What’s New In Python 3.12¶
- Release
3.12.0b1
- Date
May 31, 2023
This article explains the new features in Python 3.12, compared to 3.11.
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 3.12 moves towards release, so it’s worth checking back even after reading earlier versions.
Summary – Release highlights¶
New grammar features:
PEP 701: Syntactic formalization of f-strings
New typing features:
PEP 688: Making the buffer protocol accessible in Python
PEP 698: Override Decorator for Static Typing
Important deprecations, removals or restrictions:
Improved Error Messages¶
Modules from the standard library are now potentially suggested as part of the error messages displayed by the interpreter when a
NameError
is raised to the top level. Contributed by Pablo Galindo in gh-98254.>>> sys.version_info Traceback (most recent call last): File "<stdin>", line 1, in <module> NameError: name 'sys' is not defined. Did you forget to import 'sys'?
Improve the error suggestion for
NameError
exceptions for instances. Now if aNameError
is raised in a method and the instance has an attribute that’s exactly equal to the name in the exception, the suggestion will includeself.<NAME>
instead of the closest match in the method scope. Contributed by Pablo Galindo in gh-99139.>>> class A: ... def __init__(self): ... self.blech = 1 ... ... def foo(self): ... somethin = blech
>>> A().foo() File "<stdin>", line 1 somethin = blech ^^^^^ NameError: name 'blech' is not defined. Did you mean: 'self.blech'?
Improve the
SyntaxError
error message when the user typesimport x from y
instead offrom y import x
. Contributed by Pablo Galindo in gh-98931.>>> import a.y.z from b.y.z File "<stdin>", line 1 import a.y.z from b.y.z ^^^^^^^^^^^^^^^^^^^^^^^ SyntaxError: Did you mean to use 'from ... import ...' instead?
ImportError
exceptions raised from failedfrom <module> import <name>
statements now include suggestions for the value of<name>
based on the available names in<module>
. Contributed by Pablo Galindo in gh-91058.>>> from collections import chainmap Traceback (most recent call last): File "<stdin>", line 1, in <module> ImportError: cannot import name 'chainmap' from 'collections'. Did you mean: 'ChainMap'?
New Features¶
PEP 701: Syntactic formalization of f-strings¶
PEP 701 lifts some restrictions on the usage of f-strings. Expression components inside f-strings can now be any valid Python expression including backslashes, unicode escaped sequences, multi-line expressions, comments and strings reusing the same quote as the containing f-string. Let’s cover these in detail:
Quote reuse: in Python 3.11, reusing the same quotes as the containing f-string raises a
SyntaxError
, forcing the user to either use other available quotes (like using double quotes or triple quotes if the f-string uses single quotes). In Python 3.12, you can now do things like this:>>> songs = ['Take me back to Eden', 'Alkaline', 'Ascensionism'] >>> f"This is the playlist: {", ".join(songs)}" 'This is the playlist: Take me back to Eden, Alkaline, Ascensionism'
Note that before this change there was no explicit limit in how f-strings can be nested, but the fact that string quotes cannot be reused inside the expression component of f-strings made it impossible to nest f-strings arbitrarily. In fact, this is the most nested f-string that could be written:
>>> f"""{f'''{f'{f"{1+1}"}'}'''}""" '2'
As now f-strings can contain any valid Python expression inside expression components, it is now possible to nest f-strings arbitrarily:
>>> f"{f"{f"{f"{f"{f"{1+1}"}"}"}"}"}" '2'
Multi-line expressions and comments: In Python 3.11, f-strings expressions must be defined in a single line even if outside f-strings expressions could span multiple lines (like literal lists being defined over multiple lines), making them harder to read. In Python 3.12 you can now define expressions spaning multiple lines and include comments on them:
>>> f"This is the playlist: {", ".join([ ... 'Take me back to Eden', # My, my, those eyes like fire ... 'Alkaline', # Not acid nor alkaline ... 'Ascensionism' # Take to the broken skies at last ... ])}" 'This is the playlist: Take me back to Eden, Alkaline, Ascensionism'
Backslashes and unicode characters: before Python 3.12 f-string expressions couldn’t contain any
\
character. This also affected unicode escaped sequences (such as\N{snowman}
) as these contain the\N
part that previously could not be part of expression components of f-strings. Now, you can define expressions like this:>>> print(f"This is the playlist: {"\n".join(songs)}") This is the playlist: Take me back to Eden Alkaline Ascensionism >>> print(f"This is the playlist: {"\N{BLACK HEART SUIT}".join(songs)}") This is the playlist: Take me back to Eden♥Alkaline♥Ascensionism
See PEP 701 for more details.
(Contributed by Pablo Galindo, Batuhan Taskaya, Lysandros Nikolaou, Cristián Maureira-Fredes and Marta Gómez in gh-102856. PEP written by Pablo Galindo, Batuhan Taskaya, Lysandros Nikolaou and Marta Gómez).
PEP 709: Comprehension inlining¶
Dictionary, list, and set comprehensions are now inlined, rather than creating a new single-use function object for each execution of the comprehension. This speeds up execution of a comprehension by up to 2x.
Comprehension iteration variables remain isolated; they don’t overwrite a variable of the same name in the outer scope, nor are they visible after the comprehension. This isolation is now maintained via stack/locals manipulation, not via separate function scope.
Inlining does result in a few visible behavior changes:
There is no longer a separate frame for the comprehension in tracebacks, and tracing/profiling no longer shows the comprehension as a function call.
Calling
locals()
inside a comprehension now includes variables from outside the comprehension, and no longer includes the synthetic.0
variable for the comprehension “argument”.
Contributed by Carl Meyer and Vladimir Matveev in PEP 709.
PEP 688: Making the buffer protocol accessible in Python¶
PEP 688 introduces a way to use the buffer protocol
from Python code. Classes that implement the __buffer__()
method
are now usable as buffer types.
The new collections.abc.Buffer
ABC provides a standard
way to represent buffer objects, for example in type annotations.
The new inspect.BufferFlags
enum represents the flags that
can be used to customize buffer creation.
(Contributed by Jelle Zijlstra in gh-102500.)
Other Language Changes¶
Add Python support for the Linux perf profiler through the new environment variable
PYTHONPERFSUPPORT
, the new command-line option-X perf
, as well as the newsys.activate_stack_trampoline()
,sys.deactivate_stack_trampoline()
, andsys.is_stack_trampoline_active()
APIs. (Design by Pablo Galindo. Contributed by Pablo Galindo and Christian Heimes with contributions from Gregory P. Smith [Google] and Mark Shannon in gh-96123.)The extraction methods in
tarfile
, andshutil.unpack_archive()
, have a new a filter argument that allows limiting tar features than may be surprising or dangerous, such as creating files outside the destination directory. See Extraction filters for details. In Python 3.14, the default will switch to'data'
. (Contributed by Petr Viktorin in PEP 706.)types.MappingProxyType
instances are now hashable if the underlying mapping is hashable. (Contributed by Serhiy Storchaka in gh-87995.)memoryview
now supports the half-float type (the “e” format code). (Contributed by Dong-hee Na and Antoine Pitrou in gh-90751.)The parser now raises
SyntaxError
when parsing source code containing null bytes. (Contributed by Pablo Galindo in gh-96670.)ast.parse()
now raisesSyntaxError
instead ofValueError
when parsing source code containing null bytes. (Contributed by Pablo Galindo in gh-96670.)The Garbage Collector now runs only on the eval breaker mechanism of the Python bytecode evaluation loop instead of object allocations. The GC can also run when
PyErr_CheckSignals()
is called so C extensions that need to run for a long time without executing any Python code also have a chance to execute the GC periodically. (Contributed by Pablo Galindo in gh-97922.)A backslash-character pair that is not a valid escape sequence now generates a
SyntaxWarning
, instead ofDeprecationWarning
. For example,re.compile("\d+\.\d+")
now emits aSyntaxWarning
("\d"
is an invalid escape sequence), use raw strings for regular expression:re.compile(r"\d+\.\d+")
. In a future Python version,SyntaxError
will eventually be raised, instead ofSyntaxWarning
. (Contributed by Victor Stinner in gh-98401.)Octal escapes with value larger than
0o377
(ex:"\477"
), deprecated in Python 3.11, now produce aSyntaxWarning
, instead ofDeprecationWarning
. In a future Python version they will be eventually aSyntaxError
. (Contributed by Victor Stinner in gh-98401.)All builtin and extension callables expecting boolean parameters now accept arguments of any type instead of just
bool
andint
. (Contributed by Serhiy Storchaka in gh-60203.)Variables used in the target part of comprehensions that are not stored to can now be used in assignment expressions (
:=
). For example, in[(b := 1) for a, b.prop in some_iter]
, the assignment tob
is now allowed. Note that assigning to variables stored to in the target part of comprehensions (likea
) is still disallowed, as per PEP 572. (Contributed by Nikita Sobolev in gh-100581.)slice
objects are now hashable, allowing them to be used as dict keys and set items. (Contributed by Will Bradshaw, Furkan Onder, and Raymond Hettinger in gh-101264.)sum()
now uses Neumaier summation to improve accuracy when summing floats or mixed ints and floats. (Contributed by Raymond Hettinger in gh-100425.)Exceptions raised in a typeobject’s
__set_name__
method are no longer wrapped by aRuntimeError
. Context information is added to the exception as a PEP 678 note. (Contributed by Irit Katriel in gh-77757.)When a
try-except*
construct handles the entireExceptionGroup
and raises one other exception, that exception is no longer wrapped in anExceptionGroup
. Also changed in version 3.11.4. (Contributed by Irit Katriel in gh-103590.)
New Modules¶
None yet.
Improved Modules¶
array¶
The
array.array
class now supports subscripting, making it a generic type. (Contributed by Jelle Zijlstra in gh-98658.)
asyncio¶
The performance of writing to sockets in
asyncio
has been significantly improved.asyncio
now avoids unnecessary copying when writing to sockets and usessendmsg()
if the platform supports it. (Contributed by Kumar Aditya in gh-91166.)Added
asyncio.eager_task_factory()
andasyncio.create_eager_task_factory()
functions to allow opting an event loop in to eager task execution, making some use-cases 2x to 5x faster. (Contributed by Jacob Bower & Itamar O in gh-102853, gh-104140, and gh-104138)On Linux,
asyncio
usesPidfdChildWatcher
by default ifos.pidfd_open()
is available and functional instead ofThreadedChildWatcher
. (Contributed by Kumar Aditya in gh-98024.)The child watcher classes
MultiLoopChildWatcher
,FastChildWatcher
,AbstractChildWatcher
andSafeChildWatcher
are deprecated and will be removed in Python 3.14. It is recommended to not manually configure a child watcher as the event loop now uses the best available child watcher for each platform (PidfdChildWatcher
if supported andThreadedChildWatcher
otherwise). (Contributed by Kumar Aditya in gh-94597.)asyncio.set_child_watcher()
,asyncio.get_child_watcher()
,asyncio.AbstractEventLoopPolicy.set_child_watcher()
andasyncio.AbstractEventLoopPolicy.get_child_watcher()
are deprecated and will be removed in Python 3.14. (Contributed by Kumar Aditya in gh-94597.)Add loop_factory parameter to
asyncio.run()
to allow specifying a custom event loop factory. (Contributed by Kumar Aditya in gh-99388.)Add C implementation of
asyncio.current_task()
for 4x-6x speedup. (Contributed by Itamar Ostricher and Pranav Thulasiram Bhat in gh-100344.)asyncio.iscoroutine()
now returnsFalse
for generators asasyncio
does not support legacy generator-based coroutines. (Contributed by Kumar Aditya in gh-102748.)asyncio.wait()
andasyncio.as_completed()
now accepts generators yielding tasks. (Contributed by Kumar Aditya in gh-78530.)
calendar¶
csv¶
Add
QUOTE_NOTNULL
andQUOTE_STRINGS
flags to provide finer grained control ofNone
and empty strings bywriter
objects.
inspect¶
Add
inspect.markcoroutinefunction()
to mark sync functions that return a coroutine for use withinspect.iscoroutinefunction()
. (Contributed Carlton Gibson in gh-99247.)Add
inspect.getasyncgenstate()
andinspect.getasyncgenlocals()
for determining the current state of asynchronous generators. (Contributed by Thomas Krennwallner in bpo-35759.)The performance of
inspect.getattr_static()
has been considerably improved. Most calls to the function should be at least 2x faster than they were in Python 3.11, and some may be 6x faster or more. (Contributed by Alex Waygood in gh-103193.)
pathlib¶
Add support for subclassing
pathlib.PurePath
andPath
, plus their Posix- and Windows-specific variants. Subclasses may override thewith_segments()
method to pass information between path instances.Add
walk()
for walking the directory trees and generating all file or directory names within them, similar toos.walk()
. (Contributed by Stanislav Zmiev in gh-90385.)Add walk_up optional parameter to
pathlib.PurePath.relative_to()
to allow the insertion of..
entries in the result; this behavior is more consistent withos.path.relpath()
. (Contributed by Domenico Ragusa in bpo-40358.)Add
pathlib.Path.is_junction()
as a proxy toos.path.isjunction()
. (Contributed by Charles Machalow in gh-99547.)Add case_sensitive optional parameter to
pathlib.Path.glob()
,pathlib.Path.rglob()
andpathlib.PurePath.match()
for matching the path’s case sensitivity, allowing for more precise control over the matching process.
dis¶
Pseudo instruction opcodes (which are used by the compiler but do not appear in executable bytecode) are now exposed in the
dis
module.HAVE_ARGUMENT
is still relevant to real opcodes, but it is not useful for pseudo instructions. Use the newhasarg
collection instead. (Contributed by Irit Katriel in gh-94216.)
fractions¶
Objects of type
fractions.Fraction
now support float-style formatting. (Contributed by Mark Dickinson in gh-100161.)
itertools¶
Added
itertools.batched()
for collecting into even-sized tuples where the last batch may be shorter than the rest. (Contributed by Raymond Hettinger in gh-98363.)
json¶
Added
json.AttrDict
for use withobject_hook
injson.load()
orjson.loads()
. This is a subclass ofdict
that also supports attribute style dotted access. (Contributed by Raymond Hettinger in gh-96145.)
math¶
Added
math.sumprod()
for computing a sum of products. (Contributed by Raymond Hettinger in gh-100485.)Extended
math.nextafter()
to include a steps argument for moving up or down multiple steps at a time. (By Matthias Goergens, Mark Dickinson, and Raymond Hettinger in gh-94906.)
os¶
Add
os.PIDFD_NONBLOCK
to open a file descriptor for a process withos.pidfd_open()
in non-blocking mode. (Contributed by Kumar Aditya in gh-93312.)os.DirEntry
now includes anos.DirEntry.is_junction()
method to check if the entry is a junction. (Contributed by Charles Machalow in gh-99547.)Add
os.listdrives()
,os.listvolumes()
andos.listmounts()
functions on Windows for enumerating drives, volumes and mount points. (Contributed by Steve Dower in gh-102519.)os.stat()
andos.lstat()
are now more accurate on Windows. Thest_birthtime
field will now be filled with the creation time of the file, andst_ctime
is deprecated but still contains the creation time (but in the future will return the last metadata change, for consistency with other platforms).st_dev
may be up to 64 bits andst_ino
up to 128 bits depending on your file system, andst_rdev
is always set to zero rather than incorrect values. Both functions may be significantly faster on newer releases of Windows. (Contributed by Steve Dower in gh-99726.)
os.path¶
Add
os.path.isjunction()
to check if a given path is a junction. (Contributed by Charles Machalow in gh-99547.)Add
os.path.splitroot()
to split a path into a triad(drive, root, tail)
. (Contributed by Barney Gale in gh-101000.)
pdb¶
Add convenience variables to hold values temporarily for debug session and provide quick access to values like the current frame or the return value. (Contributed by Tian Gao in gh-103693.)
random¶
Added
random.binomialvariate()
. (Contributed by Raymond Hettinger in gh-81620.)Added a default of
lamb=1.0
torandom.expovariate()
. (Contributed by Raymond Hettinger in gh-100234.)
shutil¶
shutil.make_archive()
now passes the root_dir argument to custom archivers which support it. In this case it no longer temporarily changes the current working directory of the process to root_dir to perform archiving. (Contributed by Serhiy Storchaka in gh-74696.)shutil.rmtree()
now accepts a new argument onexc which is an error handler like onerror but which expects an exception instance rather than a (typ, val, tb) triplet. onerror is deprecated and will be removed in Python 3.14. (Contributed by Irit Katriel in gh-102828.)shutil.which()
now consults the PATHEXT environment variable to find matches within PATH on Windows even when the given cmd includes a directory component. (Contributed by Charles Machalow in gh-103179.)shutil.which()
will callNeedCurrentDirectoryForExePathW
when querying for executables on Windows to determine if the current working directory should be prepended to the search path. (Contributed by Charles Machalow in gh-103179.)shutil.which()
will return a path matching the cmd with a component fromPATHEXT
prior to a direct match elsewhere in the search path on Windows. (Contributed by Charles Machalow in gh-103179.)
sqlite3¶
Add a command-line interface. (Contributed by Erlend E. Aasland in gh-77617.)
Add the
autocommit
attribute toConnection
and the autocommit parameter toconnect()
to control PEP 249-compliant transaction handling. (Contributed by Erlend E. Aasland in gh-83638.)Add entrypoint keyword-only parameter to
load_extension()
, for overriding the SQLite extension entry point. (Contributed by Erlend E. Aasland in gh-103015.)Add
getconfig()
andsetconfig()
toConnection
to make configuration changes to a database connection. (Contributed by Erlend E. Aasland in gh-103489.)
statistics¶
Extended
statistics.correlation()
to include as aranked
method for computing the Spearman correlation of ranked data. (Contributed by Raymond Hettinger in gh-95861.)
threading¶
Add
threading.settrace_all_threads()
andthreading.setprofile_all_threads()
that allow to set tracing and profiling functions in all running threads in addition to the calling one. (Contributed by Pablo Galindo in gh-93503.)
tkinter¶
tkinter.Canvas.coords()
now flattens its arguments. It now accepts not only coordinates as separate arguments (x1, y1, x2, y2, ...
) and a sequence of coordinates ([x1, y1, x2, y2, ...]
), but also coordinates grouped in pairs ((x1, y1), (x2, y2), ...
and[(x1, y1), (x2, y2), ...]
), likecreate_*()
methods. (Contributed by Serhiy Storchaka in gh-94473.)
tokenize¶
The
tokenize
module includes the changes introduced in PEP 701. ( Contributed by Marta Gómez Macías and Pablo Galindo in gh-102856.) See Porting to Python 3.12 for more information on the changes to thetokenize
module.
types¶
Add
types.get_original_bases()
to allow for further introspection of User-defined generic types when subclassed. (Contributed by James Hilton-Balfe and Alex Waygood in gh-101827.)
unicodedata¶
The Unicode database has been updated to version 15.0.0. (Contributed by Benjamin Peterson in gh-96734).
unittest¶
Added --durations
command line option, showing the N slowest test cases:
python3 -m unittest --durations=3 lib.tests.test_threading
.....
Slowest test durations
----------------------------------------------------------------------
1.210s test_timeout (Lib.test.test_threading.BarrierTests)
1.003s test_default_timeout (Lib.test.test_threading.BarrierTests)
0.518s test_timeout (Lib.test.test_threading.EventTests)
(0.000 durations hidden. Use -v to show these durations.)
----------------------------------------------------------------------
Ran 158 tests in 9.869s
OK (skipped=3)
(Contributed by Giampaolo Rodola in bpo-4080)
uuid¶
Add a command-line interface. (Contributed by Adam Chhina in gh-88597.)
tempfile¶
The
tempfile.NamedTemporaryFile
function has a new optional parameter delete_on_close (Contributed by Evgeny Zorin in gh-58451.)tempfile.mkdtemp()
now always returns an absolute path, even if the argument provided to the dir parameter is a relative path.
typing¶
isinstance()
checks againstruntime-checkable protocols
now useinspect.getattr_static()
rather thanhasattr()
to lookup whether attributes exist. This means that descriptors and__getattr__()
methods are no longer unexpectedly evaluated duringisinstance()
checks against runtime-checkable protocols. However, it may also mean that some objects which used to be considered instances of a runtime-checkable protocol may no longer be considered instances of that protocol on Python 3.12+, and vice versa. Most users are unlikely to be affected by this change. (Contributed by Alex Waygood in gh-102433.)The members of a runtime-checkable protocol are now considered “frozen” at runtime as soon as the class has been created. Monkey-patching attributes onto a runtime-checkable protocol will still work, but will have no impact on
isinstance()
checks comparing objects to the protocol. For example:>>> from typing import Protocol, runtime_checkable >>> @runtime_checkable ... class HasX(Protocol): ... x = 1 ... >>> class Foo: ... ... >>> f = Foo() >>> isinstance(f, HasX) False >>> f.x = 1 >>> isinstance(f, HasX) True >>> HasX.y = 2 >>> isinstance(f, HasX) # unchanged, even though HasX now also has a "y" attribute True
This change was made in order to speed up
isinstance()
checks against runtime-checkable protocols.The performance profile of
isinstance()
checks againstruntime-checkable protocols
has changed significantly. Mostisinstance()
checks against protocols with only a few members should be at least 2x faster than in 3.11, and some may be 20x faster or more. However,isinstance()
checks against protocols with fourteen or more members may be slower than in Python 3.11. (Contributed by Alex Waygood in gh-74690 and gh-103193.)All
typing.TypedDict
andtyping.NamedTuple
classes now have the__orig_bases__
attribute. (Contributed by Adrian Garcia Badaracco in gh-103699.)Add
frozen_default
parameter totyping.dataclass_transform()
. (Contributed by Erik De Bonte in gh-99957.)
sys¶
Add
sys.activate_stack_trampoline()
andsys.deactivate_stack_trampoline()
for activating and deactivating stack profiler trampolines, andsys.is_stack_trampoline_active()
for querying if stack profiler trampolines are active. (Contributed by Pablo Galindo and Christian Heimes with contributions from Gregory P. Smith [Google] and Mark Shannon in gh-96123.)Add
sys.last_exc
which holds the last unhandled exception that was raised (for post-mortem debugging use cases). Deprecate the three fields that have the same information in its legacy form:sys.last_type
,sys.last_value
andsys.last_traceback
. (Contributed by Irit Katriel in gh-102778.)sys._current_exceptions()
now returns a mapping from thread-id to an exception instance, rather than to a(typ, exc, tb)
tuple. (Contributed by Irit Katriel in gh-103176.)
Optimizations¶
Removed
wstr
andwstr_length
members from Unicode objects. It reduces object size by 8 or 16 bytes on 64bit platform. (PEP 623) (Contributed by Inada Naoki in gh-92536.)Added experimental support for using the BOLT binary optimizer in the build process, which improves performance by 1-5%. (Contributed by Kevin Modzelewski in gh-90536 and tuned by Dong-hee Na in gh-101525)
Speed up the regular expression substitution (functions
re.sub()
andre.subn()
and correspondingre.Pattern
methods) for replacement strings containing group references by 2–3 times. (Contributed by Serhiy Storchaka in gh-91524.)Speed up
asyncio.Task
creation by deferring expensive string formatting. (Contributed by Itamar O in gh-103793.)The
tokenize.tokenize()
andtokenize.generate_tokens()
functions are up to 64% faster as a side effect of the changes required to cover PEP 701 in thetokenize
module. (Contributed by Marta Gómez Macías and Pablo Galindo in gh-102856.)
CPython bytecode changes¶
Remove the
LOAD_METHOD
instruction. It has been merged intoLOAD_ATTR
.LOAD_ATTR
will now behave like the oldLOAD_METHOD
instruction if the low bit of its oparg is set. (Contributed by Ken Jin in gh-93429.)Remove the
JUMP_IF_FALSE_OR_POP
andJUMP_IF_TRUE_OR_POP
instructions. (Contributed by Irit Katriel in gh-102859.)Add the
LOAD_FROM_DICT_OR_DEREF
,LOAD_FROM_DICT_OR_GLOBALS
, andLOAD_LOCALS
opcodes as part of the implementation of PEP 695. Remove theLOAD_CLASSDEREF
opcode, which can be replaced withLOAD_LOCALS
plusLOAD_FROM_DICT_OR_DEREF
. (Contributed by Jelle Zijlstra in gh-103764.)
Demos and Tools¶
Remove the
Tools/demo/
directory which contained old demo scripts. A copy can be found in the old-demos project. (Contributed by Victor Stinner in gh-97681.)Remove outdated example scripts of the
Tools/scripts/
directory. A copy can be found in the old-demos project. (Contributed by Victor Stinner in gh-97669.)
Deprecated¶
typing.Hashable
andtyping.Sized
aliases forcollections.abc.Hashable
andcollections.abc.Sized
. (gh-94309.)The
sqlite3
default adapters and converters are now deprecated. Instead, use the Adapter and converter recipes and tailor them to your needs. (Contributed by Erlend E. Aasland in gh-90016.)In
execute()
,DeprecationWarning
is now emitted when named placeholders are used together with parameters supplied as a sequence instead of as adict
. Starting from Python 3.14, using named placeholders with parameters supplied as a sequence will raise aProgrammingError
. (Contributed by Erlend E. Aasland in gh-101698.)The 3-arg signatures (type, value, traceback) of
throw()
,throw()
andathrow()
are deprecated and may be removed in a future version of Python. Use the single-arg versions of these functions instead. (Contributed by Ofey Chan in gh-89874.)DeprecationWarning
is now raised when__package__
on a module differs from__spec__.parent
(previously it wasImportWarning
). (Contributed by Brett Cannon in gh-65961.)The
get_event_loop()
method of the default event loop policy now emits aDeprecationWarning
if there is no current event loop set and it decides to create one. (Contributed by Serhiy Storchaka and Guido van Rossum in gh-100160.)The
xml.etree.ElementTree
module now emitsDeprecationWarning
when testing the truth value of anxml.etree.ElementTree.Element
. Before, the Python implementation emittedFutureWarning
, and the C implementation emitted nothing.In accordance with PEP 699, the
ma_version_tag
field inPyDictObject
is deprecated for extension modules. Accessing this field will generate a compiler warning at compile time. This field will be removed in Python 3.14. (Contributed by Ramvikrams and Kumar Aditya in gh-101193. PEP by Ken Jin.)The
st_ctime
fields return byos.stat()
andos.lstat()
on Windows are deprecated. In a future release, they will contain the last metadata change time, consistent with other platforms. For now, they still contain the creation time, which is also available in the newst_birthtime
field. (Contributed by Steve Dower in gh-99726.)The
sys.last_type
,sys.last_value
andsys.last_traceback
fields are deprecated. Usesys.last_exc
instead. (Contributed by Irit Katriel in gh-102778.)The onerror argument of
shutil.rmtree()
is deprecated as will be removed in Python 3.14. Use onexc instead. (Contributed by Irit Katriel in gh-102828.)Extracting tar archives without specifying filter is deprecated until Python 3.14, when
'data'
filter will become the default. See Extraction filters for details.calendar.January
andcalendar.February
constants are deprecated and replaced bycalendar.Month.JANUARY
andcalendar.Month.FEBRUARY
. (Contributed by Prince Roshan in gh-103636.)The bitwise inversion operator (
~
) on bool is deprecated. It will throw an error in Python 3.14. Usenot
for logical negation of bools instead. In the rare case that you really need the bitwise inversion of the underlyingint
, convert to int explicitly with~int(x)
. (Contributed by Tim Hoffmann in gh-103487.)datetime.datetime
’sutcnow()
andutcfromtimestamp()
are deprecated and will be removed in a future version. Instead, use timezone-aware objects to represent datetimes in UTC: respectively, callnow()
andfromtimestamp()
with the tz parameter set todatetime.UTC
. (Contributed by Paul Ganssle in gh-103857.)
Pending Removal in Python 3.13¶
The following modules and APIs have been deprecated in earlier Python releases, and will be removed in Python 3.13.
Modules (see PEP 594):
APIs:
configparser.LegacyInterpolation
(gh-90765)turtle.RawTurtle.settiltangle()
(gh-50096)unittest.findTestCases()
(gh-50096)unittest.getTestCaseNames()
(gh-50096)unittest.makeSuite()
(gh-50096)unittest.TestProgram.usageExit()
(gh-67048)webbrowser.MacOSX
(gh-86421)classmethod
descriptor chaining (gh-89519)
Pending Removal in Python 3.14¶
Deprecated the following
importlib.abc
classes, scheduled for removal in Python 3.14:importlib.abc.ResourceReader
importlib.abc.Traversable
importlib.abc.TraversableResources
Use
importlib.resources.abc
classes instead:(Contributed by Jason R. Coombs and Hugo van Kemenade in gh-93963.)
Deprecated
collections.abc.ByteString
. PreferSequence
orcollections.abc.Buffer
. For use in typing, prefer a union, likebytes | bytearray
, orcollections.abc.Buffer
. (Contributed by Shantanu Jain in gh-91896.)typing.ByteString
, deprecated since Python 3.9, now causes aDeprecationWarning
to be emitted when it is used.Creating immutable types (
Py_TPFLAGS_IMMUTABLETYPE
) with mutable bases using the C API.Deprecated the isdst parameter in
email.utils.localtime()
. (Contributed by Alan Williams in gh-72346.)__package__
and__cached__
will cease to be set or taken into consideration by the import system (gh-97879).Testing the truth value of an
xml.etree.ElementTree.Element
is deprecated and will raise an exception in Python 3.14.The default
multiprocessing
start method will change to a safer one on Linux, BSDs, and other non-macOS POSIX platforms where'fork'
is currently the default (gh-84559). Adding a runtime warning about this was deemed too disruptive as the majority of code is not expected to care. Use theget_context()
orset_start_method()
APIs to explicitly specify when your code requires'fork'
. See Contexts and start methods.pty
has two undocumentedmaster_open()
andslave_open()
functions that have been deprecated since Python 2 but only gained a properDeprecationWarning
in 3.12. Remove them in 3.14.itertools
had undocumented, inefficient, historically buggy, and inconsistent support for copy, deepcopy, and pickle operations. This will be removed in 3.14 for a significant reduction in code volume and maintenance burden. (Contributed by Raymond Hettinger in gh-101588.)Accessing
co_lnotab
was deprecated in PEP 626 since 3.10 and was planned to be removed in 3.12 but it only got a properDeprecationWarning
in 3.12. May be removed in 3.14. (Contributed by Nikita Sobolev in gh-101866.)The onerror argument of
shutil.rmtree()
is deprecated in 3.12, and will be removed in 3.14.The type, choices, and metavar parameters of
argparse.BooleanOptionalAction
are deprecated and will be removed in 3.14. (Contributed by Nikita Sobolev in gh-92248.)pkgutil.find_loader()
andpkgutil.get_loader()
now raiseDeprecationWarning
; useimportlib.util.find_spec()
instead. (Contributed by Nikita Sobolev in gh-97850.)The following
ast
features have been deprecated in documentation since Python 3.8, now cause aDeprecationWarning
to be emitted at runtime when they are accessed or used, and will be removed in Python 3.14:ast.Num
ast.Str
ast.Bytes
ast.NameConstant
ast.Ellipsis
Use
ast.Constant
instead. (Contributed by Serhiy Storchaka in gh-90953.)
Pending Removal in Future Versions¶
The following APIs were deprecated in earlier Python versions and will be removed, although there is currently no date scheduled for their removal.
Currently Python accepts numeric literals immediately followed by keywords, for example
0in x
,1or x
,0if 1else 2
. It allows confusing and ambiguous expressions like[0x1for x in y]
(which can be interpreted as[0x1 for x in y]
or[0x1f or x in y]
). A syntax warning is raised if the numeric literal is immediately followed by one of keywordsand
,else
,for
,if
,in
,is
andor
. In a future release it will be changed to a syntax error. (gh-87999)
Removed¶
Remove the
distutils
package. It was deprecated in Python 3.10 by PEP 632 “Deprecate distutils module”. For projects still usingdistutils
and cannot be updated to something else, thesetuptools
project can be installed: it still providesdistutils
. (Contributed by Victor Stinner in gh-92584.)Remove the bundled setuptools wheel from
ensurepip
, and stop installing setuptools in environments created byvenv
.pip (>= 22.1)
does not require setuptools to be installed in the environment.setuptools
-based (anddistutils
-based) packages can still be used withpip install
, since pip will providesetuptools
in the build environment it uses for building a package.easy_install
,pkg_resources
,setuptools
anddistutils
are no longer provided by default in environments created withvenv
or bootstrapped withensurepip
, since they are part of thesetuptools
package. For projects relying on these at runtime, thesetuptools
project should be declared as a dependency and installed separately (typically, using pip).(Contributed by Pradyun Gedam in gh-95299.)
Removed many old deprecated
unittest
features:A number of
TestCase
method aliases:Deprecated alias
Method Name
Deprecated in
failUnless
3.1
failIf
3.1
failUnlessEqual
3.1
failIfEqual
3.1
failUnlessAlmostEqual
3.1
failIfAlmostEqual
3.1
failUnlessRaises
3.1
assert_
3.2
assertEquals
3.2
assertNotEquals
3.2
assertAlmostEquals
3.2
assertNotAlmostEquals
3.2
assertRegexpMatches
3.2
assertRaisesRegexp
3.2
assertNotRegexpMatches
3.5
You can use https://github.com/isidentical/teyit to automatically modernise your unit tests.
Undocumented and broken
TestCase
methodassertDictContainsSubset
(deprecated in Python 3.2).Undocumented
TestLoader.loadTestsFromModule
parameter use_load_tests (deprecated and ignored since Python 3.2).An alias of the
TextTestResult
class:_TextTestResult
(deprecated in Python 3.2).
(Contributed by Serhiy Storchaka in bpo-45162.)
Several names deprecated in the
configparser
way back in 3.2 have been removed per gh-89336:configparser.ParsingError
no longer has afilename
attribute or argument. Use thesource
attribute and argument instead.configparser
no longer has aSafeConfigParser
class. Use the shorterConfigParser
name instead.configparser.ConfigParser
no longer has areadfp
method. Useread_file()
instead.
The following undocumented
sqlite3
features, deprecated in Python 3.10, are now removed:sqlite3.enable_shared_cache()
sqlite3.OptimizedUnicode
If a shared cache must be used, open the database in URI mode using the
cache=shared
query parameter.The
sqlite3.OptimizedUnicode
text factory has been an alias forstr
since Python 3.3. Code that previously set the text factory toOptimizedUnicode
can either usestr
explicitly, or rely on the default value which is alsostr
.(Contributed by Erlend E. Aasland in gh-92548.)
smtpd
has been removed according to the schedule in PEP 594, having been deprecated in Python 3.4.7 and 3.5.4. Use aiosmtpd PyPI module or any otherasyncio
-based server instead. (Contributed by Oleg Iarygin in gh-93243.)
asynchat
andasyncore
have been removed according to the schedule in PEP 594, having been deprecated in Python 3.6. Useasyncio
instead. (Contributed by Nikita Sobolev in gh-96580.)Remove
io.OpenWrapper
and_pyio.OpenWrapper
, deprecated in Python 3.10: just useopen()
instead. Theopen()
(io.open()
) function is a built-in function. Since Python 3.10,_pyio.open()
is also a static method. (Contributed by Victor Stinner in gh-94169.)Remove the
ssl.RAND_pseudo_bytes()
function, deprecated in Python 3.6: useos.urandom()
orssl.RAND_bytes()
instead. (Contributed by Victor Stinner in gh-94199.)gzip
: Remove thefilename
attribute ofgzip.GzipFile
, deprecated since Python 2.6, use thename
attribute instead. In write mode, thefilename
attribute added'.gz'
file extension if it was not present. (Contributed by Victor Stinner in gh-94196.)Remove the
ssl.match_hostname()
function. It was deprecated in Python 3.7. OpenSSL performs hostname matching since Python 3.7, Python no longer uses thessl.match_hostname()
function. (Contributed by Victor Stinner in gh-94199.)Remove the
locale.format()
function, deprecated in Python 3.7: uselocale.format_string()
instead. (Contributed by Victor Stinner in gh-94226.)hashlib
: Remove the pure Python implementation ofhashlib.pbkdf2_hmac()
, deprecated in Python 3.10. Python 3.10 and newer requires OpenSSL 1.1.1 (PEP 644): this OpenSSL version provides a C implementation ofpbkdf2_hmac()
which is faster. (Contributed by Victor Stinner in gh-94199.)xml.etree.ElementTree
: Remove theElementTree.Element.copy()
method of the pure Python implementation, deprecated in Python 3.10, use thecopy.copy()
function instead. The C implementation ofxml.etree.ElementTree
has nocopy()
method, only a__copy__()
method. (Contributed by Victor Stinner in gh-94383.)zipimport
: Removefind_loader()
andfind_module()
methods, deprecated in Python 3.10: use thefind_spec()
method instead. See PEP 451 for the rationale. (Contributed by Victor Stinner in gh-94379.)Remove the
ssl.wrap_socket()
function, deprecated in Python 3.7: instead, create assl.SSLContext
object and call itsssl.SSLContext.wrap_socket
method. Any package that still usesssl.wrap_socket()
is broken and insecure. The function neither sends a SNI TLS extension nor validates server hostname. Code is subject to CWE-295: Improper Certificate Validation. (Contributed by Victor Stinner in gh-94199.)Many previously deprecated cleanups in
importlib
have now been completed:References to, and support for
module_repr()
has been removed. (Contributed by Barry Warsaw in gh-97850.)importlib.util.set_package
has been removed. (Contributed by Brett Cannon in gh-65961.)Support for
find_loader()
andfind_module()
APIs have been removed. (Contributed by Barry Warsaw in gh-98040.)importlib.abc.Finder
,pkg.ImpImporter
, andpkg.ImpLoader
have been removed. (Contributed by Barry Warsaw in gh-98040.)The
imp
module has been removed. (Contributed by Barry Warsaw in gh-98040.)
Removed the
suspicious
rule from the documentation Makefile, and removedDoc/tools/rstlint.py
, both in favor of sphinx-lint. (Contributed by Julien Palard in gh-98179.)Remove the keyfile and certfile parameters from the
ftplib
,imaplib
,poplib
andsmtplib
modules, and the key_file, cert_file and check_hostname parameters from thehttp.client
module, all deprecated since Python 3.6. Use the context parameter (ssl_context inimaplib
) instead. (Contributed by Victor Stinner in gh-94172.)ftplib
: Remove theFTP_TLS.ssl_version
class attribute: use the context parameter instead. (Contributed by Victor Stinner in gh-94172.)Remove support for obsolete browsers from
webbrowser
. Removed browsers include: Grail, Mosaic, Netscape, Galeon, Skipstone, Iceape, Firebird, and Firefox versions 35 and below (gh-102871).
Porting to Python 3.12¶
This section lists previously described changes and other bugfixes that may require changes to your code.
Changes in the Python API¶
More strict rules are now applied for numerical group references and group names in regular expressions. Only sequence of ASCII digits is now accepted as a numerical reference. The group name in bytes patterns and replacement strings can now only contain ASCII letters and digits and underscore. (Contributed by Serhiy Storchaka in gh-91760.)
Removed
randrange()
functionality deprecated since Python 3.10. Formerly,randrange(10.0)
losslessly converted torandrange(10)
. Now, it raises aTypeError
. Also, the exception raised for non-integral values such asrandrange(10.5)
orrandrange('10')
has been changed fromValueError
toTypeError
. This also prevents bugs whererandrange(1e25)
would silently select from a larger range thanrandrange(10**25)
. (Originally suggested by Serhiy Storchaka gh-86388.)argparse.ArgumentParser
changed encoding and error handler for reading arguments from file (e.g.fromfile_prefix_chars
option) from default text encoding (e.g.locale.getpreferredencoding(False)
) to filesystem encoding and error handler. Argument files should be encoded in UTF-8 instead of ANSI Codepage on Windows.Removed the
asyncore
-basedsmtpd
module deprecated in Python 3.4.7 and 3.5.4. A recommended replacement is theasyncio
-based aiosmtpd PyPI module.shlex.split()
: PassingNone
for s argument now raises an exception, rather than readingsys.stdin
. The feature was deprecated in Python 3.9. (Contributed by Victor Stinner in gh-94352.)The
os
module no longer accepts bytes-like paths, likebytearray
andmemoryview
types: only the exactbytes
type is accepted for bytes strings. (Contributed by Victor Stinner in gh-98393.)syslog.openlog()
andsyslog.closelog()
now fail if used in subinterpreters.syslog.syslog()
may still be used in subinterpreters, but now only ifsyslog.openlog()
has already been called in the main interpreter. These new restrictions do not apply to the main interpreter, so only a very small set of users might be affected. This change helps with interpreter isolation. Furthermore,syslog
is a wrapper around process-global resources, which are best managed from the main interpreter. (Contributed by Dong-hee Na in gh-99127.)The undocumented locking behavior of
cached_property()
is removed, because it locked across all instances of the class, leading to high lock contention. This means that a cached property getter function could now run more than once for a single instance, if two threads race. For most simple cached properties (e.g. those that are idempotent and simply calculate a value based on other attributes of the instance) this will be fine. If synchronization is needed, implement locking within the cached property getter function or around multi-threaded access points.sys._current_exceptions()
now returns a mapping from thread-id to an exception instance, rather than to a(typ, exc, tb)
tuple. (Contributed by Irit Katriel in gh-103176.)When extracting tar files using
tarfile
orshutil.unpack_archive()
, pass the filter argument to limit features that may be surprising or dangerous. See Extraction filters for details.The output of the
tokenize.tokenize()
andtokenize.generate_tokens()
functions is now changed due to the changes introduced in PEP 701. This means thatSTRING
tokens are not emitted any more for f-strings and the tokens described in PEP 701 are now produced instead:FSTRING_START
,FSRING_MIDDLE
andFSTRING_END
are now emitted for f-string “string” parts in addition to the appropriate tokens for the tokenization in the expression components. For example for the f-stringf"start {1+1} end"
the old version of the tokenizer emitted:1,0-1,18: STRING 'f"start {1+1} end"'
while the new version emits:
1,0-1,2: FSTRING_START 'f"' 1,2-1,8: FSTRING_MIDDLE 'start ' 1,8-1,9: OP '{' 1,9-1,10: NUMBER '1' 1,10-1,11: OP '+' 1,11-1,12: NUMBER '1' 1,12-1,13: OP '}' 1,13-1,17: FSTRING_MIDDLE ' end' 1,17-1,18: FSTRING_END '"'
Aditionally, there may be some minor behavioral changes as a consecuence of the changes required to support PEP 701. Some of these changes include:
Some final
DEDENT
tokens are now emitted within the bounds of the input. This means that for a file containing 3 lines, the old version of the tokenizer returned aDEDENT
token in line 4 whilst the new version returns the token in line 3.The
type
attribute of the tokens emitted when tokenizing some invalid Python characters such as!
has changed fromERRORTOKEN
toOP
.
Build Changes¶
Python no longer uses
setup.py
to build shared C extension modules. Build parameters like headers and libraries are detected inconfigure
script. Extensions are built byMakefile
. Most extensions usepkg-config
and fall back to manual detection. (Contributed by Christian Heimes in gh-93939.)va_start()
with two parameters, likeva_start(args, format),
is now required to build Python.va_start()
is no longer called with a single parameter. (Contributed by Kumar Aditya in gh-93207.)CPython now uses the ThinLTO option as the default link time optimization policy if the Clang compiler accepts the flag. (Contributed by Dong-hee Na in gh-89536.)
Add
COMPILEALL_OPTS
variable in Makefile to overridecompileall
options (default:-j0
) inmake install
. Also merged the 3compileall
commands into a single command to build .pyc files for all optimization levels (0, 1, 2) at once. (Contributed by Victor Stinner in gh-99289.)Add platform triplets for 64-bit LoongArch:
loongarch64-linux-gnusf
loongarch64-linux-gnuf32
loongarch64-linux-gnu
(Contributed by Zhang Na in gh-90656.)
PYTHON_FOR_REGEN
now require Python 3.10 or newer.
C API Changes¶
New Features¶
PEP 697: Introduced the Unstable C API tier, intended for low-level tools like debuggers and JIT compilers. This API may change in each minor release of CPython without deprecation warnings. Its contents are marked by the
PyUnstable_
prefix in names.Code object constructors:
PyUnstable_Code_New()
(renamed fromPyCode_New
)PyUnstable_Code_NewWithPosOnlyArgs()
(renamed fromPyCode_NewWithPosOnlyArgs
)
Extra storage for code objects (PEP 523):
PyUnstable_Eval_RequestCodeExtraIndex()
(renamed from_PyEval_RequestCodeExtraIndex
)PyUnstable_Code_GetExtra()
(renamed from_PyCode_GetExtra
)PyUnstable_Code_SetExtra()
(renamed from_PyCode_SetExtra
)
The original names will continue to be available until the respective API changes.
(Contributed by Petr Viktorin in gh-101101.)
PEP 697: Added API for extending types whose instance memory layout is opaque:
PyType_Spec.basicsize
can be zero or negative to specify inheriting or extending the base class size.PyObject_GetTypeData()
andPyType_GetTypeDataSize()
added to allow access to subclass-specific instance data.Py_TPFLAGS_ITEMS_AT_END
andPyObject_GetItemData()
added to allow safely extending certain variable-sized types, includingPyType_Type
.Py_RELATIVE_OFFSET
added to allow definingmembers
in terms of a subclass-specific struct.
(Contributed by Petr Viktorin in gh-103509.)
Added the new limited C API function
PyType_FromMetaclass()
, which generalizes the existingPyType_FromModuleAndSpec()
using an additional metaclass argument. (Contributed by Wenzel Jakob in gh-93012.)API for creating objects that can be called using the vectorcall protocol was added to the Limited API:
The
Py_TPFLAGS_HAVE_VECTORCALL
flag is now removed from a class when the class’s__call__()
method is reassigned. This makes vectorcall safe to use with mutable types (i.e. heap types without the immutable flag,Py_TPFLAGS_IMMUTABLETYPE
). Mutable types that do not overridetp_call
now inherit thePy_TPFLAGS_HAVE_VECTORCALL
flag. (Contributed by Petr Viktorin in gh-93274.)The
Py_TPFLAGS_MANAGED_DICT
andPy_TPFLAGS_MANAGED_WEAKREF
flags have been added. This allows extensions classes to support object__dict__
and weakrefs with less bookkeeping, using less memory and with faster access.API for performing calls using the vectorcall protocol was added to the Limited API:
This means that both the incoming and outgoing ends of the vector call protocol are now available in the Limited API. (Contributed by Wenzel Jakob in gh-98586.)
Added two new public functions,
PyEval_SetProfileAllThreads()
andPyEval_SetTraceAllThreads()
, that allow to set tracing and profiling functions in all running threads in addition to the calling one. (Contributed by Pablo Galindo in gh-93503.)Added new function
PyFunction_SetVectorcall()
to the C API which sets the vectorcall field of a givenPyFunctionObject
. (Contributed by Andrew Frost in gh-92257.)The C API now permits registering callbacks via
PyDict_AddWatcher()
,PyDict_Watch()
and related APIs to be called whenever a dictionary is modified. This is intended for use by optimizing interpreters, JIT compilers, or debuggers. (Contributed by Carl Meyer in gh-91052.)Added
PyType_AddWatcher()
andPyType_Watch()
API to register callbacks to receive notification on changes to a type. (Contributed by Carl Meyer in gh-91051.)Added
PyCode_AddWatcher()
andPyCode_ClearWatcher()
APIs to register callbacks to receive notification on creation and destruction of code objects. (Contributed by Itamar Ostricher in gh-91054.)Add
PyFrame_GetVar()
andPyFrame_GetVarString()
functions to get a frame variable by its name. (Contributed by Victor Stinner in gh-91248.)Add
PyErr_GetRaisedException()
andPyErr_SetRaisedException()
for saving and restoring the current exception. These functions return and accept a single exception object, rather than the triple arguments of the now-deprecatedPyErr_Fetch()
andPyErr_Restore()
. This is less error prone and a bit more efficient. (Contributed by Mark Shannon in gh-101578.)Add
_PyErr_ChainExceptions1
, which takes an exception instance, to replace the legacy-API_PyErr_ChainExceptions
, which is now deprecated. (Contributed by Mark Shannon in gh-101578.)Add
PyException_GetArgs()
andPyException_SetArgs()
as convenience functions for retrieving and modifying theargs
passed to the exception’s constructor. (Contributed by Mark Shannon in gh-101578.)Add
PyErr_DisplayException()
, which takes an exception instance, to replace the legacy-apiPyErr_Display()
. (Contributed by Irit Katriel in gh-102755).PEP 683: Introduced Immortal Objects to Python which allows objects to bypass reference counts and introduced changes to the C-API:
_Py_IMMORTAL_REFCNT
: The reference count that defines an objectas immortal.
_Py_IsImmortal
Checks if an object has the immortal reference count.PyObject_HEAD_INIT
This will now initialize reference count to_Py_IMMORTAL_REFCNT
when used withPy_BUILD_CORE
.
SSTATE_INTERNED_IMMORTAL
An identifier for interned unicode objectsthat are immortal.
SSTATE_INTERNED_IMMORTAL_STATIC
An identifier for interned unicodeobjects that are immortal and static
sys.getunicodeinternedsize
This returns the total number of unicodeobjects that have been interned. This is now needed for refleak.py to correctly track reference counts and allocated blocks
(Contributed by Eddie Elizondo in gh-84436.)
Porting to Python 3.12¶
Legacy Unicode APIs based on
Py_UNICODE*
representation has been removed. Please migrate to APIs based on UTF-8 orwchar_t*
.Argument parsing functions like
PyArg_ParseTuple()
doesn’t supportPy_UNICODE*
based format (e.g.u
,Z
) anymore. Please migrate to other formats for Unicode likes
,z
,es
, andU
.tp_weaklist
for all static builtin types is alwaysNULL
. This is an internal-only field onPyTypeObject
but we’re pointing out the change in case someone happens to be accessing the field directly anyway. To avoid breakage, consider using the existing public C-API instead, or, if necessary, the (internal-only)_PyObject_GET_WEAKREFS_LISTPTR()
macro.This internal-only
PyTypeObject.tp_subclasses
may now not be a valid object pointer. Its type was changed to void* to reflect this. We mention this in case someone happens to be accessing the internal-only field directly.To get a list of subclasses, call the Python method
__subclasses__()
(usingPyObject_CallMethod()
, for example).Add support of more formatting options (left aligning, octals, uppercase hexadecimals,
intmax_t
,ptrdiff_t
,wchar_t
C strings, variable width and precision) inPyUnicode_FromFormat()
andPyUnicode_FromFormatV()
. (Contributed by Serhiy Storchaka in gh-98836.)An unrecognized format character in
PyUnicode_FromFormat()
andPyUnicode_FromFormatV()
now sets aSystemError
. In previous versions it caused all the rest of the format string to be copied as-is to the result string, and any extra arguments discarded. (Contributed by Serhiy Storchaka in gh-95781.)Fixed wrong sign placement in
PyUnicode_FromFormat()
andPyUnicode_FromFormatV()
. (Contributed by Philip Georgi in gh-95504.)Extension classes wanting to add a
__dict__
or weak reference slot should usePy_TPFLAGS_MANAGED_DICT
andPy_TPFLAGS_MANAGED_WEAKREF
instead oftp_dictoffset
andtp_weaklistoffset
, respectively. The use oftp_dictoffset
andtp_weaklistoffset
is still supported, but does not fully support multiple inheritance (gh-95589), and performance may be worse. Classes declaringPy_TPFLAGS_MANAGED_DICT
should call_PyObject_VisitManagedDict()
and_PyObject_ClearManagedDict()
to traverse and clear their instance’s dictionaries. To clear weakrefs, callPyObject_ClearWeakRefs()
, as before.The
PyUnicode_FSDecoder()
function no longer accepts bytes-like paths, likebytearray
andmemoryview
types: only the exactbytes
type is accepted for bytes strings. (Contributed by Victor Stinner in gh-98393.)The
Py_CLEAR
,Py_SETREF
andPy_XSETREF
macros now only evaluate their arguments once. If an argument has side effects, these side effects are no longer duplicated. (Contributed by Victor Stinner in gh-98724.)The interpreter’s error indicator is now always normalized. This means that
PyErr_SetObject()
,PyErr_SetString()
and the other functions that set the error indicator now normalize the exception before storing it. (Contributed by Mark Shannon in gh-101578.)_Py_RefTotal
is no longer authoritative and only kept around for ABI compabitility. Note that it is an internal global and only available on debug builds. If you happen to be using it then you’ll need to start using_Py_GetGlobalRefTotal()
.The following functions now select an appropriate metaclass for the newly created type:
Creating classes whose metaclass overrides
tp_new
is deprecated, and in Python 3.14+ it will be disallowed. Note that these functions ignoretp_new
of the metaclass, possibly allowing incomplete initialization.Note that
PyType_FromMetaclass()
(added in Python 3.12) already disallows creating classes whose metaclass overridestp_new
.PyOS_InputHook
andPyOS_ReadlineFunctionPointer
are no longer called in subinterpreters. This is because clients generally rely on process-wide global state (since these callbacks have no way of recovering extension module state).This also avoids situations where extensions may find themselves running in a subinterpreter that they don’t support (or haven’t yet been loaded in). See gh-104668 for more info.
Deprecated¶
Deprecate global configuration variable:
Py_HashRandomizationFlag
: usePyConfig.use_hash_seed
andPyConfig.hash_seed
Py_LegacyWindowsFSEncodingFlag
: usePyPreConfig.legacy_windows_fs_encoding
Py_LegacyWindowsStdioFlag
: usePyConfig.legacy_windows_stdio
Py_FileSystemDefaultEncoding
: usePyConfig.filesystem_encoding
Py_FileSystemDefaultEncodeErrors
: usePyConfig.filesystem_errors
Py_UTF8Mode
: usePyPreConfig.utf8_mode
(seePy_PreInitialize()
)
The
Py_InitializeFromConfig()
API should be used withPyConfig
instead. (Contributed by Victor Stinner in gh-77782.)Creating immutable types (
Py_TPFLAGS_IMMUTABLETYPE
) with mutable bases is deprecated and will be disabled in Python 3.14.The
structmember.h
header is deprecated, though it continues to be available and there are no plans to remove it.Its contents are now available just by including
Python.h
, with aPy
prefix added if it was missing:Type macros like
Py_T_INT
,Py_T_DOUBLE
, etc. (previouslyT_INT
,T_DOUBLE
, etc.)The flags
Py_READONLY
(previouslyREADONLY
) andPy_AUDIT_READ
(previously all uppercase)
Several items are not exposed from
Python.h
:T_OBJECT
(usePy_T_OBJECT_EX
)T_NONE
(previously undocumented, and pretty quirky)The macro
WRITE_RESTRICTED
which does nothing.The macros
RESTRICTED
andREAD_RESTRICTED
, equivalents ofPy_AUDIT_READ
.In some configurations,
<stddef.h>
is not included fromPython.h
. It should be included manually when usingoffsetof()
.
The deprecated header continues to provide its original contents under the original names. Your old code can stay unchanged, unless the extra include and non-namespaced macros bother you greatly.
(Contributed in gh-47146 by Petr Viktorin, based on earlier work by Alexander Belopolsky and Matthias Braun.)
PyErr_Fetch()
andPyErr_Restore()
are deprecated. UsePyErr_GetRaisedException()
andPyErr_SetRaisedException()
instead. (Contributed by Mark Shannon in gh-101578.)PyErr_Display()
is deprecated. UsePyErr_DisplayException()
instead. (Contributed by Irit Katriel in gh-102755)._PyErr_ChainExceptions
is deprecated. Use_PyErr_ChainExceptions1
instead. (Contributed by Irit Katriel in gh-102192.)Using
PyType_FromSpec()
,PyType_FromSpecWithBases()
orPyType_FromModuleAndSpec()
to create a class whose metaclass overridestp_new
is deprecated. Call the metaclass instead.
Removed¶
Remove the
token.h
header file. There was never any public tokenizer C API. Thetoken.h
header file was only designed to be used by Python internals. (Contributed by Victor Stinner in gh-92651.)Legacy Unicode APIs have been removed. See PEP 623 for detail.
PyUnicode_WCHAR_KIND
PyUnicode_AS_UNICODE()
PyUnicode_AsUnicode()
PyUnicode_AsUnicodeAndSize()
PyUnicode_AS_DATA()
PyUnicode_FromUnicode()
PyUnicode_GET_SIZE()
PyUnicode_GetSize()
PyUnicode_GET_DATA_SIZE()
Remove the
PyUnicode_InternImmortal()
function macro. (Contributed by Victor Stinner in gh-85858.)Remove
Jython
compatibility hacks from several stdlib modules and tests. (Contributed by Nikita Sobolev in gh-99482.)Remove
_use_broken_old_ctypes_structure_semantics_
flag fromctypes
module. (Contributed by Nikita Sobolev in gh-99285.)