3.10.rst

What's New In Python 3.10

Release:	|release|
Date:	|today|

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

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

base64

Add :func:`base64.b32hexencode` and :func:`base64.b32hexdecode` to support the Base32 Encoding with Extended Hex Alphabet.

curses

The extended color functions added in ncurses 6.1 will be used transparently by :func:`curses.color_content`, :func:`curses.init_color`, :func:`curses.init_pair`, and :func:`curses.pair_content`. A new function, :func:`curses.has_extended_color_support`, indicates whether extended color support is provided by the underlying ncurses library. (Contributed by Jeffrey Kintscher and Hans Petter Jansson in :issue:`36982`.)

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`.)

os

Added :func:`os.cpu_count()` support for VxWorks RTOS. (Contributed by Peixing Xin in :issue:`41440`.)

pathlib

Subclasses of :class:`pathlib.Path` and :class:`pathlib.PurePath` now call the :func:`__new__` and :func:`__init__` functions of the subclasses when instantiating new subclass objects returned by various :class:`pathlib.Path` and :class:`pathlib.PurePath` functions and properties. (Contributed by Jeffrey Kintscher in :issue:`41109`.)

py_compile

Added --quiet option to command-line interface of :mod:`py_compile`. (Contributed by Gregory Schevchenko in :issue:`38731`.)

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`.)

xml

Add a :class:`~xml.sax.handler.LexicalHandler` class to the :mod:`xml.sax.handler` module. (Contributed by Jonathan Gossage and Zackery Spytz in :issue:`35018`.)

Optimizations

• Constructors :func:`str`, :func:`bytes` and :func:`bytearray` are now faster (around 30--40% for small objects). (Contributed by Serhiy Storchaka in :issue:`41334`.)
• 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`.)