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What's New In Python 3.10P

Release

    3.10.0a5

Date

    February 16, 2021

This article explains the new features in Python 3.10, compared to
3.9.

For full details, see the 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 highlightsP

New FeaturesP

Parenthesized context managersP

Using enclosing parentheses for continuation across multiple lines in
context managers is now supported. This allows formatting a long
collection of context managers in multiple lines in a similar way as
it was previously possible with import statements. For instance, all
these examples are now valid:

with (CtxManager() as example):
    ...

with (
    CtxManager1(),
    CtxManager2()
):
    ...

with (CtxManager1() as example,
      CtxManager2()):
    ...

with (CtxManager1(),
      CtxManager2() as example):
    ...

with (
    CtxManager1() as example1,
    CtxManager2() as example2
):
    ...

it is also possible to use a trailing comma at the end of the
enclosed group:

with (
    CtxManager1() as example1,
    CtxManager2() as example2,
    CtxManager3() as example3,
):
    ...

This new syntax uses the non LL(1) capacities of the new parser.
Check PEP 617 for more details.

(Contributed by Guido van Rossum, Pablo Galindo and Lysandros
Nikolaou in bpo-12782 and bpo-40334.)

PEP 563: Postponed Evaluation of Annotations Becomes DefaultP

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 __annotations__
will be strings. If needed, annotations can be resolved at runtime
using typing.get_type_hints(). See PEP 563 for a full description.
Also, the 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 bpo-38605.)

  * The int type has a new method 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
    bpo-29882.)

  * The views returned by dict.keys(), dict.values() and dict.items()
    now all have a mapping attribute that gives a
    types.MappingProxyType object wrapping the original dictionary.
    (Contributed by Dennis Sweeney in bpo-40890.)

  * PEP 618: The zip() function now has an optional strict flag, used
    to require that all the iterables have an equal length.

PEP 613: TypeAlias AnnotationP

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 typing module has a special annotation 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 bpo-41923.)

PEP 604: New Type Union OperatorP

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 typing.Union, especially in type hints
(annotations).

In previous versions of Python, to apply a type hint for functions
accepting arguments of multiple types, 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

This new syntax is also accepted as the second argument to isinstance
() and issubclass():

>>> isinstance(1, int | str)
True

See Union Type and PEP 604 for more details.

(Contributed by Maggie Moss and Philippe Prados in bpo-41428.)

PEP 612: Parameter Specification VariablesP

Two new options to improve the information provided to static type
checkers for PEP 484's Callable have been added to the typing module.

The first is the parameter specification variable. They are used to
forward the parameter types of one callable to another callable - a
pattern commonly found in higher order functions and decorators.
Examples of usage can be found in typing.ParamSpec. Previously, there
was no easy way to type annotate dependency of parameter types in
such a precise manner.

The second option is the new Concatenate operator. It's used in
conjunction with parameter specification variables to type annotate a
higher order callable which adds or removes parameters of another
callable. Examples of usage can be found in typing.Concatenate.

See typing.Callable, typing.ParamSpec, typing.Concatenate and PEP 612
for more details.

(Contributed by Ken Jin in bpo-41559.)

Better error messages in the parserP

When parsing code that contains unclosed parentheses or brackets the
interpreter now includes the location of the unclosed bracket of
parentheses instead of displaying SyntaxError: unexpected EOF while
parsing or pointing to some incorrect location. For instance,
consider the following code (notice the unclosed '{'):

expected = {9: 1, 18: 2, 19: 2, 27: 3, 28: 3, 29: 3, 36: 4, 37: 4,
            38: 4, 39: 4, 45: 5, 46: 5, 47: 5, 48: 5, 49: 5, 54: 6,
some_other_code = foo()

previous versions of the interpreter reported confusing places as the
location of the syntax error:

File "example.py", line 3
    some_other_code = foo()
                    ^
SyntaxError: invalid syntax

but in Python3.10 a more informative error is emitted:

File "example.py", line 1
    expected = {9: 1, 18: 2, 19: 2, 27: 3, 28: 3, 29: 3, 36: 4, 37: 4,
               ^
SyntaxError: '{' was never closed

In a similar way, errors involving unclosed string literals (single
and triple quoted) now point to the start of the string instead of
reporting EOF/EOL.

These improvements are inspired by previous work in the PyPy
interpreter.

(Contributed by Pablo Galindo in bpo-42864 and Batuhan Taskaya in
bpo-40176.)

Other Language ChangesP

  * Builtin and extension functions that take integer arguments no
    longer accept Decimals, Fractions and other objects that can be
    converted to integers only with a loss (e.g. that have the
    __int__() method but do not have the __index__() method).
    (Contributed by Serhiy Storchaka in bpo-37999.)

  * Assignment expressions can now be used unparenthesized within set
    literals and set comprehensions, as well as in sequence indexes
    (but not slices).

New ModulesP

  * None yet.

Improved ModulesP

argparseP

Misleading phrase "optional arguments" was replaced with "options" in
argparse help. Some tests might require adaptation if they rely on
exact output match. (Contributed by Raymond Hettinger in bpo-9694.)

base64P

Add base64.b32hexencode() and base64.b32hexdecode() to support the
Base32 Encoding with Extended Hex Alphabet.

codecsP

Add a codecs.unregister() function to unregister a codec search
function. (Contributed by Hai Shi in bpo-41842.)

collections.abcP

The __args__ of the parameterized generic for
collections.abc.Callable are now consistent with typing.Callable.
collections.abc.Callable generic now flattens type parameters,
similar to what typing.Callable currently does. This means that 
collections.abc.Callable[[int, str], str] will have __args__ of (int,
str, str); previously this was ([int, str], str). To allow this
change, types.GenericAlias can now be subclassed, and a subclass will
be returned when subscripting the collections.abc.Callable type. Note
that a TypeError may be raised for invalid forms of parameterizing
collections.abc.Callable which may have passed silently in Python
3.9. (Contributed by Ken Jin in bpo-42195.)

contextlibP

Add a contextlib.aclosing() context manager to safely close async
generators and objects representing asynchronously released
resources. (Contributed by Joongi Kim and John Belmonte in bpo-41229
.)

Add asynchronous context manager support to contextlib.nullcontext().
(Contributed by Tom Gringauz in bpo-41543.)

cursesP

The extended color functions added in ncurses 6.1 will be used
transparently by curses.color_content(), curses.init_color(),
curses.init_pair(), and curses.pair_content(). A new function,
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 bpo-36982.)

The BUTTON5_* constants are now exposed in the curses module if they
are provided by the underlying curses library. (Contributed by
Zackery Spytz in bpo-39273.)

distutilsP

The entire distutils package is deprecated, to be removed in Python
3.12. Its functionality for specifying package builds has already
been completely replaced by third-party packages setuptools and 
packaging, and most other commonly used APIs are available elsewhere
in the standard library (such as platform, shutil, subprocess or
sysconfig). There are no plans to migrate any other functionality
from distutils, and applications that are using other functions
should plan to make private copies of the code. Refer to PEP 632 for
discussion.

The bdist_wininst command deprecated in Python 3.8 has been removed.
The bdist_wheel command is now recommended to distribute binary
packages on Windows. (Contributed by Victor Stinner in bpo-42802.)

doctestP

When a module does not define __loader__, fall back to 
__spec__.loader. (Contributed by Brett Cannon in bpo-42133.)

encodingsP

encodings.normalize_encoding() now ignores non-ASCII characters.
(Contributed by Hai Shi in bpo-39337.)

globP

Added the root_dir and dir_fd parameters in glob() and iglob() which
allow to specify the root directory for searching. (Contributed by
Serhiy Storchaka in bpo-38144.)

inspectP

When a module does not define __loader__, fall back to 
__spec__.loader. (Contributed by Brett Cannon in bpo-42133.)

Added globalns and localns parameters in signature() and
inspect.Signature.from_callable() to retrieve the annotations in
given local and global namespaces. (Contributed by Batuhan Taskaya in
bpo-41960.)

linecacheP

When a module does not define __loader__, fall back to 
__spec__.loader. (Contributed by Brett Cannon in bpo-42133.)

osP

Added os.cpu_count() support for VxWorks RTOS. (Contributed by
Peixing Xin in bpo-41440.)

Added a new function os.eventfd() and related helpers to wrap the 
eventfd2 syscall on Linux. (Contributed by Christian Heimes in
bpo-41001.)

Added os.splice() that allows to move data between two file
descriptors without copying between kernel address space and user
address space, where one of the file descriptors must refer to a
pipe. (Contributed by Pablo Galindo in bpo-41625.)

Added O_EVTONLY, O_FSYNC, O_SYMLINK and O_NOFOLLOW_ANY for macOS.
(Contributed by Dong-hee Na in bpo-43106.)

pathlibP

Added slice support to PurePath.parents. (Contributed by Joshua
Cannon in bpo-35498)

Added negative indexing support to PurePath.parents. (Contributed by
Yaroslav Pankovych in bpo-21041)

platformP

Added platform.freedesktop_os_release() to retrieve operation system
identification from freedesktop.org os-release standard file.
(Contributed by Christian Heimes in bpo-28468)

py_compileP

Added --quiet option to command-line interface of py_compile.
(Contributed by Gregory Schevchenko in bpo-38731.)

pyclbrP

Added an end_lineno attribute to the Function and Class objects in
the tree returned by pyclbr.readline() and pyclbr.readline_ex(). It
matches the existing (start) lineno. (Contributed by Aviral
Srivastava in bpo-38307.)

shelveP

The shelve module now uses pickle.DEFAULT_PROTOCOL by default instead
of pickle protocol 3 when creating shelves. (Contributed by Zackery
Spytz in bpo-34204.)

siteP

When a module does not define __loader__, fall back to 
__spec__.loader. (Contributed by Brett Cannon in bpo-42133.)

socketP

The exception socket.timeout is now an alias of TimeoutError.
(Contributed by Christian Heimes in bpo-42413.)

sysP

Add sys.orig_argv attribute: the list of the original command line
arguments passed to the Python executable. (Contributed by Victor
Stinner in bpo-23427.)

Add sys.stdlib_module_names, containing the list of the standard
library module names. (Contributed by Victor Stinner in bpo-42955.)

threadingP

Added threading.gettrace() and threading.getprofile() to retrieve the
functions set by threading.settrace() and threading.setprofile()
respectively. (Contributed by Mario Corchero in bpo-42251.)

Add threading.__excepthook__ to allow retrieving the original value
of threading.excepthook() in case it is set to a broken or a
different value. (Contributed by Mario Corchero in bpo-42308.)

tracebackP

The format_exception(), format_exception_only(), and print_exception
() functions can now take an exception object as a positional-only
argument. (Contributed by Zackery Spytz and Matthias Bussonnier in
bpo-26389.)

typesP

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

typingP

The behavior of typing.Literal was changed to conform with PEP 586
and to match the behavior of static type checkers specified in the
PEP.

 1. Literal now de-duplicates parameters.

 2. Equality comparisons between Literal objects are now order
    independent.

 3. Literal comparisons now respects types. For example, Literal[0] =
    = Literal[False] previously evaluated to True. It is now False.
    To support this change, the internally used type cache now
    supports differentiating types.

 4. Literal objects will now raise a TypeError exception during
    equality comparisons if one of their parameters are not immutable
    . Note that declaring Literal with mutable parameters will not
    throw an error:

    >>> from typing import Literal
    >>> Literal[{0}]
    >>> Literal[{0}] == Literal[{False}]
    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
    TypeError: unhashable type: 'set'

(Contributed by Yurii Karabas in bpo-42345.)

unittestP

Add new method assertNoLogs() to complement the existing assertLogs()
. (Contributed by Kit Yan Choi in bpo-39385.)

urllib.parseP

Python versions earlier than Python 3.10 allowed using both ; and &
as query parameter separators in urllib.parse.parse_qs() and
urllib.parse.parse_qsl(). Due to security concerns, and to conform
with newer W3C recommendations, this has been changed to allow only a
single separator key, with & as the default. This change also affects
cgi.parse() and cgi.parse_multipart() as they use the affected
functions internally. For more details, please see their respective
documentation. (Contributed by Adam Goldschmidt, Senthil Kumaran and
Ken Jin in bpo-42967.)

xmlP

Add a LexicalHandler class to the xml.sax.handler module.
(Contributed by Jonathan Gossage and Zackery Spytz in bpo-35018.)

zipimportP

Add methods related to PEP 451: find_spec(),
zipimport.zipimporter.create_module(), and
zipimport.zipimporter.exec_module(). (Contributed by Brett Cannon in
bpo-42131.

OptimizationsP

  * Constructors str(), bytes() and bytearray() are now faster
    (around 30-40% for small objects). (Contributed by Serhiy
    Storchaka in bpo-41334.)

  * The 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 bpo-41006.)

  * The LOAD_ATTR instruction now uses new "per opcode cache"
    mechanism. It is about 36% faster now for regular attributes and
    44% faster for slots. (Contributed by Pablo Galindo and Yury
    Selivanov in bpo-42093 and Guido van Rossum in bpo-42927, 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
    bpo-38980.)

  * Function parameters and their annotations are no longer computed
    at runtime, but rather at compilation time. They are stored as a
    tuple of strings at the bytecode level. It is now around 100%
    faster to create a function with parameter annotations.
    (Contributed by Yurii Karabas and Inada Naoki in bpo-42202)

DeprecatedP

  * Starting in this release, there will be a concerted effort to
    begin cleaning up old import semantics that were kept for Python
    2.7 compatibility. Specifically, find_loader()/find_module()
    (superseded by find_spec()), load_module() (superseded by
    exec_module()), module_repr() (which the import system takes care
    of for you), the __package__ attribute (superseded by 
    __spec__.parent), the __loader__ attribute (superseded by 
    __spec__.loader), and the __cached__ attribute (superseded by 
    __spec__.cached) will slowly be removed (as well as other classes
    and methods in importlib). ImportWarning and/or
    DeprecationWarning will be raised as appropriate to help identify
    code which needs updating during this transition.

  * The entire distutils namespace is deprecated, to be removed in
    Python 3.12. Refer to the module changes section for more
    information.

  * Non-integer arguments to random.randrange() are deprecated. The
    ValueError is deprecated in favor of a TypeError. (Contributed by
    Serhiy Storchaka and Raymond Hettinger in bpo-37319.)

  * The various load_module() methods of importlib have been
    documented as deprecated since Python 3.6, but will now also
    trigger a DeprecationWarning. Use exec_module() instead.
    (Contributed by Brett Cannon in bpo-26131.)

  * zimport.zipimporter.load_module() has been deprecated in
    preference for exec_module(). (Contributed by Brett Cannon in
    bpo-26131.)

  * The use of load_module() by the import system now triggers an
    ImportWarning as exec_module() is preferred. (Contributed by
    Brett Cannon in bpo-26131.)

  * sqlite3.OptimizedUnicode has been undocumented and obsolete since
    Python 3.3, when it was made an alias to str. It is now
    deprecated, scheduled for removal in Python 3.12. (Contributed by
    Erlend E. Aasland in bpo-42264.)

  * The undocumented built-in function sqlite3.enable_shared_cache is
    now deprecated, scheduled for removal in Python 3.12. Its use is
    strongly discouraged by the SQLite3 documentation. See the
    SQLite3 docs for more details. If shared cache must be used, open
    the database in URI mode using the cache=shared query parameter.
    (Contributed by Erlend E. Aasland in bpo-24464.)

RemovedP

  * Removed special methods __int__, __float__, __floordiv__, __mod__
    , __divmod__, __rfloordiv__, __rmod__ and __rdivmod__ of the
    complex class. They always raised a TypeError. (Contributed by
    Serhiy Storchaka in bpo-41974.)

  * The ParserBase.error() method from the private and undocumented 
    _markupbase module has been removed. 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 bpo-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 bpo-42157.)

  * Removed the parser module, which was deprecated in 3.9 due to the
    switch to the new PEG parser, as well as all the C source and
    header files that were only being used by the old parser,
    including node.h, parser.h, graminit.h and grammar.h.

  * Removed the Public C API functions
    PyParser_SimpleParseStringFlags(),
    PyParser_SimpleParseStringFlagsFilename(),
    PyParser_SimpleParseFileFlags() and PyNode_Compile() that were
    deprecated in 3.9 due to the switch to the new PEG parser.

  * Removed the formatter module, which was deprecated in Python 3.4.
    It is somewhat obsolete, little used, and not tested. It was
    originally scheduled to be removed in Python 3.6, but such
    removals were delayed until after Python 2.7 EOL. Existing users
    should copy whatever classes they use into their code.
    (Contributed by Dong-hee Na and Terry J. Reedy in bpo-42299.)

  * Removed the PyModule_GetWarningsModule() function that was
    useless now due to the _warnings module was converted to a
    builtin module in 2.6. (Contributed by Hai Shi in bpo-42599.)

  * Remove deprecated aliases to Collections Abstract Base Classes
    from the collections module. (Contributed by Victor Stinner in
    bpo-37324.)

  * The loop parameter has been removed from most of asyncio's
    high-level API following deprecation in Python 3.8. The
    motivation behind this change is multifold:

     1. This simplifies the high-level API.

     2. The functions in the high-level API have been implicitly
        getting the current thread's running event loop since Python
        3.7. There isn't a need to pass the event loop to the API in
        most normal use cases.

     3. Event loop passing is error-prone especially when dealing
        with loops running in different threads.

    Note that the low-level API will still accept loop. See Changes
    in the Python API for examples of how to replace existing code.

    (Contributed by Yurii Karabas, Andrew Svetlov, Yury Selivanov and
    Kyle Stanley in bpo-42392.)

Porting to Python 3.10P

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

Changes in the Python APIP

  * The etype parameters of the format_exception(),
    format_exception_only(), and print_exception() functions in the
    traceback module have been renamed to exc. (Contributed by
    Zackery Spytz and Matthias Bussonnier in bpo-26389.)

  * atexit: At Python exit, if a callback registered with
    atexit.register() fails, its exception is now logged. Previously,
    only some exceptions were logged, and the last exception was
    always silently ignored. (Contributed by Victor Stinner in
    bpo-42639.)

  * collections.abc.Callable generic now flattens type parameters,
    similar to what typing.Callable currently does. This means that 
    collections.abc.Callable[[int, str], str] will have __args__ of 
    (int, str, str); previously this was ([int, str], str). Code
    which accesses the arguments via typing.get_args() or __args__
    need to account for this change. Furthermore, TypeError may be
    raised for invalid forms of parameterizing
    collections.abc.Callable which may have passed silently in Python
    3.9. (Contributed by Ken Jin in bpo-42195.)

  * socket.htons() and socket.ntohs() now raise OverflowError instead
    of DeprecationWarning if the given parameter will not fit in a
    16-bit unsigned integer. (Contributed by Erlend E. Aasland in
    bpo-42393.)

  * The loop parameter has been removed from most of asyncio's
    high-level API following deprecation in Python 3.8.

    A coroutine that currently look like this:

    async def foo(loop):
        await asyncio.sleep(1, loop=loop)

    Should be replaced with this:

    async def foo():
        await asyncio.sleep(1)

    If foo() was specifically designed not to run in the current
    thread's running event loop (e.g. running in another thread's
    event loop), consider using asyncio.run_coroutine_threadsafe()
    instead.

    (Contributed by Yurii Karabas, Andrew Svetlov, Yury Selivanov and
    Kyle Stanley in bpo-42392.)

CPython bytecode changesP

  * The MAKE_FUNCTION instruction accepts tuple of strings as
    annotations instead of dictionary. (Contributed by Yurii Karabas
    and Inada Naoki in bpo-42202)

Build ChangesP

  * The C99 functions snprintf() and vsnprintf() are now required to
    build Python. (Contributed by Victor Stinner in bpo-36020.)

  * sqlite3 requires SQLite 3.7.15 or higher. (Contributed by Sergey
    Fedoseev and Erlend E. Aasland bpo-40744 and bpo-40810.)

  * The atexit module must now always be built as a built-in module.
    (Contributed by Victor Stinner in bpo-42639.)

  * Added --disable-test-modules option to the configure script:
    don't build nor install test modules. (Contributed by Xavier de
    Gaye, Thomas Petazzoni and Peixing Xin in bpo-27640.)

  * Add --with-wheel-pkg-dir=PATH option to the ./configure script.
    If specified, the ensurepip module looks for setuptools and pip
    wheel packages in this directory: if both are present, these
    wheel packages are used instead of ensurepip bundled wheel
    packages.

    Some Linux distribution packaging policies recommend against
    bundling dependencies. For example, Fedora installs wheel
    packages in the /usr/share/python-wheels/ directory and don't
    install the ensurepip._bundled package.

    (Contributed by Victor Stinner in bpo-42856.)

C API ChangesP

New FeaturesP

  * The result of PyNumber_Index() now always has exact type int.
    Previously, the result could have been an instance of a subclass
    of int. (Contributed by Serhiy Storchaka in bpo-40792.)

  * Add a new orig_argv member to the PyConfig structure: the list of
    the original command line arguments passed to the Python
    executable. (Contributed by Victor Stinner in bpo-23427.)

  * The PyDateTime_DATE_GET_TZINFO() and PyDateTime_TIME_GET_TZINFO()
    macros have been added for accessing the tzinfo attributes of
    datetime.datetime and datetime.time objects. (Contributed by
    Zackery Spytz in bpo-30155.)

  * Add a PyCodec_Unregister() function to unregister a codec search
    function. (Contributed by Hai Shi in bpo-41842.)

  * The PyIter_Send() function was added to allow sending value into
    iterator without raising StopIteration exception. (Contributed by
    Vladimir Matveev in bpo-41756.)

  * Added PyUnicode_AsUTF8AndSize() to the limited C API.
    (Contributed by Alex Gaynor in bpo-41784.)

  * Added PyModule_AddObjectRef() function: similar to
    PyModule_AddObject() but don't steal a reference to the value on
    success. (Contributed by Victor Stinner in bpo-1635741.)

  * Added Py_NewRef() and Py_XNewRef() functions to increment the
    reference count of an object and return the object. (Contributed
    by Victor Stinner in bpo-42262.)

  * The PyType_FromSpecWithBases() and PyType_FromModuleAndSpec()
    functions now accept a single class as the bases argument.
    (Contributed by Serhiy Storchaka in bpo-42423.)

  * The PyType_FromModuleAndSpec() function now accepts NULL tp_doc
    slot. (Contributed by Hai Shi in bpo-41832.)

  * The PyType_GetSlot() function can accept static types.
    (Contributed by Hai Shi and Petr Viktorin in bpo-41073.)

Porting to Python 3.10P

  * The PY_SSIZE_T_CLEAN macro must now be defined to use
    PyArg_ParseTuple() and Py_BuildValue() formats which use #: es#, 
    et#, s#, u#, y#, z#, U# and Z#. See Parsing arguments and
    building values and the PEP 353. (Contributed by Victor Stinner
    in bpo-40943.)

  * Since 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 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 bpo-39573.)

  * Calling PyDict_GetItem() without GIL held had been allowed for
    historical reason. It is no longer allowed. (Contributed by
    Victor Stinner in bpo-40839.)

  * PyUnicode_FromUnicode(NULL, size) and PyUnicode_FromStringAndSize
    (NULL, size) raise DeprecationWarning now. Use PyUnicode_New() to
    allocate Unicode object without initial data. (Contributed by
    Inada Naoki in bpo-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 bpo-42157.)

  * Py_GetPath(), Py_GetPrefix(), Py_GetExecPrefix(),
    Py_GetProgramFullPath(), Py_GetPythonHome() and Py_GetProgramName
    () functions now return NULL if called before Py_Initialize()
    (before Python is initialized). Use the new Python Initialization
    Configuration API to get the Python Path Configuration..
    (Contributed by Victor Stinner in bpo-42260.)

  * PyList_SET_ITEM(), PyTuple_SET_ITEM() and PyCell_SET() macros can
    no longer be used as l-value or r-value. For example, x = 
    PyList_SET_ITEM(a, b, c) and PyList_SET_ITEM(a, b, c) = x now
    fail with a compiler error. It prevents bugs like if 
    (PyList_SET_ITEM (a, b, c) < 0) ... test. (Contributed by Zackery
    Spytz and Victor Stinner in bpo-30459.)

DeprecatedP

  * The PyUnicode_InternImmortal() function is now deprecated and
    will be removed in Python 3.12: use PyUnicode_InternInPlace()
    instead. (Contributed by Victor Stinner in bpo-41692.)

RemovedP

  * PyObject_AsCharBuffer(), PyObject_AsReadBuffer(), 
    PyObject_CheckReadBuffer(), and PyObject_AsWriteBuffer() are
    removed. Please migrate to new buffer protocol;
    PyObject_GetBuffer() and PyBuffer_Release(). (Contributed by
    Inada Naoki in bpo-41103.)

  * Removed Py_UNICODE_str* functions manipulating Py_UNICODE*
    strings. (Contributed by Inada Naoki in bpo-41123.)

          o Py_UNICODE_strlen: use PyUnicode_GetLength() or
            PyUnicode_GET_LENGTH

          o Py_UNICODE_strcat: use PyUnicode_CopyCharacters() or
            PyUnicode_FromFormat()

          o Py_UNICODE_strcpy, Py_UNICODE_strncpy: use
            PyUnicode_CopyCharacters() or PyUnicode_Substring()

          o Py_UNICODE_strcmp: use PyUnicode_Compare()

          o Py_UNICODE_strncmp: use PyUnicode_Tailmatch()

          o Py_UNICODE_strchr, Py_UNICODE_strrchr: use
            PyUnicode_FindChar()

  * Removed PyUnicode_GetMax(). Please migrate to new (PEP 393) APIs.
    (Contributed by Inada Naoki in bpo-41103.)

  * Removed PyLong_FromUnicode(). Please migrate to
    PyLong_FromUnicodeObject(). (Contributed by Inada Naoki in
    bpo-41103.)

  * Removed PyUnicode_AsUnicodeCopy(). Please use
    PyUnicode_AsUCS4Copy() or PyUnicode_AsWideCharString()
    (Contributed by Inada Naoki in bpo-41103.)

  * Removed _Py_CheckRecursionLimit variable: it has been replaced by
    ceval.recursion_limit of the PyInterpreterState structure.
    (Contributed by Victor Stinner in bpo-41834.)

  * Removed undocumented macros Py_ALLOW_RECURSION and 
    Py_END_ALLOW_RECURSION and the recursion_critical field of the
    PyInterpreterState structure. (Contributed by Serhiy Storchaka in
    bpo-41936.)

  * Removed the undocumented PyOS_InitInterrupts() function.
    Initializing Python already implicitly installs signal handlers:
    see PyConfig.install_signal_handlers. (Contributed by Victor
    Stinner in bpo-41713.)

Table of Contents

  * What's New In Python 3.10
      + Summary - Release highlights
      + New Features
          o Parenthesized context managers
          o PEP 563: Postponed Evaluation of Annotations Becomes
            Default
          o PEP 613: TypeAlias Annotation
          o PEP 604: New Type Union Operator
          o PEP 612: Parameter Specification Variables
          o Better error messages in the parser
      + Other Language Changes
      + New Modules
      + Improved Modules
          o argparse
          o base64
          o codecs
          o collections.abc
          o contextlib
          o curses
          o distutils
          o doctest
          o encodings
          o glob
          o inspect
          o linecache
          o os
          o pathlib
          o platform
          o py_compile
          o pyclbr
          o shelve
          o site
          o socket
          o sys
          o threading
          o traceback
          o types
          o typing
          o unittest
          o urllib.parse
          o xml
          o zipimport
      + Optimizations
      + Deprecated
      + Removed
      + Porting to Python 3.10
          o Changes in the Python API
      + CPython bytecode changes
      + Build Changes
      + C API Changes
          o New Features
          o Porting to Python 3.10
          o Deprecated
          o Removed

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