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****************************
What's new in Python 3.14
****************************
:Editor: TBD
.. Rules for maintenance:
* Anyone can add text to this document. Do not spend very much time
on the wording of your changes, because your text will probably
get rewritten to some degree.
* The maintainer will go through Misc/NEWS periodically and add
changes; it's therefore more important to add your changes to
Misc/NEWS than to this file.
* This is not a complete list of every single change; completeness
is the purpose of Misc/NEWS. Some changes I consider too small
or esoteric to include. If such a change is added to the text,
I'll just remove it. (This is another reason you shouldn't spend
too much time on writing your addition.)
* If you want to draw your new text to the attention of the
maintainer, add 'XXX' to the beginning of the paragraph or
section.
* It's OK to just add a fragmentary note about a change. For
example: "XXX Describe the transmogrify() function added to the
socket module." The maintainer will research the change and
write the necessary text.
* You can comment out your additions if you like, but it's not
necessary (especially when a final release is some months away).
* Credit the author of a patch or bugfix. Just the name is
sufficient; the e-mail address isn't necessary.
* It's helpful to add the issue number as a comment:
XXX Describe the transmogrify() function added to the socket
module.
(Contributed by P.Y. Developer in :gh:`12345`.)
This saves the maintainer the effort of going through the VCS log
when researching a change.
This article explains the new features in Python 3.14, compared to 3.13.
For full details, see the :ref:`changelog <changelog>`.
.. note::
Prerelease users should be aware that this document is currently in draft
form. It will be updated substantially as Python 3.14 moves towards release,
so it's worth checking back even after reading earlier versions.
Summary -- release highlights
=============================
.. This section singles out the most important changes in Python 3.14.
Brevity is key.
.. PEP-sized items next.
* :ref:`PEP 649: deferred evaluation of annotations <whatsnew314-pep649>`
* :ref:`PEP 741: Python Configuration C API <whatsnew314-pep741>`
* :ref:`PEP 750: Template Strings <whatsnew314-pep750>`
* :ref:`PEP 758: Allow except and except* expressions without parentheses <whatsnew314-pep758>`
* :ref:`PEP 761: Discontinuation of PGP signatures <whatsnew314-pep761>`
* :ref:`PEP 765: Disallow return/break/continue that exit a finally block <whatsnew314-pep765>`
* :ref:`PEP 768: Safe external debugger interface for CPython <whatsnew314-pep768>`
* :ref:`A new type of interpreter <whatsnew314-tail-call>`
* :ref:`Syntax highlighting in PyREPL <whatsnew314-pyrepl-highlighting>`,
and color output in :ref:`unittest <whatsnew314-color-unittest>`,
:ref:`argparse <whatsnew314-color-argparse>`,
:ref:`json <whatsnew314-color-json>` and
:ref:`calendar <whatsnew314-color-calendar>` CLIs
Incompatible changes
====================
On platforms other than macOS and Windows, the default :ref:`start
method <multiprocessing-start-methods>` for :mod:`multiprocessing`
and :class:`~concurrent.futures.ProcessPoolExecutor` switches from
*fork* to *forkserver*.
See :ref:`(1) <whatsnew314-concurrent-futures-start-method>` and
:ref:`(2) <whatsnew314-multiprocessing-start-method>` for details.
If you encounter :exc:`NameError`\s or pickling errors coming out of
:mod:`multiprocessing` or :mod:`concurrent.futures`, see the
:ref:`forkserver restrictions <multiprocessing-programming-forkserver>`.
The interpreter avoids some reference count modifications internally when
it's safe to do so. This can lead to different values returned from
:func:`sys.getrefcount` and :c:func:`Py_REFCNT` compared to previous versions
of Python. See :ref:`below <whatsnew314-refcount>` for details.
New features
============
.. _whatsnew314-pep750:
PEP 750: Template Strings
-------------------------
Template string literals (t-strings) are a generalization of f-strings,
using a ``t`` in place of the ``f`` prefix. Instead of evaluating
to :class:`str`, t-strings evaluate to a new :class:`!string.templatelib.Template` type:
.. code-block:: python
from string.templatelib import Template
name = "World"
template: Template = t"Hello {name}"
The template can then be combined with functions that operate on the template's
structure to produce a :class:`str` or a string-like result.
For example, sanitizing input:
.. code-block:: python
evil = "<script>alert('evil')</script>"
template = t"<p>{evil}</p>"
assert html(template) == "<p>&lt;script&gt;alert('evil')&lt;/script&gt;</p>"
As another example, generating HTML attributes from data:
.. code-block:: python
attributes = {"src": "shrubbery.jpg", "alt": "looks nice"}
template = t"<img {attributes} />"
assert html(template) == '<img src="shrubbery.jpg" alt="looks nice" class="looks-nice" />'
Unlike f-strings, the ``html`` function has access to template attributes
containing the original information: static strings, interpolations, and values
from the original scope. Unlike existing templating approaches, t-strings build
from the well-known f-string syntax and rules. Template systems thus benefit
from Python tooling as they are much closer to the Python language, syntax,
scoping, and more.
Writing template handlers is straightforward:
.. code-block:: python
from string.templatelib import Template, Interpolation
def lower_upper(template: Template) -> str:
"""Render static parts lowercased and interpolations uppercased."""
parts: list[str] = []
for item in template:
if isinstance(item, Interpolation):
parts.append(str(item.value).upper())
else:
parts.append(item.lower())
return "".join(parts)
name = "world"
assert lower_upper(t"HELLO {name}") == "hello WORLD"
With this in place, developers can write template systems to sanitize SQL, make
safe shell operations, improve logging, tackle modern ideas in web development
(HTML, CSS, and so on), and implement lightweight, custom business DSLs.
See :pep:`750` for more details.
(Contributed by Jim Baker, Guido van Rossum, Paul Everitt, Koudai Aono,
Lysandros Nikolaou, Dave Peck, Adam Turner, Jelle Zijlstra, Bénédikt Tran,
and Pablo Galindo Salgado in :gh:`132661`.)
.. _whatsnew314-pep768:
PEP 768: Safe external debugger interface for CPython
-----------------------------------------------------
:pep:`768` introduces a zero-overhead debugging interface that allows debuggers and profilers
to safely attach to running Python processes. This is a significant enhancement to Python's
debugging capabilities allowing debuggers to forego unsafe alternatives. See
:ref:`below <whatsnew314-remote-pdb>` for how this feature is leveraged to
implement the new :mod:`pdb` module's remote attaching capabilities.
The new interface provides safe execution points for attaching debugger code without modifying
the interpreter's normal execution path or adding runtime overhead. This enables tools to
inspect and interact with Python applications in real-time without stopping or restarting
them — a crucial capability for high-availability systems and production environments.
For convenience, CPython implements this interface through the :mod:`sys` module with a
:func:`sys.remote_exec` function::
sys.remote_exec(pid, 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.
Here's a simple example that inspects object types in a running Python process:
.. code-block:: python
import os
import sys
import tempfile
# Create a temporary script
with tempfile.NamedTemporaryFile(mode='w', suffix='.py', delete=False) as f:
script_path = f.name
f.write(f"import my_debugger; my_debugger.connect({os.getpid()})")
try:
# Execute in process with PID 1234
print("Behold! An offering:")
sys.remote_exec(1234, script_path)
finally:
os.unlink(script_path)
The debugging interface has been carefully designed with security in mind and includes several
mechanisms to control access:
* A :envvar:`PYTHON_DISABLE_REMOTE_DEBUG` environment variable.
* A :option:`-X disable-remote-debug` command-line option.
* A :option:`--without-remote-debug` configure flag to completely disable the feature at build time.
A key implementation detail is that the interface piggybacks on the interpreter's existing evaluation
loop and safe points, ensuring zero overhead during normal execution while providing a reliable way
for external processes to coordinate debugging operations.
See :pep:`768` for more details.
(Contributed by Pablo Galindo Salgado, Matt Wozniski, and Ivona Stojanovic in :gh:`131591`.)
.. _whatsnew314-remote-pdb:
Remote attaching to a running Python process with PDB
-----------------------------------------------------
The :mod:`pdb` module now supports remote attaching to a running Python process
using a new ``-p PID`` command-line option:
.. code-block:: sh
python -m pdb -p 1234
This will connect to the Python process with the given PID and allow you to
debug it interactively. Notice that due to how the Python interpreter works
attaching to a remote process that is blocked in a system call or waiting for
I/O will only work once the next bytecode instruction is executed or when the
process receives a signal.
This feature leverages :pep:`768` and the :func:`sys.remote_exec` function
to attach to the remote process and send the PDB commands to it.
(Contributed by Matt Wozniski and Pablo Galindo in :gh:`131591`.)
.. _whatsnew314-pep758:
PEP 758 – Allow except and except* expressions without parentheses
------------------------------------------------------------------
The :keyword:`except` and :keyword:`except* <except_star>` expressions now allow
parentheses to be omitted when there are multiple exception types and the ``as`` clause is not used.
For example the following expressions are now valid:
.. code-block:: python
try:
release_new_sleep_token_album()
except AlbumNotFound, SongsTooGoodToBeReleased:
print("Sorry, no new album this year.")
# The same applies to except* (for exception groups):
try:
release_new_sleep_token_album()
except* AlbumNotFound, SongsTooGoodToBeReleased:
print("Sorry, no new album this year.")
Check :pep:`758` for more details.
(Contributed by Pablo Galindo and Brett Cannon in :gh:`131831`.)
.. _whatsnew314-pep649:
PEP 649: deferred evaluation of annotations
-------------------------------------------
The :term:`annotations <annotation>` on functions, classes, and modules are no
longer evaluated eagerly. Instead, annotations are stored in special-purpose
:term:`annotate functions <annotate function>` and evaluated only when
necessary. This is specified in :pep:`649` and :pep:`749`.
This change is designed to make annotations in Python more performant and more
usable in most circumstances. The runtime cost for defining annotations is
minimized, but it remains possible to introspect annotations at runtime.
It is usually no longer necessary to enclose annotations in strings if they
contain forward references.
The new :mod:`annotationlib` module provides tools for inspecting deferred
annotations. Annotations may be evaluated in the :attr:`~annotationlib.Format.VALUE`
format (which evaluates annotations to runtime values, similar to the behavior in
earlier Python versions), the :attr:`~annotationlib.Format.FORWARDREF` format
(which replaces undefined names with special markers), and the
:attr:`~annotationlib.Format.STRING` format (which returns annotations as strings).
This example shows how these formats behave:
.. doctest::
>>> from annotationlib import get_annotations, Format
>>> def func(arg: Undefined):
... pass
>>> get_annotations(func, format=Format.VALUE)
Traceback (most recent call last):
...
NameError: name 'Undefined' is not defined
>>> get_annotations(func, format=Format.FORWARDREF)
{'arg': ForwardRef('Undefined', owner=<function func at 0x...>)}
>>> get_annotations(func, format=Format.STRING)
{'arg': 'Undefined'}
Implications for annotated code
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
If you define annotations in your code (for example, for use with a static type
checker), then this change probably does not affect you: you can keep
writing annotations the same way you did with previous versions of Python.
You will likely be able to remove quoted strings in annotations, which are frequently
used for forward references. Similarly, if you use ``from __future__ import annotations``
to avoid having to write strings in annotations, you may well be able to
remove that import. However, if you rely on third-party libraries that read annotations,
those libraries may need changes to support unquoted annotations before they
work as expected.
Implications for readers of ``__annotations__``
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
If your code reads the ``__annotations__`` attribute on objects, you may want
to make changes in order to support code that relies on deferred evaluation of
annotations. For example, you may want to use :func:`annotationlib.get_annotations`
with the :attr:`~annotationlib.Format.FORWARDREF` format, as the :mod:`dataclasses`
module now does.
Related changes
^^^^^^^^^^^^^^^
The changes in Python 3.14 are designed to rework how ``__annotations__``
works at runtime while minimizing breakage to code that contains
annotations in source code and to code that reads ``__annotations__``. However,
if you rely on undocumented details of the annotation behavior or on private
functions in the standard library, there are many ways in which your code may
not work in Python 3.14. To safeguard your code against future changes,
use only the documented functionality of the :mod:`annotationlib` module.
``from __future__ import annotations``
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
In Python 3.7, :pep:`563` introduced the ``from __future__ import annotations``
directive, which turns all annotations into strings. This directive is now
considered deprecated and it is expected to be removed in a future version of Python.
However, this removal will not happen until after Python 3.13, the last version of
Python without deferred evaluation of annotations, reaches its end of life in 2029.
In Python 3.14, the behavior of code using ``from __future__ import annotations``
is unchanged.
Improved error messages
-----------------------
* The interpreter now provides helpful suggestions when it detects typos in Python
keywords. When a word that closely resembles a Python keyword is encountered,
the interpreter will suggest the correct keyword in the error message. This
feature helps programmers quickly identify and fix common typing mistakes. For
example:
.. code-block:: python
>>> whille True:
... pass
Traceback (most recent call last):
File "<stdin>", line 1
whille True:
^^^^^^
SyntaxError: invalid syntax. Did you mean 'while'?
>>> asynch def fetch_data():
... pass
Traceback (most recent call last):
File "<stdin>", line 1
asynch def fetch_data():
^^^^^^
SyntaxError: invalid syntax. Did you mean 'async'?
>>> async def foo():
... awaid fetch_data()
Traceback (most recent call last):
File "<stdin>", line 2
awaid fetch_data()
^^^^^
SyntaxError: invalid syntax. Did you mean 'await'?
>>> raisee ValueError("Error")
Traceback (most recent call last):
File "<stdin>", line 1
raisee ValueError("Error")
^^^^^^
SyntaxError: invalid syntax. Did you mean 'raise'?
While the feature focuses on the most common cases, some variations of
misspellings may still result in regular syntax errors.
(Contributed by Pablo Galindo in :gh:`132449`.)
* When unpacking assignment fails due to incorrect number of variables, the
error message prints the received number of values in more cases than before.
(Contributed by Tushar Sadhwani in :gh:`122239`.)
.. code-block:: python
>>> x, y, z = 1, 2, 3, 4
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
x, y, z = 1, 2, 3, 4
^^^^^^^
ValueError: too many values to unpack (expected 3, got 4)
* :keyword:`elif` statements that follow an :keyword:`else` block now have a specific error message.
(Contributed by Steele Farnsworth in :gh:`129902`.)
.. code-block:: pycon
>>> if who == "me":
... print("It's me!")
... else:
... print("It's not me!")
... elif who is None:
... print("Who is it?")
File "<stdin>", line 5
elif who is None:
^^^^
SyntaxError: 'elif' block follows an 'else' block
* If a statement (:keyword:`pass`, :keyword:`del`, :keyword:`return`,
:keyword:`yield`, :keyword:`raise`, :keyword:`break`, :keyword:`continue`,
:keyword:`assert`, :keyword:`import`, :keyword:`from`) is passed to the
:ref:`if_expr` after :keyword:`else`, or one of :keyword:`pass`,
:keyword:`break`, or :keyword:`continue` is passed before :keyword:`if`, then the
error message highlights where the :token:`~python-grammar:expression` is
required. (Contributed by Sergey Miryanov in :gh:`129515`.)
.. code-block:: pycon
>>> x = 1 if True else pass
Traceback (most recent call last):
File "<string>", line 1
x = 1 if True else pass
^^^^
SyntaxError: expected expression after 'else', but statement is given
>>> x = continue if True else break
Traceback (most recent call last):
File "<string>", line 1
x = continue if True else break
^^^^^^^^
SyntaxError: expected expression before 'if', but statement is given
* When incorrectly closed strings are detected, the error message suggests
that the string may be intended to be part of the string. (Contributed by
Pablo Galindo in :gh:`88535`.)
.. code-block:: python
>>> "The interesting object "The important object" is very important"
Traceback (most recent call last):
SyntaxError: invalid syntax. Is this intended to be part of the string?
* When strings have incompatible prefixes, the error now shows
which prefixes are incompatible. (Contributed by
Nikita Sobolev in :gh:`133197`.)
.. code-block:: pycon
>>> ub'abc'
File "<python-input-0>", line 1
ub'abc'
^^
SyntaxError: 'u' and 'b' prefixes are incompatible
* Improved error messages when using ``as`` with incompatible targets in:
- Imports: ``import ... as ...``
- From imports: ``from ... import ... as ...``
- Except handlers: ``except ... as ...``
- Pattern-match cases: ``case ... as ...``
(Contributed by Nikita Sobolev in :gh:`123539`,
:gh:`123562`, and :gh:`123440`.)
.. code-block:: pycon
>>> import ast as arr[0]
File "<python-input-1>", line 1
import ast as arr[0]
^^^^^^
SyntaxError: cannot use subscript as import target
.. _whatsnew314-pep741:
PEP 741: Python Configuration C API
-----------------------------------
Add a :ref:`PyInitConfig C API <pyinitconfig_api>` to configure the Python
initialization without relying on C structures and the ability to make
ABI-compatible changes in the future.
Complete the :pep:`587` :ref:`PyConfig C API <pyconfig_api>` by adding
:c:func:`PyInitConfig_AddModule` which can be used to add a built-in extension
module; feature previously referred to as the “inittab”.
Add :c:func:`PyConfig_Get` and :c:func:`PyConfig_Set` functions to get and set
the current runtime configuration.
PEP 587 “Python Initialization Configuration” unified all the ways to configure
the Python initialization. This PEP unifies also the configuration of the
Python preinitialization and the Python initialization in a single API.
Moreover, this PEP only provides a single choice to embed Python, instead of
having two “Python” and “Isolated” choices (PEP 587), to simplify the API
further.
The lower level PEP 587 PyConfig API remains available for use cases with an
intentionally higher level of coupling to CPython implementation details (such
as emulating the full functionality of CPython’s CLI, including its
configuration mechanisms).
(Contributed by Victor Stinner in :gh:`107954`.)
.. seealso::
:pep:`741`.
.. _whatsnew314-asyncio-introspection:
Asyncio introspection capabilities
----------------------------------
Added a new command-line interface to inspect running Python processes using
asynchronous tasks, available via:
.. code-block:: bash
python -m asyncio ps PID
This tool 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.
.. code-block:: bash
python -m asyncio pstree PID
This tool fetches the same information, but renders a visual async call tree,
showing coroutine relationships in a hierarchical format. This command is
particularly useful for debugging long-running or stuck asynchronous programs.
It can help developers quickly identify where a program is blocked, what tasks
are pending, and how coroutines are chained together.
For example given this code:
.. code-block:: python
import asyncio
async def play(track):
await asyncio.sleep(5)
print(f"🎵 Finished: {track}")
async def album(name, tracks):
async with asyncio.TaskGroup() as tg:
for track in tracks:
tg.create_task(play(track), name=track)
async def main():
async with asyncio.TaskGroup() as tg:
tg.create_task(
album("Sundowning", ["TNDNBTG", "Levitate"]), name="Sundowning")
tg.create_task(
album("TMBTE", ["DYWTYLM", "Aqua Regia"]), name="TMBTE")
if __name__ == "__main__":
asyncio.run(main())
Executing the new tool on the running process will yield a table like this:
.. code-block:: bash
python -m asyncio ps 12345
tid task id task name coroutine chain awaiter name awaiter id
---------------------------------------------------------------------------------------------------------------------------------------
8138752 0x564bd3d0210 Task-1 0x0
8138752 0x564bd3d0410 Sundowning _aexit -> __aexit__ -> main Task-1 0x564bd3d0210
8138752 0x564bd3d0610 TMBTE _aexit -> __aexit__ -> main Task-1 0x564bd3d0210
8138752 0x564bd3d0810 TNDNBTG _aexit -> __aexit__ -> album Sundowning 0x564bd3d0410
8138752 0x564bd3d0a10 Levitate _aexit -> __aexit__ -> album Sundowning 0x564bd3d0410
8138752 0x564bd3e0550 DYWTYLM _aexit -> __aexit__ -> album TMBTE 0x564bd3d0610
8138752 0x564bd3e0710 Aqua Regia _aexit -> __aexit__ -> album TMBTE 0x564bd3d0610
or:
.. code-block:: bash
python -m asyncio pstree 12345
└── (T) Task-1
└── main
└── __aexit__
└── _aexit
├── (T) Sundowning
│ └── album
│ └── __aexit__
│ └── _aexit
│ ├── (T) TNDNBTG
│ └── (T) Levitate
└── (T) TMBTE
└── album
└── __aexit__
└── _aexit
├── (T) DYWTYLM
└── (T) Aqua Regia
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.
(Contributed by Pablo Galindo, Łukasz Langa, Yury Selivanov, and Marta
Gomez Macias in :gh:`91048`.)
.. _whatsnew314-tail-call:
A new type of interpreter
-------------------------
A new type of interpreter has been added to CPython.
It uses tail calls between small C functions that implement individual
Python opcodes, rather than one large C case statement.
For certain newer compilers, this interpreter provides
significantly better performance. Preliminary numbers on our machines suggest
anywhere up to 30% faster Python code, and a geometric mean of 3-5%
faster on ``pyperformance`` depending on platform and architecture. The
baseline is Python 3.14 built with Clang 19 without this new interpreter.
This interpreter currently only works with Clang 19 and newer
on x86-64 and AArch64 architectures. However, we expect
that a future release of GCC will support this as well.
This feature is opt-in for now. We highly recommend enabling profile-guided
optimization with the new interpreter as it is the only configuration we have
tested and can validate its improved performance.
For further information on how to build Python, see
:option:`--with-tail-call-interp`.
.. note::
This is not to be confused with `tail call optimization`__ of Python
functions, which is currently not implemented in CPython.
This new interpreter type is an internal implementation detail of the CPython
interpreter. It doesn't change the visible behavior of Python programs at
all. It can improve their performance, but doesn't change anything else.
__ https://en.wikipedia.org/wiki/Tail_call
.. attention::
This section previously reported a 9-15% geometric mean speedup. This number has since been
cautiously revised down to 3-5%. While we expect performance results to be better
than what we report, our estimates are more conservative due to a
`compiler bug <https://github.com/llvm/llvm-project/issues/106846>`_ found in
Clang/LLVM 19, which causes the normal interpreter to be slower. We were unaware of this bug,
resulting in inaccurate results. We sincerely apologize for
communicating results that were only accurate for LLVM v19.1.x and v20.1.0. In the meantime,
the bug has been fixed in LLVM v20.1.1 and for the upcoming v21.1, but it will remain
unfixed for LLVM v19.1.x and v20.1.0. Thus
any benchmarks with those versions of LLVM may produce inaccurate numbers.
(Thanks to Nelson Elhage for bringing this to light.)
(Contributed by Ken Jin in :gh:`128563`, with ideas on how to implement this
in CPython by Mark Shannon, Garrett Gu, Haoran Xu, and Josh Haberman.)
.. _whatsnew314-pyrepl-highlighting:
Syntax highlighting in PyREPL
-----------------------------
The default :term:`interactive` shell now highlights Python syntax as you
type. The feature is enabled by default unless the
:envvar:`PYTHON_BASIC_REPL` environment is set or any color-disabling
environment variables are used. See :ref:`using-on-controlling-color` for
details.
The default color theme for syntax highlighting strives for good contrast
and uses exclusively the 4-bit VGA standard ANSI color codes for maximum
compatibility. The theme can be customized using an experimental API
``_colorize.set_theme()``. This can be called interactively, as well as
in the :envvar:`PYTHONSTARTUP` script.
(Contributed by Łukasz Langa in :gh:`131507`.)
Other language changes
======================
* The :func:`map` built-in now has an optional keyword-only *strict* flag
like :func:`zip` to check that all the iterables are of equal length.
(Contributed by Wannes Boeykens in :gh:`119793`.)
* Incorrect usage of :keyword:`await` and asynchronous comprehensions
is now detected even if the code is optimized away by the :option:`-O`
command-line option. For example, ``python -O -c 'assert await 1'``
now produces a :exc:`SyntaxError`. (Contributed by Jelle Zijlstra in :gh:`121637`.)
* Writes to ``__debug__`` are now detected even if the code is optimized
away by the :option:`-O` command-line option. For example,
``python -O -c 'assert (__debug__ := 1)'`` now produces a
:exc:`SyntaxError`. (Contributed by Irit Katriel in :gh:`122245`.)
* Add class methods :meth:`float.from_number` and :meth:`complex.from_number`
to convert a number to :class:`float` or :class:`complex` type correspondingly.
They raise an error if the argument is a string.
(Contributed by Serhiy Storchaka in :gh:`84978`.)
* Implement mixed-mode arithmetic rules combining real and complex numbers as
specified by C standards since C99.
(Contributed by Sergey B Kirpichev in :gh:`69639`.)
* All Windows code pages are now supported as "cpXXX" codecs on Windows.
(Contributed by Serhiy Storchaka in :gh:`123803`.)
* :class:`super` objects are now :mod:`pickleable <pickle>` and
:mod:`copyable <copy>`.
(Contributed by Serhiy Storchaka in :gh:`125767`.)
* The :class:`memoryview` type now supports subscription,
making it a :term:`generic type`.
(Contributed by Brian Schubert in :gh:`126012`.)
* Support underscore and comma as thousands separators in the fractional part
for floating-point presentation types of the new-style string formatting
(with :func:`format` or :ref:`f-strings`).
(Contributed by Sergey B Kirpichev in :gh:`87790`.)
* The :func:`bytes.fromhex` and :func:`bytearray.fromhex` methods now accept
ASCII :class:`bytes` and :term:`bytes-like objects <bytes-like object>`.
(Contributed by Daniel Pope in :gh:`129349`.)
* Support ``\z`` as a synonym for ``\Z`` in :mod:`regular expressions <re>`.
It is interpreted unambiguously in many other regular expression engines,
unlike ``\Z``, which has subtly different behavior.
(Contributed by Serhiy Storchaka in :gh:`133306`.)
* ``\B`` in :mod:`regular expression <re>` now matches empty input string.
Now it is always the opposite of ``\b``.
(Contributed by Serhiy Storchaka in :gh:`124130`.)
* iOS and macOS apps can now be configured to redirect ``stdout`` and
``stderr`` content to the system log. (Contributed by Russell Keith-Magee in
:gh:`127592`.)
* The iOS testbed is now able to stream test output while the test is running.
The testbed can also be used to run the test suite of projects other than
CPython itself. (Contributed by Russell Keith-Magee in :gh:`127592`.)
* Three-argument :func:`pow` now try calling :meth:`~object.__rpow__` if necessary.
Previously it was only called in two-argument :func:`!pow` and the binary
power operator.
(Contributed by Serhiy Storchaka in :gh:`130104`.)
* Add a built-in implementation for HMAC (:rfc:`2104`) using formally verified
code from the `HACL* <https://github.com/hacl-star/hacl-star/>`__ project.
This implementation is used as a fallback when the OpenSSL implementation
of HMAC is not available.
(Contributed by Bénédikt Tran in :gh:`99108`.)
* When subclassing from a pure C type, the C slots for the new type are no
longer replaced with a wrapped version on class creation if they are not
explicitly overridden in the subclass.
(Contributed by Tomasz Pytel in :gh:`132329`.)
* The command line option :option:`-c` now automatically dedents its code
argument before execution. The auto-dedentation behavior mirrors
:func:`textwrap.dedent`.
(Contributed by Jon Crall and Steven Sun in :gh:`103998`.)
* Improve error message when an object supporting the synchronous (resp.
asynchronous) context manager protocol is entered using :keyword:`async
with` (resp. :keyword:`with`) instead of :keyword:`with` (resp.
:keyword:`async with`).
(Contributed by Bénédikt Tran in :gh:`128398`.)
* :option:`!-J` is no longer a reserved flag for Jython_,
and now has no special meaning.
(Contributed by Adam Turner in :gh:`133336`.)
.. _Jython: https://www.jython.org/
.. _whatsnew314-pep765:
PEP 765: Disallow return/break/continue that exit a finally block
-----------------------------------------------------------------
The compiler emits a :exc:`SyntaxWarning` when a :keyword:`return`, :keyword:`break` or
:keyword:`continue` statements appears where it exits a :keyword:`finally` block.
This change is specified in :pep:`765`.
New modules
===========
* :mod:`annotationlib`: For introspecting :term:`annotations <annotation>`.
See :pep:`749` for more details.
(Contributed by Jelle Zijlstra in :gh:`119180`.)
Improved modules
================
argparse
--------
* The default value of the :ref:`program name <prog>` for
:class:`argparse.ArgumentParser` now reflects the way the Python
interpreter was instructed to find the ``__main__`` module code.
(Contributed by Serhiy Storchaka and Alyssa Coghlan in :gh:`66436`.)
* Introduced the optional *suggest_on_error* parameter to
:class:`argparse.ArgumentParser`, enabling suggestions for argument choices
and subparser names if mistyped by the user.
(Contributed by Savannah Ostrowski in :gh:`124456`.)
.. _whatsnew314-color-argparse:
* Introduced the optional *color* parameter to
:class:`argparse.ArgumentParser`, enabling color for help text.
This can be controlled via the :envvar:`PYTHON_COLORS` environment
variable as well as the canonical |NO_COLOR|_
and |FORCE_COLOR|_ environment variables.
See also :ref:`using-on-controlling-color`.
(Contributed by Hugo van Kemenade in :gh:`130645`.)
ast
---
* Add :func:`ast.compare` for comparing two ASTs.
(Contributed by Batuhan Taskaya and Jeremy Hylton in :gh:`60191`.)
* Add support for :func:`copy.replace` for AST nodes.
(Contributed by Bénédikt Tran in :gh:`121141`.)
* Docstrings are now removed from an optimized AST in optimization level 2.
(Contributed by Irit Katriel in :gh:`123958`.)
* The ``repr()`` output for AST nodes now includes more information.
(Contributed by Tomas R in :gh:`116022`.)
* :func:`ast.parse`, when called with an AST as input, now always verifies
that the root node type is appropriate.
(Contributed by Irit Katriel in :gh:`130139`.)
* Add new ``--feature-version``, ``--optimize``, ``--show-empty`` options to
command-line interface.
(Contributed by Semyon Moroz in :gh:`133367`.)
bdb
---
* The :mod:`bdb` module now supports the :mod:`sys.monitoring` backend.
(Contributed by Tian Gao in :gh:`124533`.)
.. _whatsnew314-color-calendar:
calendar
--------
* By default, today's date is highlighted in color in :mod:`calendar`'s
:ref:`command-line <calendar-cli>` text output.
This can be controlled via the :envvar:`PYTHON_COLORS` environment
variable as well as the canonical |NO_COLOR|_
and |FORCE_COLOR|_ environment variables.
See also :ref:`using-on-controlling-color`.
(Contributed by Hugo van Kemenade in :gh:`128317`.)
concurrent.futures
------------------
* Add :class:`~concurrent.futures.InterpreterPoolExecutor`,
which exposes "subinterpreters (multiple Python interpreters in the
same process) to Python code. This is separate from the proposed API
in :pep:`734`.
(Contributed by Eric Snow in :gh:`124548`.)
.. _whatsnew314-concurrent-futures-start-method:
* The default :class:`~concurrent.futures.ProcessPoolExecutor`
:ref:`start method <multiprocessing-start-methods>` changed
from :ref:`fork <multiprocessing-start-method-fork>` to :ref:`forkserver
<multiprocessing-start-method-forkserver>` on platforms other than macOS and
Windows where it was already :ref:`spawn <multiprocessing-start-method-spawn>`.
If the threading incompatible *fork* method is required, you must explicitly
request it by supplying a multiprocessing context *mp_context* to
:class:`~concurrent.futures.ProcessPoolExecutor`.
See :ref:`forkserver restrictions <multiprocessing-programming-forkserver>`
for information and differences with the *fork* method and how this change
may affect existing code with mutable global shared variables and/or shared
objects that can not be automatically :mod:`pickled <pickle>`.
(Contributed by Gregory P. Smith in :gh:`84559`.)
* Add :meth:`concurrent.futures.ProcessPoolExecutor.terminate_workers` and
:meth:`concurrent.futures.ProcessPoolExecutor.kill_workers` as
ways to terminate or kill all living worker processes in the given pool.
(Contributed by Charles Machalow in :gh:`130849`.)
* Add the optional ``buffersize`` parameter to
:meth:`concurrent.futures.Executor.map` to limit the number of submitted
tasks whose results have not yet been yielded. If the buffer is full,
iteration over the *iterables* pauses until a result is yielded from the
buffer.
(Contributed by Enzo Bonnal and Josh Rosenberg in :gh:`74028`.)
contextvars
-----------
* Support context manager protocol by :class:`contextvars.Token`.
(Contributed by Andrew Svetlov in :gh:`129889`.)
ctypes
------
* The layout of :ref:`bit fields <ctypes-bit-fields-in-structures-unions>`
in :class:`~ctypes.Structure` and :class:`~ctypes.Union`
now matches platform defaults (GCC/Clang or MSVC) more closely.
In particular, fields no longer overlap.
(Contributed by Matthias Görgens in :gh:`97702`.)
* The :attr:`.Structure._layout_` class attribute can now be set
to help match a non-default ABI.
(Contributed by Petr Viktorin in :gh:`97702`.)
* The class of :class:`~ctypes.Structure`/:class:`~ctypes.Union`
field descriptors is now available as :class:`~ctypes.CField`,
and has new attributes to aid debugging and introspection.
(Contributed by Petr Viktorin in :gh:`128715`.)
* On Windows, the :exc:`~ctypes.COMError` exception is now public.
(Contributed by Jun Komoda in :gh:`126686`.)
* On Windows, the :func:`~ctypes.CopyComPointer` function is now public.
(Contributed by Jun Komoda in :gh:`127275`.)
* :func:`ctypes.memoryview_at` now exists to create a
:class:`memoryview` object that refers to the supplied pointer and
length. This works like :func:`ctypes.string_at` except it avoids a
buffer copy, and is typically useful when implementing pure Python
callback functions that are passed dynamically-sized buffers.
(Contributed by Rian Hunter in :gh:`112018`.)
* Complex types, :class:`~ctypes.c_float_complex`,
:class:`~ctypes.c_double_complex` and :class:`~ctypes.c_longdouble_complex`,
are now available if both the compiler and the ``libffi`` library support
complex C types.
(Contributed by Sergey B Kirpichev in :gh:`61103`).
* Add :func:`ctypes.util.dllist` for listing the shared libraries
loaded by the current process.
(Contributed by Brian Ward in :gh:`119349`.)
* Move :func:`ctypes.POINTER` types cache from a global internal cache
(``_pointer_type_cache``) to the :attr:`ctypes._CData.__pointer_type__`
attribute of the corresponding :mod:`ctypes` types.
This will stop the cache from growing without limits in some situations.
(Contributed by Sergey Miryanov in :gh:`100926`).
* The :class:`ctypes.py_object` type now supports subscription,
making it a :term:`generic type`.
(Contributed by Brian Schubert in :gh:`132168`.)
curses
------
* Add the :func:`~curses.assume_default_colors` function,
a refinement of the :func:`~curses.use_default_colors` function which
allows to change the color pair ``0``.
(Contributed by Serhiy Storchaka in :gh:`133139`.)
datetime
--------
* Add :meth:`datetime.time.strptime` and :meth:`datetime.date.strptime`.
(Contributed by Wannes Boeykens in :gh:`41431`.)
decimal
-------
* Add alternative :class:`~decimal.Decimal` constructor
:meth:`Decimal.from_number() <decimal.Decimal.from_number>`.
(Contributed by Serhiy Storchaka in :gh:`121798`.)
* Expose :func:`decimal.IEEEContext` to support creation of contexts
corresponding to the IEEE 754 (2008) decimal interchange formats.
(Contributed by Sergey B Kirpichev in :gh:`53032`.)
difflib
-------
* Comparison pages with highlighted changes generated by the
:class:`difflib.HtmlDiff` class now support dark mode.
(Contributed by Jiahao Li in :gh:`129939`.)
dis
---
* Add support for rendering full source location information of
:class:`instructions <dis.Instruction>`, rather than only the line number.
This feature is added to the following interfaces via the *show_positions*
keyword argument:
- :class:`dis.Bytecode`
- :func:`dis.dis`
- :func:`dis.distb`
- :func:`dis.disassemble`
This feature is also exposed via :option:`dis --show-positions`.
(Contributed by Bénédikt Tran in :gh:`123165`.)
* Add the :option:`dis --specialized` command-line option to
show specialized bytecode.
(Contributed by Bénédikt Tran in :gh:`127413`.)
errno
-----
* Add :data:`errno.EHWPOISON` error code.
(Contributed by James Roy in :gh:`126585`.)
faulthandler
------------
* Add support for printing the C stack trace on systems that
:ref:`support it <c-stack-compatibility>` via :func:`faulthandler.dump_c_stack`
or via the *c_stack* argument in :func:`faulthandler.enable`.
(Contributed by Peter Bierma in :gh:`127604`.)
fnmatch
-------
* Added :func:`fnmatch.filterfalse` for excluding names matching a pattern.
(Contributed by Bénédikt Tran in :gh:`74598`.)
fractions
---------
* Add support for converting any objects that have the
:meth:`!as_integer_ratio` method to a :class:`~fractions.Fraction`.
(Contributed by Serhiy Storchaka in :gh:`82017`.)
* Add alternative :class:`~fractions.Fraction` constructor
:meth:`Fraction.from_number() <fractions.Fraction.from_number>`.
(Contributed by Serhiy Storchaka in :gh:`121797`.)
functools
---------
* Add support to :func:`functools.partial` and
:func:`functools.partialmethod` for :data:`functools.Placeholder` sentinels
to reserve a place for positional arguments.
(Contributed by Dominykas Grigonis in :gh:`119127`.)
* Allow the *initial* parameter of :func:`functools.reduce` to be passed
as a keyword argument.
(Contributed by Sayandip Dutta in :gh:`125916`.)
getopt
------
* Add support for options with optional arguments.
(Contributed by Serhiy Storchaka in :gh:`126374`.)
* Add support for returning intermixed options and non-option arguments in order.
(Contributed by Serhiy Storchaka in :gh:`126390`.)
graphlib
--------
* Allow :meth:`graphlib.TopologicalSorter.prepare` to be called more than once
as long as sorting has not started.
(Contributed by Daniel Pope in :gh:`130914`)
heapq
-----
* Add functions for working with max-heaps:
* :func:`heapq.heapify_max`,
* :func:`heapq.heappush_max`,
* :func:`heapq.heappop_max`,
* :func:`heapq.heapreplace_max`
* :func:`heapq.heappushpop_max`
hmac
----
* Add a built-in implementation for HMAC (:rfc:`2104`) using formally verified
code from the `HACL* <https://github.com/hacl-star/hacl-star/>`__ project.
(Contributed by Bénédikt Tran in :gh:`99108`.)
http
----
* Directory lists and error pages generated by the :mod:`http.server`
module allow the browser to apply its default dark mode.
(Contributed by Yorik Hansen in :gh:`123430`.)
* The :mod:`http.server` module now supports serving over HTTPS using the
:class:`http.server.HTTPSServer` class. This functionality is exposed by
the command-line interface (``python -m http.server``) through the following
options:
* ``--tls-cert <path>``: Path to the TLS certificate file.
* ``--tls-key <path>``: Optional path to the private key file.
* ``--tls-password-file <path>``: Optional path to the password file for the private key.
(Contributed by Semyon Moroz in :gh:`85162`.)
imaplib
-------
* Add :meth:`IMAP4.idle() <imaplib.IMAP4.idle>`, implementing the IMAP4
``IDLE`` command as defined in :rfc:`2177`.
(Contributed by Forest in :gh:`55454`.)
inspect
-------
* :func:`inspect.signature` takes a new argument *annotation_format* to control
the :class:`annotationlib.Format` used for representing annotations.
(Contributed by Jelle Zijlstra in :gh:`101552`.)
* :meth:`inspect.Signature.format` takes a new argument *unquote_annotations*.
If true, string :term:`annotations <annotation>` are displayed without surrounding quotes.
(Contributed by Jelle Zijlstra in :gh:`101552`.)
* Add function :func:`inspect.ispackage` to determine whether an object is a
:term:`package` or not.
(Contributed by Zhikang Yan in :gh:`125634`.)
io
--
* Reading text from a non-blocking stream with ``read`` may now raise a
:exc:`BlockingIOError` if the operation cannot immediately return bytes.
(Contributed by Giovanni Siragusa in :gh:`109523`.)
* Add protocols :class:`io.Reader` and :class:`io.Writer` as a simpler
alternatives to the pseudo-protocols :class:`typing.IO`,
:class:`typing.TextIO`, and :class:`typing.BinaryIO`.
(Contributed by Sebastian Rittau in :gh:`127648`.)
json
----
* Add notes for JSON serialization errors that allow to identify the source
of the error.
(Contributed by Serhiy Storchaka in :gh:`122163`.)
* Enable the :mod:`json` module to work as a script using the :option:`-m`
switch: :program:`python -m json`.
See the :ref:`JSON command-line interface <json-commandline>` documentation.
(Contributed by Trey Hunner in :gh:`122873`.)
.. _whatsnew314-color-json:
* By default, the output of the :ref:`JSON command-line interface <json-commandline>`
is highlighted in color. This can be controlled via the
:envvar:`PYTHON_COLORS` environment variable as well as the canonical
|NO_COLOR|_ and |FORCE_COLOR|_ environment variables. See also
:ref:`using-on-controlling-color`.
(Contributed by Tomas Roun in :gh:`131952`.)
linecache
---------
* :func:`linecache.getline` can retrieve source code for frozen modules.
(Contributed by Tian Gao in :gh:`131638`.)
logging.handlers
----------------
* :class:`logging.handlers.QueueListener` now implements the context
manager protocol, allowing it to be used in a :keyword:`with` statement.
(Contributed by Charles Machalow in :gh:`132106`.)
* :meth:`QueueListener.start <logging.handlers.QueueListener.start>` now
raises a :exc:`RuntimeError` if the listener is already started.
(Contributed by Charles Machalow in :gh:`132106`.)
math
----
* Added more detailed error messages for domain errors in the module.
(Contributed by by Charlie Zhao and Sergey B Kirpichev in :gh:`101410`.)
mimetypes
---------
* Document the command-line for :mod:`mimetypes`.
It now exits with ``1`` on failure instead of ``0``
and ``2`` on incorrect command-line parameters instead of ``1``.
Also, errors are printed to stderr instead of stdout and their text is made
tighter.
(Contributed by Oleg Iarygin and Hugo van Kemenade in :gh:`93096`.)
* Add MS and :rfc:`8081` MIME types for fonts:
* Embedded OpenType: ``application/vnd.ms-fontobject``
* OpenType Layout (OTF) ``font/otf``
* TrueType: ``font/ttf``
* WOFF 1.0 ``font/woff``
* WOFF 2.0 ``font/woff2``
(Contributed by Sahil Prajapati and Hugo van Kemenade in :gh:`84852`.)
* Add :rfc:`9559` MIME types for Matroska audiovisual data container
structures, containing:
* audio with no video: ``audio/matroska`` (``.mka``)
* video: ``video/matroska`` (``.mkv``)
* stereoscopic video: ``video/matroska-3d`` (``.mk3d``)
(Contributed by Hugo van Kemenade in :gh:`89416`.)
* Add MIME types for images with RFCs:
* :rfc:`1494`: CCITT Group 3 (``.g3``)
* :rfc:`3362`: Real-time Facsimile, T.38 (``.t38``)
* :rfc:`3745`: JPEG 2000 (``.jp2``), extension (``.jpx``) and compound (``.jpm``)
* :rfc:`3950`: Tag Image File Format Fax eXtended, TIFF-FX (``.tfx``)
* :rfc:`4047`: Flexible Image Transport System (``.fits``)
* :rfc:`7903`: Enhanced Metafile (``.emf``) and Windows Metafile (``.wmf``)
(Contributed by Hugo van Kemenade in :gh:`85957`.)
* More MIME type changes:
* :rfc:`2361`: Change type for ``.avi`` to ``video/vnd.avi``
and for ``.wav`` to ``audio/vnd.wave``
* :rfc:`4337`: Add MPEG-4 ``audio/mp4`` (``.m4a``)
* :rfc:`5334`: Add Ogg media (``.oga``, ``.ogg`` and ``.ogx``)
* :rfc:`6713`: Add gzip ``application/gzip`` (``.gz``)
* :rfc:`9639`: Add FLAC ``audio/flac`` (``.flac``)
* 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
<https://ecma-international.org/publications-and-standards/standards/ecma-376/>`__:
Add ``.docx``, ``.pptx`` and ``.xlsx`` types
* `OASIS
<https://docs.oasis-open.org/office/v1.2/cs01/OpenDocument-v1.2-cs01-part1.html#Appendix_C>`__:
Add OpenDocument ``.odg``, ``.odp``, ``.ods`` and ``.odt`` types
* `W3C <https://www.w3.org/TR/epub-33/#app-media-type>`__:
Add EPUB ``application/epub+zip`` (``.epub``)
(Contributed by Hugo van Kemenade in :gh:`129965`.)
* Add :rfc:`9512` ``application/yaml`` MIME type for YAML files (``.yaml``
and ``.yml``). (Contributed by Sasha "Nelie" Chernykh and Hugo van Kemenade
in :gh:`132056`.)
multiprocessing
---------------
.. _whatsnew314-multiprocessing-start-method:
* The default :ref:`start method <multiprocessing-start-methods>` changed
from :ref:`fork <multiprocessing-start-method-fork>` to :ref:`forkserver
<multiprocessing-start-method-forkserver>` on platforms other than macOS and
Windows where it was already :ref:`spawn <multiprocessing-start-method-spawn>`.
If the threading incompatible *fork* method is required, you must explicitly
request it via a context from :func:`multiprocessing.get_context` (preferred)
or change the default via :func:`multiprocessing.set_start_method`.
See :ref:`forkserver restrictions <multiprocessing-programming-forkserver>`
for information and differences with the *fork* method and how this change
may affect existing code with mutable global shared variables and/or shared
objects that can not be automatically :mod:`pickled <pickle>`.
(Contributed by Gregory P. Smith in :gh:`84559`.)
* :mod:`multiprocessing`'s ``"forkserver"`` start method now authenticates
its control socket to avoid solely relying on filesystem permissions
to restrict what other processes could cause the forkserver to spawn workers
and run code.
(Contributed by Gregory P. Smith for :gh:`97514`.)
* The :ref:`multiprocessing proxy objects <multiprocessing-proxy_objects>`
for *list* and *dict* types gain previously overlooked missing methods:
* :meth:`!clear` and :meth:`!copy` for proxies of :class:`list`.
* :meth:`~dict.fromkeys`, ``reversed(d)``, ``d | {}``, ``{} | d``,
``d |= {'b': 2}`` for proxies of :class:`dict`.
(Contributed by Roy Hyunjin Han for :gh:`103134`.)
* Add support for shared :class:`set` objects via
:meth:`SyncManager.set() <multiprocessing.managers.SyncManager.set>`.
The :func:`set` in :func:`multiprocessing.Manager` method is now available.
(Contributed by Mingyu Park in :gh:`129949`.)
* Add :func:`multiprocessing.Process.interrupt` which terminates the child
process by sending :py:const:`~signal.SIGINT`. This enables "finally" clauses
and printing stack trace for the terminated process.
(Contributed by Artem Pulkin in :gh:`131913`.)
operator
--------
* Two new functions :func:`operator.is_none` and :func:`operator.is_not_none`
have been added, such that ``operator.is_none(obj)`` is equivalent
to ``obj is None`` and ``operator.is_not_none(obj)`` is equivalent
to ``obj is not None``.
(Contributed by Raymond Hettinger and Nico Mexis in :gh:`115808`.)
os
--
* Add the :func:`os.reload_environ` function to update :data:`os.environ` and
:data:`os.environb` with changes to the environment made by
:func:`os.putenv`, by :func:`os.unsetenv`, or made outside Python in the
same process.
(Contributed by Victor Stinner in :gh:`120057`.)
* Add the :data:`~os.SCHED_DEADLINE` and :data:`~os.SCHED_NORMAL` constants
to the :mod:`os` module.
(Contributed by James Roy in :gh:`127688`.)
* Add the :func:`os.readinto` function to read into a
:ref:`buffer object <bufferobjects>` from a file descriptor.
(Contributed by Cody Maloney in :gh:`129205`.)
pathlib
-------
* Add methods to :class:`pathlib.Path` to recursively copy or move files and
directories:
* :meth:`~pathlib.Path.copy` copies a file or directory tree to a destination.
* :meth:`~pathlib.Path.copy_into` copies *into* a destination directory.
* :meth:`~pathlib.Path.move` moves a file or directory tree to a destination.
* :meth:`~pathlib.Path.move_into` moves *into* a destination directory.
(Contributed by Barney Gale in :gh:`73991`.)
* Add :attr:`pathlib.Path.info` attribute, which stores an object
implementing the :class:`pathlib.types.PathInfo` protocol (also new). The
object supports querying the file type and internally caching
:func:`~os.stat` results. Path objects generated by
:meth:`~pathlib.Path.iterdir` are initialized with file type information
gleaned from scanning the parent directory.
(Contributed by Barney Gale in :gh:`125413`.)
pdb
---
* Hardcoded breakpoints (:func:`breakpoint` and :func:`pdb.set_trace`) now
reuse the most recent :class:`~pdb.Pdb` instance that calls
:meth:`~pdb.Pdb.set_trace`, instead of creating a new one each time.
As a result, all the instance specific data like :pdbcmd:`display` and
:pdbcmd:`commands` are preserved across hardcoded breakpoints.
(Contributed by Tian Gao in :gh:`121450`.)
* Add a new argument *mode* to :class:`pdb.Pdb`. Disable the ``restart``
command when :mod:`pdb` is in ``inline`` mode.
(Contributed by Tian Gao in :gh:`123757`.)
* A confirmation prompt will be shown when the user tries to quit :mod:`pdb`
in ``inline`` mode. ``y``, ``Y``, ``<Enter>`` or ``EOF`` will confirm
the quit and call :func:`sys.exit`, instead of raising :exc:`bdb.BdbQuit`.
(Contributed by Tian Gao in :gh:`124704`.)
* Inline breakpoints like :func:`breakpoint` or :func:`pdb.set_trace` will
always stop the program at calling frame, ignoring the ``skip`` pattern
(if any).
(Contributed by Tian Gao in :gh:`130493`.)
* ``<tab>`` at the beginning of the line in :mod:`pdb` multi-line input will
fill in a 4-space indentation now, instead of inserting a ``\t`` character.
(Contributed by Tian Gao in :gh:`130471`.)
* ``$_asynctask`` is added to access the current asyncio task if applicable.
(Contributed by Tian Gao in :gh:`124367`.)
* :mod:`pdb` now supports two backends: :func:`sys.settrace` and
:mod:`sys.monitoring`. Using :mod:`pdb` CLI or :func:`breakpoint` will
always use the :mod:`sys.monitoring` backend. Explicitly instantiating
:class:`pdb.Pdb` and its derived classes will use the :func:`sys.settrace`
backend by default, which is configurable.
(Contributed by Tian Gao in :gh:`124533`.)
* :func:`pdb.set_trace_async` is added to support debugging asyncio
coroutines. :keyword:`await` statements are supported with this
function.
(Contributed by Tian Gao in :gh:`132576`.)
* Source code displayed in :mod:`pdb` will be syntax-highlighted. This feature
can be controlled using the same methods as PyREPL, in addition to the newly
added ``colorize`` argument of :class:`pdb.Pdb`.
(Contributed by Tian Gao in :gh:`133355`.)
pickle
------
* Set the default protocol version on the :mod:`pickle` module to 5.
For more details, see :ref:`pickle protocols <pickle-protocols>`.
* Add notes for pickle serialization errors that allow to identify the source
of the error.
(Contributed by Serhiy Storchaka in :gh:`122213`.)
platform
--------
* Add :func:`platform.invalidate_caches` to invalidate the cached results.
(Contributed by Bénédikt Tran in :gh:`122549`.)
pydoc
-----
* :term:`Annotations <annotation>` in help output are now usually
displayed in a format closer to that in the original source.
(Contributed by Jelle Zijlstra in :gh:`101552`.)
socket
------
* Improve and fix support for Bluetooth sockets.
* Fix support of Bluetooth sockets on NetBSD and DragonFly BSD.
(Contributed by Serhiy Storchaka in :gh:`132429`.)
* Fix support for :const:`~socket.BTPROTO_HCI` on FreeBSD.
(Contributed by Victor Stinner in :gh:`111178`.)
* Add support for :const:`~socket.BTPROTO_SCO` on FreeBSD.
(Contributed by Serhiy Storchaka in :gh:`85302`.)
* Add support for *cid* and *bdaddr_type* in the address for
:const:`~socket.BTPROTO_L2CAP` on FreeBSD.
(Contributed by Serhiy Storchaka in :gh:`132429`.)
* Add support for *channel* in the address for
:const:`~socket.BTPROTO_HCI` on Linux.
(Contributed by Serhiy Storchaka in :gh:`70145`.)
* Accept an integer as the address for
:const:`~socket.BTPROTO_HCI` on Linux
(Contributed by Serhiy Storchaka in :gh:`132099`.)
* Return *cid* in :meth:`~socket.socket.getsockname` for
:const:`~socket.BTPROTO_L2CAP`.
(Contributed by Serhiy Storchaka in :gh:`132429`.)
* Add many new constants.
(Contributed by Serhiy Storchaka in :gh:`132734`.)
ssl
---
* Indicate through :data:`ssl.HAS_PHA` whether the :mod:`ssl` module supports
TLSv1.3 post-handshake client authentication (PHA).
(Contributed by Will Childs-Klein in :gh:`128036`.)
struct
------
* Support the :c:expr:`float complex` and :c:expr:`double complex` C types in
the :mod:`struct` module (formatting characters ``'F'`` and ``'D'``
respectively).
(Contributed by Sergey B Kirpichev in :gh:`121249`.)
symtable
--------
* Expose the following :class:`symtable.Symbol` methods:
* :meth:`~symtable.Symbol.is_comp_cell`
* :meth:`~symtable.Symbol.is_comp_iter`
* :meth:`~symtable.Symbol.is_free_class`
(Contributed by Bénédikt Tran in :gh:`120029`.)
sys
---
* The previously undocumented special function :func:`sys.getobjects`,
which only exists in specialized builds of Python, may now return objects
from other interpreters than the one it's called in.
* Add :func:`sys._is_immortal` for determining if an object is :term:`immortal`.
(Contributed by Peter Bierma in :gh:`128509`.)
* On FreeBSD, :data:`sys.platform` doesn't contain the major version anymore.
It is always ``'freebsd'``, instead of ``'freebsd13'`` or ``'freebsd14'``.
* Raise :exc:`DeprecationWarning` for :func:`sys._clear_type_cache`. This
function was deprecated in Python 3.13 but it didn't raise a runtime warning.
sys.monitoring
--------------
* Two new events are added: :monitoring-event:`BRANCH_LEFT` and
:monitoring-event:`BRANCH_RIGHT`. The ``BRANCH`` event is deprecated.
sysconfig
---------
* Add ``ABIFLAGS`` key to :func:`sysconfig.get_config_vars` on Windows.
(Contributed by Xuehai Pan in :gh:`131799`.)
threading
---------
* :meth:`threading.Thread.start` now sets the operating system thread name
to :attr:`threading.Thread.name`.
(Contributed by Victor Stinner in :gh:`59705`.)
tkinter
-------
* Make tkinter widget methods :meth:`!after` and :meth:`!after_idle` accept
arguments passed by keyword.
(Contributed by Zhikang Yan in :gh:`126899`.)
* Add ability to specify name for :class:`!tkinter.OptionMenu` and
:class:`!tkinter.ttk.OptionMenu`.
(Contributed by Zhikang Yan in :gh:`130482`.)
turtle
------
* Add context managers for :func:`turtle.fill`, :func:`turtle.poly`
and :func:`turtle.no_animation`.
(Contributed by Marie Roald and Yngve Mardal Moe in :gh:`126350`.)
types
-----
* :class:`types.UnionType` is now an alias for :class:`typing.Union`.
See :ref:`below <whatsnew314-typing-union>` for more details.
(Contributed by Jelle Zijlstra in :gh:`105499`.)
typing
------
.. _whatsnew314-typing-union:
* :class:`types.UnionType` and :class:`typing.Union` 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()``. 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. Users should use ``==`` to compare unions for equality, not
``is``. New-style unions have never been cached this way.
This change could increase memory usage for some programs that use a large number of
unions created by subscripting ``typing.Union``. However, several factors offset this cost:
unions used in annotations are no longer evaluated by default in Python 3.14
because of :pep:`649`; an instance of :class:`types.UnionType` is
itself much smaller than the object returned by ``Union[]`` was on prior Python
versions; and removing the cache also saves some space. It is therefore
unlikely that this change will cause a significant increase in memory usage for most
users.
- Previously, old-style unions were implemented using the private class
``typing._UnionGenericAlias``. This class is no longer needed for the implementation,
but it has been retained for backward compatibility, with removal scheduled for Python
3.17. Users should use documented introspection helpers like :func:`typing.get_origin`
and :func:`typing.get_args` instead of relying on private implementation details.
- It is now possible to use :class:`typing.Union` itself in :func:`isinstance` checks.
For example, ``isinstance(int | str, typing.Union)`` will return ``True``; previously
this raised :exc:`TypeError`.
- The ``__args__`` attribute of :class:`typing.Union` objects is no longer writable.
- It is no longer possible to set any attributes on :class:`typing.Union` objects.
This only ever worked for dunder attributes on previous versions, was never
documented to work, and was subtly broken in many cases.
(Contributed by Jelle Zijlstra in :gh:`105499`.)
unicodedata
-----------
* The Unicode database has been updated to Unicode 16.0.0.
.. _whatsnew314-color-unittest:
unittest
--------
* :mod:`unittest` output is now colored by default.
This can be controlled via the :envvar:`PYTHON_COLORS` environment
variable as well as the canonical |NO_COLOR|_
and |FORCE_COLOR|_ environment variables.
See also :ref:`using-on-controlling-color`.
(Contributed by Hugo van Kemenade in :gh:`127221`.)
* unittest discovery supports :term:`namespace package` as start
directory again. It was removed in Python 3.11.
(Contributed by Jacob Walls in :gh:`80958`.)
* A number of new methods were added in the :class:`~unittest.TestCase` class
that provide more specialized tests.
- :meth:`~unittest.TestCase.assertHasAttr` and
:meth:`~unittest.TestCase.assertNotHasAttr` check whether the object
has a particular attribute.
- :meth:`~unittest.TestCase.assertIsSubclass` and
:meth:`~unittest.TestCase.assertNotIsSubclass` check whether the object
is a subclass of a particular class, or of one of a tuple of classes.
- :meth:`~unittest.TestCase.assertStartsWith`,
:meth:`~unittest.TestCase.assertNotStartsWith`,
:meth:`~unittest.TestCase.assertEndsWith` and
:meth:`~unittest.TestCase.assertNotEndsWith` check whether the Unicode
or byte string starts or ends with particular string(s).
(Contributed by Serhiy Storchaka in :gh:`71339`.)
urllib
------
* Upgrade HTTP digest authentication algorithm for :mod:`urllib.request` by
supporting SHA-256 digest authentication as specified in :rfc:`7616`.
(Contributed by Calvin Bui in :gh:`128193`.)
* Improve ergonomics and standards compliance when parsing and emitting
``file:`` URLs.
In :func:`urllib.request.url2pathname`:
- 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.
- Raise :exc:`~urllib.error.URLError` if a URL authority isn't local,
except on Windows where we return a UNC path as before.
In :func:`urllib.request.pathname2url`:
- 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 :exc:`OSError`
exception to be raised.
(Contributed by Barney Gale in :gh:`125866`.)
uuid
----
* Add support for UUID versions 6, 7, and 8 via :func:`uuid.uuid6`,
:func:`uuid.uuid7`, and :func:`uuid.uuid8` respectively, as specified
in :rfc:`9562`.
(Contributed by Bénédikt Tran in :gh:`89083`.)
* :const:`uuid.NIL` and :const:`uuid.MAX` are now available to represent the
Nil and Max UUID formats as defined by :rfc:`9562`.
(Contributed by Nick Pope in :gh:`128427`.)
* Allow to generate multiple UUIDs at once via :option:`python -m uuid --count <uuid --count>`.
(Contributed by Simon Legner in :gh:`131236`.)
webbrowser
----------
* Names in the :envvar:`BROWSER` environment variable can now refer to already
registered browsers for the :mod:`webbrowser` module, instead of always
generating a new browser command.
This makes it possible to set :envvar:`BROWSER` to the value of one of the
supported browsers on macOS.
zipinfo
-------
* Added :func:`ZipInfo._for_archive <zipfile.ZipInfo._for_archive>`
to resolve suitable defaults for a :class:`~zipfile.ZipInfo` object
as used by :func:`ZipFile.writestr <zipfile.ZipFile.writestr>`.
(Contributed by Bénédikt Tran in :gh:`123424`.)
* :meth:`zipfile.ZipFile.writestr` now respect ``SOURCE_DATE_EPOCH`` that
distributions can set centrally and have build tools consume this in order
to produce reproducible output.
(Contributed by Jiahao Li in :gh:`91279`.)
.. Add improved modules above alphabetically, not here at the end.
Optimizations
=============
* The import time for several standard library modules has been improved,
including :mod:`ast`, :mod:`asyncio`, :mod:`base64`, :mod:`cmd`, :mod:`csv`,
:mod:`gettext`, :mod:`importlib.util`, :mod:`locale`, :mod:`mimetypes`,
:mod:`optparse`, :mod:`pickle`, :mod:`pprint`, :mod:`pstats`, :mod:`socket`,
:mod:`subprocess`, :mod:`threading`, :mod:`tomllib`, and :mod:`zipfile`.
(Contributed by Adam Turner, Bénédikt Tran, Chris Markiewicz, Eli Schwartz,
Hugo van Kemenade, Jelle Zijlstra, and others in :gh:`118761`.)
asyncio
-------
* :mod:`asyncio` now uses double linked list implementation for native tasks
which speeds up execution by 10% on standard pyperformance benchmarks and
reduces memory usage.
(Contributed by Kumar Aditya in :gh:`107803`.)
* :mod:`asyncio` has new utility functions for introspecting and printing
the program's call graph: :func:`asyncio.capture_call_graph` and
:func:`asyncio.print_call_graph`.
(Contributed by Yury Selivanov, Pablo Galindo Salgado, and Łukasz Langa
in :gh:`91048`.)
base64
------
* Improve the performance of :func:`base64.b16decode` by up to ten times,
and reduce the import time of :mod:`base64` by up to six times.
(Contributed by Bénédikt Tran, Chris Markiewicz, and Adam Turner in :gh:`118761`.)
io
---
* :mod:`io` which provides the built-in :func:`open` makes less system calls
when opening regular files as well as reading whole files. Reading a small
operating system cached file in full is up to 15% faster.
:func:`pathlib.Path.read_bytes` has the most optimizations for reading a
file's bytes in full. (Contributed by Cody Maloney and Victor Stinner in
:gh:`120754` and :gh:`90102`.)
uuid
----
* Improve generation of :class:`~uuid.UUID` objects via their dedicated
functions:
* :func:`~uuid.uuid3` and :func:`~uuid.uuid5` are both roughly 40% faster
for 16-byte names and 20% faster for 1024-byte names. Performance for
longer names remains unchanged.
* :func:`~uuid.uuid4` and :func:`~uuid.uuid8` are 30% and 40% faster
respectively.
(Contributed by Bénédikt Tran in :gh:`128150`.)
zlib
----
* On Windows, ``zlib-ng`` is now used as the implementation of the
:mod:`zlib` module. This should produce compatible and comparable
results with better performance, though it is worth noting that
``zlib.Z_BEST_SPEED`` (1) may result in significantly less
compression than the previous implementation (while also significantly
reducing the time taken to compress).
(Contributed by Steve Dower in :gh:`91349`.)
Deprecated
==========
* :mod:`argparse`:
* Passing the undocumented keyword argument *prefix_chars* to
:meth:`~argparse.ArgumentParser.add_argument_group` is now
deprecated.
(Contributed by Savannah Ostrowski in :gh:`125563`.)
* Deprecated the :class:`argparse.FileType` type converter.
Anything with resource management should be done downstream after the
arguments are parsed.
(Contributed by Serhiy Storchaka in :gh:`58032`.)
* :mod:`asyncio`:
* :func:`!asyncio.iscoroutinefunction` is deprecated
and will be removed in Python 3.16;
use :func:`inspect.iscoroutinefunction` instead.
(Contributed by Jiahao Li and Kumar Aditya in :gh:`122875`.)
* :mod:`asyncio` policy system is deprecated and will be removed in Python 3.16.
In particular, the following classes and functions are deprecated:
* :class:`asyncio.AbstractEventLoopPolicy`
* :class:`asyncio.DefaultEventLoopPolicy`
* :class:`asyncio.WindowsSelectorEventLoopPolicy`
* :class:`asyncio.WindowsProactorEventLoopPolicy`
* :func:`asyncio.get_event_loop_policy`
* :func:`asyncio.set_event_loop_policy`
* :func:`asyncio.set_event_loop`
Users should use :func:`asyncio.run` or :class:`asyncio.Runner` with
*loop_factory* to use the desired event loop implementation.
For example, to use :class:`asyncio.SelectorEventLoop` on Windows::
import asyncio
async def main():
...
asyncio.run(main(), loop_factory=asyncio.SelectorEventLoop)
(Contributed by Kumar Aditya in :gh:`127949`.)
* :mod:`builtins`:
Passing a complex number as the *real* or *imag* argument in the
:func:`complex` constructor is now deprecated; it should only be passed
as a single positional argument.
(Contributed by Serhiy Storchaka in :gh:`109218`.)
* :mod:`codecs`:
:func:`codecs.open` is now deprecated. Use :func:`open` instead.
(Contributed by Inada Naoki in :gh:`133036`.)
* :mod:`ctypes`:
On non-Windows platforms, setting :attr:`.Structure._pack_` to use a
MSVC-compatible default memory layout is deprecated in favor of setting
:attr:`.Structure._layout_` to ``'ms'``.
(Contributed by Petr Viktorin in :gh:`131747`.)
* :mod:`ctypes`:
Calling :func:`ctypes.POINTER` on a string is deprecated.
Use :ref:`ctypes-incomplete-types` for self-referential structures.
Also, the internal ``ctypes._pointer_type_cache`` is deprecated.
See :func:`ctypes.POINTER` for updated implementation details.
(Contributed by Sergey Myrianov in :gh:`100926`.)
* :mod:`functools`:
Calling the Python implementation of :func:`functools.reduce` with *function*
or *sequence* as keyword arguments is now deprecated.
(Contributed by Kirill Podoprigora in :gh:`121676`.)
* :mod:`logging`:
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 :gh:`115032`.)
* :mod:`mimetypes`:
Valid extensions start with a '.' or are empty for
:meth:`mimetypes.MimeTypes.add_type`.
Undotted extensions are deprecated and will
raise a :exc:`ValueError` in Python 3.16.
(Contributed by Hugo van Kemenade in :gh:`75223`.)
* :mod:`!nturl2path`: This module is now deprecated. Call
:func:`urllib.request.url2pathname` and :func:`~urllib.request.pathname2url`
instead.
(Contributed by Barney Gale in :gh:`125866`.)
* :mod:`os`:
:term:`Soft deprecate <soft deprecated>` :func:`os.popen` and
:func:`os.spawn* <os.spawnl>` functions. They should no longer be used to
write new code. The :mod:`subprocess` module is recommended instead.
(Contributed by Victor Stinner in :gh:`120743`.)
* :mod:`pathlib`:
:meth:`!pathlib.PurePath.as_uri` is deprecated and will be removed in Python
3.19. Use :meth:`pathlib.Path.as_uri` instead.
(Contributed by Barney Gale in :gh:`123599`.)
* :mod:`pdb`:
The undocumented ``pdb.Pdb.curframe_locals`` attribute is now a deprecated
read-only property. The low overhead dynamic frame locals access added in
Python 3.13 by PEP 667 means the frame locals cache reference previously
stored in this attribute is no longer needed. Derived debuggers should access
``pdb.Pdb.curframe.f_locals`` directly in Python 3.13 and later versions.
(Contributed by Tian Gao in :gh:`124369` and :gh:`125951`.)
* :mod:`symtable`:
Deprecate :meth:`symtable.Class.get_methods` due to the lack of interest.
(Contributed by Bénédikt Tran in :gh:`119698`.)
* :mod:`tkinter`:
The :class:`!tkinter.Variable` methods :meth:`!trace_variable`,
:meth:`!trace_vdelete` and :meth:`!trace_vinfo` are now deprecated.
Use :meth:`!trace_add`, :meth:`!trace_remove` and :meth:`!trace_info`
instead.
(Contributed by Serhiy Storchaka in :gh:`120220`.)
* :mod:`urllib.parse`:
Accepting objects with false values (like ``0`` and ``[]``) except empty
strings, byte-like objects and ``None`` in :mod:`urllib.parse` functions
:func:`~urllib.parse.parse_qsl` and :func:`~urllib.parse.parse_qs` is now
deprecated.
(Contributed by Serhiy Storchaka in :gh:`116897`.)
.. Add deprecations above alphabetically, not here at the end.
.. include:: ../deprecations/pending-removal-in-3.15.rst
.. include:: ../deprecations/pending-removal-in-3.16.rst
.. include:: ../deprecations/pending-removal-in-3.17.rst
.. include:: ../deprecations/pending-removal-in-3.19.rst
.. include:: ../deprecations/pending-removal-in-future.rst
Removed
=======
argparse
--------
* Remove the *type*, *choices*, and *metavar* parameters
of :class:`!argparse.BooleanOptionalAction`.
They were deprecated since 3.12.
* Calling :meth:`~argparse.ArgumentParser.add_argument_group` on an argument
group, and calling :meth:`~argparse.ArgumentParser.add_argument_group` or
:meth:`~argparse.ArgumentParser.add_mutually_exclusive_group` on a mutually
exclusive group now raise exceptions. This nesting was never supported,
often failed to work correctly, and was unintentionally exposed through
inheritance. This functionality has been deprecated since Python 3.11.
(Contributed by Savannah Ostrowski in :gh:`127186`.)
ast
---
* Remove the following classes. They were all deprecated since Python 3.8,
and have emitted deprecation warnings since Python 3.12:
* :class:`!ast.Bytes`
* :class:`!ast.Ellipsis`
* :class:`!ast.NameConstant`
* :class:`!ast.Num`
* :class:`!ast.Str`
Use :class:`ast.Constant` instead. As a consequence of these removals,
user-defined ``visit_Num``, ``visit_Str``, ``visit_Bytes``,
``visit_NameConstant`` and ``visit_Ellipsis`` methods on custom
:class:`ast.NodeVisitor` subclasses will no longer be called when the
:class:`!NodeVisitor` subclass is visiting an AST. Define a ``visit_Constant``
method instead.
Also, remove the following deprecated properties on :class:`ast.Constant`,
which were present for compatibility with the now-removed AST classes:
* :attr:`!ast.Constant.n`
* :attr:`!ast.Constant.s`
Use :attr:`!ast.Constant.value` instead.
(Contributed by Alex Waygood in :gh:`119562`.)
asyncio
-------
* Remove the following classes and functions. They were all deprecated and
emitted deprecation warnings since Python 3.12:
* :func:`!asyncio.get_child_watcher`
* :func:`!asyncio.set_child_watcher`
* :meth:`!asyncio.AbstractEventLoopPolicy.get_child_watcher`
* :meth:`!asyncio.AbstractEventLoopPolicy.set_child_watcher`
* :class:`!asyncio.AbstractChildWatcher`
* :class:`!asyncio.FastChildWatcher`
* :class:`!asyncio.MultiLoopChildWatcher`
* :class:`!asyncio.PidfdChildWatcher`
* :class:`!asyncio.SafeChildWatcher`
* :class:`!asyncio.ThreadedChildWatcher`
(Contributed by Kumar Aditya in :gh:`120804`.)
* Removed implicit creation of event loop by :func:`asyncio.get_event_loop`.
It now raises a :exc:`RuntimeError` if there is no current event loop.
(Contributed by Kumar Aditya in :gh:`126353`.)
There's a few patterns that use :func:`asyncio.get_event_loop`, most
of them can be replaced with :func:`asyncio.run`.
If you're running an async function, simply use :func:`asyncio.run`.
Before::
async def main():
...
loop = asyncio.get_event_loop()
try:
loop.run_until_complete(main())
finally:
loop.close()
After::
async def main():
...
asyncio.run(main())
If you need to start something, e.g. a server listening on a socket
and then run forever, use :func:`asyncio.run` and an
:class:`asyncio.Event`.
Before::
def start_server(loop):
...
loop = asyncio.get_event_loop()
try:
start_server(loop)
loop.run_forever()
finally:
loop.close()
After::
def start_server(loop):
...
async def main():
start_server(asyncio.get_running_loop())
await asyncio.Event().wait()
asyncio.run(main())
If you need to run something in an event loop, then run some blocking
code around it, use :class:`asyncio.Runner`.
Before::
async def operation_one():
...
def blocking_code():
...
async def operation_two():
...
loop = asyncio.get_event_loop()
try:
loop.run_until_complete(operation_one())
blocking_code()
loop.run_until_complete(operation_two())
finally:
loop.close()
After::
async def operation_one():
...
def blocking_code():
...
async def operation_two():
...
with asyncio.Runner() as runner:
runner.run(operation_one())
blocking_code()
runner.run(operation_two())
collections.abc
---------------
* Remove :class:`!collections.abc.ByteString`. It had previously raised a
:exc:`DeprecationWarning` since Python 3.12.
email
-----
* Remove the *isdst* parameter from :func:`email.utils.localtime`.
(Contributed by Hugo van Kemenade in :gh:`118798`.)
importlib
---------
* Remove deprecated :mod:`importlib.abc` classes:
* :class:`!importlib.abc.ResourceReader`
* :class:`!importlib.abc.Traversable`
* :class:`!importlib.abc.TraversableResources`
Use :mod:`importlib.resources.abc` classes instead:
* :class:`importlib.resources.abc.Traversable`
* :class:`importlib.resources.abc.TraversableResources`
(Contributed by Jason R. Coombs and Hugo van Kemenade in :gh:`93963`.)
itertools
---------
* Remove :mod:`itertools` support for copy, deepcopy, and pickle operations.
These had previously raised a :exc:`DeprecationWarning` since Python 3.12.
(Contributed by Raymond Hettinger in :gh:`101588`.)
pathlib
-------
* Remove support for passing additional keyword arguments to
:class:`pathlib.Path`. In previous versions, any such arguments are ignored.
* Remove support for passing additional positional arguments to
:meth:`pathlib.PurePath.relative_to` and
:meth:`~pathlib.PurePath.is_relative_to`. In previous versions, any such
arguments are joined onto *other*.
pkgutil
-------
* Remove deprecated :func:`!pkgutil.get_loader` and :func:`!pkgutil.find_loader`.
These had previously raised a :exc:`DeprecationWarning` since Python 3.12.
(Contributed by Bénédikt Tran in :gh:`97850`.)
pty
---
* Remove deprecated :func:`!pty.master_open` and :func:`!pty.slave_open`.
They had previously raised a :exc:`DeprecationWarning` since Python 3.12.
Use :func:`pty.openpty` instead.
(Contributed by Nikita Sobolev in :gh:`118824`.)
sqlite3
-------
* Remove :data:`!version` and :data:`!version_info` from :mod:`sqlite3`.
(Contributed by Hugo van Kemenade in :gh:`118924`.)
* Disallow using a sequence of parameters with named placeholders.
This had previously raised a :exc:`DeprecationWarning` since Python 3.12;
it will now raise a :exc:`sqlite3.ProgrammingError`.
(Contributed by Erlend E. Aasland in :gh:`118928` and :gh:`101693`.)
typing
------
* Remove :class:`!typing.ByteString`. It had previously raised a
:exc:`DeprecationWarning` since Python 3.12.
* :class:`typing.TypeAliasType` now supports star unpacking.
urllib
------
* Remove deprecated :class:`!Quoter` class from :mod:`urllib.parse`.
It had previously raised a :exc:`DeprecationWarning` since Python 3.11.
(Contributed by Nikita Sobolev in :gh:`118827`.)
* Remove deprecated :class:`!URLopener` and :class:`!FancyURLopener` classes
from :mod:`urllib.request`. They had previously raised a
:exc:`DeprecationWarning` since Python 3.3.
``myopener.open()`` can be replaced with :func:`~urllib.request.urlopen`,
and ``myopener.retrieve()`` can be replaced with
:func:`~urllib.request.urlretrieve`. Customizations to the opener
classes can be replaced by passing customized handlers to
:func:`~urllib.request.build_opener`.
(Contributed by Barney Gale in :gh:`84850`.)
Others
------
* Using :data:`NotImplemented` in a boolean context will now raise a :exc:`TypeError`.
It had previously raised a :exc:`DeprecationWarning` since Python 3.9. (Contributed
by Jelle Zijlstra in :gh:`118767`.)
* The :func:`int` built-in no longer delegates to
:meth:`~object.__trunc__`. Classes that want to support conversion to
integer must implement either :meth:`~object.__int__` or
:meth:`~object.__index__`. (Contributed by Mark Dickinson in :gh:`119743`.)
* The default :term:`interactive` shell now supports import autocompletion.
This means that typing ``import foo`` and pressing ``<tab>`` will suggest
modules starting with ``foo``. Similarly, typing ``from foo import b`` will
suggest submodules of ``foo`` starting with ``b``. Note that autocompletion
of module attributes is not currently supported.
(Contributed by Tomas Roun in :gh:`69605`.)
CPython Bytecode Changes
========================
* Replaced the opcode ``BINARY_SUBSCR`` by :opcode:`BINARY_OP` with oparg ``NB_SUBSCR``.
(Contributed by Irit Katriel in :gh:`100239`.)
Porting to Python 3.14
======================
This section lists previously described changes and other bugfixes
that may require changes to your code.
Changes in the Python API
-------------------------
* :class:`functools.partial` is now a method descriptor.
Wrap it in :func:`staticmethod` if you want to preserve the old behavior.
(Contributed by Serhiy Storchaka and Dominykas Grigonis in :gh:`121027`.)
* The :func:`locale.nl_langinfo` function now sets temporarily the ``LC_CTYPE``
locale in some cases.
This temporary change affects other threads.
(Contributed by Serhiy Storchaka in :gh:`69998`.)
* :class:`types.UnionType` is now an alias for :class:`typing.Union`,
causing changes in some behaviors.
See :ref:`above <whatsnew314-typing-union>` for more details.
(Contributed by Jelle Zijlstra in :gh:`105499`.)
Build changes
=============
* GNU Autoconf 2.72 is now required to generate :file:`configure`.
(Contributed by Erlend Aasland in :gh:`115765`.)
* ``#pragma``-based linking with ``python3*.lib`` can now be switched off
with :c:expr:`Py_NO_LINK_LIB`. (Contributed by Jean-Christophe
Fillion-Robin in :gh:`82909`.)
.. _whatsnew314-pep761:
PEP 761: Discontinuation of PGP signatures
------------------------------------------
PGP signatures will not be available for CPython 3.14 and onwards.
Users verifying artifacts must use `Sigstore verification materials`_ for
verifying CPython artifacts. This change in release process is specified
in :pep:`761`.
.. _Sigstore verification materials: https://www.python.org/downloads/metadata/sigstore/
C API changes
=============
New features
------------
* Add :c:func:`PyLong_GetSign` function to get the sign of :class:`int` objects.
(Contributed by Sergey B Kirpichev in :gh:`116560`.)
* Add a new :c:type:`PyUnicodeWriter` API to create a Python :class:`str`
object:
* :c:func:`PyUnicodeWriter_Create`
* :c:func:`PyUnicodeWriter_DecodeUTF8Stateful`
* :c:func:`PyUnicodeWriter_Discard`
* :c:func:`PyUnicodeWriter_Finish`
* :c:func:`PyUnicodeWriter_Format`
* :c:func:`PyUnicodeWriter_WriteChar`
* :c:func:`PyUnicodeWriter_WriteRepr`
* :c:func:`PyUnicodeWriter_WriteStr`
* :c:func:`PyUnicodeWriter_WriteSubstring`
* :c:func:`PyUnicodeWriter_WriteUCS4`
* :c:func:`PyUnicodeWriter_WriteUTF8`
* :c:func:`PyUnicodeWriter_WriteWideChar`
(Contributed by Victor Stinner in :gh:`119182`.)
* Add :c:func:`PyIter_NextItem` to replace :c:func:`PyIter_Next`,
which has an ambiguous return value.
(Contributed by Irit Katriel and Erlend Aasland in :gh:`105201`.)
* Add :c:func:`PyLong_IsPositive`, :c:func:`PyLong_IsNegative`
and :c:func:`PyLong_IsZero` for checking if :c:type:`PyLongObject`
is positive, negative, or zero, respectively.
(Contributed by James Roy and Sergey B Kirpichev in :gh:`126061`.)
* Add new functions to convert C ``<stdint.h>`` numbers from/to Python
:class:`int`:
* :c:func:`PyLong_AsInt32`
* :c:func:`PyLong_AsInt64`
* :c:func:`PyLong_AsUInt32`
* :c:func:`PyLong_AsUInt64`
* :c:func:`PyLong_FromInt32`
* :c:func:`PyLong_FromInt64`
* :c:func:`PyLong_FromUInt32`
* :c:func:`PyLong_FromUInt64`
(Contributed by Victor Stinner in :gh:`120389`.)
* Add :c:func:`PyBytes_Join(sep, iterable) <PyBytes_Join>` function,
similar to ``sep.join(iterable)`` in Python.
(Contributed by Victor Stinner in :gh:`121645`.)
* Add :c:func:`Py_HashBuffer` to compute and return the hash value of a buffer.
(Contributed by Antoine Pitrou and Victor Stinner in :gh:`122854`.)
* Add functions to get and set the current runtime Python configuration
(:pep:`741`):
* :c:func:`PyConfig_Get`
* :c:func:`PyConfig_GetInt`
* :c:func:`PyConfig_Set`
* :c:func:`PyConfig_Names`
(Contributed by Victor Stinner in :gh:`107954`.)
* Add functions to configure the Python initialization (:pep:`741`):
* :c:func:`Py_InitializeFromInitConfig`
* :c:func:`PyInitConfig_AddModule`
* :c:func:`PyInitConfig_Create`
* :c:func:`PyInitConfig_Free`
* :c:func:`PyInitConfig_FreeStrList`
* :c:func:`PyInitConfig_GetError`
* :c:func:`PyInitConfig_GetExitCode`
* :c:func:`PyInitConfig_GetInt`
* :c:func:`PyInitConfig_GetStr`
* :c:func:`PyInitConfig_GetStrList`
* :c:func:`PyInitConfig_HasOption`
* :c:func:`PyInitConfig_SetInt`
* :c:func:`PyInitConfig_SetStr`
* :c:func:`PyInitConfig_SetStrList`
(Contributed by Victor Stinner in :gh:`107954`.)
* Add a new import and export API for Python :class:`int` objects (:pep:`757`):
* :c:func:`PyLong_GetNativeLayout`;
* :c:func:`PyLong_Export`;
* :c:func:`PyLong_FreeExport`;
* :c:func:`PyLongWriter_Create`;
* :c:func:`PyLongWriter_Finish`;
* :c:func:`PyLongWriter_Discard`.
(Contributed by Sergey B Kirpichev and Victor Stinner in :gh:`102471`.)
* Add :c:func:`PyType_GetBaseByToken` and :c:data:`Py_tp_token` slot for easier
superclass identification, which attempts to resolve the `type checking issue
<https://peps.python.org/pep-0630/#type-checking>`__ mentioned in :pep:`630`
(:gh:`124153`).
* Add :c:func:`PyUnicode_Equal` function to the limited C API:
test if two strings are equal.
(Contributed by Victor Stinner in :gh:`124502`.)
* Add :c:func:`PyType_Freeze` function to make a type immutable.
(Contributed by Victor Stinner in :gh:`121654`.)
* Add :c:func:`PyUnstable_Object_EnableDeferredRefcount` for enabling
deferred reference counting, as outlined in :pep:`703`.
* Add :c:func:`PyMonitoring_FireBranchLeftEvent` and
:c:func:`PyMonitoring_FireBranchRightEvent` for generating
:monitoring-event:`BRANCH_LEFT` and :monitoring-event:`BRANCH_RIGHT`
events, respectively.
* Add :c:func:`Py_fopen` function to open a file. Similar to the
:c:func:`!fopen` function, but the *path* parameter is a Python object and an
exception is set on error. Add also :c:func:`Py_fclose` function to close a
file.
(Contributed by Victor Stinner in :gh:`127350`.)
* Add support of nullable arguments in :c:func:`PyArg_ParseTuple` and
similar functions.
Adding ``?`` after any format unit makes ``None`` be accepted as a value.
(Contributed by Serhiy Storchaka in :gh:`112068`.)
* The ``k`` and ``K`` formats in :c:func:`PyArg_ParseTuple` and
similar functions now use :meth:`~object.__index__` if available,
like all other integer formats.
(Contributed by Serhiy Storchaka in :gh:`112068`.)
* Add macros :c:func:`Py_PACK_VERSION` and :c:func:`Py_PACK_FULL_VERSION` for
bit-packing Python version numbers.
(Contributed by Petr Viktorin in :gh:`128629`.)
* Add :c:func:`PyUnstable_IsImmortal` for determining whether an object is :term:`immortal`,
for debugging purposes.
* Add :c:func:`PyImport_ImportModuleAttr` and
:c:func:`PyImport_ImportModuleAttrString` helper functions to import a module
and get an attribute of the module.
(Contributed by Victor Stinner in :gh:`128911`.)
* Add support for a new ``p`` format unit in :c:func:`Py_BuildValue` that allows to
take a C integer and produce a Python :class:`bool` object. (Contributed by
Pablo Galindo in :issue:`45325`.)
* Add :c:func:`PyUnstable_Object_IsUniqueReferencedTemporary` to determine if an object
is a unique temporary object on the interpreter's operand stack. This can
be used in some cases as a replacement for checking if :c:func:`Py_REFCNT`
is ``1`` for Python objects passed as arguments to C API functions.
Limited C API changes
---------------------
* In the limited C API 3.14 and newer, :c:func:`Py_TYPE` and
:c:func:`Py_REFCNT` are now implemented as an opaque function call to hide
implementation details.
(Contributed by Victor Stinner in :gh:`120600` and :gh:`124127`.)
* Remove the :c:macro:`PySequence_Fast_GET_SIZE`,
:c:macro:`PySequence_Fast_GET_ITEM` and :c:macro:`PySequence_Fast_ITEMS`
macros from the limited C API, since these macros never worked in the limited
C API. Keep :c:func:`PySequence_Fast` in the limited C API.
(Contributed by Victor Stinner in :gh:`91417`.)
Porting to Python 3.14
----------------------
* :c:func:`Py_Finalize` now deletes all interned strings. This
is backwards incompatible to any C-Extension that holds onto an interned
string after a call to :c:func:`Py_Finalize` and is then reused after a
call to :c:func:`Py_Initialize`. Any issues arising from this behavior will
normally result in crashes during the execution of the subsequent call to
:c:func:`Py_Initialize` from accessing uninitialized memory. To fix, use
an address sanitizer to identify any use-after-free coming from
an interned string and deallocate it during module shutdown.
(Contributed by Eddie Elizondo in :gh:`113601`.)
* The :ref:`Unicode Exception Objects <unicodeexceptions>` C API
now raises a :exc:`TypeError` if its exception argument is not
a :exc:`UnicodeError` object.
(Contributed by Bénédikt Tran in :gh:`127691`.)
.. _whatsnew314-refcount:
* The interpreter internally avoids some reference count modifications when
loading objects onto the operands stack by :term:`borrowing <borrowed reference>`
references when possible. This can lead to smaller reference count values
compared to previous Python versions. C API extensions that checked
:c:func:`Py_REFCNT` of ``1`` to determine if an function argument is not
referenced by any other code should instead use
:c:func:`PyUnstable_Object_IsUniqueReferencedTemporary` as a safer replacement.
* Private functions promoted to public C APIs:
* ``_PyBytes_Join()``: :c:func:`PyBytes_Join`.
* ``_PyLong_IsNegative()``: :c:func:`PyLong_IsNegative`.
* ``_PyLong_IsPositive()``: :c:func:`PyLong_IsPositive`.
* ``_PyLong_IsZero()``: :c:func:`PyLong_IsZero`.
* ``_PyLong_Sign()``: :c:func:`PyLong_GetSign`.
* ``_PyUnicodeWriter_Dealloc()``: :c:func:`PyUnicodeWriter_Discard`.
* ``_PyUnicodeWriter_Finish()``: :c:func:`PyUnicodeWriter_Finish`.
* ``_PyUnicodeWriter_Init()``: use :c:func:`PyUnicodeWriter_Create`.
* ``_PyUnicodeWriter_Prepare()``: (no replacement).
* ``_PyUnicodeWriter_PrepareKind()``: (no replacement).
* ``_PyUnicodeWriter_WriteChar()``: :c:func:`PyUnicodeWriter_WriteChar`.
* ``_PyUnicodeWriter_WriteStr()``: :c:func:`PyUnicodeWriter_WriteStr`.
* ``_PyUnicodeWriter_WriteSubstring()``: :c:func:`PyUnicodeWriter_WriteSubstring`.
* ``_PyUnicode_EQ()``: :c:func:`PyUnicode_Equal`.
* ``_PyUnicode_Equal()``: :c:func:`PyUnicode_Equal`.
* ``_Py_GetConfig()``: :c:func:`PyConfig_Get` and :c:func:`PyConfig_GetInt`.
* ``_Py_HashBytes()``: :c:func:`Py_HashBuffer`.
* ``_Py_fopen_obj()``: :c:func:`Py_fopen`.
The `pythoncapi-compat project`_ can be used to get most of these new
functions on Python 3.13 and older.
.. _pythoncapi-compat project: https://github.com/python/pythoncapi-compat/
.. _whatsnew314-c-api-deprecated:
Deprecated
----------
* The :c:macro:`!Py_HUGE_VAL` macro is :term:`soft deprecated`,
use :c:macro:`!Py_INFINITY` instead.
(Contributed by Sergey B Kirpichev in :gh:`120026`.)
* Macros :c:macro:`!Py_IS_NAN`, :c:macro:`!Py_IS_INFINITY`
and :c:macro:`!Py_IS_FINITE` are :term:`soft deprecated`,
use instead :c:macro:`!isnan`, :c:macro:`!isinf` and
:c:macro:`!isfinite` available from :file:`math.h`
since C99. (Contributed by Sergey B Kirpichev in :gh:`119613`.)
* Non-tuple sequences are deprecated as argument for the ``(items)``
format unit in :c:func:`PyArg_ParseTuple` and other
:ref:`argument parsing <arg-parsing>` functions if *items* contains
format units which store a :ref:`borrowed buffer <c-arg-borrowed-buffer>`
or a :term:`borrowed reference`.
(Contributed by Serhiy Storchaka in :gh:`50333`.)
* The previously undocumented function :c:func:`PySequence_In` is :term:`soft deprecated`.
Use :c:func:`PySequence_Contains` instead.
(Contributed by Yuki Kobayashi in :gh:`127896`.)
.. Add C API deprecations above alphabetically, not here at the end.
* The ``PyMonitoring_FireBranchEvent`` function is deprecated and should
be replaced with calls to :c:func:`PyMonitoring_FireBranchLeftEvent`
and :c:func:`PyMonitoring_FireBranchRightEvent`.
* The following private functions are deprecated and planned for removal in
Python 3.18:
* :c:func:`!_PyBytes_Join`: use :c:func:`PyBytes_Join`.
* :c:func:`!_PyDict_GetItemStringWithError`: use :c:func:`PyDict_GetItemStringRef`.
* :c:func:`!_PyDict_Pop()`: use :c:func:`PyDict_Pop`.
* :c:func:`!_PyLong_Sign()`: use :c:func:`PyLong_GetSign`.
* :c:func:`!_PyLong_FromDigits` and :c:func:`!_PyLong_New`:
use :c:func:`PyLongWriter_Create`.
* :c:func:`!_PyThreadState_UncheckedGet`: use :c:func:`PyThreadState_GetUnchecked`.
* :c:func:`!_PyUnicode_AsString`: use :c:func:`PyUnicode_AsUTF8`.
* :c:func:`!_PyUnicodeWriter_Init`:
replace ``_PyUnicodeWriter_Init(&writer)`` with
:c:func:`writer = PyUnicodeWriter_Create(0) <PyUnicodeWriter_Create>`.
* :c:func:`!_PyUnicodeWriter_Finish`:
replace ``_PyUnicodeWriter_Finish(&writer)`` with
:c:func:`PyUnicodeWriter_Finish(writer) <PyUnicodeWriter_Finish>`.
* :c:func:`!_PyUnicodeWriter_Dealloc`:
replace ``_PyUnicodeWriter_Dealloc(&writer)`` with
:c:func:`PyUnicodeWriter_Discard(writer) <PyUnicodeWriter_Discard>`.
* :c:func:`!_PyUnicodeWriter_WriteChar`:
replace ``_PyUnicodeWriter_WriteChar(&writer, ch)`` with
:c:func:`PyUnicodeWriter_WriteChar(writer, ch) <PyUnicodeWriter_WriteChar>`.
* :c:func:`!_PyUnicodeWriter_WriteStr`:
replace ``_PyUnicodeWriter_WriteStr(&writer, str)`` with
:c:func:`PyUnicodeWriter_WriteStr(writer, str) <PyUnicodeWriter_WriteStr>`.
* :c:func:`!_PyUnicodeWriter_WriteSubstring`:
replace ``_PyUnicodeWriter_WriteSubstring(&writer, str, start, end)`` with
:c:func:`PyUnicodeWriter_WriteSubstring(writer, str, start, end) <PyUnicodeWriter_WriteSubstring>`.
* :c:func:`!_PyUnicodeWriter_WriteASCIIString`:
replace ``_PyUnicodeWriter_WriteASCIIString(&writer, str)`` with
:c:func:`PyUnicodeWriter_WriteUTF8(writer, str) <PyUnicodeWriter_WriteUTF8>`.
* :c:func:`!_PyUnicodeWriter_WriteLatin1String`:
replace ``_PyUnicodeWriter_WriteLatin1String(&writer, str)`` with
:c:func:`PyUnicodeWriter_WriteUTF8(writer, str) <PyUnicodeWriter_WriteUTF8>`.
* :c:func:`!_Py_HashPointer`: use :c:func:`Py_HashPointer`.
* :c:func:`!_Py_fopen_obj`: use :c:func:`Py_fopen`.
The `pythoncapi-compat project`_ can be used to get these new public
functions on Python 3.13 and older.
(Contributed by Victor Stinner in :gh:`128863`.)
.. include:: ../deprecations/c-api-pending-removal-in-3.15.rst
.. include:: ../deprecations/c-api-pending-removal-in-3.18.rst
.. include:: ../deprecations/c-api-pending-removal-in-future.rst
.. _whatsnew314-c-api-removed:
Removed
-------
* Creating :c:data:`immutable types <Py_TPFLAGS_IMMUTABLETYPE>` with mutable
bases was deprecated since 3.12 and now raises a :exc:`TypeError`.
* Remove ``PyDictObject.ma_version_tag`` member which was deprecated since
Python 3.12. Use the :c:func:`PyDict_AddWatcher` API instead.
(Contributed by Sam Gross in :gh:`124296`.)
* Remove the private ``_Py_InitializeMain()`` function. It was a
:term:`provisional API` added to Python 3.8 by :pep:`587`.
(Contributed by Victor Stinner in :gh:`129033`.)
* The undocumented APIs :c:macro:`!Py_C_RECURSION_LIMIT` and
:c:member:`!PyThreadState.c_recursion_remaining`, added in 3.13, are removed
without a deprecation period.
Please use :c:func:`Py_EnterRecursiveCall` to guard against runaway recursion
in C code.
(Removed in :gh:`133079`, see also :gh:`130396`.)