433 lines
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ReStructuredText
433 lines
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ReStructuredText
****************************
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What's New In Python 3.10
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****************************
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:Release: |release|
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:Date: |today|
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.. Rules for maintenance:
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* Anyone can add text to this document. Do not spend very much time
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on the wording of your changes, because your text will probably
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get rewritten to some degree.
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* The maintainer will go through Misc/NEWS periodically and add
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changes; it's therefore more important to add your changes to
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Misc/NEWS than to this file.
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* This is not a complete list of every single change; completeness
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is the purpose of Misc/NEWS. Some changes I consider too small
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or esoteric to include. If such a change is added to the text,
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I'll just remove it. (This is another reason you shouldn't spend
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too much time on writing your addition.)
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* If you want to draw your new text to the attention of the
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maintainer, add 'XXX' to the beginning of the paragraph or
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section.
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* It's OK to just add a fragmentary note about a change. For
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example: "XXX Describe the transmogrify() function added to the
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socket module." The maintainer will research the change and
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write the necessary text.
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* You can comment out your additions if you like, but it's not
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necessary (especially when a final release is some months away).
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* Credit the author of a patch or bugfix. Just the name is
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sufficient; the e-mail address isn't necessary.
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* It's helpful to add the bug/patch number as a comment:
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XXX Describe the transmogrify() function added to the socket
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module.
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(Contributed by P.Y. Developer in :issue:`12345`.)
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This saves the maintainer the effort of going through the Mercurial log
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when researching a change.
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This article explains the new features in Python 3.10, compared to 3.9.
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For full details, see the :ref:`changelog <changelog>`.
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.. note::
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Prerelease users should be aware that this document is currently in draft
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form. It will be updated substantially as Python 3.10 moves towards release,
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so it's worth checking back even after reading earlier versions.
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Summary -- Release highlights
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=============================
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.. This section singles out the most important changes in Python 3.10.
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Brevity is key.
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.. PEP-sized items next.
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New Features
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============
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.. _whatsnew310-pep563:
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PEP 563: Postponed Evaluation of Annotations Becomes Default
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------------------------------------------------------------
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In Python 3.7, postponed evaluation of annotations was added,
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to be enabled with a ``from __future__ import annotations``
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directive. In 3.10 this became the default behavior, even
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without that future directive. With this being default, all
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annotations stored in :attr:`__annotations__` will be strings.
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If needed, annotations can be resolved at runtime using
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:func:`typing.get_type_hints`. See :pep:`563` for a full
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description. Also, the :func:`inspect.signature` will try to
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resolve types from now on, and when it fails it will fall back to
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showing the string annotations. (Contributed by Batuhan Taskaya
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in :issue:`38605`.)
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* The :class:`int` type has a new method :meth:`int.bit_count`, returning the
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number of ones in the binary expansion of a given integer, also known
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as the population count. (Contributed by Niklas Fiekas in :issue:`29882`.)
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* The views returned by :meth:`dict.keys`, :meth:`dict.values` and
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:meth:`dict.items` now all have a ``mapping`` attribute that gives a
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:class:`types.MappingProxyType` object wrapping the original
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dictionary. (Contributed by Dennis Sweeney in :issue:`40890`.)
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* :pep:`618`: The :func:`zip` function now has an optional ``strict`` flag, used
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to require that all the iterables have an equal length.
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PEP 613: TypeAlias Annotation
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-----------------------------
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:pep:`484` introduced the concept of type aliases, only requiring them to be
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top-level unannotated assignments. This simplicity sometimes made it difficult
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for type checkers to distinguish between type aliases and ordinary assignments,
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especially when forward references or invalid types were involved. Compare::
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StrCache = 'Cache[str]' # a type alias
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LOG_PREFIX = 'LOG[DEBUG]' # a module constant
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Now the :mod:`typing` module has a special annotation :data:`TypeAlias` to
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declare type aliases more explicitly::
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StrCache: TypeAlias = 'Cache[str]' # a type alias
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LOG_PREFIX = 'LOG[DEBUG]' # a module constant
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See :pep:`613` for more details.
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(Contributed by Mikhail Golubev in :issue:`41923`.)
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PEP604: New Type Union Operator
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-------------------------------
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A new type union operator was introduced which enables the syntax ``X | Y``.
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This provides a cleaner way of expressing 'either type X or type Y' instead of
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using :data:`typing.Union`, especially in type hints (annotations).
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In previous versions of Python, to apply a type hint for functions accepting
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arguments of multiple types, :data:`typing.Union` was used::
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def square(number: Union[int, float]) -> Union[int, float]:
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return number ** 2
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Now, type hints can be written in a more succinct manner::
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def square(number: int | float) -> int | float:
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return number ** 2
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See :pep:`604` for more details.
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(Contributed by Maggie Moss and Philippe Prados in :issue:`41428`.)
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Other Language Changes
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======================
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* Builtin and extension functions that take integer arguments no longer accept
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:class:`~decimal.Decimal`\ s, :class:`~fractions.Fraction`\ s and other
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objects that can be converted to integers only with a loss (e.g. that have
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the :meth:`~object.__int__` method but do not have the
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:meth:`~object.__index__` method).
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(Contributed by Serhiy Storchaka in :issue:`37999`.)
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New Modules
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===========
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* None yet.
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Improved Modules
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================
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base64
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------
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Add :func:`base64.b32hexencode` and :func:`base64.b32hexdecode` to support the
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Base32 Encoding with Extended Hex Alphabet.
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codecs
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------
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Add a :func:`codecs.unregister` function to unregister a codec search function.
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(Contributed by Hai Shi in :issue:`41842`.)
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curses
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------
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The extended color functions added in ncurses 6.1 will be used transparently
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by :func:`curses.color_content`, :func:`curses.init_color`,
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:func:`curses.init_pair`, and :func:`curses.pair_content`. A new function,
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:func:`curses.has_extended_color_support`, indicates whether extended color
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support is provided by the underlying ncurses library.
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(Contributed by Jeffrey Kintscher and Hans Petter Jansson in :issue:`36982`.)
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encodings
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---------
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:func:`encodings.normalize_encoding` now ignores non-ASCII characters.
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(Contributed by Hai Shi in :issue:`39337`.)
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glob
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----
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Added the *root_dir* and *dir_fd* parameters in :func:`~glob.glob` and
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:func:`~glob.iglob` which allow to specify the root directory for searching.
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(Contributed by Serhiy Storchaka in :issue:`38144`.)
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os
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--
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Added :func:`os.cpu_count()` support for VxWorks RTOS.
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(Contributed by Peixing Xin in :issue:`41440`.)
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py_compile
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----------
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Added ``--quiet`` option to command-line interface of :mod:`py_compile`.
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(Contributed by Gregory Schevchenko in :issue:`38731`.)
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sys
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---
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Add :data:`sys.orig_argv` attribute: the list of the original command line
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arguments passed to the Python executable.
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(Contributed by Victor Stinner in :issue:`23427`.)
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types
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-----
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Reintroduced the :data:`types.EllipsisType`, :data:`types.NoneType`
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and :data:`types.NotImplementedType` classes, providing a new set
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of types readily interpretable by type checkers.
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(Contributed by Bas van Beek in :issue:`41810`.)
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unittest
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--------
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Add new method :meth:`~unittest.TestCase.assertNoLogs` to complement the
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existing :meth:`~unittest.TestCase.assertLogs`. (Contributed by Kit Yan Choi
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in :issue:`39385`.)
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xml
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---
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Add a :class:`~xml.sax.handler.LexicalHandler` class to the
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:mod:`xml.sax.handler` module.
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(Contributed by Jonathan Gossage and Zackery Spytz in :issue:`35018`.)
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Optimizations
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=============
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* Constructors :func:`str`, :func:`bytes` and :func:`bytearray` are now faster
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(around 30--40% for small objects).
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(Contributed by Serhiy Storchaka in :issue:`41334`.)
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* The :mod:`runpy` module now imports fewer modules.
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The ``python3 -m module-name`` command startup time is 1.3x faster in
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average.
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(Contributed by Victor Stinner in :issue:`41006`.)
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* The ``LOAD_ATTR`` instruction now uses new "per opcode cache" mechanism.
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It is about 36% faster now. (Contributed by Pablo Galindo and Yury Selivanov
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in :issue:`42093`.)
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Deprecated
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==========
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Removed
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=======
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* Removed special methods ``__int__``, ``__float__``, ``__floordiv__``,
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``__mod__``, ``__divmod__``, ``__rfloordiv__``, ``__rmod__`` and
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``__rdivmod__`` of the :class:`complex` class. They always raised
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a :exc:`TypeError`.
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(Contributed by Serhiy Storchaka in :issue:`41974`.)
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* The ``ParserBase.error()`` method from the private and undocumented ``_markupbase``
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module has been removed. :class:`html.parser.HTMLParser` is the only subclass of
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``ParserBase`` and its ``error()`` implementation has already been removed in
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Python 3.5.
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(Contributed by Berker Peksag in :issue:`31844`.)
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Porting to Python 3.10
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======================
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This section lists previously described changes and other bugfixes
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that may require changes to your code.
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Build Changes
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=============
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* The C99 functions :c:func:`snprintf` and :c:func:`vsnprintf` are now required
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to build Python.
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(Contributed by Victor Stinner in :issue:`36020`.)
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* :mod:`sqlite3` requires SQLite 3.7.3 or higher.
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(Contributed by Sergey Fedoseev and Erlend E. Aasland :issue:`40744`.)
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C API Changes
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=============
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New Features
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------------
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* The result of :c:func:`PyNumber_Index` now always has exact type :class:`int`.
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Previously, the result could have been an instance of a subclass of ``int``.
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(Contributed by Serhiy Storchaka in :issue:`40792`.)
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* Add a new :c:member:`~PyConfig.orig_argv` member to the :c:type:`PyConfig`
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structure: the list of the original command line arguments passed to the
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Python executable.
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(Contributed by Victor Stinner in :issue:`23427`.)
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* The :c:func:`PyDateTime_DATE_GET_TZINFO` and
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:c:func:`PyDateTime_TIME_GET_TZINFO` macros have been added for accessing
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the ``tzinfo`` attributes of :class:`datetime.datetime` and
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:class:`datetime.time` objects.
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(Contributed by Zackery Spytz in :issue:`30155`.)
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* Add a :c:func:`PyCodec_Unregister` function to unregister a codec
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search function.
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(Contributed by Hai Shi in :issue:`41842`.)
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* The :c:func:`PyIter_Send` function was added to allow
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sending value into iterator without raising ``StopIteration`` exception.
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(Contributed by Vladimir Matveev in :issue:`41756`.)
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* Added :c:func:`PyUnicode_AsUTF8AndSize` to the limited C API.
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(Contributed by Alex Gaynor in :issue:`41784`.)
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Porting to Python 3.10
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----------------------
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* The ``PY_SSIZE_T_CLEAN`` macro must now be defined to use
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:c:func:`PyArg_ParseTuple` and :c:func:`Py_BuildValue` formats which use
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``#``: ``es#``, ``et#``, ``s#``, ``u#``, ``y#``, ``z#``, ``U#`` and ``Z#``.
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See :ref:`Parsing arguments and building values
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<arg-parsing>` and the :pep:`353`.
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(Contributed by Victor Stinner in :issue:`40943`.)
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* Since :c:func:`Py_TYPE()` is changed to the inline static function,
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``Py_TYPE(obj) = new_type`` must be replaced with ``Py_SET_TYPE(obj, new_type)``:
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see :c:func:`Py_SET_TYPE()` (available since Python 3.9). For backward
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compatibility, this macro can be used::
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#if PY_VERSION_HEX < 0x030900A4
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# define Py_SET_TYPE(obj, type) ((Py_TYPE(obj) = (type)), (void)0)
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#endif
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(Contributed by Dong-hee Na in :issue:`39573`.)
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* Since :c:func:`Py_REFCNT()` is changed to the inline static function,
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``Py_REFCNT(obj) = new_refcnt`` must be replaced with ``Py_SET_REFCNT(obj, new_refcnt)``:
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see :c:func:`Py_SET_REFCNT()` (available since Python 3.9). For backward
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compatibility, this macro can be used::
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#if PY_VERSION_HEX < 0x030900A4
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# define Py_SET_REFCNT(obj, refcnt) ((Py_REFCNT(obj) = (refcnt)), (void)0)
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#endif
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(Contributed by Victor Stinner in :issue:`39573`.)
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* Since :c:func:`Py_SIZE()` is changed to the inline static function,
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``Py_SIZE(obj) = new_size`` must be replaced with ``Py_SET_SIZE(obj, new_size)``:
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see :c:func:`Py_SET_SIZE()` (available since Python 3.9). For backward
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compatibility, this macro can be used::
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#if PY_VERSION_HEX < 0x030900A4
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# define Py_SET_SIZE(obj, size) ((Py_SIZE(obj) = (size)), (void)0)
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#endif
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(Contributed by Victor Stinner in :issue:`39573`.)
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* Calling :c:func:`PyDict_GetItem` without :term:`GIL` held had been allowed
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for historical reason. It is no longer allowed.
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(Contributed by Victor Stinner in :issue:`40839`.)
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* ``PyUnicode_FromUnicode(NULL, size)`` and ``PyUnicode_FromStringAndSize(NULL, size)``
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raise ``DeprecationWarning`` now. Use :c:func:`PyUnicode_New` to allocate
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Unicode object without initial data.
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(Contributed by Inada Naoki in :issue:`36346`.)
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Deprecated
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----------
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* The ``PyUnicode_InternImmortal()`` function is now deprecated
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and will be removed in Python 3.12: use :c:func:`PyUnicode_InternInPlace`
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instead.
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(Contributed by Victor Stinner in :issue:`41692`.)
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Removed
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-------
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* ``PyObject_AsCharBuffer()``, ``PyObject_AsReadBuffer()``, ``PyObject_CheckReadBuffer()``,
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and ``PyObject_AsWriteBuffer()`` are removed. Please migrate to new buffer protocol;
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:c:func:`PyObject_GetBuffer` and :c:func:`PyBuffer_Release`.
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(Contributed by Inada Naoki in :issue:`41103`.)
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* Removed ``Py_UNICODE_str*`` functions manipulating ``Py_UNICODE*`` strings.
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(Contributed by Inada Naoki in :issue:`41123`.)
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* ``Py_UNICODE_strlen``: use :c:func:`PyUnicode_GetLength` or
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:c:macro:`PyUnicode_GET_LENGTH`
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* ``Py_UNICODE_strcat``: use :c:func:`PyUnicode_CopyCharacters` or
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:c:func:`PyUnicode_FromFormat`
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* ``Py_UNICODE_strcpy``, ``Py_UNICODE_strncpy``: use
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:c:func:`PyUnicode_CopyCharacters` or :c:func:`PyUnicode_Substring`
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* ``Py_UNICODE_strcmp``: use :c:func:`PyUnicode_Compare`
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* ``Py_UNICODE_strncmp``: use :c:func:`PyUnicode_Tailmatch`
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* ``Py_UNICODE_strchr``, ``Py_UNICODE_strrchr``: use
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:c:func:`PyUnicode_FindChar`
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* Removed ``PyUnicode_GetMax()``. Please migrate to new (:pep:`393`) APIs.
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(Contributed by Inada Naoki in :issue:`41103`.)
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* Removed ``PyLong_FromUnicode()``. Please migrate to :c:func:`PyLong_FromUnicodeObject`.
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(Contributed by Inada Naoki in :issue:`41103`.)
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* Removed ``PyUnicode_AsUnicodeCopy()``. Please use :c:func:`PyUnicode_AsUCS4Copy` or
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:c:func:`PyUnicode_AsWideCharString`
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(Contributed by Inada Naoki in :issue:`41103`.)
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* Removed ``_Py_CheckRecursionLimit`` variable: it has been replaced by
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``ceval.recursion_limit`` of the :c:type:`PyInterpreterState` structure.
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(Contributed by Victor Stinner in :issue:`41834`.)
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* Removed undocumented macros ``Py_ALLOW_RECURSION`` and
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``Py_END_ALLOW_RECURSION`` and the ``recursion_critical`` field of the
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:c:type:`PyInterpreterState` structure.
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(Contributed by Serhiy Storchaka in :issue:`41936`.)
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