
****************************
  What's new in Python 3.16
****************************

:Editor: TBD

.. Rules for maintenance:

   * Anyone can add text to this document.  Do not spend very much time
   on the wording of your changes, because your text will probably
   get rewritten to some degree.

   * The maintainer will go through Misc/NEWS periodically and add
   changes; it's therefore more important to add your changes to
   Misc/NEWS than to this file.

   * This is not a complete list of every single change; completeness
   is the purpose of Misc/NEWS.  Some changes I consider too small
   or esoteric to include.  If such a change is added to the text,
   I'll just remove it.  (This is another reason you shouldn't spend
   too much time on writing your addition.)

   * If you want to draw your new text to the attention of the
   maintainer, add 'XXX' to the beginning of the paragraph or
   section.

   * It's OK to just add a fragmentary note about a change.  For
   example: "XXX Describe the transmogrify() function added to the
   socket module."  The maintainer will research the change and
   write the necessary text.

   * You can comment out your additions if you like, but it's not
   necessary (especially when a final release is some months away).

   * Credit the author of a patch or bugfix.   Just the name is
   sufficient; the e-mail address isn't necessary.

   * It's helpful to add the issue number as a comment:

   XXX Describe the transmogrify() function added to the socket
   module.
   (Contributed by P.Y. Developer in :gh:`12345`.)

   This saves the maintainer the effort of going through the VCS log
   when researching a change.

This article explains the new features in Python 3.16, compared to 3.15.

For full details, see the :ref:`changelog <changelog>`.

.. note::

   Prerelease users should be aware that this document is currently in draft
   form. It will be updated substantially as Python 3.16 moves towards release,
   so it's worth checking back even after reading earlier versions.


Summary --- release highlights
==============================

.. This section singles out the most important changes in Python 3.16.
   Brevity is key.


.. PEP-sized items next.



New features
============



Other language changes
======================



New modules
===========

* None yet.


Improved modules
================

curses
------

* The :mod:`curses` character-cell window methods now accept a full character
  cell --- a spacing character optionally followed by combining characters ---
  in addition to a single integer or byte character.  This affects
  :meth:`~curses.window.addch`, :meth:`~curses.window.bkgd`,
  :meth:`~curses.window.bkgdset`, :meth:`~curses.window.border`,
  :meth:`~curses.window.box`, :meth:`~curses.window.echochar`,
  :meth:`~curses.window.hline`, :meth:`~curses.window.insch` and
  :meth:`~curses.window.vline`.
  Also add the wide-character read methods :meth:`~curses.window.get_wstr` and
  :meth:`~curses.window.in_wstr`, the counterparts of
  :meth:`~curses.window.getstr` and :meth:`~curses.window.instr` that return a
  :class:`str` rather than :class:`bytes`,
  and the module functions :func:`curses.erasewchar`, :func:`curses.killwchar`
  and :func:`curses.wunctrl`, the wide-character counterparts of
  :func:`curses.erasechar`, :func:`curses.killchar` and :func:`curses.unctrl`.
  These features are only available when built against the wide-character
  ncursesw library.
  (Contributed by Serhiy Storchaka in :gh:`151757`.)

* Add :func:`curses.nofilter`, which undoes the effect of :func:`curses.filter`.
  (Contributed by Serhiy Storchaka in :gh:`151744`.)

gzip
----

* :func:`gzip.open` now accepts an optional argument ``mtime``
  which is passed on to the constructor of the :class:`~gzip.GzipFile` class.
  (Contributed by Marin Misur in :gh:`91372`.)


logging
-------

* :class:`~logging.handlers.TimedRotatingFileHandler` now uses the creation
  time instead of the last modification time of an existing log file as
  the basis for the first rotation after handler creation, if supported by
  the OS and file system.
  This allows it to be used in short-running programs that start and end
  before the rotation interval expires.
  (Contributed by Iván Márton and Serhiy Storchaka in :gh:`84649`.)


lzma
----

* Add support of new BCJ filters ARM64 and RISC-V via
  :const:`!lzma.FILTER_ARM64` and :const:`!lzma.FILTER_RISCV`.  Note that the
  new filters will work only if the runtime library supports them. ARM64 filter
  requires ``lzma`` 5.4.0 or newer while RISC-V requires 5.6.0 or newer.
  (Contributed by Chien Wong in :gh:`115988`.)


math
----

* Added trigonometric functions that work in units of half turns, rather than
  radians. The new functions :func:`math.acospi`, :func:`math.asinpi`,
  :func:`math.atanpi`, and :func:`math.atan2pi` return half-turn angles. The
  new functions :func:`math.cospi`, :func:`math.sinpi`, and :func:`math.tanpi`
  take half-turn angle arguments. These functions are recommended by IEEE
  754-2019 and standardized in C23.
  (Contributed by Jeff Epler in :gh:`150534`.)


os
--

* Add :func:`os.pidfd_getfd` for duplicating a file descriptor from another
  process via a pidfd.  Available on Linux 5.6+.
  (Contributed by Maurycy Pawłowski-Wieroński in :gh:`149464`.)


shlex
-----

* Add keyword-only parameter *force* to :func:`shlex.quote` to force quoting
  a string, even if it is already safe for a shell without being quoted.
  (Contributed by Jay Berry in :gh:`148846`.)


tkinter
-------

* Added many :class:`tkinter.ttk.Treeview` methods wrapping the enhanced
  ``ttk::treeview`` widget commands from Tk 9.1, such as
  :meth:`~tkinter.ttk.Treeview.sort`, :meth:`~tkinter.ttk.Treeview.search`,
  :meth:`~tkinter.ttk.Treeview.expand`, :meth:`~tkinter.ttk.Treeview.collapse`,
  :meth:`~tkinter.ttk.Treeview.hide`, :meth:`~tkinter.ttk.Treeview.unhide`, and
  methods for cell focus, selection and tagging.  The
  :meth:`~tkinter.ttk.Treeview.expand` and :meth:`~tkinter.ttk.Treeview.collapse`
  methods (without recursion) also work on Tk older than 9.1.
  (Contributed by Serhiy Storchaka in :gh:`151910`.)

* Added new :class:`!tkinter.Text` methods :meth:`~tkinter.Text.edit_canundo`
  and :meth:`~tkinter.Text.edit_canredo` which return whether an undo or redo
  is possible.
  (Contributed by Serhiy Storchaka in :gh:`151674`.)

* Added new :class:`!tkinter.Text` methods :meth:`~tkinter.Text.sync` and
  :meth:`~tkinter.Text.pendingsync` which control and report the
  synchronization of the displayed view with the underlying text.
  (Contributed by Serhiy Storchaka in :gh:`151675`.)

* Added the :meth:`ttk.Style.theme_styles
  <tkinter.ttk.Style.theme_styles>` method which returns the list of styles
  defined in a theme.
  (Contributed by Serhiy Storchaka in :gh:`151920`.)

* Added new :class:`!tkinter.Canvas` methods :meth:`~tkinter.Canvas.rchars`
  which replaces the text or coordinates of canvas items, and
  :meth:`~tkinter.Canvas.rotate` which rotates the coordinates of canvas items.
  (Contributed by Serhiy Storchaka in :gh:`151876`.)

* Added a :meth:`!validate` method to the :class:`!tkinter.Entry` and
  :class:`!tkinter.Spinbox` widgets, which forces an evaluation of the
  validation command.
  (Contributed by Serhiy Storchaka in :gh:`151878`.)

* Added the :meth:`tkinter.Menu.postcascade` method, and the
  :meth:`~tkinter.Misc.tk_scaling` and :meth:`~tkinter.Misc.tk_inactive`
  methods which respectively query or set the display scaling factor and
  report the user idle time.
  (Contributed by Serhiy Storchaka in :gh:`151881`.)

* Added new window-management methods :meth:`~tkinter.Misc.winfo_isdark`
  (dark mode detection), :meth:`~tkinter.Wm.wm_iconbadge` (application icon
  badge) and :meth:`~tkinter.Wm.wm_stackorder` (toplevel stacking order).
  (Contributed by Serhiy Storchaka in :gh:`151874`.)

* Added the :meth:`~tkinter.Misc.tk_appname`,
  :meth:`~tkinter.Misc.tk_useinputmethods` and :meth:`~tkinter.Misc.tk_caret`
  methods, exposing the application send name, the X Input Methods state and
  the input method caret location.
  (Contributed by Serhiy Storchaka in :gh:`151886`.)

* Added support for more options in :class:`!tkinter.PhotoImage` methods: the
  *format* parameter of :meth:`~tkinter.PhotoImage.put`, the *metadata*
  parameter of :meth:`~tkinter.PhotoImage.put`, :meth:`~tkinter.PhotoImage.read`,
  :meth:`~tkinter.PhotoImage.write` and :meth:`~tkinter.PhotoImage.data`, and
  the *withalpha* parameter of :meth:`~tkinter.PhotoImage.get`.
  (Contributed by Serhiy Storchaka in :gh:`151890`.)

* Added the :meth:`~tkinter.PhotoImage.redither` method which recalculates the
  dithered image when its data was supplied in pieces.
  (Contributed by Serhiy Storchaka in :gh:`151888`.)

* :class:`tkinter.OptionMenu` now accepts arbitrary :class:`!tkinter.Menubutton`
  options as keyword arguments, which can also override its default appearance.
  (Contributed by Serhiy Storchaka in :gh:`101284`.)

* The :mod:`tkinter.simpledialog` dialogs were modernized to match the look
  and feel of the native Tk dialogs.
  :class:`!tkinter.simpledialog.SimpleDialog` and the
  :func:`~tkinter.simpledialog.askinteger`,
  :func:`~tkinter.simpledialog.askfloat` and
  :func:`~tkinter.simpledialog.askstring` dialogs are now built from the themed
  :mod:`tkinter.ttk` widgets instead of the classic :mod:`tkinter` widgets;
  the :class:`!tkinter.simpledialog.Dialog` base class still defaults to the
  classic widgets for compatibility.  Both :class:`!Dialog` and
  :class:`!SimpleDialog` gained a *use_ttk* parameter that selects between the
  classic Tk widgets and the themed ttk widgets.  :class:`!SimpleDialog` also
  gained *bitmap* and
  *detail* parameters, draws the standard icons with themed images in the
  ttk version, and accepts mappings of button options as *buttons* entries.
  (Contributed by Serhiy Storchaka in :gh:`59396`.)

xml
---

* Add support for multiple multi-byte encodings in the :mod:`XML parser
  <xml.parsers.expat>`: "cp932", "cp949", "cp950", "Big5", "EUC-JP",
  "GB2312", "GBK", "johab", and "Shift_JIS".
  Add partial support (only BMP characters) for multi-byte encodings
  "Big5-HKSCS", "EUC_JIS-2004", "EUC_JISX0213", "Shift_JIS-2004",
  "Shift_JISX0213", "utf-8-sig" and non-standard aliases like "UTF8"
  (without hyphen).
  The parser now raises :exc:`ValueError` for known unsupported
  multi-byte encodings such as "ISO-2022-JP" or "raw-unicode-escape"
  instead of failing later, when encountering non-ASCII data.
  (Contributed by Serhiy Storchaka in :gh:`62259`.)

zipfile
-------

* Add :meth:`ZipFile.remove() <zipfile.ZipFile.remove>` to remove a member
  from an archive's central directory, and
  :meth:`ZipFile.repack() <zipfile.ZipFile.repack>` to reclaim the space used
  by the local file entries of removed members.
  (Contributed by Danny Lin in :gh:`51067`.)

.. Add improved modules above alphabetically, not here at the end.

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

re
--

* Character class escapes (``\d``, ``\D``, ``\s``, ``\S``, ``\w`` and ``\W``)
  outside a character set are now compiled to a single ``CATEGORY`` opcode
  instead of being wrapped in an ``IN`` block.  This speeds up matching of
  patterns such as ``\d+`` and reduces the size of the compiled byte code.
  (Contributed by Serhiy Storchaka in :gh:`152033`.)

module_name
-----------

* TODO



Removed
=======

annotationlib
-------------

* The :meth:`!annotationlib.ForwardRef._evaluate` method
  which has been deprecated since Python 3.14.
  Use :meth:`annotationlib.ForwardRef.evaluate`
  or :func:`typing.evaluate_forward_ref` instead.

array
-----

* The ``'u'`` format code (:c:type:`wchar_t`) which has been deprecated in
  documentation since Python 3.3 and at runtime since Python 3.13.
  Use ``'w'`` format code instead (:c:type:`Py_UCS4`, always 4 bytes).

asyncio
-------

* The :func:`!asyncio.iscoroutinefunction`
  which has been deprecated since Python 3.14.
  Use :func:`inspect.iscoroutinefunction` instead.

functools
---------

* Calling the Python implementation of :func:`functools.reduce` with *function*
  or *sequence* as keyword arguments has been deprecated since Python 3.14.

logging
-------

* 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.

mimetypes
---------

* Valid extensions start with a '.' or are empty for
  :meth:`mimetypes.MimeTypes.add_type`.
  Undotted extensions now raise a :exc:`ValueError`.

shutil
------

* The :exc:`!ExecError` exception which has been deprecated since Python 3.14.
  It has not been used by any function in :mod:`!shutil` since Python 3.4.
  (Contributed by Stan Ulbrych in :gh:`149567`.)

symtable
--------

* The :meth:`!symtable.Class.get_methods` method
  which has been deprecated since Python 3.14.

sys
---

* The :func:`!_enablelegacywindowsfsencoding` function
  which has been deprecated since Python 3.13.
  Use the :envvar:`PYTHONLEGACYWINDOWSFSENCODING` environment variable instead.
  (Contributed by Stan Ulbrych in :gh:`149595`.)

sysconfig
---------

* The :func:`!sysconfig.expand_makefile_vars` function
  which has been deprecated since Python 3.14.
  Use the ``vars`` argument of :func:`sysconfig.get_paths` instead.
  (Contributed by Stan Ulbrych in :gh:`149499`.)

tarfile
-------

* The undocumented and unused :attr:`!tarfile.TarFile.tarfile` attribute
  has been deprecated since Python 3.13.

.. Add removals above alphabetically, not here at the end.


Deprecated
==========

New deprecations
----------------

* :mod:`abc`

  * Soft-deprecated since Python 3.3 :class:`abc.abstractclassmethod`,
    :class:`abc.abstractstaticmethod`, and :class:`abc.abstractproperty`
    now raise a :exc:`DeprecationWarning`.
    These classes will be removed in Python 3.21, instead
    use :func:`abc.abstractmethod` with :func:`classmethod`,
    :func:`staticmethod`, and :class:`property` respectively.

* :mod:`ast`:

  * Classes ``slice``, ``Index``, ``ExtSlice``, ``Suite``, ``Param``,
    ``AugLoad`` and ``AugStore``, deprecated since Python 3.9, are no longer
    imported by ``from ast import *`` and issue a deprecation warning on
    use. The classes are slated for removal in Python 3.21. These types are not
    generated by the parser or accepted by the code generator.
  * The ``dims`` property of ``ast.Tuple`` objects, deprecated since Python
    3.9, now issues a deprecation warning on use. This property is slated for
    removal in 3.21. Use ``ast.Tuple.elts`` instead.

.. Add deprecations above alphabetically, not here at the end.

.. include:: ../deprecations/pending-removal-in-3.17.rst

.. include:: ../deprecations/pending-removal-in-3.18.rst

.. include:: ../deprecations/pending-removal-in-3.19.rst

.. include:: ../deprecations/pending-removal-in-3.20.rst

.. include:: ../deprecations/pending-removal-in-3.21.rst

.. include:: ../deprecations/pending-removal-in-future.rst


Porting to Python 3.16
======================

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


Build changes
=============

* Remove the bundled copy of the libmpdec_ decimal library from the CPython source tree
  to simplify maintenance and updates. The :mod:`decimal` module will now
  unconditionally use the system's libmpdec decimal library. Also remove the
  now unused :option:`!--with-system-libmpdec` :program:`configure` flag.
  This change has no impact on binary releases of Python, which have been
  built against a separate copy of libmpdec for the past several releases.

  (Contributed by Sergey B Kirpichev in :gh:`115119`.)

  .. _libmpdec: https://www.bytereef.org/mpdecimal/

* Add a :option:`--with-build-details-suffix` configure flag to allow
  Linux distributions that co-install multiple versions of Python in the
  same tree to avoid ``build-details.json`` clashes.

  (Contributed by Stefano Rivera in :gh:`131372`.)


C API changes
=============

New features
------------

* TODO

Porting to Python 3.16
----------------------

* TODO

Deprecated C APIs
-----------------

* :c:func:`PyGen_New`, :c:func:`PyGen_NewWithQualName`, :c:func:`PyCoro_New`,
  and :c:func:`PyAsyncGen_New` are deprecated.
  They are scheduled for removal in 3.18.

.. Add C API deprecations above alphabetically, not here at the end.

.. include:: ../deprecations/c-api-pending-removal-in-3.18.rst

.. include:: ../deprecations/c-api-pending-removal-in-3.19.rst

.. include:: ../deprecations/c-api-pending-removal-in-3.20.rst

.. include:: ../deprecations/c-api-pending-removal-in-future.rst

Removed C APIs
--------------
