What's New In Python 3.14
*************************

Editor:
   TBD

This article explains the new features in Python 3.14, compared to
3.13.

For full details, see the changelog.

Nota:

  Prerelease users should be aware that this document is currently in
  draft form. It will be updated substantially as Python 3.14 moves
  towards release, so it's worth checking back even after reading
  earlier versions.


Summary -- Release highlights
=============================


New Features
============


Other Language Changes
======================


New Modules
===========

* None yet.


Improved Modules
================


ast
---

Added "ast.compare()" for comparing two ASTs. (Contributed by Batuhan
Taskaya and Jeremy Hylton in bpo-15987.)


os
--

* Added the "os.environ.refresh()" method to update "os.environ" with
  changes to the environment made by "os.putenv()", by
  "os.unsetenv()", or made outside Python in the same process.
  (Contributed by Victor Stinner in gh-120057.)


pathlib
-------

* Add "pathlib.Path.copy()", which copies the content of one file to
  another, like "shutil.copyfile()". (Contributed by Barney Gale in
  gh-73991.)

* Add "pathlib.Path.copytree()", which copies one directory tree to
  another. (Contributed by Barney Gale in gh-73991.)


symtable
--------

* Expose the following "symtable.Symbol" methods:

  * "is_free_class()"

  * "is_comp_iter()"

  * "is_comp_cell()"

  (Contributed by Bénédikt Tran in gh-120029.)


Optimizations
=============


asyncio
-------

* "asyncio" now uses double linked list implementation for native
  tasks which speeds up execution by 10% on standard pyperformance
  benchmarks and reduces memory usage. (Contributed by Kumar Aditya in
  gh-107803.)


Deprecated
==========

* 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.)

* *Soft deprecate* "os.popen()" and "os.spawn*" functions. They should
  no longer be used to write new code.  The "subprocess" module is
  recommended instead. (Contributed by Victor Stinner in gh-120743.)


Removed
=======


argparse
--------

* Remove the *type*, *choices*, and *metavar* parameters of
  "argparse.BooleanOptionalAction". They were deprecated since 3.12.


ast
---

* Remove the following classes. They were all deprecated since Python
  3.8, and have emitted deprecation warnings since Python 3.12:

  * "ast.Num"

  * "ast.Str"

  * "ast.Bytes"

  * "ast.NameConstant"

  * "ast.Ellipsis"

  Use "ast.Constant" instead. As a consequence of these removals,
  user-defined "visit_Num", "visit_Str", "visit_Bytes",
  "visit_NameConstant" and "visit_Ellipsis" methods on custom
  "ast.NodeVisitor" subclasses will no longer be called when the
  "NodeVisitor" subclass is visiting an AST. Define a "visit_Constant"
  method instead.

  Also, remove the following deprecated properties on "ast.Constant",
  which were present for compatibility with the now-removed AST
  classes:

  * "ast.Constant.n"

  * "ast.Constant.s"

  Use "ast.Constant.value" instead.

  (Contributed by Alex Waygood in gh-119562.)


asyncio
-------

* Remove the following classes and functions. They were all deprecated
  and emitted deprecation warnings since Python 3.12:

  * "asyncio.AbstractChildWatcher"

  * "asyncio.SafeChildWatcher"

  * "asyncio.MultiLoopChildWatcher"

  * "asyncio.FastChildWatcher"

  * "asyncio.ThreadedChildWatcher"

  * "asyncio.PidfdChildWatcher"

  * "asyncio.AbstractEventLoopPolicy.get_child_watcher()"

  * "asyncio.AbstractEventLoopPolicy.set_child_watcher()"

  * "asyncio.get_child_watcher()"

  * "asyncio.set_child_watcher()"

  (Contributed by Kumar Aditya in gh-120804.)


collections.abc
---------------

* Remove "collections.abc.ByteString". It had previously raised a
  "DeprecationWarning" since Python 3.12.


email
-----

* Remove the *isdst* parameter from "email.utils.localtime()".
  (Contributed by Hugo van Kemenade in gh-118798.)


importlib
---------

* Remove deprecated "importlib.abc" classes:

  * "importlib.abc.ResourceReader"

  * "importlib.abc.Traversable"

  * "importlib.abc.TraversableResources"

  Use "importlib.resources.abc" classes instead:

  * "importlib.resources.abc.Traversable"

  * "importlib.resources.abc.TraversableResources"

  (Contributed by Jason R. Coombs and Hugo van Kemenade in gh-93963.)


itertools
---------

* Remove "itertools" support for copy, deepcopy, and pickle
  operations. These had previously raised a "DeprecationWarning" since
  Python 3.12. (Contributed by Raymond Hettinger in gh-101588.)


pathlib
-------

* Remove support for passing additional keyword arguments to
  "pathlib.Path". In previous versions, any such arguments are
  ignored.

* Remove support for passing additional positional arguments to
  "pathlib.PurePath.relative_to()" and "is_relative_to()". In previous
  versions, any such arguments are joined onto *other*.


pty
~~~

* Remove deprecated "pty.master_open()" and "pty.slave_open()". They
  had previously raised a "DeprecationWarning" since Python 3.12. Use
  "pty.openpty()" instead. (Contributed by Nikita Sobolev in
  gh-118824.)


sqlite3
-------

* Remove "version" and "version_info" from "sqlite3". (Contributed by
  Hugo van Kemenade in gh-118924.)

* Disallow using a sequence of parameters with named placeholders.
  This had previously raised a "DeprecationWarning" since Python 3.12;
  it will now raise a "sqlite3.ProgrammingError". (Contributed by
  Erlend E. Aasland in gh-118928 and gh-101693.)


typing
------

* Remove "typing.ByteString". It had previously raised a
  "DeprecationWarning" since Python 3.12.


urllib
------

* Remove deprecated "Quoter" class from "urllib.parse". It had
  previously raised a "DeprecationWarning" since Python 3.11.
  (Contributed by Nikita Sobolev in gh-118827.)


Others
------

* Using "NotImplemented" in a boolean context will now raise a
  "TypeError". It had previously raised a "DeprecationWarning" since
  Python 3.9. (Contributed by Jelle Zijlstra in gh-118767.)

* The "int()" built-in no longer delegates to "__trunc__()". Classes
  that want to support conversion to integer must implement either
  "__int__()" or "__index__()". (Contributed by Mark Dickinson in
  gh-119743.)


Porting to Python 3.14
======================

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


Build Changes
=============


C API Changes
=============


New Features
------------

* Add "PyLong_GetSign()" function to get the sign of "int" objects.
  (Contributed by Sergey B Kirpichev in gh-116560.)

* Add a new "PyUnicodeWriter" API to create a Python "str" object:

  * "PyUnicodeWriter_Create()".

  * "PyUnicodeWriter_Discard()".

  * "PyUnicodeWriter_Finish()".

  * "PyUnicodeWriter_WriteChar()".

  * "PyUnicodeWriter_WriteUTF8()".

  * "PyUnicodeWriter_WriteUCS4()".

  * "PyUnicodeWriter_WriteWideChar()".

  * "PyUnicodeWriter_WriteStr()".

  * "PyUnicodeWriter_WriteRepr()".

  * "PyUnicodeWriter_WriteSubstring()".

  * "PyUnicodeWriter_Format()".

  * "PyUnicodeWriter_DecodeUTF8Stateful()".

  (Contributed by Victor Stinner in gh-119182.)


Porting to Python 3.14
----------------------

* In the limited C API 3.14 and newer, "Py_TYPE()" is now implemented
  as an opaque function call to hide implementation details.
  (Contributed by Victor Stinner in gh-120600.)


Deprecated
----------

* Macros "Py_IS_NAN", "Py_IS_INFINITY" and "Py_IS_FINITE" are *soft
  deprecated*, use instead "isnan", "isinf" and "isfinite" available
  from "math.h" since C99.  (Contributed by Sergey B Kirpichev in
  gh-119613.)


Removed
-------

* Creating "immutable types" with mutable bases was deprecated since
  3.12 and now raises a "TypeError".
