Doc/whatsnew/3.10.rst - platform/external/python/cpython3 - Gitiles

 ****************************
   What's New In Python 3.10
 ****************************

 :Release: |release|
 :Date: |today|

 .. 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 bug/patch number as a comment:

    XXX Describe the transmogrify() function added to the socket
    module.
    (Contributed by P.Y. Developer in :issue:`12345`.)

    This saves the maintainer the effort of going through the Mercurial log
    when researching a change.

 This article explains the new features in Python 3.10, compared to 3.9.

 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 3.10 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 3.10.
    Brevity is key.


 .. PEP-sized items next.


 New Features
 ============

 * The :class:`int` type has a new method :meth:`int.bit_count`, returning the
   number of ones in the binary expansion of a given integer, also known
   as the population count. (Contributed by Niklas Fiekas in :issue:`29882`.)

 * The views returned by :meth:`dict.keys`, :meth:`dict.values` and
   :meth:`dict.items` now all have a ``mapping`` attribute that gives a
   :class:`types.MappingProxyType` object wrapping the original
   dictionary. (Contributed by Dennis Sweeney in :issue:`40890`.)

 * :pep:`618`: The :func:`zip` function now has an optional ``strict`` flag, used
   to require that all the iterables have an equal length.


 Other Language Changes
 ======================

 * Builtin and extension functions that take integer arguments no longer accept
   :class:`~decimal.Decimal`\ s, :class:`~fractions.Fraction`\ s and other
   objects that can be converted to integers only with a loss (e.g. that have
   the :meth:`~object.__int__` method but do not have the
   :meth:`~object.__index__` method).
   (Contributed by Serhiy Storchaka in :issue:`37999`.)


 New Modules
 ===========

 * None yet.


 Improved Modules
 ================

 glob
 ----

 Added the *root_dir* and *dir_fd* parameters in :func:`~glob.glob` and
 :func:`~glob.iglob` which allow to specify the root directory for searching.
 (Contributed by Serhiy Storchaka in :issue:`38144`.)

 sys
 ---

 Add :data:`sys.orig_argv` attribute: the list of the original command line
 arguments passed to the Python executable.
 (Contributed by Victor Stinner in :issue:`23427`.)


 Optimizations
 =============

 * The :mod:`runpy` module now imports fewer modules.
   The ``python3 -m module-name`` command startup time is 1.3x faster in
   average.
   (Contributed by Victor Stinner in :issue:`41006`.)


 Deprecated
 ==========


 Removed
 =======

 * The ``ParserBase.error()`` method from the private and undocumented ``_markupbase``
   module has been removed.  :class:`html.parser.HTMLParser` is the only subclass of
   ``ParserBase`` and its ``error()`` implementation has already been removed in
   Python 3.5.
   (Contributed by Berker Peksag in :issue:`31844`.)


 Porting to Python 3.10
 ======================

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


 Build Changes
 =============

 * The C99 functions :c:func:`snprintf` and :c:func:`vsnprintf` are now required
   to build Python.
   (Contributed by Victor Stinner in :issue:`36020`.)


 C API Changes
 =============

 New Features
 ------------

 * The result of :c:func:`PyNumber_Index` now always has exact type :class:`int`.
   Previously, the result could have been an instance of a subclass of ``int``.
   (Contributed by Serhiy Storchaka in :issue:`40792`.)

 * Add a new :c:member:`~PyConfig.orig_argv` member to the :c:type:`PyConfig`
   structure: the list of the original command line arguments passed to the
   Python executable.
   (Contributed by Victor Stinner in :issue:`23427`.)

 Porting to Python 3.10
 ----------------------

 * The ``PY_SSIZE_T_CLEAN`` macro must now be defined to use
   :c:func:`PyArg_ParseTuple` and :c:func:`Py_BuildValue` formats which use
   ``#``: ``es#``, ``et#``, ``s#``, ``u#``, ``y#``, ``z#``, ``U#`` and ``Z#``.
   See :ref:`Parsing arguments and building values
   <arg-parsing>` and the :pep:`353`.
   (Contributed by Victor Stinner in :issue:`40943`.)

 * Since :c:func:`Py_TYPE()` is changed to the inline static function,
   ``Py_TYPE(obj) = new_type`` must be replaced with ``Py_SET_TYPE(obj, new_type)``:
   see :c:func:`Py_SET_TYPE()` (available since Python 3.9). For backward
   compatibility, this macro can be used::

       #if PY_VERSION_HEX < 0x030900A4
       #  define Py_SET_TYPE(obj, type) ((Py_TYPE(obj) = (type)), (void)0)
       #endif

   (Contributed by Dong-hee Na in :issue:`39573`.)

 * Since :c:func:`Py_REFCNT()` is changed to the inline static function,
   ``Py_REFCNT(obj) = new_refcnt`` must be replaced with ``Py_SET_REFCNT(obj, new_refcnt)``:
   see :c:func:`Py_SET_REFCNT()` (available since Python 3.9). For backward
   compatibility, this macro can be used::

       #if PY_VERSION_HEX < 0x030900A4
       #  define Py_SET_REFCNT(obj, refcnt) ((Py_REFCNT(obj) = (refcnt)), (void)0)
       #endif

   (Contributed by Victor Stinner in :issue:`39573`.)

 * Since :c:func:`Py_SIZE()` is changed to the inline static function,
   ``Py_SIZE(obj) = new_size`` must be replaced with ``Py_SET_SIZE(obj, new_size)``:
   see :c:func:`Py_SET_SIZE()` (available since Python 3.9). For backward
   compatibility, this macro can be used::

       #if PY_VERSION_HEX < 0x030900A4
       #  define Py_SET_SIZE(obj, size) ((Py_SIZE(obj) = (size)), (void)0)
       #endif

   (Contributed by Victor Stinner in :issue:`39573`.)

 * Calling :c:func:`PyDict_GetItem` without :term:`GIL` held had been allowed
   for historical reason. It is no longer allowed.
   (Contributed by Victor Stinner in :issue:`40839`.)

 * ``PyUnicode_FromUnicode(NULL, size)`` and ``PyUnicode_FromStringAndSize(NULL, size)``
   raise ``DeprecationWarning`` now.  Use :c:func:`PyUnicode_New` to allocate
   Unicode object without initial data.
   (Contributed by Inada Naoki in :issue:`36346`.)

 Removed
 -------

 * ``PyObject_AsCharBuffer()``, ``PyObject_AsReadBuffer()``, ``PyObject_CheckReadBuffer()``,
   and ``PyObject_AsWriteBuffer()`` are removed. Please migrate to new buffer protocol;
   :c:func:`PyObject_GetBuffer` and :c:func:`PyBuffer_Release`.
   (Contributed by Inada Naoki in :issue:`41103`.)

 * Removed ``Py_UNICODE_str*`` functions manipulating ``Py_UNICODE*`` strings.
   (Contributed by Inada Naoki in :issue:`41123`.)

    * ``Py_UNICODE_strlen``: use :c:func:`PyUnicode_GetLength` or
      :c:macro:`PyUnicode_GET_LENGTH`
    * ``Py_UNICODE_strcat``: use :c:func:`PyUnicode_CopyCharacters` or
      :c:func:`PyUnicode_FromFormat`
    * ``Py_UNICODE_strcpy``, ``Py_UNICODE_strncpy``: use
      :c:func:`PyUnicode_CopyCharacters` or :c:func:`PyUnicode_Substring`
    * ``Py_UNICODE_strcmp``: use :c:func:`PyUnicode_Compare`
    * ``Py_UNICODE_strncmp``: use :c:func:`PyUnicode_Tailmatch`
    * ``Py_UNICODE_strchr``, ``Py_UNICODE_strrchr``: use
      :c:func:`PyUnicode_FindChar`

 * Removed ``PyUnicode_GetMax()``. Please migrate to new (:pep:`393`) APIs.
   (Contributed by Inada Naoki in :issue:`41103`.)

 * Removed ``PyLong_FromUnicode()``. Please migrate to :c:func:`PyLong_FromUnicodeObject`.
   (Contributed by Inada Naoki in :issue:`41103`.)

 * Removed ``PyUnicode_AsUnicodeCopy()``. Please use :c:func:`PyUnicode_AsUCS4Copy` or
   :c:func:`PyUnicode_AsWideCharString`
   (Contributed by Inada Naoki in :issue:`41103`.)
	****************************
	What's New In Python 3.10
	****************************

	:Release: \|release\|
	:Date: \|today\|

	.. 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 bug/patch number as a comment:

	XXX Describe the transmogrify() function added to the socket
	module.
	(Contributed by P.Y. Developer in :issue:`12345`.)

	This saves the maintainer the effort of going through the Mercurial log
	when researching a change.

	This article explains the new features in Python 3.10, compared to 3.9.

	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 3.10 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 3.10.
	Brevity is key.


	.. PEP-sized items next.



	New Features
	============

	* The :class:`int` type has a new method :meth:`int.bit_count`, returning the
	number of ones in the binary expansion of a given integer, also known
	as the population count. (Contributed by Niklas Fiekas in :issue:`29882`.)

	* The views returned by :meth:`dict.keys`, :meth:`dict.values` and
	:meth:`dict.items` now all have a ``mapping`` attribute that gives a
	:class:`types.MappingProxyType` object wrapping the original
	dictionary. (Contributed by Dennis Sweeney in :issue:`40890`.)

	* :pep:`618`: The :func:`zip` function now has an optional ``strict`` flag, used
	to require that all the iterables have an equal length.


	Other Language Changes
	======================

	* Builtin and extension functions that take integer arguments no longer accept
	:class:`~decimal.Decimal`\ s, :class:`~fractions.Fraction`\ s and other
	objects that can be converted to integers only with a loss (e.g. that have
	the :meth:`~object.__int__` method but do not have the
	:meth:`~object.__index__` method).
	(Contributed by Serhiy Storchaka in :issue:`37999`.)


	New Modules
	===========

	* None yet.


	Improved Modules
	================

	glob
	----

	Added the root_dir and dir_fd parameters in :func:`~glob.glob` and
	:func:`~glob.iglob` which allow to specify the root directory for searching.
	(Contributed by Serhiy Storchaka in :issue:`38144`.)

	sys
	---

	Add :data:`sys.orig_argv` attribute: the list of the original command line
	arguments passed to the Python executable.
	(Contributed by Victor Stinner in :issue:`23427`.)


	Optimizations
	=============

	* The :mod:`runpy` module now imports fewer modules.
	The ``python3 -m module-name`` command startup time is 1.3x faster in
	average.
	(Contributed by Victor Stinner in :issue:`41006`.)


	Deprecated
	==========


	Removed
	=======

	* The ``ParserBase.error()`` method from the private and undocumented ``_markupbase``
	module has been removed. :class:`html.parser.HTMLParser` is the only subclass of
	``ParserBase`` and its ``error()`` implementation has already been removed in
	Python 3.5.
	(Contributed by Berker Peksag in :issue:`31844`.)


	Porting to Python 3.10
	======================

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



	Build Changes
	=============

	* The C99 functions :c:func:`snprintf` and :c:func:`vsnprintf` are now required
	to build Python.
	(Contributed by Victor Stinner in :issue:`36020`.)


	C API Changes
	=============

	New Features
	------------

	* The result of :c:func:`PyNumber_Index` now always has exact type :class:`int`.
	Previously, the result could have been an instance of a subclass of ``int``.
	(Contributed by Serhiy Storchaka in :issue:`40792`.)

	* Add a new :c:member:`~PyConfig.orig_argv` member to the :c:type:`PyConfig`
	structure: the list of the original command line arguments passed to the
	Python executable.
	(Contributed by Victor Stinner in :issue:`23427`.)

	Porting to Python 3.10
	----------------------

	* The ``PY_SSIZE_T_CLEAN`` macro must now be defined to use
	:c:func:`PyArg_ParseTuple` and :c:func:`Py_BuildValue` formats which use
	``#``: ``es#``, ``et#``, ``s#``, ``u#``, ``y#``, ``z#``, ``U#`` and ``Z#``.
	See :ref:`Parsing arguments and building values
	<arg-parsing>` and the :pep:`353`.
	(Contributed by Victor Stinner in :issue:`40943`.)

	* Since :c:func:`Py_TYPE()` is changed to the inline static function,
	``Py_TYPE(obj) = new_type`` must be replaced with ``Py_SET_TYPE(obj, new_type)``:
	see :c:func:`Py_SET_TYPE()` (available since Python 3.9). For backward
	compatibility, this macro can be used::

	#if PY_VERSION_HEX < 0x030900A4
	# define Py_SET_TYPE(obj, type) ((Py_TYPE(obj) = (type)), (void)0)
	#endif

	(Contributed by Dong-hee Na in :issue:`39573`.)

	* Since :c:func:`Py_REFCNT()` is changed to the inline static function,
	``Py_REFCNT(obj) = new_refcnt`` must be replaced with ``Py_SET_REFCNT(obj, new_refcnt)``:
	see :c:func:`Py_SET_REFCNT()` (available since Python 3.9). For backward
	compatibility, this macro can be used::

	#if PY_VERSION_HEX < 0x030900A4
	# define Py_SET_REFCNT(obj, refcnt) ((Py_REFCNT(obj) = (refcnt)), (void)0)
	#endif

	(Contributed by Victor Stinner in :issue:`39573`.)

	* Since :c:func:`Py_SIZE()` is changed to the inline static function,
	``Py_SIZE(obj) = new_size`` must be replaced with ``Py_SET_SIZE(obj, new_size)``:
	see :c:func:`Py_SET_SIZE()` (available since Python 3.9). For backward
	compatibility, this macro can be used::

	#if PY_VERSION_HEX < 0x030900A4
	# define Py_SET_SIZE(obj, size) ((Py_SIZE(obj) = (size)), (void)0)
	#endif

	(Contributed by Victor Stinner in :issue:`39573`.)

	* Calling :c:func:`PyDict_GetItem` without :term:`GIL` held had been allowed
	for historical reason. It is no longer allowed.
	(Contributed by Victor Stinner in :issue:`40839`.)

	* ``PyUnicode_FromUnicode(NULL, size)`` and ``PyUnicode_FromStringAndSize(NULL, size)``
	raise ``DeprecationWarning`` now. Use :c:func:`PyUnicode_New` to allocate
	Unicode object without initial data.
	(Contributed by Inada Naoki in :issue:`36346`.)

	Removed
	-------

	* ``PyObject_AsCharBuffer()``, ``PyObject_AsReadBuffer()``, ``PyObject_CheckReadBuffer()``,
	and ``PyObject_AsWriteBuffer()`` are removed. Please migrate to new buffer protocol;
	:c:func:`PyObject_GetBuffer` and :c:func:`PyBuffer_Release`.
	(Contributed by Inada Naoki in :issue:`41103`.)

	* Removed ``Py_UNICODE_str`` functions manipulating ``Py_UNICODE`` strings.
	(Contributed by Inada Naoki in :issue:`41123`.)

	* ``Py_UNICODE_strlen``: use :c:func:`PyUnicode_GetLength` or
	:c:macro:`PyUnicode_GET_LENGTH`
	* ``Py_UNICODE_strcat``: use :c:func:`PyUnicode_CopyCharacters` or
	:c:func:`PyUnicode_FromFormat`
	* ``Py_UNICODE_strcpy``, ``Py_UNICODE_strncpy``: use
	:c:func:`PyUnicode_CopyCharacters` or :c:func:`PyUnicode_Substring`
	* ``Py_UNICODE_strcmp``: use :c:func:`PyUnicode_Compare`
	* ``Py_UNICODE_strncmp``: use :c:func:`PyUnicode_Tailmatch`
	* ``Py_UNICODE_strchr``, ``Py_UNICODE_strrchr``: use
	:c:func:`PyUnicode_FindChar`

	* Removed ``PyUnicode_GetMax()``. Please migrate to new (:pep:`393`) APIs.
	(Contributed by Inada Naoki in :issue:`41103`.)

	* Removed ``PyLong_FromUnicode()``. Please migrate to :c:func:`PyLong_FromUnicodeObject`.
	(Contributed by Inada Naoki in :issue:`41103`.)

	* Removed ``PyUnicode_AsUnicodeCopy()``. Please use :c:func:`PyUnicode_AsUCS4Copy` or
	:c:func:`PyUnicode_AsWideCharString`
	(Contributed by Inada Naoki in :issue:`41103`.)