWriter{.interpreted-text role="c:type"} API to create a Python str{.interpreted-text role="class"} object, with the following functions:
- PyUnicodeWriter_Create{.interpreted-text role="c:func"}
- PyUnicodeWriter_DecodeUTF8Stateful{.interpreted-text role="c:func"}
- PyUnicodeWriter_Discard{.interpreted-text role="c:func"}
- PyUnicodeWriter_Finish{.interpreted-text role="c:func"}
- PyUnicodeWriter_Format{.interpreted-text role="c:func"}
- PyUnicodeWriter_WriteASCII{.interpreted-text role="c:func"}
- PyUnicodeWriter_WriteChar{.interpreted-text role="c:func"}
- PyUnicodeWriter_WriteRepr{.interpreted-text role="c:func"}
- PyUnicodeWriter_WriteStr{.interpreted-text role="c:func"}
- PyUnicodeWriter_WriteSubstring{.interpreted-text role="c:func"}
- PyUnicodeWriter_WriteUCS4{.interpreted-text role="c:func"}
- PyUnicodeWriter_WriteUTF8{.interpreted-text role="c:func"}
- PyUnicodeWriter_WriteWideChar{.interpreted-text role="c:func"}
(Contributed by Victor Stinner in 119182{.interpreted-text role="gh"}.)
The k and K formats in PyArg_ParseTuple{.interpreted-text role="c:func"} and similar functions now use ~object.__index__{.interpreted-text role="meth"} if available, like all other integer formats. (Contributed by Serhiy Storchaka in 112068{.interpreted-text role="gh"}.)
Add support for a new p format unit in Py_BuildValue{.interpreted-text role="c:func"} that produces a Python bool{.interpreted-text role="class"} object from a C integer. (Contributed by Pablo Galindo in 45325{.interpreted-text role="issue"}.)
Add PyUnstable_IsImmortal{.interpreted-text role="c:func"} for determining if an object is immortal{.interpreted-text role="term"}, for debugging purposes. (Contributed by Peter Bierma in 128509{.interpreted-text role="gh"}.)
Add PyUnstable_Object_EnableDeferredRefcount{.interpreted-text role="c:func"} for enabling deferred reference counting, as outlined in 703{.interpreted-text role="pep"}.
Add PyUnstable_Object_IsUniquelyReferenced{.interpreted-text role="c:func"} as a replacement for Py_REFCNT(op) == 1 on free threaded <free threading>{.interpreted-text role="term"} builds. (Contributed by Peter Bierma in 133140{.interpreted-text role="gh"}.)
Add PyUnstable_Object_IsUniqueReferencedTemporary{.interpreted-text role="c:func"} 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 Py_REFCNT{.interpreted-text role="c:func"} is 1 for Python objects passed as arguments to C API functions. (Contributed by Sam Gross in 133164{.interpreted-text role="gh"}.)

Limited C API changes

In the limited C API version 3.14 and newer, Py_TYPE{.interpreted-text role="c:func"} and Py_REFCNT{.interpreted-text role="c:func"} are now implemented as an opaque function call to hide implementation details. (Contributed by Victor Stinner in 120600{.interpreted-text role="gh"} and 124127{.interpreted-text role="gh"}.)
Remove the PySequence_Fast_GET_SIZE{.interpreted-text role="c:macro"}, PySequence_Fast_GET_ITEM{.interpreted-text role="c:macro"}, and PySequence_Fast_ITEMS{.interpreted-text role="c:macro"} macros from the limited C API, since they have always been broken in the limited C API. (Contributed by Victor Stinner in 91417{.interpreted-text role="gh"}.)

Removed C APIs {#whatsnew314-c-api-removed}

Creating immutable types <Py_TPFLAGS_IMMUTABLETYPE>{.interpreted-text role="c:data"} with mutable bases was deprecated in Python 3.12, and now raises a TypeError{.interpreted-text role="exc"}. (Contributed by Nikita Sobolev in 119775{.interpreted-text role="gh"}.)
Remove PyDictObject.ma_version_tag member, which was deprecated in Python 3.12. Use the PyDict_AddWatcher{.interpreted-text role="c:func"} API instead. (Contributed by Sam Gross in 124296{.interpreted-text role="gh"}.)
Remove the private _Py_InitializeMain() function. It was a provisional API{.interpreted-text role="term"} added to Python 3.8 by 587{.interpreted-text role="pep"}. (Contributed by Victor Stinner in 129033{.interpreted-text role="gh"}.)
Remove the undocumented APIs !Py_C_RECURSION_LIMIT{.interpreted-text role="c:macro"} and !PyThreadState.c_recursion_remaining{.interpreted-text role="c:member"}. These were added in 3.13 and have been removed without deprecation. Use Py_EnterRecursiveCall{.interpreted-text role="c:func"} to guard against runaway recursion in C code. (Removed by Petr Viktorin in 133079{.interpreted-text role="gh"}, see also 130396{.interpreted-text role="gh"}.)

Deprecated C APIs {#whatsnew314-c-api-deprecated}

The !Py_HUGE_VAL{.interpreted-text role="c:macro"} macro is now soft deprecated{.interpreted-text role="term"}. Use !INFINITY{.interpreted-text role="c:macro"} instead. (Contributed by Sergey B Kirpichev in 120026{.interpreted-text role="gh"}.)
The !Py_IS_NAN{.interpreted-text role="c:macro"}, !Py_IS_INFINITY{.interpreted-text role="c:macro"}, and !Py_IS_FINITE{.interpreted-text role="c:macro"} macros are now soft deprecated{.interpreted-text role="term"}. Use !isnan{.interpreted-text role="c:macro"}, !isinf{.interpreted-text role="c:macro"} and !isfinite{.interpreted-text role="c:macro"} instead, available from math.h{.interpreted-text role="file"} since C99. (Contributed by Sergey B Kirpichev in 119613{.interpreted-text role="gh"}.)
Non-tuple sequences are now deprecated as argument for the (items) format unit in PyArg_ParseTuple{.interpreted-text role="c:func"} and other argument parsing <arg-parsing>{.interpreted-text role="ref"} functions if items contains format units which store a borrowed buffer <c-arg-borrowed-buffer>{.interpreted-text role="ref"} or a borrowed reference{.interpreted-text role="term"}. (Contributed by Serhiy Storchaka in 50333{.interpreted-text role="gh"}.)
The _PyMonitoring_FireBranchEvent function is now deprecated and should be replaced with calls to PyMonitoring_FireBranchLeftEvent{.interpreted-text role="c:func"} and PyMonitoring_FireBranchRightEvent{.interpreted-text role="c:func"}.
The previously undocumented function PySequence_In{.interpreted-text role="c:func"} is now soft deprecated{.interpreted-text role="term"}. Use PySequence_Contains{.interpreted-text role="c:func"} instead. (Contributed by Yuki Kobayashi in 127896{.interpreted-text role="gh"}.)

Pending removal in Python 3.15

The !PyImport_ImportModuleNoBlock{.interpreted-text role="c:func"}: Use PyImport_ImportModule{.interpreted-text role="c:func"} instead.
!PyWeakref_GetObject{.interpreted-text role="c:func"} and !PyWeakref_GET_OBJECT{.interpreted-text role="c:func"}: Use PyWeakref_GetRef{.interpreted-text role="c:func"} instead. The pythoncapi-compat project can be used to get PyWeakref_GetRef{.interpreted-text role="c:func"} on Python 3.12 and older.
Py_UNICODE{.interpreted-text role="c:type"} type and the !Py_UNICODE_WIDE{.interpreted-text role="c:macro"} macro: Use wchar_t{.interpreted-text role="c:type"} instead.
!PyUnicode_AsDecodedObject{.interpreted-text role="c:func"}: Use PyCodec_Decode{.interpreted-text role="c:func"} instead.
!PyUnicode_AsDecodedUnicode{.interpreted-text role="c:func"}: Use PyCodec_Decode{.interpreted-text role="c:func"} instead; Note that some codecs (for example, "base64") may return a type other than str{.interpreted-text role="class"}, such as bytes{.interpreted-text role="class"}.
!PyUnicode_AsEncodedObject{.interpreted-text role="c:func"}: Use PyCodec_Encode{.interpreted-text role="c:func"} instead.
!PyUnicode_AsEncodedUnicode{.interpreted-text role="c:func"}: Use PyCodec_Encode{.interpreted-text role="c:func"} instead; Note that some codecs (for example, "base64") may return a type other than bytes{.interpreted-text role="class"}, such as str{.interpreted-text role="class"}.
Python initialization functions, deprecated in Python 3.13:
- !Py_GetPath{.interpreted-text role="c:func"}: Use PyConfig_Get("module_search_paths") <PyConfig_Get>{.interpreted-text role="c:func"} (sys.path{.interpreted-text role="data"}) instead.
- !Py_GetPrefix{.interpreted-text role="c:func"}: Use PyConfig_Get("base_prefix") <PyConfig_Get>{.interpreted-text role="c:func"} (sys.base_prefix{.interpreted-text role="data"}) instead. Use PyConfig_Get("prefix") <PyConfig_Get>{.interpreted-text role="c:func"} (sys.prefix{.interpreted-text role="data"}) if virtual environments <venv-def>{.interpreted-text role="ref"} need to be handled.
- !Py_GetExecPrefix{.interpreted-text role="c:func"}: Use PyConfig_Get("base_exec_prefix") <PyConfig_Get>{.interpreted-text role="c:func"} (sys.base_exec_prefix{.interpreted-text role="data"}) instead. Use PyConfig_Get("exec_prefix") <PyConfig_Get>{.interpreted-text role="c:func"} (sys.exec_prefix{.interpreted-text role="data"}) if virtual environments <venv-def>{.interpreted-text role="ref"} need to be handled.
- !Py_GetProgramFullPath{.interpreted-text role="c:func"}: Use PyConfig_Get("executable") <PyConfig_Get>{.interpreted-text role="c:func"} (sys.executable{.interpreted-text role="data"}) instead.
- !Py_GetProgramName{.interpreted-text role="c:func"}: Use PyConfig_Get("executable") <PyConfig_Get>{.interpreted-text role="c:func"} (sys.executable{.interpreted-text role="data"}) instead.
- !Py_GetPythonHome{.interpreted-text role="c:func"}: Use PyConfig_Get("home") <PyConfig_Get>{.interpreted-text role="c:func"} or the PYTHONHOME{.interpreted-text role="envvar"} environment variable instead.
The pythoncapi-compat project can be used to get PyConfig_Get{.interpreted-text role="c:func"} on Python 3.13 and older.
Functions to configure Python's initialization, deprecated in Python 3.11:
- !PySys_SetArgvEx(){.interpreted-text role="c:func"}: Set PyConfig.argv{.interpreted-text role="c:member"} instead.
- !PySys_SetArgv(){.interpreted-text role="c:func"}: Set PyConfig.argv{.interpreted-text role="c:member"} instead.
- !Py_SetProgramName(){.interpreted-text role="c:func"}: Set PyConfig.program_name{.interpreted-text role="c:member"} instead.
- !Py_SetPythonHome(){.interpreted-text role="c:func"}: Set PyConfig.home{.interpreted-text role="c:member"} instead.
- !PySys_ResetWarnOptions{.interpreted-text role="c:func"}: Clear sys.warnoptions{.interpreted-text role="data"} and !warnings.filters{.interpreted-text role="data"} instead.
The Py_InitializeFromConfig{.interpreted-text role="c:func"} API should be used with PyConfig{.interpreted-text role="c:type"} instead.
Global configuration variables:
- Py_DebugFlag{.interpreted-text role="c:var"}: Use PyConfig.parser_debug{.interpreted-text role="c:member"} or PyConfig_Get("parser_debug") <PyConfig_Get>{.interpreted-text role="c:func"} instead.
- Py_VerboseFlag{.interpreted-text role="c:var"}: Use PyConfig.verbose{.interpreted-text role="c:member"} or PyConfig_Get("verbose") <PyConfig_Get>{.interpreted-text role="c:func"} instead.
- Py_QuietFlag{.interpreted-text role="c:var"}: Use PyConfig.quiet{.interpreted-text role="c:member"} or PyConfig_Get("quiet") <PyConfig_Get>{.interpreted-text role="c:func"} instead.
- Py_InteractiveFlag{.interpreted-text role="c:var"}: Use PyConfig.interactive{.interpreted-text role="c:member"} or PyConfig_Get("interactive") <PyConfig_Get>{.interpreted-text role="c:func"} instead.
- Py_InspectFlag{.interpreted-text role="c:var"}: Use PyConfig.inspect{.interpreted-text role="c:member"} or PyConfig_Get("inspect") <PyConfig_Get>{.interpreted-text role="c:func"} instead.
- Py_OptimizeFlag{.interpreted-text role="c:var"}: Use PyConfig.optimization_level{.interpreted-text role="c:member"} or PyConfig_Get("optimization_level") <PyConfig_Get>{.interpreted-text role="c:func"} instead.
- Py_NoSiteFlag{.interpreted-text role="c:var"}: Use PyConfig.site_import{.interpreted-text role="c:member"} or PyConfig_Get("site_import") <PyConfig_Get>{.interpreted-text role="c:func"} instead.
- Py_BytesWarningFlag{.interpreted-text role="c:var"}: Use PyConfig.bytes_warning{.interpreted-text role="c:member"} or PyConfig_Get("bytes_warning") <PyConfig_Get>{.interpreted-text role="c:func"} instead.
- Py_FrozenFlag{.interpreted-text role="c:var"}: Use PyConfig.pathconfig_warnings{.interpreted-text role="c:member"} or PyConfig_Get("pathconfig_warnings") <PyConfig_Get>{.interpreted-text role="c:func"} instead.
- Py_IgnoreEnvironmentFlag{.interpreted-text role="c:var"}: Use PyConfig.use_environment{.interpreted-text role="c:member"} or PyConfig_Get("use_environment") <PyConfig_Get>{.interpreted-text role="c:func"} instead.
- Py_DontWriteBytecodeFlag{.interpreted-text role="c:var"}: Use PyConfig.write_bytecode{.interpreted-text role="c:member"} or PyConfig_Get("write_bytecode") <PyConfig_Get>{.interpreted-text role="c:func"} instead.
- Py_NoUserSiteDirectory{.interpreted-text role="c:var"}: Use PyConfig.user_site_directory{.interpreted-text role="c:member"} or PyConfig_Get("user_site_directory") <PyConfig_Get>{.interpreted-text role="c:func"} instead.
- Py_UnbufferedStdioFlag{.interpreted-text role="c:var"}: Use PyConfig.buffered_stdio{.interpreted-text role="c:member"} or PyConfig_Get("buffered_stdio") <PyConfig_Get>{.interpreted-text role="c:func"} instead.
- Py_HashRandomizationFlag{.interpreted-text role="c:var"}: Use PyConfig.use_hash_seed{.interpreted-text role="c:member"} and PyConfig.hash_seed{.interpreted-text role="c:member"} or PyConfig_Get("hash_seed") <PyConfig_Get>{.interpreted-text role="c:func"} instead.
- Py_IsolatedFlag{.interpreted-text role="c:var"}: Use PyConfig.isolated{.interpreted-text role="c:member"} or PyConfig_Get("isolated") <PyConfig_Get>{.interpreted-text role="c:func"} instead.
- Py_LegacyWindowsFSEncodingFlag{.interpreted-text role="c:var"}: Use PyPreConfig.legacy_windows_fs_encoding{.interpreted-text role="c:member"} or PyConfig_Get("legacy_windows_fs_encoding") <PyConfig_Get>{.interpreted-text role="c:func"} instead.
- Py_LegacyWindowsStdioFlag{.interpreted-text role="c:var"}: Use PyConfig.legacy_windows_stdio{.interpreted-text role="c:member"} or PyConfig_Get("legacy_windows_stdio") <PyConfig_Get>{.interpreted-text role="c:func"} instead.
- !Py_FileSystemDefaultEncoding{.interpreted-text role="c:var"}, !Py_HasFileSystemDefaultEncoding{.interpreted-text role="c:var"}: Use PyConfig.filesystem_encoding{.interpreted-text role="c:member"} or PyConfig_Get("filesystem_encoding") <PyConfig_Get>{.interpreted-text role="c:func"} instead.
- !Py_FileSystemDefaultEncodeErrors{.interpreted-text role="c:var"}: Use PyConfig.filesystem_errors{.interpreted-text role="c:member"} or PyConfig_Get("filesystem_errors") <PyConfig_Get>{.interpreted-text role="c:func"} instead.
- !Py_UTF8Mode{.interpreted-text role="c:var"}: Use PyPreConfig.utf8_mode{.interpreted-text role="c:member"} or PyConfig_Get("utf8_mode") <PyConfig_Get>{.interpreted-text role="c:func"} instead. (see Py_PreInitialize{.interpreted-text role="c:func"})
The Py_InitializeFromConfig{.interpreted-text role="c:func"} API should be used with PyConfig{.interpreted-text role="c:type"} to set these options. Or PyConfig_Get{.interpreted-text role="c:func"} can be used to get these options at runtime.

Pending removal in Python 3.16

The bundled copy of libmpdec.

Pending removal in Python 3.18

The following private functions are deprecated and planned for removal in Python 3.18:
- !_PyBytes_Join{.interpreted-text role="c:func"}: use PyBytes_Join{.interpreted-text role="c:func"}.
- !_PyDict_GetItemStringWithError{.interpreted-text role="c:func"}: use PyDict_GetItemStringRef{.interpreted-text role="c:func"}.
- !_PyDict_Pop(){.interpreted-text role="c:func"}: use PyDict_Pop{.interpreted-text role="c:func"}.
- !_PyLong_Sign(){.interpreted-text role="c:func"}: use PyLong_GetSign{.interpreted-text role="c:func"}.
- !_PyLong_FromDigits{.interpreted-text role="c:func"} and !_PyLong_New{.interpreted-text role="c:func"}: use PyLongWriter_Create{.interpreted-text role="c:func"}.
- !_PyThreadState_UncheckedGet{.interpreted-text role="c:func"}: use PyThreadState_GetUnchecked{.interpreted-text role="c:func"}.
- !_PyUnicode_AsString{.interpreted-text role="c:func"}: use PyUnicode_AsUTF8{.interpreted-text role="c:func"}.
- !_PyUnicodeWriter_Init{.interpreted-text role="c:func"}: replace _PyUnicodeWriter_Init(&writer) with writer = PyUnicodeWriter_Create(0) <PyUnicodeWriter_Create>{.interpreted-text role="c:func"}.
- !_PyUnicodeWriter_Finish{.interpreted-text role="c:func"}: replace _PyUnicodeWriter_Finish(&writer) with PyUnicodeWriter_Finish(writer) <PyUnicodeWriter_Finish>{.interpreted-text role="c:func"}.
- !_PyUnicodeWriter_Dealloc{.interpreted-text role="c:func"}: replace _PyUnicodeWriter_Dealloc(&writer) with PyUnicodeWriter_Discard(writer) <PyUnicodeWriter_Discard>{.interpreted-text role="c:func"}.
- !_PyUnicodeWriter_WriteChar{.interpreted-text role="c:func"}: replace _PyUnicodeWriter_WriteChar(&writer, ch) with PyUnicodeWriter_WriteChar(writer, ch) <PyUnicodeWriter_WriteChar>{.interpreted-text role="c:func"}.
- !_PyUnicodeWriter_WriteStr{.interpreted-text role="c:func"}: replace _PyUnicodeWriter_WriteStr(&writer, str) with PyUnicodeWriter_WriteStr(writer, str) <PyUnicodeWriter_WriteStr>{.interpreted-text role="c:func"}.
- !_PyUnicodeWriter_WriteSubstring{.interpreted-text role="c:func"}: replace _PyUnicodeWriter_WriteSubstring(&writer, str, start, end) with PyUnicodeWriter_WriteSubstring(writer, str, start, end) <PyUnicodeWriter_WriteSubstring>{.interpreted-text role="c:func"}.
- !_PyUnicodeWriter_WriteASCIIString{.interpreted-text role="c:func"}: replace _PyUnicodeWriter_WriteASCIIString(&writer, str) with PyUnicodeWriter_WriteASCII(writer, str) <PyUnicodeWriter_WriteASCII>{.interpreted-text role="c:func"}.
- !_PyUnicodeWriter_WriteLatin1String{.interpreted-text role="c:func"}: replace _PyUnicodeWriter_WriteLatin1String(&writer, str) with PyUnicodeWriter_WriteUTF8(writer, str) <PyUnicodeWriter_WriteUTF8>{.interpreted-text role="c:func"}.
- !_PyUnicodeWriter_Prepare{.interpreted-text role="c:func"}: (no replacement).
- !_PyUnicodeWriter_PrepareKind{.interpreted-text role="c:func"}: (no replacement).
- !_Py_HashPointer{.interpreted-text role="c:func"}: use Py_HashPointer{.interpreted-text role="c:func"}.
- !_Py_fopen_obj{.interpreted-text role="c:func"}: use Py_fopen{.interpreted-text role="c:func"}.
The pythoncapi-compat project can be used to get these new public functions on Python 3.13 and older. (Contributed by Victor Stinner in 128863{.interpreted-text role="gh"}.)

Pending removal in future versions

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

Py_TPFLAGS_HAVE_FINALIZE{.interpreted-text role="c:macro"}: Unneeded since Python 3.8.
PyErr_Fetch{.interpreted-text role="c:func"}: Use PyErr_GetRaisedException{.interpreted-text role="c:func"} instead.
PyErr_NormalizeException{.interpreted-text role="c:func"}: Use PyErr_GetRaisedException{.interpreted-text role="c:func"} instead.
PyErr_Restore{.interpreted-text role="c:func"}: Use PyErr_SetRaisedException{.interpreted-text role="c:func"} instead.
PyModule_GetFilename{.interpreted-text role="c:func"}: Use PyModule_GetFilenameObject{.interpreted-text role="c:func"} instead.
PyOS_AfterFork{.interpreted-text role="c:func"}: Use PyOS_AfterFork_Child{.interpreted-text role="c:func"} instead.
PySlice_GetIndicesEx{.interpreted-text role="c:func"}: Use PySlice_Unpack{.interpreted-text role="c:func"} and PySlice_AdjustIndices{.interpreted-text role="c:func"} instead.
PyUnicode_READY{.interpreted-text role="c:func"}: Unneeded since Python 3.12
!PyErr_Display{.interpreted-text role="c:func"}: Use PyErr_DisplayException{.interpreted-text role="c:func"} instead.
!_PyErr_ChainExceptions{.interpreted-text role="c:func"}: Use !_PyErr_ChainExceptions1{.interpreted-text role="c:func"} instead.
!PyBytesObject.ob_shash{.interpreted-text role="c:member"} member: call PyObject_Hash{.interpreted-text role="c:func"} instead.
Thread Local Storage (TLS) API:
- PyThread_create_key{.interpreted-text role="c:func"}: Use PyThread_tss_alloc{.interpreted-text role="c:func"} instead.
- PyThread_delete_key{.interpreted-text role="c:func"}: Use PyThread_tss_free{.interpreted-text role="c:func"} instead.
- PyThread_set_key_value{.interpreted-text role="c:func"}: Use PyThread_tss_set{.interpreted-text role="c:func"} instead.
- PyThread_get_key_value{.interpreted-text role="c:func"}: Use PyThread_tss_get{.interpreted-text role="c:func"} instead.
- PyThread_delete_key_value{.interpreted-text role="c:func"}: Use PyThread_tss_delete{.interpreted-text role="c:func"} instead.
- PyThread_ReInitTLS{.interpreted-text role="c:func"}: Unneeded since Python 3.7.

Build changes {#whatsnew314-build-changes}

776{.interpreted-text role="pep"}: Emscripten is now an officially supported platform at tier 3 <11#tier-3>{.interpreted-text role="pep"}. As a part of this effort, more than 25 bugs in Emscripten libc were fixed. Emscripten now includes support for ctypes{.interpreted-text role="mod"}, termios{.interpreted-text role="mod"}, and fcntl{.interpreted-text role="mod"}, as well as experimental support for the new default interactive shell <tut-interactive>{.interpreted-text role="ref"}. (Contributed by R. Hood Chatham in 127146{.interpreted-text role="gh"}, 127683{.interpreted-text role="gh"}, and 136931{.interpreted-text role="gh"}.)
Official Android binary releases are now provided on python.org.
GNU Autoconf 2.72 is now required to generate configure{.interpreted-text role="file"}. (Contributed by Erlend Aasland in 115765{.interpreted-text role="gh"}.)
wasm32-unknown-emscripten is now a 11{.interpreted-text role="pep"} tier 3 platform. (Contributed by R. Hood Chatham in 127146{.interpreted-text role="gh"}, 127683{.interpreted-text role="gh"}, and 136931{.interpreted-text role="gh"}.)
#pragma-based linking with python3*.lib can now be switched off with Py_NO_LINK_LIB{.interpreted-text role="c:expr"}. (Contributed by Jean-Christophe Fillion-Robin in 82909{.interpreted-text role="gh"}.)
CPython now enables a set of recommended compiler options by default for improved security. Use the --disable-safety{.interpreted-text role="option"} configure{.interpreted-text role="file"} option to disable them, or the --enable-slower-safety{.interpreted-text role="option"} option for a larger set of compiler options, albeit with a performance cost.
The WITH_FREELISTS macro and --without-freelists configure{.interpreted-text role="file"} option have been removed.
The new configure{.interpreted-text role="file"} option --with-tail-call-interp{.interpreted-text role="option"} may be used to enable the experimental tail call interpreter. See whatsnew314-tail-call-interpreter{.interpreted-text role="ref"} for further details.
To disable the new remote debugging support, use the --without-remote-debug{.interpreted-text role="option"} configure{.interpreted-text role="file"} 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 127592{.interpreted-text role="gh"}.)
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 127592{.interpreted-text role="gh"}.)

`build-details.json`{.interpreted-text role="file"} {#whatsnew314-build_details}

Installations of Python now contain a new file, build-details.json{.interpreted-text role="file"}. 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.

build-details.json{.interpreted-text role="file"} must be installed in the platform-independent standard library directory. This corresponds to the 'stdlib' <installation_paths>{.interpreted-text role="ref"} sysconfig{.interpreted-text role="mod"} installation path, which can be found by running sysconfig.get_path('stdlib').

::: seealso 739{.interpreted-text role="pep"} -- build-details.json 1.0 -- a static description file for Python build details :::

Discontinuation of PGP signatures {#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. Releases have been signed using Sigstore since Python 3.11.

This change in release process was specified in 761{.interpreted-text role="pep"}.

Free-threaded Python is officially supported {#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 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, 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 779{.interpreted-text role="pep"}

PEP 779's acceptance :::

Binary releases for the experimental just-in-time compiler {#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 PYTHON_JIT=1 <PYTHON_JIT>{.interpreted-text role="envvar"} as an environment variable. Downstream source builds and redistributors can use the --enable-experimental-jit=yes-off{.interpreted-text role="option"} 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 sys._jit{.interpreted-text role="data"} namespace. sys._jit.is_available{.interpreted-text role="func"} can be used to determine if the current executable supports JIT compilation, while sys._jit.is_enabled{.interpreted-text role="func"} 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 pdb{.interpreted-text role="mod"} or profile{.interpreted-text role="mod"}, 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 744{.interpreted-text role="pep"} :::

Porting to Python 3.14

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

Changes in the Python API

On Unix platforms other than macOS, forkserver is now the default start method <multiprocessing-start-methods>{.interpreted-text role="ref"} for multiprocessing{.interpreted-text role="mod"} and ~concurrent.futures.ProcessPoolExecutor{.interpreted-text role="class"}, instead of fork.

See (1) <whatsnew314-concurrent-futures-start-method>{.interpreted-text role="ref"} and (2) <whatsnew314-multiprocessing-start-method>{.interpreted-text role="ref"} for details.

If you encounter NameError{.interpreted-text role="exc"}s or pickling errors coming out of multiprocessing{.interpreted-text role="mod"} or concurrent.futures{.interpreted-text role="mod"}, see the forkserver restrictions <multiprocessing-programming-forkserver>{.interpreted-text role="ref"}.

This change does not affect Windows or macOS, where 'spawn' <multiprocessing-start-method-spawn>{.interpreted-text role="ref"} remains the default start method.
functools.partial{.interpreted-text role="class"} is now a method descriptor. Wrap it in staticmethod{.interpreted-text role="func"} if you want to preserve the old behavior. (Contributed by Serhiy Storchaka and Dominykas Grigonis in 121027{.interpreted-text role="gh"}.)
The garbage collector is now incremental <whatsnew314-incremental-gc>{.interpreted-text role="ref"}, which means that the behavior of gc.collect{.interpreted-text role="func"} changes slightly:
- gc.collect(1): Performs an increment of garbage collection, rather than collecting generation 1.
- Other calls to !gc.collect{.interpreted-text role="func"} are unchanged.
The locale.nl_langinfo{.interpreted-text role="func"} function now temporarily sets the LC_CTYPE locale in some cases. This temporary change affects other threads. (Contributed by Serhiy Storchaka in 69998{.interpreted-text role="gh"}.)
types.UnionType{.interpreted-text role="class"} is now an alias for typing.Union{.interpreted-text role="class"}, causing changes in some behaviors. See above <whatsnew314-typing-union>{.interpreted-text role="ref"} for more details. (Contributed by Jelle Zijlstra in 105499{.interpreted-text role="gh"}.)
The runtime behavior of annotations has changed in various ways; see above <whatsnew314-deferred-annotations>{.interpreted-text role="ref"} for details. While most code that interacts with annotations should continue to work, some undocumented details may behave differently.
As part of making the mimetypes{.interpreted-text role="mod"} 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, sys.platform{.interpreted-text role="data"} no longer contains the major version number.

Changes in annotations (`649`{.interpreted-text role="pep"} and `749`{.interpreted-text role="pep"}) {#whatsnew314-porting-annotations}

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 deferred evaluation of annotations <whatsnew314-deferred-annotations>{.interpreted-text role="ref"}.

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 ~object.__annotations__{.interpreted-text role="attr"} attribute on objects, you may want to make changes in order to support code that relies on deferred evaluation of annotations. For example, you may want to use annotationlib.get_annotations{.interpreted-text role="func"} with the ~annotationlib.Format.FORWARDREF{.interpreted-text role="attr"} format, as the dataclasses{.interpreted-text role="mod"} module now does.

The external typing_extensions{.interpreted-text role="pypi"} package provides partial backports of some of the functionality of the annotationlib{.interpreted-text role="mod"} module, such as the ~annotationlib.Format{.interpreted-text role="class"} enum and the ~annotationlib.get_annotations{.interpreted-text role="func"} 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 !__annotations__{.interpreted-text role="attr"} works at runtime while minimizing breakage to code that contains annotations in source code and to code that reads !__annotations__{.interpreted-text role="attr"}. 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 annotationlib{.interpreted-text role="mod"} module.

In particular, do not read annotations directly from the namespace dictionary attribute of type objects. Use annotationlib.get_annotate_from_class_namespace{.interpreted-text role="func"} during class construction and annotationlib.get_annotations{.interpreted-text role="func"} 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, 563{.interpreted-text role="pep"} introduced the from __future__ import annotations future statement <future>{.interpreted-text role="ref"}, 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.

Changes in the C API

Py_Finalize{.interpreted-text role="c:func"} now deletes all interned strings. This is backwards incompatible to any C extension that holds onto an interned string after a call to Py_Finalize{.interpreted-text role="c:func"} and is then reused after a call to Py_Initialize{.interpreted-text role="c:func"}. Any issues arising from this behavior will normally result in crashes during the execution of the subsequent call to Py_Initialize{.interpreted-text role="c:func"} 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 113601{.interpreted-text role="gh"}.)
The Unicode Exception Objects <unicodeexceptions>{.interpreted-text role="ref"} C API now raises a TypeError{.interpreted-text role="exc"} if its exception argument is not a UnicodeError{.interpreted-text role="exc"} object. (Contributed by Bénédikt Tran in 127691{.interpreted-text role="gh"}.)

::: {#whatsnew314-refcount}

The interpreter internally avoids some reference count modifications when loading objects onto the operands stack by borrowing <borrowed reference>{.interpreted-text role="term"} references when possible. This can lead to smaller reference count values compared to previous Python versions. C API extensions that checked Py_REFCNT{.interpreted-text role="c:func"} of 1 to determine if an function argument is not referenced by any other code should instead use PyUnstable_Object_IsUniqueReferencedTemporary{.interpreted-text role="c:func"} as a safer replacement.
Private functions promoted to public C APIs:
- _PyBytes_Join(): PyBytes_Join{.interpreted-text role="c:func"}
- _PyLong_IsNegative(): PyLong_IsNegative{.interpreted-text role="c:func"}
- _PyLong_IsPositive(): PyLong_IsPositive{.interpreted-text role="c:func"}
- _PyLong_IsZero(): PyLong_IsZero{.interpreted-text role="c:func"}
- _PyLong_Sign(): PyLong_GetSign{.interpreted-text role="c:func"}
- _PyUnicodeWriter_Dealloc(): PyUnicodeWriter_Discard{.interpreted-text role="c:func"}
- _PyUnicodeWriter_Finish(): PyUnicodeWriter_Finish{.interpreted-text role="c:func"}
- _PyUnicodeWriter_Init(): use PyUnicodeWriter_Create{.interpreted-text role="c:func"}
- _PyUnicodeWriter_Prepare(): (no replacement)
- _PyUnicodeWriter_PrepareKind(): (no replacement)
- _PyUnicodeWriter_WriteChar(): PyUnicodeWriter_WriteChar{.interpreted-text role="c:func"}
- _PyUnicodeWriter_WriteStr(): PyUnicodeWriter_WriteStr{.interpreted-text role="c:func"}
- _PyUnicodeWriter_WriteSubstring(): PyUnicodeWriter_WriteSubstring{.interpreted-text role="c:func"}
- _PyUnicode_EQ(): PyUnicode_Equal{.interpreted-text role="c:func"}
- _PyUnicode_Equal(): PyUnicode_Equal{.interpreted-text role="c:func"}
- _Py_GetConfig(): PyConfig_Get{.interpreted-text role="c:func"} and PyConfig_GetInt{.interpreted-text role="c:func"}
- _Py_HashBytes(): Py_HashBuffer{.interpreted-text role="c:func"}
- _Py_fopen_obj(): Py_fopen{.interpreted-text role="c:func"}
- PyMutex_IsLocked() : PyMutex_IsLocked{.interpreted-text role="c:func"}
The pythoncapi-compat project can be used to get most of these new functions on Python 3.13 and older.

:::

What's new in Python 3.14

Summary -- Release highlights

New features

649{.interpreted-text role="pep"} & 749{.interpreted-text role="pep"}: Deferred evaluation of annotations {#whatsnew314-deferred-annotations}

734{.interpreted-text role="pep"}: Multiple interpreters in the standard library {#whatsnew314-multiple-interpreters}

750{.interpreted-text role="pep"}: Template string literals {#whatsnew314-template-string-literals}

768{.interpreted-text role="pep"}: Safe external debugger interface {#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}

784{.interpreted-text role="pep"}: Zstandard support in the standard library {#whatsnew314-zstandard}

Asyncio introspection capabilities {#whatsnew314-asyncio-introspection}

Concurrent safe warnings control {#whatsnew314-concurrent-warnings-control}

Other language changes

Built-ins

Command line and environment

PEP 758: Allow except and except* expressions without brackets {#whatsnew314-bracketless-except}

PEP 765: Control flow in finally{.interpreted-text role="keyword"} blocks {#whatsnew314-finally-syntaxwarning}

Incremental garbage collection {#whatsnew314-incremental-gc}

Default interactive shell

New modules

Improved modules

argparse

ast

asyncio

calendar

concurrent.futures

configparser

contextvars

ctypes

curses

datetime

decimal

difflib

dis

errno

faulthandler

fnmatch

fractions

functools

getopt

getpass

graphlib

heapq

hmac

http

imaplib

inspect

io

json

linecache

logging.handlers

math

mimetypes

multiprocessing

operator

os

os.path

pathlib

pdb

pickle

platform

pydoc

re

socket

ssl

struct

symtable

sys

sys.monitoring

sysconfig

tarfile

threading

tkinter

turtle

types

typing

unicodedata

unittest

urllib

`649`{.interpreted-text role="pep"} & `749`{.interpreted-text role="pep"}: Deferred evaluation of annotations {#whatsnew314-deferred-annotations}

`734`{.interpreted-text role="pep"}: Multiple interpreters in the standard library {#whatsnew314-multiple-interpreters}

`750`{.interpreted-text role="pep"}: Template string literals {#whatsnew314-template-string-literals}

`768`{.interpreted-text role="pep"}: Safe external debugger interface {#whatsnew314-remote-debugging}

`784`{.interpreted-text role="pep"}: Zstandard support in the standard library {#whatsnew314-zstandard}

PEP 758: Allow `except` and `except*` expressions without brackets {#whatsnew314-bracketless-except}

PEP 765: Control flow in `finally`{.interpreted-text role="keyword"} blocks {#whatsnew314-finally-syntaxwarning}

`build-details.json`{.interpreted-text role="file"} {#whatsnew314-build_details}

Changes in annotations (`649`{.interpreted-text role="pep"} and `749`{.interpreted-text role="pep"}) {#whatsnew314-porting-annotations}

Implications for readers of `annotations`

`from future import annotations`