Every new feature in the early release alpha 2 preview of Python 3.10
This article explains the new features in Python 3.10, compared to 3.9.
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.
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.)
mapping
attribute that gives a types.MappingProxyType object wrapping the original dictionary. (Contributed by Dennis Sweeney in bpo-40890.)strict
flag, used to require that all the iterables have an equal length.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.)
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
See PEP 604 for more details.
(Contributed by Maggie Moss and Philippe Prados in bpo-41428.)
Add base64.b32hexencode() and base64.b32hexdecode() to support the Base32 Encoding with Extended Hex Alphabet.
Add a codecs.unregister() function to unregister a codec search function. (Contributed by Hai Shi in bpo-41842.)
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.)
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.)
When a module does not define _loader_
, fall back to _spec_.loader
. (Contributed by Brett Cannon in bpo-42133.)
encodings.normalize_encoding()
now ignores non-ASCII characters. (Contributed by Hai Shi in bpo-39337.)
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.)
When a module does not define _loader_
, fall back to _spec_.loader
. (Contributed by Brett Cannon in bpo-42133.)
When a module does not define _loader_
, fall back to _spec_.loader
. (Contributed by Brett Cannon in bpo-42133.)
Added os.cpu_count() support for VxWorks RTOS. (Contributed by Peixing Xin in bpo-41440.)
Added --quiet
option to command-line interface of py_compile. (Contributed by Gregory Schevchenko in bpo-38731.)
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.)
When a module does not define _loader_
, fall back to _spec_.loader
. (Contributed by Brett Cannon in bpo-42133.)
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.)
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.)
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.)
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.)
Add new method assertNoLogs() to complement the existing assertLogs(). (Contributed by Kit Yan Choi in bpo-39385.)
Add a LexicalHandler class to the xml.sax.handler module. (Contributed by Jonathan Gossage and Zackery Spytz in bpo-35018.)
python3 -m module-name
command startup time is 1.3x faster in average. (Contributed by Victor Stinner in bpo-41006.)LOAD_ATTR
instruction now uses new “per opcode cache” mechanism. It is about 36% faster now. (Contributed by Pablo Galindo and Yury Selivanov in bpo-42093, based on ideas implemented originally in PyPy and MicroPython.)--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)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._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.)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.)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.)This section lists previously described changes and other bugfixes that may require changes to your code.
snprintf()
and vsnprintf()
are now required to build Python. (Contributed by Victor Stinner in bpo-36020.)int
. (Contributed by Serhiy Storchaka in bpo-40792.)StopIteration
exception. (Contributed by Vladimir Matveev in bpo-41756.)tp_doc
slot. (Contributed by Hai Shi in bpo-41832.)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.)is changed to the inline static function,
Py_TYPE(obj) = new_typemust be replaced with
Py_SET_TYPE(obj, new_type): see
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
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
Py_SIZE(obj) = new_size
must be replaced with Py_SET_SIZE(obj, new_size)
: see 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
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.)_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.)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.)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.)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.)Py_UNICODE_str*
functions manipulating Py_UNICODE*
strings. (Contributed by Inada Naoki in bpo-41123.)Py_UNICODE_strlen
: use PyUnicode_GetLength() or PyUnicode_GET_LENGTHPy_UNICODE_strcat
: use PyUnicode_CopyCharacters() or PyUnicode_FromFormat()Py_UNICODE_strcpy
, Py_UNICODE_strncpy
: use PyUnicode_CopyCharacters() or PyUnicode_Substring()Py_UNICODE_strcmp
: use PyUnicode_Compare()Py_UNICODE_strncmp
: use PyUnicode_Tailmatch()Py_UNICODE_strchr
, Py_UNICODE_strrchr
: use PyUnicode_FindChar()PyUnicode_GetMax()
. Please migrate to new (PEP 393) APIs. (Contributed by Inada Naoki in bpo-41103.)PyLong_FromUnicode()
. Please migrate to PyLong_FromUnicodeObject(). (Contributed by Inada Naoki in bpo-41103.)PyUnicode_AsUnicodeCopy()
. Please use PyUnicode_AsUCS4Copy() or PyUnicode_AsWideCharString() (Contributed by Inada Naoki in bpo-41103.)_Py_CheckRecursionLimit
variable: it has been replaced by ceval.recursion_limit
of the PyInterpreterState structure. (Contributed by Victor Stinner in bpo-41834.)Py_ALLOW_RECURSION
and Py_END_ALLOW_RECURSION
and the recursion_critical
field of the PyInterpreterState structure. (Contributed by Serhiy Storchaka in bpo-41936.)The Original Article can be found on python.org
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