cpython/Doc/whatsnew/3.11.rst

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****************************
What's New In Python 3.11
****************************
: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 3.11, compared to 3.10.
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 3.11 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 3.11.
Brevity is key.
.. PEP-sized items next.
New Features
============
.. _whatsnew311-pep657:
Enhanced error locations in tracebacks
--------------------------------------
When printing tracebacks, the interpreter will now point to the exact expression
that caused the error instead of just the line. For example:
.. code-block:: python
Traceback (most recent call last):
File "distance.py", line 11, in <module>
print(manhattan_distance(p1, p2))
^^^^^^^^^^^^^^^^^^^^^^^^^^
File "distance.py", line 6, in manhattan_distance
return abs(point_1.x - point_2.x) + abs(point_1.y - point_2.y)
^^^^^^^^^
AttributeError: 'NoneType' object has no attribute 'x'
Previous versions of the interpreter would point to just the line making it
ambiguous which object was ``None``. These enhanced errors can also be helpful
when dealing with deeply nested dictionary objects and multiple function calls,
.. code-block:: python
Traceback (most recent call last):
File "query.py", line 37, in <module>
magic_arithmetic('foo')
^^^^^^^^^^^^^^^^^^^^^^^
File "query.py", line 18, in magic_arithmetic
return add_counts(x) / 25
^^^^^^^^^^^^^
File "query.py", line 24, in add_counts
return 25 + query_user(user1) + query_user(user2)
^^^^^^^^^^^^^^^^^
File "query.py", line 32, in query_user
return 1 + query_count(db, response['a']['b']['c']['user'], retry=True)
~~~~~~~~~~~~~~~~~~^^^^^
TypeError: 'NoneType' object is not subscriptable
as well as complex arithmetic expressions:
.. code-block:: python
Traceback (most recent call last):
File "calculation.py", line 54, in <module>
result = (x / y / z) * (a / b / c)
~~~~~~^~~
ZeroDivisionError: division by zero
See :pep:`657` for more details. (Contributed by Pablo Galindo, Batuhan Taskaya
and Ammar Askar in :issue:`43950`.)
.. note::
This feature requires storing column positions in code objects which may
result in a small increase of disk usage of compiled Python files or
interpreter memory usage. To avoid storing the extra information and/or
deactivate printing the extra traceback information, the
:option:`-X` ``no_debug_ranges`` command line flag or the :envvar:`PYTHONNODEBUGRANGES`
environment variable can be used.
Column information for code objects
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The information used by the enhanced traceback feature is made available as a
general API that can be used to correlate bytecode instructions with source
code. This information can be retrieved using:
- The :meth:`codeobject.co_positions` method in Python.
- The :c:func:`PyCode_Addr2Location` function in the C-API.
The :option:`-X` ``no_debug_ranges`` option and the environment variable
:envvar:`PYTHONNODEBUGRANGES` can be used to disable this feature.
See :pep:`657` for more details. (Contributed by Pablo Galindo, Batuhan Taskaya
and Ammar Askar in :issue:`43950`.)
Other Language Changes
======================
* Asynchronous comprehensions are now allowed inside comprehensions in
asynchronous functions. Outer comprehensions implicitly become
asynchronous. (Contributed by Serhiy Storchaka in :issue:`33346`.)
* A :exc:`TypeError` is now raised instead of an :exc:`AttributeError` in
:meth:`contextlib.ExitStack.enter_context` and
:meth:`contextlib.AsyncExitStack.enter_async_context` for objects which do not
support the :term:`context manager` or :term:`asynchronous context manager`
protocols correspondingly.
(Contributed by Serhiy Storchaka in :issue:`44471`.)
* A :exc:`TypeError` is now raised instead of an :exc:`AttributeError` in
:keyword:`with` and :keyword:`async with` statements for objects which do not
support the :term:`context manager` or :term:`asynchronous context manager`
protocols correspondingly.
(Contributed by Serhiy Storchaka in :issue:`12022`.)
Other CPython Implementation Changes
====================================
* Special methods :meth:`complex.__complex__` and :meth:`bytes.__bytes__` are implemented to
support :class:`typing.SupportsComplex` and :class:`typing.SupportsBytes` protocols.
(Contributed by Mark Dickinson and Dong-hee Na in :issue:`24234`.)
New Modules
===========
* None yet.
Improved Modules
================
fractions
---------
Support :PEP:`515`-style initialization of :class:`~fractions.Fraction` from
string. (Contributed by Sergey B Kirpichev in :issue:`44258`.)
math
----
* Add :func:`math.cbrt`: return the cube root of x.
(Contributed by Ajith Ramachandran in :issue:`44357`.)
* The behaviour of two :func:`math.pow` corner cases was changed, for
consistency with the IEEE 754 specification. The operations
``math.pow(0.0, -math.inf)`` and ``math.pow(-0.0, -math.inf)`` now return
``inf``. Previously they raised :exc:`ValueError`. (Contributed by Mark
Dickinson in :issue:`44339`.)
operator
--------
* A new function ``operator.call`` has been added, such that
``operator.call(obj, *args, **kwargs) == obj(*args, **kwargs)``.
(Contributed by Antony Lee in :issue:`44019`.)
os
--
* On Windows, :func:`os.urandom` now uses ``BCryptGenRandom()``,
instead of ``CryptGenRandom()`` which is deprecated.
(Contributed by Dong-hee Na in :issue:`44611`.)
sqlite3
-------
* You can now disable the authorizer by passing :const:`None` to
:meth:`~sqlite3.Connection.set_authorizer`.
(Contributed by Erlend E. Aasland in :issue:`44491`.)
* Collation name :meth:`~sqlite3.Connection.create_collation` can now
contain any Unicode character. Collation names with invalid characters
now raise :exc:`UnicodeEncodeError` instead of :exc:`sqlite3.ProgrammingError`.
(Contributed by Erlend E. Aasland in :issue:`44688`.)
* :mod:`sqlite3` exceptions now include the SQLite error code as
:attr:`~sqlite3.Error.sqlite_errorcode` and the SQLite error name as
:attr:`~sqlite3.Error.sqlite_errorname`.
(Contributed by Aviv Palivoda, Daniel Shahaf, and Erlend E. Aasland in
:issue:`16379`.)
threading
---------
* On Unix, if the ``sem_clockwait()`` function is available in the C library
(glibc 2.30 and newer), the :meth:`threading.Lock.acquire` method now uses
the monotonic clock (:data:`time.CLOCK_MONOTONIC`) for the timeout, rather
than using the system clock (:data:`time.CLOCK_REALTIME`), to not be affected
by system clock changes.
(Contributed by Livius and Victor Stinner in :issue:`41710`.)
time
----
* On Unix, :func:`time.sleep` now uses the ``clock_nanosleep()`` or
``nanosleep()`` function, if available, which has a resolution of 1 nanosecond
(10\ :sup:`-9` seconds), rather than using ``select()`` which has a resolution
of 1 microsecond (10\ :sup:`-6` seconds).
(Contributed by Livius and Victor Stinner in :issue:`21302`.)
* On Windows, :func:`time.sleep` now uses a waitable timer which has a
resolution of 100 nanoseconds (10\ :sup:`-7` seconds). Previously, it had
a resolution of 1 millisecond (10\ :sup:`-3` seconds).
(Contributed by Livius and Victor Stinner in :issue:`21302`.)
unicodedata
-----------
* The Unicode database has been updated to version 14.0.0. (:issue:`45190`).
Optimizations
=============
* Compiler now optimizes simple C-style formatting with literal format
containing only format codes ``%s``, ``%r`` and ``%a`` and makes it as
fast as corresponding f-string expression.
(Contributed by Serhiy Storchaka in :issue:`28307`.)
* "Zero-cost" exceptions are implemented. The cost of ``try`` statements is
almost eliminated when no exception is raised.
(Contributed by Mark Shannon in :issue:`40222`.)
* Method calls with keywords are now faster due to bytecode
changes which avoid creating bound method instances. Previously, this
optimization was applied only to method calls with purely positional
arguments.
(Contributed by Ken Jin and Mark Shannon in :issue:`26110`, based on ideas
implemented in PyPy.)
* Pure ASCII strings are now normalized in constant time by :func:`unicodedata.normalize`.
(Contributed by Dong-hee Na in :issue:`44987`.)
CPython bytecode changes
========================
* Added a new :opcode:`CALL_METHOD_KW` opcode. Calls a method in a similar
fashion as :opcode:`CALL_METHOD`, but also supports keyword arguments. Works
in tandem with :opcode:`LOAD_METHOD`.
Deprecated
==========
* The :mod:`lib2to3` package is now deprecated and may not be able to parse
Python 3.10 or newer. See the :pep:`617` (New PEG parser for CPython).
(Contributed by Victor Stinner in :issue:`40360`.)
* :class:`webbrowser.MacOSX` is deprecated and will be removed in Python 3.13.
It is untested and undocumented and also not used by webbrowser itself.
(Contributed by Dong-hee Na in :issue:`42255`.)
* The behavior of returning a value from a :class:`~unittest.TestCase` and
:class:`~unittest.IsolatedAsyncioTestCase` test methods (other than the
default ``None`` value), is now deprecated.
* Deprecated the following :mod:`unittest` functions, scheduled for removal in
Python 3.13:
* :func:`unittest.findTestCases`
* :func:`unittest.makeSuite`
* :func:`unittest.getTestCaseNames`
Use :class:`~unittest.TestLoader` method instead:
* :meth:`unittest.TestLoader.loadTestsFromModule`
* :meth:`unittest.TestLoader.loadTestsFromTestCase`
* :meth:`unittest.TestLoader.getTestCaseNames`
(Contributed by Erlend E. Aasland in :issue:`5846`.)
Removed
=======
* :class:`smtpd.MailmanProxy` is now removed as it is unusable without
an external module, ``mailman``. (Contributed by Dong-hee Na in :issue:`35800`.)
* The ``binhex`` module, deprecated in Python 3.9, is now removed.
The following :mod:`binascii` functions, deprecated in Python 3.9, are now
also removed:
* ``a2b_hqx()``, ``b2a_hqx()``;
* ``rlecode_hqx()``, ``rledecode_hqx()``.
The :func:`binascii.crc_hqx` function remains available.
(Contributed by Victor Stinner in :issue:`45085`.)
* The distutils ``bdist_msi`` command, deprecated in Python 3.9, is now removed.
Use ``bdist_wheel`` (wheel packages) instead.
(Contributed by Hugo van Kemenade in :issue:`45124`.)
* Due to significant security concerns, the *reuse_address* parameter of
:meth:`asyncio.loop.create_datagram_endpoint`, disabled in Python 3.9, is
now entirely removed. This is because of the behavior of the socket option
``SO_REUSEADDR`` in UDP.
(Contributed by Hugo van Kemenade in :issue:`45129`.)
* Remove :meth:`__getitem__` methods of
:class:`xml.dom.pulldom.DOMEventStream`, :class:`wsgiref.util.FileWrapper`
and :class:`fileinput.FileInput`, deprecated since Python 3.9.
(Contributed by Hugo van Kemenade in :issue:`45132`.)
* Removed many old deprecated :mod:`unittest` features:
- :class:`~unittest.TestCase` method aliases ``failUnlessEqual``,
``failIfEqual``, ``failUnless``, ``failIf``, ``failUnlessRaises``,
``failUnlessAlmostEqual``, ``failIfAlmostEqual`` (deprecated in Python 3.1),
``assertEquals``, ``assertNotEquals``, ``assert_``, ``assertAlmostEquals``,
``assertNotAlmostEquals``, ``assertRegexpMatches``, ``assertRaisesRegexp``
(deprecated in Python 3.2), and ``assertNotRegexpMatches`` (deprecated in
Python 3.5).
- Undocumented and broken :class:`~unittest.TestCase` method
``assertDictContainsSubset`` (deprecated in Python 3.2).
- Undocumented :meth:`<unittest.TestLoader.loadTestsFromModule>
TestLoader.loadTestsFromModule` parameter *use_load_tests* (deprecated
and ignored since Python 3.2).
- An alias of the :class:`~unittest.TextTestResult` class:
``_TextTestResult`` (deprecated in Python 3.2).
(Contributed by Serhiy Storchaka in :issue:`45162`.)
* The following deprecated functions and methods are removed in the :mod:`gettext`
module: :func:`~gettext.lgettext`, :func:`~gettext.ldgettext`,
:func:`~gettext.lngettext` and :func:`~gettext.ldngettext`.
Function :func:`~gettext.bind_textdomain_codeset`, methods
:meth:`~gettext.NullTranslations.output_charset` and
:meth:`~gettext.NullTranslations.set_output_charset`, and the *codeset*
parameter of functions :func:`~gettext.translation` and
:func:`~gettext.install` are also removed, since they are only used for
the ``l*gettext()`` functions.
(Contributed by Dong-hee Na and Serhiy Storchaka in :issue:`44235`.)
* Remove from the :mod:`configparser` module:
the :class:`SafeConfigParser` class,
the :attr:`filename` property of the :class:`ParsingError` class,
the :meth:`readfp` method of the :class:`ConfigParser` class,
deprecated since Python 3.2.
(Contributed by Hugo van Kemenade in :issue:`45173`.)
* The :func:`@asyncio.coroutine <asyncio.coroutine>` :term:`decorator` enabling
legacy generator-based coroutines to be compatible with async/await code.
The function has been deprecated since Python 3.8 and the removal was
initially scheduled for Python 3.10. Use :keyword:`async def` instead.
(Contributed by Illia Volochii in :issue:`43216`.)
* :class:`asyncio.coroutines.CoroWrapper` used for wrapping legacy
generator-based coroutine objects in the debug mode.
(Contributed by Illia Volochii in :issue:`43216`.)
* Remove the deprecated ``split()`` method of :class:`_tkinter.TkappType`.
(Contributed by Erlend E. Aasland in :issue:`38371`.)
Porting to Python 3.11
======================
This section lists previously described changes and other bugfixes
that may require changes to your code.
Changes in the Python API
-------------------------
* Prohibited passing non-:class:`concurrent.futures.ThreadPoolExecutor`
executors to :meth:`loop.set_default_executor` following a deprecation in
Python 3.8.
(Contributed by Illia Volochii in :issue:`43234`.)
* :func:`open`, :func:`io.open`, :func:`codecs.open` and
:class:`fileinput.FileInput` no longer accept ``'U'`` ("universal newline")
in the file mode. This flag was deprecated since Python 3.3. In Python 3, the
"universal newline" is used by default when a file is open in text mode. The
:ref:`newline parameter <open-newline-parameter>` of :func:`open` controls
how universal newlines works.
(Contributed by Victor Stinner in :issue:`37330`.)
* The :mod:`pdb` module now reads the :file:`.pdbrc` configuration file with
the ``'utf-8'`` encoding.
(Contributed by Srinivas Reddy Thatiparthy (శ్రీనివాస్ రెడ్డి తాటిపర్తి) in :issue:`41137`.)
Build Changes
=============
* CPython can now be built with the ThinLTO option via ``--with-lto=thin``.
(Contributed by Dong-hee Na and Brett Holman in :issue:`44340`.)
C API Changes
=============
New Features
------------
* Add a new :c:func:`PyType_GetName` function to get type's short name.
(Contributed by Hai Shi in :issue:`42035`.)
* Add a new :c:func:`PyType_GetQualName` function to get type's qualified name.
(Contributed by Hai Shi in :issue:`42035`.)
Porting to Python 3.11
----------------------
* The old trashcan macros (``Py_TRASHCAN_SAFE_BEGIN``/``Py_TRASHCAN_SAFE_END``)
are now deprecated. They should be replaced by the new macros
``Py_TRASHCAN_BEGIN`` and ``Py_TRASHCAN_END``.
A tp_dealloc function that has the old macros, such as::
static void
mytype_dealloc(mytype *p)
{
PyObject_GC_UnTrack(p);
Py_TRASHCAN_SAFE_BEGIN(p);
...
Py_TRASHCAN_SAFE_END
}
should migrate to the new macros as follows::
static void
mytype_dealloc(mytype *p)
{
PyObject_GC_UnTrack(p);
Py_TRASHCAN_BEGIN(p, mytype_dealloc)
...
Py_TRASHCAN_END
}
Note that ``Py_TRASHCAN_BEGIN`` has a second argument which
should be the deallocation function it is in.
To support older Python versions in the same codebase, you
can define the following macros and use them throughout
the code (credit: these were copied from the ``mypy`` codebase)::
#if PY_MAJOR_VERSION >= 3 && PY_MINOR_VERSION >= 8
# define CPy_TRASHCAN_BEGIN(op, dealloc) Py_TRASHCAN_BEGIN(op, dealloc)
# define CPy_TRASHCAN_END(op) Py_TRASHCAN_END
#else
# define CPy_TRASHCAN_BEGIN(op, dealloc) Py_TRASHCAN_SAFE_BEGIN(op)
# define CPy_TRASHCAN_END(op) Py_TRASHCAN_SAFE_END(op)
#endif
* The :c:func:`PyType_Ready` function now raises an error if a type is defined
with the :const:`Py_TPFLAGS_HAVE_GC` flag set but has no traverse function
(:c:member:`PyTypeObject.tp_traverse`).
(Contributed by Victor Stinner in :issue:`44263`.)
* Heap types with the :const:`Py_TPFLAGS_IMMUTABLETYPE` flag can now inherit
the :pep:`590` vectorcall protocol. Previously, this was only possible for
:ref:`static types <static-types>`.
(Contributed by Erlend E. Aasland in :issue:`43908`)
* Since :c:func:`Py_TYPE()` is changed to a inline static function,
``Py_TYPE(obj) = new_type`` must be replaced with
``Py_SET_TYPE(obj, new_type)``: see the :c:func:`Py_SET_TYPE()` function
(available since Python 3.9). For backward compatibility, this macro can be
used::
#if PY_VERSION_HEX < 0x030900A4 && !defined(Py_SET_TYPE)
static inline void _Py_SET_TYPE(PyObject *ob, PyTypeObject *type)
{ ob->ob_type = type; }
#define Py_SET_TYPE(ob, type) _Py_SET_TYPE((PyObject*)(ob), type)
#endif
(Contributed by Victor Stinner in :issue:`39573`.)
* Since :c:func:`Py_SIZE()` is changed to a inline static function,
``Py_SIZE(obj) = new_size`` must be replaced with
``Py_SET_SIZE(obj, new_size)``: see the :c:func:`Py_SET_SIZE()` function
(available since Python 3.9). For backward compatibility, this macro can be
used::
#if PY_VERSION_HEX < 0x030900A4 && !defined(Py_SET_SIZE)
static inline void _Py_SET_SIZE(PyVarObject *ob, Py_ssize_t size)
{ ob->ob_size = size; }
#define Py_SET_SIZE(ob, size) _Py_SET_SIZE((PyVarObject*)(ob), size)
#endif
(Contributed by Victor Stinner in :issue:`39573`.)
Deprecated
----------
Removed
-------
* :c:func:`PyFrame_BlockSetup` and :c:func:`PyFrame_BlockPop` have been
removed.
(Contributed by Mark Shannon in :issue:`40222`.)
* Deprecate the following functions to configure the Python initialization:
* :c:func:`PySys_AddWarnOptionUnicode`
* :c:func:`PySys_AddWarnOption`
* :c:func:`PySys_AddXOption`
* :c:func:`PySys_HasWarnOptions`
* :c:func:`Py_SetPath`
* :c:func:`Py_SetProgramName`
* :c:func:`Py_SetPythonHome`
* :c:func:`Py_SetStandardStreamEncoding`
* :c:func:`_Py_SetProgramFullPath`
Use the new :c:type:`PyConfig` API of the :ref:`Python Initialization Configuration
<init-config>` instead (:pep:`587`).
(Contributed by Victor Stinner in :issue:`44113`.)