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What's New In Python 3.11

Release:|release|
Date: |today|

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

New Features

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:

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,

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:

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 :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

Other CPython Implementation Changes

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

sqlite3

threading

time

  • On Unix, :func:`time.sleep` now uses the clock_nanosleep() or nanosleep() function, if available, which has a resolution of 1 nanosecond (10-9 seconds), rather than using select() which has a resolution of 1 microsecond (10-6 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 (10-7 seconds). Previously, it had a resolution of 1 millisecond (10-3 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

Deprecated

Removed

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

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`.)
  • libpython is no longer linked against libcrypt. (Contributed by Mike Gilbert in :issue:`45433`.)
  • Building Python now requires a C99 <math.h> header file providing isinf(), isnan() and isfinite() functions. (Contributed by Victor Stinner in :issue:`45440`.)

C API Changes

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 <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`.)

  • The <Python.h> header file no longer includes <stdlib.h>. C extensions using <stdlib.h> must now include it explicitly. The system <stdlib.h> header provides functions like: malloc()/free(), getenv(), strtol(), abs(), strtol(), exit() and abort(). (Contributed by Victor Stinner in :issue:`45434`.)

  • The <Python.h> header file no longer includes <stdio.h> if the Py_LIMITED_API macro is defined. Functions expecting FILE* are excluded from the limited C API (PEP 384). C extensions using <stdio.h> must now include it explicitly. The system <stdio.h> header provides functions like printf() and fopen(). (Contributed by Victor Stinner in :issue:`45434`.)

  • The non-limited API files cellobject.h, classobject.h, context.h, funcobject.h, genobject.h and longintrepr.h have been moved to the Include/cpython directory. These files must not be included directly, as they are already included in Python.h: :ref:`Include Files <api-includes>`. If they have been included directly, consider including Python.h instead. (Contributed by Victor Stinner in :issue:`35134`.)

Deprecated

Removed