What’s New In Python 3.10¶
- Release
3.10.0a0
- Date
October 05, 2020
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 highlights¶
New Features¶
The
int
type has a new methodint.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()
anddict.items()
now all have amapping
attribute that gives atypes.MappingProxyType
object wrapping the original dictionary. (Contributed by Dennis Sweeney in bpo-40890.)PEP 618: The
zip()
function now has an optionalstrict
flag, used to require that all the iterables have an equal length.
PEP604: New Type Operator¶
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
Now, type hints can 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.)
Other Language Changes¶
Builtin and extension functions that take integer arguments no longer accept
Decimal
s,Fraction
s 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.)
New Modules¶
None yet.
Improved Modules¶
base64¶
Add base64.b32hexencode()
and base64.b32hexdecode()
to support the
Base32 Encoding with Extended Hex Alphabet.
codecs¶
Add a codecs.unregister()
function to unregister a codec search function.
(Contributed by Hai Shi in bpo-41842.)
curses¶
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.)
glob¶
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.)
os¶
Added os.cpu_count()
support for VxWorks RTOS.
(Contributed by Peixing Xin in bpo-41440.)
py_compile¶
Added --quiet
option to command-line interface of py_compile
.
(Contributed by Gregory Schevchenko in bpo-38731.)
sys¶
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.)
types¶
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.)
unittest¶
Add new method assertNoLogs()
to complement the
existing assertLogs()
. (Contributed by Kit Yan Choi
in bpo-39385.)
xml¶
Add a LexicalHandler
class to the
xml.sax.handler
module.
(Contributed by Jonathan Gossage and Zackery Spytz in bpo-35018.)
Optimizations¶
Constructors
str()
,bytes()
andbytearray()
are now faster (around 30–40% for small objects). (Contributed by Serhiy Storchaka in bpo-41334.)The
runpy
module now imports fewer modules. Thepython3 -m module-name
command startup time is 1.3x faster in average. (Contributed by Victor Stinner in bpo-41006.)
Deprecated¶
Removed¶
The
ParserBase.error()
method from the private and undocumented_markupbase
module has been removed.html.parser.HTMLParser
is the only subclass ofParserBase
and itserror()
implementation has already been removed in Python 3.5. (Contributed by Berker Peksag in bpo-31844.)
Porting to Python 3.10¶
This section lists previously described changes and other bugfixes that may require changes to your code.
Build Changes¶
C API Changes¶
New Features¶
The result of
PyNumber_Index()
now always has exact typeint
. Previously, the result could have been an instance of a subclass ofint
. (Contributed by Serhiy Storchaka in bpo-40792.)Add a new
orig_argv
member to thePyConfig
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()
andPyDateTime_TIME_GET_TZINFO()
macros have been added for accessing thetzinfo
attributes ofdatetime.datetime
anddatetime.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.)
Porting to Python 3.10¶
The
PY_SSIZE_T_CLEAN
macro must now be defined to usePyArg_ParseTuple()
andPy_BuildValue()
formats which use#
:es#
,et#
,s#
,u#
,y#
,z#
,U#
andZ#
. See Parsing arguments and building values and the PEP 353. (Contributed by Victor Stinner in bpo-40943.)Since
Py_TYPE()
is changed to the inline static function,Py_TYPE(obj) = new_type
must be replaced withPy_SET_TYPE(obj, new_type)
: seePy_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
(Contributed by Dong-hee Na in bpo-39573.)
Since
Py_REFCNT()
is changed to the inline static function,Py_REFCNT(obj) = new_refcnt
must be replaced withPy_SET_REFCNT(obj, new_refcnt)
: seePy_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.)
Since
Py_SIZE()
is changed to the inline static function,Py_SIZE(obj) = new_size
must be replaced withPy_SET_SIZE(obj, new_size)
: seePy_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
(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)
andPyUnicode_FromStringAndSize(NULL, size)
raiseDeprecationWarning
now. UsePyUnicode_New()
to allocate Unicode object without initial data. (Contributed by Inada Naoki in bpo-36346.)
Deprecated¶
The
PyUnicode_InternImmortal()
function is now deprecated and will be removed in Python 3.12: usePyUnicode_InternInPlace()
instead. (Contributed by Victor Stinner in bpo-41692.)
Removed¶
PyObject_AsCharBuffer()
,PyObject_AsReadBuffer()
,PyObject_CheckReadBuffer()
, andPyObject_AsWriteBuffer()
are removed. Please migrate to new buffer protocol;PyObject_GetBuffer()
andPyBuffer_Release()
. (Contributed by Inada Naoki in bpo-41103.)Removed
Py_UNICODE_str*
functions manipulatingPy_UNICODE*
strings. (Contributed by Inada Naoki in bpo-41123.)Py_UNICODE_strlen
: usePyUnicode_GetLength()
orPyUnicode_GET_LENGTH
Py_UNICODE_strcat
: usePyUnicode_CopyCharacters()
orPyUnicode_FromFormat()
Py_UNICODE_strcpy
,Py_UNICODE_strncpy
: usePyUnicode_CopyCharacters()
orPyUnicode_Substring()
Py_UNICODE_strcmp
: usePyUnicode_Compare()
Py_UNICODE_strncmp
: usePyUnicode_Tailmatch()
Py_UNICODE_strchr
,Py_UNICODE_strrchr
: usePyUnicode_FindChar()
Removed
PyUnicode_GetMax()
. Please migrate to new (PEP 393) APIs. (Contributed by Inada Naoki in bpo-41103.)Removed
PyLong_FromUnicode()
. Please migrate toPyLong_FromUnicodeObject()
. (Contributed by Inada Naoki in bpo-41103.)Removed
PyUnicode_AsUnicodeCopy()
. Please usePyUnicode_AsUCS4Copy()
orPyUnicode_AsWideCharString()
(Contributed by Inada Naoki in bpo-41103.)Removed
_Py_CheckRecursionLimit
variable: it has been replaced byceval.recursion_limit
of thePyInterpreterState
structure. (Contributed by Victor Stinner in bpo-41834.)Removed undocumented macros
Py_ALLOW_RECURSION
andPy_END_ALLOW_RECURSION
and therecursion_critical
field of thePyInterpreterState
structure. (Contributed by Serhiy Storchaka in bpo-41936.)