The behavior of:func:`!gc.collect` changes slightly:

* ``gc.collect(1)``: Performs an increment ofGC,

* ``gc.collect(1)``: Performs an increment ofgarbage collection,

rather than collecting generation 1.

* Other calls to:func:`!gc.collect` are unchanged.

non-ASCII keyword parameter names.

(Contributed by Serhiy Storchaka in:gh:`110815`.)

* The:c:func:`!PyCode_GetFirstFree` function is now unstable API

and is now named:c:func:`PyUnstable_Code_GetFirstFree`.

(Contributed by Bogdan Romanyuk in:gh:`115781`.)

* The:c:func:`PyDict_GetItem`,:c:func:`PyDict_GetItemString`,

:c:func:`PyMapping_HasKey`,:c:func:`PyMapping_HasKeyString`,

:c:func:`PyObject_HasAttr`,:c:func:`PyObject_HasAttrString`,

and:c:func:`PySys_GetObject` functions,

each of which clears all errors which occurred when calling them

now reports these errors using:func:`sys.unraisablehook`.

You may replace them with other functions as recommended in the documentation.

(Contributed by Serhiy Storchaka in:gh:`106672`.)

* Add support for the ``%T``, ``%#T``, ``%N`` and ``%#N`` formats

to:c:func:`PyUnicode_FromFormat`:

Changes in the Python API

* An:exc:`OSError` is now raised by:func:`getpass.getuser` for any failure to

retrieve a username, instead of:exc:`ImportError` on non-Unix platforms or

:exc:`KeyError` on Unix platforms where the password database is empty.

.. _pep667-porting-notes-py:

* The:mod:`threading` module now expects the:mod:`!_thread` module to have

an ``_is_main_interpreter`` attribute. It is a function with no

arguments that returns ``True`` if the current interpreter is the

main interpreter.

*:ref:`PEP 667<whatsnew313-locals-semantics>` introduces several changes

to the semantics of:func:`locals` and:attr:`f_locals <frame.f_locals>`:

* Calling:func:`locals` in an:term:`optimized scope` now produces an

independent snapshot on each call, and hence no longer implicitly updates

previously returned references. Obtaining the legacy CPython behaviour now

requires explicit calls to update the initially returned dictionary with the

results of subsequent calls to:func:`!locals`. Code execution functions that

implicitly target:func:`!locals` (such as ``exec`` and ``eval``) must be

passed an explicit namespace to access their results in an optimized scope.

(Changed as part of:pep:`667`.)

* Calling:func:`locals` from a comprehension at module or class scope

(including via ``exec`` or ``eval``) once more behaves as if the comprehension

were running as an independent nested function (i.e. the local variables from

the containing scope are not included). In Python 3.12, this had changed

to include the local variables from the containing scope when implementing

:pep:`709`. (Changed as part of:pep:`667`.)

* Accessing:attr:`FrameType.f_locals <frame.f_locals>` in an

:term:`optimized scope` now returns a write-through proxy rather than a

snapshot that gets updated at ill-specified times. If a snapshot is desired,

it must be created explicitly with ``dict`` or the proxy's ``.copy()`` method.

(Changed as part of:pep:`667`.)

*:class:`functools.partial` now emits a:exc:`FutureWarning`

when used as a method.

The behavior will change in future Python versions.

Wrap it in:func:`staticmethod` if you want to preserve the old behavior.

(Contributed by Serhiy Storchaka in:gh:`121027`.)

Any library or application that provides a custom ``_thread`` module

must provide:func:`!_is_main_interpreter`, just like the module's

other "private" attributes.

(See:gh:`112826`.)

* The:ref:`garbage collector is now incremental<whatsnew313-incremental-gc>`,

which means that the behavior of:func:`gc.collect` changes slightly:

*:class:`mailbox.Maildir` now ignores files with a leading dot.

(Contributed by Zackery Spytz in:gh:`65559`.)

* ``gc.collect(1)``: Performs an increment of garbage collection,

rather than collecting generation 1.

* Other calls to:func:`!gc.collect` are unchanged.

*:meth:`pathlib.Path.glob` and:meth:`~pathlib.Path.rglob` now return both

directories.

*An:exc:`OSError` is now raised by:func:`getpass.getuser`

or:exc:`KeyError` on Unix platforms where the password database is empty.

* The value of the:attr:`!mode` attribute of:class:`gzip.GzipFile` was

changed from integer(``1`` or ``2``)to string(``'rb'`` or ``'wb'``).

* The value of the:attr:`!mode` attribute of:class:`gzip.GzipFile`

is now a string(``'rb'`` or ``'wb'``)instead of an integer(``1`` or ``2``).

The value of the:attr:`!mode` attribute of the readable file-like object

returned by:meth:`zipfile.ZipFile.open`was changed from``'r'``to``'rb'``.

returned by:meth:`zipfile.ZipFile.open`is now``'rb'``instead of``'r'``.

(Contributed by Serhiy Storchaka in:gh:`115961`.)

*:class:`functools.partial` now emits a:exc:`FutureWarning` when it is

used as a method.

Its behavior will be changed in future Python versions.

Wrap it in:func:`staticmethod` if you want to preserve the old behavior.

(Contributed by Serhiy Storchaka in:gh:`121027`.)

*:class:`mailbox.Maildir` now ignores files with a leading dot (``.``).

(Contributed by Zackery Spytz in:gh:`65559`.)

.. _pep667-porting-notes-py:

*:meth:`pathlib.Path.glob` and:meth:`~pathlib.Path.rglob` now return both

files and directories if a pattern that ends with "``**``" is given,

rather than directories only.

Add a trailing slash to keep the previous behavior and only match directories.

* The:mod:`threading` module now expects the:mod:`!_thread` module

to have an:func:`!_is_main_interpreter` function.

This function takes no arguments and returns ``True``

if the current interpreter is the main interpreter.

Any library or application that provides a custom:mod:`!_thread` module

must provide:func:`!_is_main_interpreter`,

just like the module's other "private" attributes.

(:gh:`112826`.)

* Calling:func:`locals` in an:term:`optimized scope` now produces an

independent snapshot on each call, and hence no longer implicitly updates

previously returned references. Obtaining the legacy CPython behaviour now

requires explicit calls to update the initially returned dictionary with the

results of subsequent calls to:func:`!locals`. Code execution functions that

implicitly target:func:`!locals` (such as ``exec`` and ``eval``) must be

passed an explicit namespace to access their results in an optimized scope.

(Changed as part of:pep:`667`.)

* Calling:func:`locals` from a comprehension at module or class scope

(including via ``exec`` or ``eval``) once more behaves as if the comprehension

were running as an independent nested function (i.e. the local variables from

the containing scope are not included). In Python 3.12, this had changed

to include the local variables from the containing scope when implementing

:pep:`709`. (Changed as part of:pep:`667`.)

* Accessing:attr:`FrameType.f_locals <frame.f_locals>` in an

:term:`optimized scope` now returns a write-through proxy rather than a

snapshot that gets updated at ill-specified times. If a snapshot is desired,

it must be created explicitly with ``dict`` or the proxy's ``.copy()`` method.

(Changed as part of:pep:`667`.)

Changes in the C API

added in Python 3.8 and the old macros were deprecated in Python 3.11.

(Contributed by Irit Katriel in:gh:`105111`.)

* Functions:c:func:`PyDict_GetItem`,:c:func:`PyDict_GetItemString`,

:c:func:`PyMapping_HasKey`,:c:func:`PyMapping_HasKeyString`,

:c:func:`PyObject_HasAttr`,:c:func:`PyObject_HasAttrString`, and

:c:func:`PySys_GetObject`, which clear all errors which occurred when calling

them, now report them using:func:`sys.unraisablehook`.

You may replace them with other functions as

recommended in the documentation.

(Contributed by Serhiy Storchaka in:gh:`106672`.)

*:c:func:`!PyCode_GetFirstFree` is an unstable API now and has been renamed

to:c:func:`PyUnstable_Code_GetFirstFree`.

(Contributed by Bogdan Romanyuk in:gh:`115781`.)

.. _pep667-porting-notes-c:

* The effects of mutating the dictionary returned from:c:func:`PyEval_GetLocals` in an

:term:`optimized scope` have changed. New dict entries added this way will now *only* be

visible to subsequent:c:func:`PyEval_GetLocals` calls in that frame, as

:c:func:`PyFrame_GetLocals`,:func:`locals`, and

:attr:`FrameType.f_locals <frame.f_locals>` no longer access the same underlying cached

dictionary. Changes made to entries for actual variable names and names added via the

write-through proxy interfaces will be overwritten on subsequent calls to

:c:func:`PyEval_GetLocals` in that frame. The recommended code update depends on how the

function was being used, so refer to the deprecation notice on the function for details.

(Changed as part of:pep:`667`.)

* Calling:c:func:`PyFrame_GetLocals` in an:term:`optimized scope` now returns a

write-through proxy rather than a snapshot that gets updated at ill-specified times.

If a snapshot is desired, it must be created explicitly (e.g. with:c:func:`PyDict_Copy`)

or by calling the new:c:func:`PyEval_GetFrameLocals` API. (Changed as part of:pep:`667`.)

*:c:func:`!PyFrame_FastToLocals` and:c:func:`!PyFrame_FastToLocalsWithError`

no longer have any effect. Calling these functions has been redundant since

Python 3.11, when:c:func:`PyFrame_GetLocals` was first introduced.

(Changed as part of:pep:`667`.)

*:c:func:`!PyFrame_LocalsToFast` no longer has any effect. Calling this function

is redundant now that:c:func:`PyFrame_GetLocals` returns a write-through proxy

for:term:`optimized scopes <optimized scope>`. (Changed as part of:pep:`667`.)

*:ref:`PEP 667<whatsnew313-locals-semantics>` introduces several changes

to frame-related functions:

* The effects of mutating the dictionary returned from

:c:func:`PyEval_GetLocals` in an:term:`optimized scope` have changed.

New dict entries added this way will now *only* be visible to

subsequent:c:func:`PyEval_GetLocals` calls in that frame,

as:c:func:`PyFrame_GetLocals`,:func:`locals`,

and:attr:`FrameType.f_locals <frame.f_locals>` no longer access

the same underlying cached dictionary.

Changes made to entries for actual variable names and names added via

the write-through proxy interfaces will be overwritten on subsequent calls

to:c:func:`PyEval_GetLocals` in that frame.

The recommended code update depends on how the function was being used,

so refer to the deprecation notice on the function for details.

* Calling:c:func:`PyFrame_GetLocals` in an:term:`optimized scope`

now returns a write-through proxy rather than a snapshot

that gets updated at ill-specified times.

If a snapshot is desired, it must be created explicitly

(e.g. with:c:func:`PyDict_Copy`),

or by calling the new:c:func:`PyEval_GetFrameLocals` API.

*:c:func:`!PyFrame_FastToLocals` and:c:func:`!PyFrame_FastToLocalsWithError`

no longer have any effect.

Calling these functions has been redundant since Python 3.11,

when:c:func:`PyFrame_GetLocals` was first introduced.

*:c:func:`!PyFrame_LocalsToFast` no longer has any effect.

Calling this function is redundant now that:c:func:`PyFrame_GetLocals`

returns a write-through proxy for:term:`optimized scopes <optimized scope>`.

Regression Test Changes