What’s New In Python 3.12

What’s New In Python 3.12¶
- Editor:
Adam Turner
This article explains the new features in Python 3.12, compared to 3.11. Python 3.12 was released on October 2, 2023. For full details, see the changelog.
See also
PEP 693 – Python 3.12 Release Schedule
Summary – Release highlights¶
Python 3.12 is a stable release of the Python programming language,
with a mix of changes to the language and the standard library.
The library changes focus on cleaning up deprecated APIs, usability, and correctness.
Of note, the distutils
package has been removed from the standard library.
Filesystem support in os
and pathlib
has seen a number of improvements,
and several modules have better performance.
The language changes focus on usability,
as f-strings have had many limitations removed
and ‘Did you mean …’ suggestions continue to improve.
The new type parameter syntax
and type
statement improve ergonomics for using generic types and type aliases with static type checkers.
This article doesn’t attempt to provide a complete specification of all new features, but instead gives a convenient overview. For full details, you should refer to the documentation, such as the Library Reference and Language Reference. If you want to understand the complete implementation and design rationale for a change, refer to the PEP for a particular new feature; but note that PEPs usually are not kept up-to-date once a feature has been fully implemented.
New syntax features:
New grammar features:
Interpreter improvements:
PEP 669, low impact monitoring
Improved ‘Did you mean …’ suggestions for
NameError
,ImportError
, andSyntaxError
exceptions
Python data model improvements:
PEP 688, using the buffer protocol from Python
Significant improvements in the standard library:
The
pathlib.Path
class now supports subclassingThe
os
module received several improvements for Windows supportA command-line interface has been added to the
sqlite3
moduleisinstance()
checks againstruntime-checkable protocols
enjoy a speed up of between two and 20 timesThe
asyncio
package has had a number of performance improvements, with some benchmarks showing a 75% speed up.A command-line interface has been added to the
uuid
moduleDue to the changes in PEP 701, producing tokens via the
tokenize
module is up to 64% faster.
Security improvements:
Replace the builtin
hashlib
implementations of SHA1, SHA3, SHA2-384, SHA2-512, and MD5 with formally verified code from the HACL* project. These builtin implementations remain as fallbacks that are only used when OpenSSL does not provide them.
C API improvements:
CPython implementation improvements:
PEP 709, comprehension inlining
CPython support for the Linux
perf
profilerImplement stack overflow protection on supported platforms
New typing features:
PEP 698,
typing.override()
decorator
Important deprecations, removals or restrictions:
PEP 623: Remove
wstr
from Unicode objects in Python’s C API, reducing the size of everystr
object by at least 8 bytes.PEP 632: Remove the
distutils
package. See the migration guide for advice replacing the APIs it provided. The third-party Setuptools package continues to providedistutils
, if you still require it in Python 3.12 and beyond.gh-95299: Do not pre-install
setuptools
in virtual environments created withvenv
. This means thatdistutils
,setuptools
,pkg_resources
, andeasy_install
will no longer available by default; to access these runpip install setuptools
in the activated virtual environment.The
asynchat
,asyncore
, andimp
modules have been removed, along with severalunittest.TestCase
method aliases.
New Features¶
PEP 695: Type Parameter Syntax¶
Generic classes and functions under PEP 484 were declared using a verbose syntax that left the scope of type parameters unclear and required explicit declarations of variance.
PEP 695 introduces a new, more compact and explicit way to create generic classes and functions:
def max[T](args: Iterable[T]) -> T:
...
class list[T]:
def __getitem__(self, index: int, /) -> T:
...
def append(self, element: T) -> None:
...
In addition, the PEP introduces a new way to declare type aliases
using the type
statement, which creates an instance of
TypeAliasType
:
type Point = tuple[float, float]
Type aliases can also be generic:
type Point[T] = tuple[T, T]
The new syntax allows declaring TypeVarTuple
and ParamSpec
parameters, as well as TypeVar
parameters with bounds or constraints:
type IntFunc[**P] = Callable[P, int] # ParamSpec
type LabeledTuple[*Ts] = tuple[str, *Ts] # TypeVarTuple
type HashableSequence[T: Hashable] = Sequence[T] # TypeVar with bound
type IntOrStrSequence[T: (int, str)] = Sequence[T] # TypeVar with constraints
The value of type aliases and the bound and constraints of type variables created through this syntax are evaluated only on demand (see lazy evaluation). This means type aliases are able to refer to other types defined later in the file.
Type parameters declared through a type parameter list are visible within the scope of the declaration and any nested scopes, but not in the outer scope. For example, they can be used in the type annotations for the methods of a generic class or in the class body. However, they cannot be used in the module scope after the class is defined. See Type parameter lists for a detailed description of the runtime semantics of type parameters.
In order to support these scoping semantics, a new kind of scope is introduced, the annotation scope. Annotation scopes behave for the most part like function scopes, but interact differently with enclosing class scopes. In Python 3.13, annotations will also be evaluated in annotation scopes.
See PEP 695 for more details.
(PEP written by Eric Traut. Implementation by Jelle Zijlstra, Eric Traut, and others in gh-103764.)
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 strings reusing the same quote as the containing f-string, multi-line expressions, comments, backslashes, and unicode escape sequences. Let’s cover these in detail:
Quote reuse: in Python 3.11, reusing the same quotes as the enclosing 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-string expressions must be defined in a single line, even if the expression within the f-string could normally span multiple lines (like literal lists being defined over multiple lines), making them harder to read. In Python 3.12 you can now define f-strings spanning multiple lines, and add inline comments:
>>> 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 escape 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.
As a positive side-effect of how this feature has been implemented (by parsing f-strings
with the PEG parser), now error messages for f-strings are more precise
and include the exact location of the error. For example, in Python 3.11, the following
f-string raises a SyntaxError
:
>>> my_string = f"{x z y}" + f"{1 + 1}"
File "<stdin>", line 1
(x z y)
^^^
SyntaxError: f-string: invalid syntax. Perhaps you forgot a comma?
but the error message doesn’t include the exact location of the error within the line and also has the expression artificially surrounded by parentheses. In Python 3.12, as f-strings are parsed with the PEG parser, error messages can be more precise and show the entire line:
>>> my_string = f"{x z y}" + f"{1 + 1}"
File "<stdin>", line 1
my_string = f"{x z y}" + f"{1 + 1}"
^^^
SyntaxError: invalid syntax. Perhaps you forgot a comma?
(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 684: A Per-Interpreter GIL¶
PEP 684 introduces a per-interpreter GIL, so that sub-interpreters may now be created with a unique GIL per interpreter. This allows Python programs to take full advantage of multiple CPU cores. This is currently only available through the C-API, though a Python API is anticipated for 3.13.
Use the new Py_NewInterpreterFromConfig()
function to
create an interpreter with its own GIL:
PyInterpreterConfig config = {
.check_multi_interp_extensions = 1,
.gil = PyInterpreterConfig_OWN_GIL,
};
PyThreadState *tstate = NULL;
PyStatus status = Py_NewInterpreterFromConfig(&tstate, &config);
if (PyStatus_Exception(status)) {
return -1;
}
/* The new interpreter is now active in the current thread. */
For further examples how to use the C-API for sub-interpreters with a
per-interpreter GIL, see Modules/_xxsubinterpretersmodule.c
.
(Contributed by Eric Snow in gh-104210, etc.)
PEP 669: Low impact monitoring for CPython¶
PEP 669 defines a new API
for profilers,
debuggers, and other tools to monitor events in CPython.
It covers a wide range of events, including calls,
returns, lines, exceptions, jumps, and more.
This means that you only pay for what you use, providing support
for near-zero overhead debuggers and coverage tools.
See sys.monitoring
for details.
(Contributed by Mark Shannon in gh-103082.)
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.)
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 two times. See PEP 709 for further details.
Comprehension iteration variables remain isolated and don’t overwrite a variable of the same name in the outer scope, nor are they visible after the comprehension. 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.
The
symtable
module will no longer produce child symbol tables for each comprehension; instead, the comprehension’s locals will be included in the parent function’s symbol table.Calling
locals()
inside a comprehension now includes variables from outside the comprehension, and no longer includes the synthetic.0
variable for the comprehension “argument”.A comprehension iterating directly over
locals()
(e.g.[k for k in locals()]
) may see “RuntimeError: dictionary changed size during iteration” when run under tracing (e.g. code coverage measurement). This is the same behavior already seen in e.g.for k in locals():
. To avoid the error, first create a list of keys to iterate over:keys = list(locals()); [k for k in keys]
.
(Contributed by Carl Meyer and Vladimir Matveev in PEP 709.)
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() Traceback (most recent call last): 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 Traceback (most recent call last): 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'?
Other Language Changes¶
The parser now raises
SyntaxError
when parsing source code containing null bytes. (Contributed by Pablo Galindo in gh-96670.)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.)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.)Exceptions raised in a class or type’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.)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.)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.)memoryview
now supports the half-float type (the “e” format code). (Contributed by Donghee Na and Antoine Pitrou in gh-90751.)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 and commutativity when summing floats or mixed ints and floats. (Contributed by Raymond Hettinger in gh-100425.)ast.parse()
now raisesSyntaxError
instead ofValueError
when parsing source code containing null bytes. (Contributed by Pablo Galindo in gh-96670.)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 tarfile 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.)Add support for the perf profiler through the new environment variable
PYTHONPERFSUPPORT
and command-line option-X perf
, as well as the newsys.activate_stack_trampoline()
,sys.deactivate_stack_trampoline()
, andsys.is_stack_trampoline_active()
functions. (Design by Pablo Galindo. Contributed by Pablo Galindo and Christian Heimes with contributions from Gregory P. Smith [Google] and Mark Shannon in gh-96123.)
New Modules¶
None.
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.)Add
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 Oren in gh-102853, gh-104140, and gh-104138)On Linux,
asyncio
usesasyncio.PidfdChildWatcher
by default ifos.pidfd_open()
is available and functional instead ofasyncio.ThreadedChildWatcher
. (Contributed by Kumar Aditya in gh-98024.)The event loop now uses the best available child watcher for each platform (
asyncio.PidfdChildWatcher
if supported andasyncio.ThreadedChildWatcher
otherwise), so manually configuring a child watcher is not recommended. (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 Oren 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¶
Add enums
calendar.Month
andcalendar.Day
defining months of the year and days of the week. (Contributed by Prince Roshan in gh-103636.)
csv¶
Add
csv.QUOTE_NOTNULL
andcsv.QUOTE_STRINGS
flags to provide finer grained control ofNone
and empty strings byreader
andwriter
objects.
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 newdis.hasarg
collection instead. (Contributed by Irit Katriel in gh-94216.)Add the
dis.hasexc
collection to signify instructions that set an exception handler. (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.)
importlib.resources¶
importlib.resources.as_file()
now supports resource directories. (Contributed by Jason R. Coombs in gh-97930.)Rename first parameter of
importlib.resources.files()
to anchor. (Contributed by Jason R. Coombs in gh-100598.)
inspect¶
Add
inspect.markcoroutinefunction()
to mark sync functions that return a coroutine for use withinspect.iscoroutinefunction()
. (Contributed by Carlton Gibson in gh-99247.)Add
inspect.getasyncgenstate()
andinspect.getasyncgenlocals()
for determining the current state of asynchronous generators. (Contributed by Thomas Krennwallner in gh-79940.)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. (Contributed by Alex Waygood in gh-103193.)
itertools¶
Add
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.)
math¶
Add
math.sumprod()
for computing a sum of products. (Contributed by Raymond Hettinger in gh-100485.)Extend
math.nextafter()
to include a steps argument for moving up or down multiple steps at a time. (Contributed 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.)
pathlib¶
Add support for subclassing
pathlib.PurePath
andpathlib.Path
, plus their Posix- and Windows-specific variants. Subclasses may override thepathlib.PurePath.with_segments()
method to pass information between path instances.Add
pathlib.Path.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 gh-84538.)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.
platform¶
Add support for detecting Windows 11 and Windows Server releases past 2012. Previously, lookups on Windows Server platforms newer than Windows Server 2012 and on Windows 11 would return
Windows-10
. (Contributed by Steve Dower in gh-89545.)
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¶
Add
random.binomialvariate()
. (Contributed by Raymond Hettinger in gh-81620.)Add a default of
lambd=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. (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
sqlite3.Connection.autocommit
attribute tosqlite3.Connection
and the autocommit parameter tosqlite3.connect()
to control PEP 249-compliant transaction handling. (Contributed by Erlend E. Aasland in gh-83638.)Add entrypoint keyword-only parameter to
sqlite3.Connection.load_extension()
, for overriding the SQLite extension entry point. (Contributed by Erlend E. Aasland in gh-103015.)Add
sqlite3.Connection.getconfig()
andsqlite3.Connection.setconfig()
tosqlite3.Connection
to make configuration changes to a database connection. (Contributed by Erlend E. Aasland in gh-103489.)
statistics¶
Extend
statistics.correlation()
to include as aranked
method for computing the Spearman correlation of ranked data. (Contributed by Raymond Hettinger in gh-95861.)
sys¶
Add the
sys.monitoring
namespace to expose the new PEP 669 monitoring API. (Contributed by Mark Shannon in gh-103082.)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.)sys.setrecursionlimit()
andsys.getrecursionlimit()
. The recursion limit now applies only to Python code. Builtin functions do not use the recursion limit, but are protected by a different mechanism that prevents recursion from causing a virtual machine crash.
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.
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.)
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 many 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.)
unicodedata¶
The Unicode database has been updated to version 15.0.0. (Contributed by Benjamin Peterson in gh-96734).
unittest¶
Add a --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 gh-48330)
uuid¶
Add a command-line interface. (Contributed by Adam Chhina in gh-88597.)
Optimizations¶
Remove
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.)Add 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 Donghee 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 Oren 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.)Speed up
super()
method calls and attribute loads via the newLOAD_SUPER_ATTR
instruction. (Contributed by Carl Meyer and Vladimir Matveev in gh-103497.)
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.)Remove the
PRECALL
instruction. (Contributed by Mark Shannon in gh-92925.)Add the
BINARY_SLICE
andSTORE_SLICE
instructions. (Contributed by Mark Shannon in gh-94163.)Add the
CALL_INTRINSIC_1
instructions. (Contributed by Mark Shannon in gh-99005.)Add the
CALL_INTRINSIC_2
instruction. (Contributed by Irit Katriel in gh-101799.)Add the
CLEANUP_THROW
instruction. (Contributed by Brandt Bucher in gh-90997.)Add the
END_SEND
instruction. (Contributed by Mark Shannon in gh-103082.)Add the
LOAD_FAST_AND_CLEAR
instruction as part of the implementation of PEP 709. (Contributed by Carl Meyer in gh-101441.)Add the
LOAD_FAST_CHECK
instruction. (Contributed by Dennis Sweeney in gh-93143.)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.)Add the
LOAD_SUPER_ATTR
instruction. (Contributed by Carl Meyer and Vladimir Matveev in gh-103497.)Add the
RETURN_CONST
instruction. (Contributed by Wenyang Wang in gh-101632.)
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¶
argparse
: The type, choices, and metavar parameters ofargparse.BooleanOptionalAction
are deprecated and will be removed in 3.14. (Contributed by Nikita Sobolev in gh-92248.)ast
: The followingast
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.)-
The child watcher classes
asyncio.MultiLoopChildWatcher
,asyncio.FastChildWatcher
,asyncio.AbstractChildWatcher
andasyncio.SafeChildWatcher
are deprecated and will be removed in Python 3.14. (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.)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.)
calendar
:calendar.January
andcalendar.February
constants are deprecated and replaced bycalendar.JANUARY
andcalendar.FEBRUARY
. (Contributed by Prince Roshan in gh-103636.)collections.abc
: Deprecatedcollections.abc.ByteString
.Use
isinstance(obj, collections.abc.Buffer)
to test ifobj
implements the buffer protocol at runtime. For use in type annotations, either useBuffer
or a union that explicitly specifies the types your code supports (e.g.,bytes | bytearray | memoryview
).ByteString
was originally intended to be an abstract class that would serve as a supertype of bothbytes
andbytearray
. However, since the ABC never had any methods, knowing that an object was an instance ofByteString
never actually told you anything useful about the object. Other common buffer types such asmemoryview
were also never understood as subtypes ofByteString
(either at runtime or by static type checkers).See PEP 688 for more details. (Contributed by Shantanu Jain in gh-91896.)
datetime
: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.)email
: Deprecate the isdst parameter inemail.utils.localtime()
. (Contributed by Alan Williams in gh-72346.)importlib.abc
: Deprecated the following 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.)
itertools
: Deprecate the support for copy, deepcopy, and pickle operations, which is undocumented, inefficient, historically buggy, and inconsistent. This will be removed in 3.14 for a significant reduction in code volume and maintenance burden. (Contributed by Raymond Hettinger in gh-101588.)multiprocessing
: In Python 3.14, the defaultmultiprocessing
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.pkgutil
:pkgutil.find_loader()
andpkgutil.get_loader()
are deprecated and will be removed in Python 3.14; useimportlib.util.find_spec()
instead. (Contributed by Nikita Sobolev in gh-97850.)pty
: The module 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. (Contributed by Soumendra Ganguly and Gregory P. Smith in gh-85984.)os
: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.)On POSIX platforms,
os.fork()
can now raise aDeprecationWarning
when it can detect being called from a multithreaded process. There has always been a fundamental incompatibility with the POSIX platform when doing so. Even if such code appeared to work. We added the warning to raise awareness as issues encountered by code doing this are becoming more frequent. See theos.fork()
documentation for more details along with this discussion on fork being incompatible with threads for why we’re now surfacing this longstanding platform compatibility problem to developers.
When this warning appears due to usage of
multiprocessing
orconcurrent.futures
the fix is to use a differentmultiprocessing
start method such as"spawn"
or"forkserver"
.shutil
: The onerror argument ofshutil.rmtree()
is deprecated; use onexc instead. (Contributed by Irit Katriel in gh-102828.)-
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.)
sys
: Thesys.last_type
,sys.last_value
andsys.last_traceback
fields are deprecated. Usesys.last_exc
instead. (Contributed by Irit Katriel in gh-102778.)tarfile
: Extracting tar archives without specifying filter is deprecated until Python 3.14, when'data'
filter will become the default. See Extraction filters for details.-
typing.Hashable
andtyping.Sized
, aliases forcollections.abc.Hashable
andcollections.abc.Sized
respectively, are deprecated. (gh-94309.)typing.ByteString
, deprecated since Python 3.9, now causes aDeprecationWarning
to be emitted when it is used. (Contributed by Alex Waygood in gh-91896.)
xml.etree.ElementTree
: The module now emitsDeprecationWarning
when testing the truth value of anxml.etree.ElementTree.Element
. Before, the Python implementation emittedFutureWarning
, and the C implementation emitted nothing. (Contributed by Jacob Walls in gh-83122.)The 3-arg signatures (type, value, traceback) of
coroutine throw()
,generator throw()
andasync generator throw()
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.)Setting
__package__
or__cached__
on a module is deprecated, and will cease to be set or taken into consideration by the import system in Python 3.14. (Contributed by Brett Cannon in gh-65961.)The bitwise inversion operator (
~
) on bool is deprecated. It will throw an error in Python 3.16. 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:~int(x)
. (Contributed by Tim Hoffmann in gh-103487.)Accessing
co_lnotab
on code objects was deprecated in Python 3.10 via PEP 626, but it only got a properDeprecationWarning
in 3.12. May be removed in 3.15. (Contributed by Nikita Sobolev in gh-101866.)
Pending removal in Python 3.13¶
Modules (see PEP 594):
aifc
audioop
cgi
cgitb
chunk
crypt
imghdr
mailcap
msilib
nis
nntplib
ossaudiodev
pipes
sndhdr
spwd
sunau
telnetlib
uu
xdrlib
Other modules:
lib2to3
, and the 2to3 program (gh-84540)
APIs:
configparser.LegacyInterpolation
(gh-90765)locale.resetlocale()
(gh-90817)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¶
argparse
: The type, choices, and metavar parameters ofargparse.BooleanOptionalAction
are deprecated and will be removed in 3.14. (Contributed by Nikita Sobolev in gh-92248.)ast
: The following 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.)-
The child watcher classes
asyncio.MultiLoopChildWatcher
,asyncio.FastChildWatcher
,asyncio.AbstractChildWatcher
andasyncio.SafeChildWatcher
are deprecated and will be removed in Python 3.14. (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.)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.)
email
: Deprecated the isdst parameter inemail.utils.localtime()
. (Contributed by Alan Williams in gh-72346.)importlib.abc
deprecated classes: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.)
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.)multiprocessing
: The default 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.pathlib
:is_relative_to()
andrelative_to()
: passing additional arguments is deprecated.pkgutil
:pkgutil.find_loader()
andpkgutil.get_loader()
now raiseDeprecationWarning
; useimportlib.util.find_spec()
instead. (Contributed by Nikita Sobolev in gh-97850.)pty
:master_open()
: usepty.openpty()
.slave_open()
: usepty.openpty()
.
-
version
andversion_info
.execute()
andexecutemany()
if named placeholders are used and parameters is a sequence instead of adict
.
urllib
:urllib.parse.Quoter
is deprecated: it was not intended to be a public API. (Contributed by Gregory P. Smith in gh-88168.)
Pending removal in Python 3.15¶
The import system:
Setting
__cached__
on a module while failing to set__spec__.cached
is deprecated. In Python 3.15,__cached__
will cease to be set or take into consideration by the import system or standard library. (gh-97879)Setting
__package__
on a module while failing to set__spec__.parent
is deprecated. In Python 3.15,__package__
will cease to be set or take into consideration by the import system or standard library. (gh-97879)
-
The undocumented
ctypes.SetPointerType()
function has been deprecated since Python 3.13.
-
The obsolete and rarely used
CGIHTTPRequestHandler
has been deprecated since Python 3.13. No direct replacement exists. Anything is better than CGI to interface a web server with a request handler.The
--cgi
flag to the python -m http.server command-line interface has been deprecated since Python 3.13.
-
load_module()
method: useexec_module()
instead.
-
The
getdefaultlocale()
function has been deprecated since Python 3.11. Its removal was originally planned for Python 3.13 (gh-90817), but has been postponed to Python 3.15. Usegetlocale()
,setlocale()
, andgetencoding()
instead. (Contributed by Hugo van Kemenade in gh-111187.)
-
PurePath.is_reserved()
has been deprecated since Python 3.13. Useos.path.isreserved()
to detect reserved paths on Windows.
-
java_ver()
has been deprecated since Python 3.13. This function is only useful for Jython support, has a confusing API, and is largely untested.
-
The check_home argument of
sysconfig.is_python_build()
has been deprecated since Python 3.12.
-
RLock()
will take no arguments in Python 3.15. Passing any arguments has been deprecated since Python 3.14, as the Python version does not permit any arguments, but the C version allows any number of positional or keyword arguments, ignoring every argument.
-
types.CodeType
: Accessingco_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 3.15. (Contributed by Nikita Sobolev in gh-101866.)
-
The undocumented keyword argument syntax for creating
NamedTuple
classes (for example,Point = NamedTuple("Point", x=int, y=int)
) has been deprecated since Python 3.13. Use the class-based syntax or the functional syntax instead.When using the functional syntax of
TypedDict
s, failing to pass a value to the fields parameter (TD = TypedDict("TD")
) or passingNone
(TD = TypedDict("TD", None)
) has been deprecated since Python 3.13. Useclass TD(TypedDict): pass
orTD = TypedDict("TD", {})
to create a TypedDict with zero field.The
typing.no_type_check_decorator()
decorator function has been deprecated since Python 3.13. After eight years in thetyping
module, it has yet to be supported by any major type checker.
wave
:The
getmark()
,setmark()
, andgetmarkers()
methods of theWave_read
andWave_write
classes have been deprecated since Python 3.13.
-
load_module()
has been deprecated since Python 3.10. Useexec_module()
instead. (Contributed by Jiahao Li in gh-125746.)
Pending removal in Python 3.16¶
The import system:
Setting
__loader__
on a module while failing to set__spec__.loader
is deprecated. In Python 3.16,__loader__
will cease to be set or taken into consideration by the import system or the standard library.
-
The
'u'
format code (wchar_t
) has been deprecated in documentation since Python 3.3 and at runtime since Python 3.13. Use the'w'
format code (Py_UCS4
) for Unicode characters instead.
-
asyncio.iscoroutinefunction()
is deprecated and will be removed in Python 3.16; useinspect.iscoroutinefunction()
instead. (Contributed by Jiahao Li and Kumar Aditya in gh-122875.)asyncio
policy system is deprecated and will be removed in Python 3.16. In particular, the following classes and functions are deprecated:Users should use
asyncio.run()
orasyncio.Runner
with loop_factory to use the desired event loop implementation.For example, to use
asyncio.SelectorEventLoop
on Windows:import asyncio async def main(): ... asyncio.run(main(), loop_factory=asyncio.SelectorEventLoop)
(Contributed by Kumar Aditya in gh-127949.)
-
Bitwise inversion on boolean types,
~True
or~False
has been deprecated since Python 3.12, as it produces surprising and unintuitive results (-2
and-1
). Usenot x
instead for the logical negation of a Boolean. In the rare case that you need the bitwise inversion of the underlying integer, convert toint
explicitly (~int(x)
).
-
Calling the Python implementation of
functools.reduce()
with function or sequence as keyword arguments has been deprecated since Python 3.14.
-
Support for custom logging handlers with the strm argument is deprecated and scheduled for removal in Python 3.16. Define handlers with the stream argument instead. (Contributed by Mariusz Felisiak in gh-115032.)
-
Valid extensions start with a ‘.’ or are empty for
mimetypes.MimeTypes.add_type()
. Undotted extensions are deprecated and will raise aValueError
in Python 3.16. (Contributed by Hugo van Kemenade in gh-75223.)
-
The
ExecError
exception has been deprecated since Python 3.14. It has not been used by any function inshutil
since Python 3.4, and is now an alias ofRuntimeError
.
-
The
Class.get_methods
method has been deprecated since Python 3.14.
sys
:The
_enablelegacywindowsfsencoding()
function has been deprecated since Python 3.13. Use thePYTHONLEGACYWINDOWSFSENCODING
environment variable instead.
-
The
sysconfig.expand_makefile_vars()
function has been deprecated since Python 3.14. Use thevars
argument ofsysconfig.get_paths()
instead.
-
The undocumented and unused
TarFile.tarfile
attribute has been deprecated since Python 3.13.
Pending removal in Python 3.17¶
-
collections.abc.ByteString
is scheduled for removal in Python 3.17.Use
isinstance(obj, collections.abc.Buffer)
to test ifobj
implements the buffer protocol at runtime. For use in type annotations, either useBuffer
or a union that explicitly specifies the types your code supports (e.g.,bytes | bytearray | memoryview
).ByteString
was originally intended to be an abstract class that would serve as a supertype of bothbytes
andbytearray
. However, since the ABC never had any methods, knowing that an object was an instance ofByteString
never actually told you anything useful about the object. Other common buffer types such asmemoryview
were also never understood as subtypes ofByteString
(either at runtime or by static type checkers).See PEP 688 for more details. (Contributed by Shantanu Jain in gh-91896.)
-
Before Python 3.14, old-style unions were implemented using the private class
typing._UnionGenericAlias
. This class is no longer needed for the implementation, but it has been retained for backward compatibility, with removal scheduled for Python 3.17. Users should use documented introspection helpers liketyping.get_origin()
andtyping.get_args()
instead of relying on private implementation details.typing.ByteString
, deprecated since Python 3.9, is scheduled for removal in Python 3.17.Use
isinstance(obj, collections.abc.Buffer)
to test ifobj
implements the buffer protocol at runtime. For use in type annotations, either useBuffer
or a union that explicitly specifies the types your code supports (e.g.,bytes | bytearray | memoryview
).ByteString
was originally intended to be an abstract class that would serve as a supertype of bothbytes
andbytearray
. However, since the ABC never had any methods, knowing that an object was an instance ofByteString
never actually told you anything useful about the object. Other common buffer types such asmemoryview
were also never understood as subtypes ofByteString
(either at runtime or by static type checkers).See PEP 688 for more details. (Contributed by Shantanu Jain in gh-91896.)
Pending removal in future versions¶
The following APIs will be removed in the future, although there is currently no date scheduled for their removal.
-
Nesting argument groups and nesting mutually exclusive groups are deprecated.
Passing the undocumented keyword argument prefix_chars to
add_argument_group()
is now deprecated.The
argparse.FileType
type converter is deprecated.
-
Generators:
throw(type, exc, tb)
andathrow(type, exc, tb)
signature is deprecated: usethrow(exc)
andathrow(exc)
instead, the single argument signature.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)Support for
__index__()
and__int__()
method returning non-int type: these methods will be required to return an instance of a strict subclass ofint
.Support for
__float__()
method returning a strict subclass offloat
: these methods will be required to return an instance offloat
.Support for
__complex__()
method returning a strict subclass ofcomplex
: these methods will be required to return an instance ofcomplex
.Passing a complex number as the real or imag argument in the
complex()
constructor is now deprecated; it should only be passed as a single positional argument. (Contributed by Serhiy Storchaka in gh-109218.)
calendar
:calendar.January
andcalendar.February
constants are deprecated and replaced bycalendar.JANUARY
andcalendar.FEBRUARY
. (Contributed by Prince Roshan in gh-103636.)codecs
: useopen()
instead ofcodecs.open()
. (gh-133038)codeobject.co_lnotab
: use thecodeobject.co_lines()
method instead.-
utcnow()
: usedatetime.datetime.now(tz=datetime.UTC)
.utcfromtimestamp()
: usedatetime.datetime.fromtimestamp(timestamp, tz=datetime.UTC)
.
gettext
: Plural value must be an integer.-
cache_from_source()
debug_override parameter is deprecated: use the optimization parameter instead.
-
EntryPoints
tuple interface.Implicit
None
on return values.
logging
: thewarn()
method has been deprecated since Python 3.3, usewarning()
instead.mailbox
: Use of StringIO input and text mode is deprecated, use BytesIO and binary mode instead.os
: Callingos.register_at_fork()
in multi-threaded process.pydoc.ErrorDuringImport
: A tuple value for exc_info parameter is deprecated, use an exception instance.re
: 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.)sre_compile
,sre_constants
andsre_parse
modules.shutil
:rmtree()
’s onerror parameter is deprecated in Python 3.12; use the onexc parameter instead.ssl
options and protocols:ssl.SSLContext
without protocol argument is deprecated.ssl.SSLContext
:set_npn_protocols()
andselected_npn_protocol()
are deprecated: use ALPN instead.ssl.OP_NO_SSL*
optionsssl.OP_NO_TLS*
optionsssl.PROTOCOL_SSLv3
ssl.PROTOCOL_TLS
ssl.PROTOCOL_TLSv1
ssl.PROTOCOL_TLSv1_1
ssl.PROTOCOL_TLSv1_2
ssl.TLSVersion.SSLv3
ssl.TLSVersion.TLSv1
ssl.TLSVersion.TLSv1_1
threading
methods:threading.Condition.notifyAll()
: usenotify_all()
.threading.Event.isSet()
: useis_set()
.threading.Thread.isDaemon()
,threading.Thread.setDaemon()
: usethreading.Thread.daemon
attribute.threading.Thread.getName()
,threading.Thread.setName()
: usethreading.Thread.name
attribute.threading.currentThread()
: usethreading.current_thread()
.threading.activeCount()
: usethreading.active_count()
.
The internal class
typing._UnionGenericAlias
is no longer used to implementtyping.Union
. To preserve compatibility with users using this private class, a compatibility shim will be provided until at least Python 3.17. (Contributed by Jelle Zijlstra in gh-105499.)unittest.IsolatedAsyncioTestCase
: it is deprecated to return a value that is notNone
from a test case.urllib.parse
deprecated functions:urlparse()
insteadsplitattr()
splithost()
splitnport()
splitpasswd()
splitport()
splitquery()
splittag()
splittype()
splituser()
splitvalue()
to_bytes()
wsgiref
:SimpleHandler.stdout.write()
should not do partial writes.xml.etree.ElementTree
: Testing the truth value of anElement
is deprecated. In a future release it will always returnTrue
. Prefer explicitlen(elem)
orelem is not None
tests instead.sys._clear_type_cache()
is deprecated: usesys._clear_internal_caches()
instead.
Removed¶
asynchat and asyncore¶
configparser¶
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.
distutils¶
ensurepip¶
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.)
enum¶
ftplib¶
gzip¶
Remove the
filename
attribute ofgzip
’sgzip.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.)
hashlib¶
Remove the pure Python implementation of
hashlib
’shashlib.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.)
importlib¶
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
,importlib.util.set_loader
andimportlib.util.module_for_loader
have all been removed. (Contributed by Brett Cannon and Nikita Sobolev in gh-65961 and gh-97850.)Support for
find_loader()
andfind_module()
APIs have been removed. (Contributed by Barry Warsaw in gh-98040.)importlib.abc.Finder
,pkgutil.ImpImporter
, andpkgutil.ImpLoader
have been removed. (Contributed by Barry Warsaw in gh-98040.)
imp¶
The
imp
module has been removed. (Contributed by Barry Warsaw in gh-98040.)To migrate, consult the following correspondence table:
imp
importlib
imp.NullImporter
Insert
None
intosys.path_importer_cache
imp.cache_from_source()
imp.find_module()
imp.get_magic()
imp.get_suffixes()
importlib.machinery.SOURCE_SUFFIXES
,importlib.machinery.EXTENSION_SUFFIXES
, andimportlib.machinery.BYTECODE_SUFFIXES
imp.get_tag()
imp.load_module()
imp.new_module(name)
types.ModuleType(name)
imp.reload()
imp.source_from_cache()
imp.load_source()
See below
Replace
imp.load_source()
with:import importlib.util import importlib.machinery def load_source(modname, filename): loader = importlib.machinery.SourceFileLoader(modname, filename) spec = importlib.util.spec_from_file_location(modname, filename, loader=loader) module = importlib.util.module_from_spec(spec) # The module is always executed and not cached in sys.modules. # Uncomment the following line to cache the module. # sys.modules[module.__name__] = module loader.exec_module(module) return module
Remove
imp
functions and attributes with no replacements:Undocumented functions:
imp.init_builtin()
imp.load_compiled()
imp.load_dynamic()
imp.load_package()
imp.lock_held()
,imp.acquire_lock()
,imp.release_lock()
: the locking scheme has changed in Python 3.3 to per-module locks.imp.find_module()
constants:SEARCH_ERROR
,PY_SOURCE
,PY_COMPILED
,C_EXTENSION
,PY_RESOURCE
,PKG_DIRECTORY
,C_BUILTIN
,PY_FROZEN
,PY_CODERESOURCE
,IMP_HOOK
.
io¶
locale¶
Remove
locale
’slocale.format()
function, deprecated in Python 3.7: uselocale.format_string()
instead. (Contributed by Victor Stinner in gh-94226.)
smtpd¶
sqlite3¶
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.)
ssl¶
Remove
ssl
’sssl.RAND_pseudo_bytes()
function, deprecated in Python 3.6: useos.urandom()
orssl.RAND_bytes()
instead. (Contributed by Victor Stinner in gh-94199.)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
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 the server hostname. Code is subject to CWE 295 (Improper Certificate Validation). (Contributed by Victor Stinner in gh-94199.)
unittest¶
Remove many long-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 3.5).An alias of the
TextTestResult
class:_TextTestResult
(deprecated in Python 3.2).
(Contributed by Serhiy Storchaka in gh-89325.)
webbrowser¶
Remove support for obsolete browsers from
webbrowser
. The removed browsers include: Grail, Mosaic, Netscape, Galeon, Skipstone, Iceape, Firebird, and Firefox versions 35 and below (gh-102871).
xml.etree.ElementTree¶
Remove the
ElementTree.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¶
Others¶
Remove the
suspicious
rule from the documentationMakefile
andDoc/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.)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.)
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.)
Remove
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-integer 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.Remove 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 Donghee 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
,FSTRING_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 '"'
Additionally, there may be some minor behavioral changes as a consequence of the changes required to support PEP 701. Some of these changes include:
The
type
attribute of the tokens emitted when tokenizing some invalid Python characters such as!
has changed fromERRORTOKEN
toOP
.Incomplete single-line strings now also raise
tokenize.TokenError
as incomplete multiline strings do.Some incomplete or invalid Python code now raises
tokenize.TokenError
instead of returning arbitraryERRORTOKEN
tokens when tokenizing it.Mixing tabs and spaces as indentation in the same file is not supported anymore and will raise a
TabError
.
The
threading
module now expects the_thread
module to have an_is_main_interpreter
attribute. It is a function with no arguments that returnsTrue
if the current interpreter is the main interpreter.Any library or application that provides a custom
_thread
module should provide_is_main_interpreter()
. (See gh-112826.)
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 Donghee Na in gh-89536.)
Add
COMPILEALL_OPTS
variable inMakefile
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.Autoconf 2.71 and aclocal 1.16.4 is now required to regenerate
configure
. (Contributed by Christian Heimes in gh-89886.)Windows builds and macOS installers from python.org now use OpenSSL 3.0.
C API Changes¶
New Features¶
PEP 697: Introduce 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: Add an 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.)
Add 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.)
Add 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.)Add 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.)Add
PyType_AddWatcher()
andPyType_Watch()
API to register callbacks to receive notification on changes to a type. (Contributed by Carl Meyer in gh-91051.)Add
PyCode_AddWatcher()
andPyCode_ClearWatcher()
APIs to register callbacks to receive notification on creation and destruction of code objects. (Contributed by Itamar Oren 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: Introduce Immortal Objects, which allows objects to bypass reference counts, and related 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.)
PEP 684: Add the new
Py_NewInterpreterFromConfig()
function andPyInterpreterConfig
, which may be used to create sub-interpreters with their own GILs. (See PEP 684: A Per-Interpreter GIL for more info.) (Contributed by Eric Snow in gh-104110.)In the limited C API version 3.12,
Py_INCREF()
andPy_DECREF()
functions are now implemented as opaque function calls to hide implementation details. (Contributed by Victor Stinner in gh-105387.)
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.)Fix 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
must 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 compatibility. 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
(__new__()
in Python).Since
tp_new
overrides almost everythingPyType_From*
functions do, the two are incompatible with each other. The existing behavior – ignoring the metaclass for several steps of type creation – is unsafe in general, since (meta)classes assume thattp_new
was called. There is no simple general workaround. One of the following may work for you:If you control the metaclass, avoid using
tp_new
in it:If initialization can be skipped, it can be done in
tp_init
instead.If the metaclass doesn’t need to be instantiated from Python, set its
tp_new
toNULL
using thePy_TPFLAGS_DISALLOW_INSTANTIATION
flag. This makes it acceptable forPyType_From*
functions.
Avoid
PyType_From*
functions: if you don’t need C-specific features (slots or setting the instance size), create types by calling the metaclass.If you know the
tp_new
can be skipped safely, filter the deprecation warning out usingwarnings.catch_warnings()
from Python.
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.
PyLongObject
has had its internals changed for better performance. Although the internals ofPyLongObject
are private, they are used by some extension modules. The internal fields should no longer be accessed directly, instead the API functions beginningPyLong_...
should be used instead. Two new unstable API functions are provided for efficient access to the value ofPyLongObject
s which fit into a single machine word:Custom allocators, set via
PyMem_SetAllocator()
, are now required to be thread-safe, regardless of memory domain. Allocators that don’t have their own state, including “hooks”, are not affected. If your custom allocator is not already thread-safe and you need guidance then please create a new GitHub issue and CC@ericsnowcurrently
.
Deprecated¶
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.)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_HasFileSystemDefaultEncoding
: 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
with mutable bases is deprecated and will be disabled in Python 3.14. (gh-95388)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.
Pending removal in Python 3.14¶
The
ma_version_tag
field inPyDictObject
for extension modules (PEP 699; gh-101193).Creating
immutable types
with mutable bases (gh-95388).
Pending removal in Python 3.15¶
The
PyImport_ImportModuleNoBlock()
: UsePyImport_ImportModule()
instead.PyWeakref_GetObject()
andPyWeakref_GET_OBJECT()
: UsePyWeakref_GetRef()
instead. The pythoncapi-compat project can be used to getPyWeakref_GetRef()
on Python 3.12 and older.Py_UNICODE
type and thePy_UNICODE_WIDE
macro: Usewchar_t
instead.PyUnicode_AsDecodedObject()
: UsePyCodec_Decode()
instead.PyUnicode_AsDecodedUnicode()
: UsePyCodec_Decode()
instead; Note that some codecs (for example, “base64”) may return a type other thanstr
, such asbytes
.PyUnicode_AsEncodedObject()
: UsePyCodec_Encode()
instead.PyUnicode_AsEncodedUnicode()
: UsePyCodec_Encode()
instead; Note that some codecs (for example, “base64”) may return a type other thanbytes
, such asstr
.Python initialization functions, deprecated in Python 3.13:
Py_GetPath()
: UsePyConfig_Get("module_search_paths")
(sys.path
) instead.Py_GetPrefix()
: UsePyConfig_Get("base_prefix")
(sys.base_prefix
) instead. UsePyConfig_Get("prefix")
(sys.prefix
) if virtual environments need to be handled.Py_GetExecPrefix()
: UsePyConfig_Get("base_exec_prefix")
(sys.base_exec_prefix
) instead. UsePyConfig_Get("exec_prefix")
(sys.exec_prefix
) if virtual environments need to be handled.Py_GetProgramFullPath()
: UsePyConfig_Get("executable")
(sys.executable
) instead.Py_GetProgramName()
: UsePyConfig_Get("executable")
(sys.executable
) instead.Py_GetPythonHome()
: UsePyConfig_Get("home")
or thePYTHONHOME
environment variable instead.
The pythoncapi-compat project can be used to get
PyConfig_Get()
on Python 3.13 and older.Functions to configure Python’s initialization, deprecated in Python 3.11:
PySys_SetArgvEx()
: SetPyConfig.argv
instead.PySys_SetArgv()
: SetPyConfig.argv
instead.Py_SetProgramName()
: SetPyConfig.program_name
instead.Py_SetPythonHome()
: SetPyConfig.home
instead.PySys_ResetWarnOptions()
: Clearsys.warnoptions
andwarnings.filters
instead.
The
Py_InitializeFromConfig()
API should be used withPyConfig
instead.Global configuration variables:
Py_DebugFlag
: UsePyConfig.parser_debug
orPyConfig_Get("parser_debug")
instead.Py_VerboseFlag
: UsePyConfig.verbose
orPyConfig_Get("verbose")
instead.Py_QuietFlag
: UsePyConfig.quiet
orPyConfig_Get("quiet")
instead.Py_InteractiveFlag
: UsePyConfig.interactive
orPyConfig_Get("interactive")
instead.Py_InspectFlag
: UsePyConfig.inspect
orPyConfig_Get("inspect")
instead.Py_OptimizeFlag
: UsePyConfig.optimization_level
orPyConfig_Get("optimization_level")
instead.Py_NoSiteFlag
: UsePyConfig.site_import
orPyConfig_Get("site_import")
instead.Py_BytesWarningFlag
: UsePyConfig.bytes_warning
orPyConfig_Get("bytes_warning")
instead.Py_FrozenFlag
: UsePyConfig.pathconfig_warnings
orPyConfig_Get("pathconfig_warnings")
instead.Py_IgnoreEnvironmentFlag
: UsePyConfig.use_environment
orPyConfig_Get("use_environment")
instead.Py_DontWriteBytecodeFlag
: UsePyConfig.write_bytecode
orPyConfig_Get("write_bytecode")
instead.Py_NoUserSiteDirectory
: UsePyConfig.user_site_directory
orPyConfig_Get("user_site_directory")
instead.Py_UnbufferedStdioFlag
: UsePyConfig.buffered_stdio
orPyConfig_Get("buffered_stdio")
instead.Py_HashRandomizationFlag
: UsePyConfig.use_hash_seed
andPyConfig.hash_seed
orPyConfig_Get("hash_seed")
instead.Py_IsolatedFlag
: UsePyConfig.isolated
orPyConfig_Get("isolated")
instead.Py_LegacyWindowsFSEncodingFlag
: UsePyPreConfig.legacy_windows_fs_encoding
orPyConfig_Get("legacy_windows_fs_encoding")
instead.Py_LegacyWindowsStdioFlag
: UsePyConfig.legacy_windows_stdio
orPyConfig_Get("legacy_windows_stdio")
instead.Py_FileSystemDefaultEncoding
,Py_HasFileSystemDefaultEncoding
: UsePyConfig.filesystem_encoding
orPyConfig_Get("filesystem_encoding")
instead.Py_FileSystemDefaultEncodeErrors
: UsePyConfig.filesystem_errors
orPyConfig_Get("filesystem_errors")
instead.Py_UTF8Mode
: UsePyPreConfig.utf8_mode
orPyConfig_Get("utf8_mode")
instead. (seePy_PreInitialize()
)
The
Py_InitializeFromConfig()
API should be used withPyConfig
to set these options. OrPyConfig_Get()
can be used to get these options at runtime.
Pending removal in Python 3.16¶
The bundled copy of
libmpdec
.
Pending removal in future versions¶
The following APIs are deprecated and will be removed, although there is currently no date scheduled for their removal.
Py_TPFLAGS_HAVE_FINALIZE
: Unneeded since Python 3.8.PyErr_Fetch()
: UsePyErr_GetRaisedException()
instead.PyErr_NormalizeException()
: UsePyErr_GetRaisedException()
instead.PyErr_Restore()
: UsePyErr_SetRaisedException()
instead.PyModule_GetFilename()
: UsePyModule_GetFilenameObject()
instead.PyOS_AfterFork()
: UsePyOS_AfterFork_Child()
instead.PySlice_GetIndicesEx()
: UsePySlice_Unpack()
andPySlice_AdjustIndices()
instead.PyUnicode_READY()
: Unneeded since Python 3.12PyErr_Display()
: UsePyErr_DisplayException()
instead._PyErr_ChainExceptions()
: Use_PyErr_ChainExceptions1()
instead.PyBytesObject.ob_shash
member: callPyObject_Hash()
instead.Thread Local Storage (TLS) API:
PyThread_create_key()
: UsePyThread_tss_alloc()
instead.PyThread_delete_key()
: UsePyThread_tss_free()
instead.PyThread_set_key_value()
: UsePyThread_tss_set()
instead.PyThread_get_key_value()
: UsePyThread_tss_get()
instead.PyThread_delete_key_value()
: UsePyThread_tss_delete()
instead.PyThread_ReInitTLS()
: Unneeded since Python 3.7.
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.)