**************************** 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 `. .. 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 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 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 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`.) os -- * On Windows, :func:`os.urandom` 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`.) Removed ======= * :class:`smtpd.MailmanProxy` is now removed as it is unusable without an external module, ``mailman``. (Contributed by Dong-hee Na in :issue:`35800`.) 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.) * :file:`.pdbrc` is now read with ``'utf-8'`` encoding. 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`. Build Changes ============= Deprecated ========== Removed ======= * The :func:`@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`.) 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`.) C API Changes ============= * 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`.) New Features ------------ 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 `. (Contributed by Erlend E. Aasland in :issue:`43908`) 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 ` instead (:pep:`587`). (Contributed by Victor Stinner in :issue:`44113`.) * 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`.) * 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.