Skip to content

3.10.rst

Latest commit

 

History

History
478 lines (342 loc) · 17 KB

3.10.rst

File metadata and controls

478 lines (342 loc) · 17 KB

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

PEP 563: Postponed Evaluation of Annotations Becomes Default

In Python 3.7, postponed evaluation of annotations was added, to be enabled with a from __future__ import annotations directive. In 3.10 this became the default behavior, even without that future directive. With this being default, all annotations stored in :attr:`__annotations__` will be strings. If needed, annotations can be resolved at runtime using :func:`typing.get_type_hints`. See PEP 563 for a full description. Also, the :func:`inspect.signature` will try to resolve types from now on, and when it fails it will fall back to showing the string annotations. (Contributed by Batuhan Taskaya in :issue:`38605`.)

PEP 613: TypeAlias Annotation

PEP 484 introduced the concept of type aliases, only requiring them to be top-level unannotated assignments. This simplicity sometimes made it difficult for type checkers to distinguish between type aliases and ordinary assignments, especially when forward references or invalid types were involved. Compare:

StrCache = 'Cache[str]'  # a type alias
LOG_PREFIX = 'LOG[DEBUG]'  # a module constant

Now the :mod:`typing` module has a special annotation :data:`TypeAlias` to declare type aliases more explicitly:

StrCache: TypeAlias = 'Cache[str]'  # a type alias
LOG_PREFIX = 'LOG[DEBUG]'  # a module constant

See PEP 613 for more details.

(Contributed by Mikhail Golubev in :issue:`41923`.)

PEP604: New Type Union Operator

A new type union operator was introduced which enables the syntax X | Y. This provides a cleaner way of expressing 'either type X or type Y' instead of using :data:`typing.Union`, especially in type hints (annotations).

In previous versions of Python, to apply a type hint for functions accepting arguments of multiple types, :data:`typing.Union` was used:

def square(number: Union[int, float]) -> Union[int, float]:
    return number ** 2

Type hints can now be written in a more succinct manner:

def square(number: int | float) -> int | float:
    return number ** 2

See PEP 604 for more details.

(Contributed by Maggie Moss and Philippe Prados in :issue:`41428`.)

Other Language Changes

New Modules

  • None yet.

Improved Modules

base64

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

codecs

Add a :func:`codecs.unregister` function to unregister a codec search function. (Contributed by Hai Shi in :issue:`41842`.)

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`.)

encodings

:func:`encodings.normalize_encoding` now ignores non-ASCII characters. (Contributed by Hai Shi in :issue:`39337`.)

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`.)

py_compile

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

shelve

The :mod:`shelve` module now uses :data:`pickle.DEFAULT_PROTOCOL` by default instead of :mod:`pickle` protocol 3 when creating shelves. (Contributed by Zackery Spytz in :issue:`34204`.)

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`.)

types

Reintroduced the :data:`types.EllipsisType`, :data:`types.NoneType` and :data:`types.NotImplementedType` classes, providing a new set of types readily interpretable by type checkers. (Contributed by Bas van Beek in :issue:`41810`.)

unittest

Add new method :meth:`~unittest.TestCase.assertNoLogs` to complement the existing :meth:`~unittest.TestCase.assertLogs`. (Contributed by Kit Yan Choi in :issue:`39385`.)

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`.)
  • The LOAD_ATTR instruction now uses new "per opcode cache" mechanism. It is about 36% faster now. (Contributed by Pablo Galindo and Yury Selivanov in :issue:`42093`, based on ideas implemented originally in PyPy and MicroPython.)
  • When building Python with --enable-optimizations now -fno-semantic-interposition is added to both the compile and link line. This speeds builds of the Python interpreter created with --enable-shared with gcc by up to 30%. See this article for more details. (Contributed by Victor Stinner and Pablo Galindo in :issue:`38980`)

Deprecated

Removed

  • Removed special methods __int__, __float__, __floordiv__, __mod__, __divmod__, __rfloordiv__, __rmod__ and __rdivmod__ of the :class:`complex` class. They always raised a :exc:`TypeError`. (Contributed by Serhiy Storchaka in :issue:`41974`.)
  • 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`.)
  • Removed the unicodedata.ucnhash_CAPI attribute which was an internal PyCapsule object. The related private _PyUnicode_Name_CAPI structure was moved to the internal C API. (Contributed by Victor Stinner in :issue:`42157`.)

Porting to Python 3.10

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

Build Changes

C API Changes

New Features

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`.)

  • The private _PyUnicode_Name_CAPI structure of the PyCapsule API unicodedata.ucnhash_CAPI has been moved to the internal C API. (Contributed by Victor Stinner in :issue:`42157`.)

Deprecated

Removed