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

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

• None yet.

• Add support for multiple terminals to the :mod:`curses` module: the new functions :func:`curses.newterm`, :func:`curses.set_term` and :func:`curses.new_prescr`, the corresponding :ref:`screen <curses-screen-objects>` object, and the :meth:`window.use() <curses.window.use>` method. (Contributed by Serhiy Storchaka in :gh:`90092`.)
• 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`.)
• Add the :mod:`curses` functions :func:`curses.alloc_pair`, :func:`curses.find_pair`, :func:`curses.free_pair` and :func:`curses.reset_color_pairs` for dynamic color-pair management, available when built against a wide-character ncurses with extended-color support. (Contributed by Serhiy Storchaka in :gh:`151774`.)
• Add :mod:`curses` functions and window methods that report state which could previously only be set, such as :meth:`curses.window.is_keypad`, :meth:`curses.window.getparent` and :func:`curses.is_cbreak`, available when built against an ncurses with NCURSES_EXT_FUNCS. (Contributed by Serhiy Storchaka in :gh:`151776`.)
• Add the :mod:`curses` window methods :meth:`~curses.window.attr_get`, :meth:`~curses.window.attr_set`, :meth:`~curses.window.attr_on`, :meth:`~curses.window.attr_off` and :meth:`~curses.window.color_set`, which pass the color pair as a separate argument instead of packing it into the attribute value, and the corresponding WA_* attribute constants. (Contributed by Serhiy Storchaka in :gh:`152219`.)
• Add the :class:`curses.complexchar` type, representing a styled wide-character cell (its text, attributes and color pair), and the window methods :meth:`~curses.window.in_wch` and :meth:`~curses.window.getbkgrnd` that return one --- the wide-character counterparts of :meth:`~curses.window.inch` and :meth:`~curses.window.getbkgd`. The character-cell methods, such as :meth:`~curses.window.addch` and :meth:`~curses.window.border`, now also accept a :class:`~curses.complexchar`. (Contributed by Serhiy Storchaka in :gh:`152233`.)
• Add the :class:`curses.complexstr` type, an immutable run of styled cells (the string counterpart of :class:`~curses.complexchar`), and the window method :meth:`~curses.window.in_wchstr` that returns one. The string-cell methods :meth:`~curses.window.addstr`, :meth:`~curses.window.addnstr`, :meth:`~curses.window.insstr` and :meth:`~curses.window.insnstr` now also accept a :class:`~curses.complexstr`. (Contributed by Serhiy Storchaka in :gh:`152233`.)
• Add the :mod:`curses` window method :meth:`~curses.window.dupwin`, which returns a new window that is an independent duplicate of an existing one. (Contributed by Serhiy Storchaka in :gh:`152258`.)

• :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`.)

• Add :meth:`io.BytesIO.peek` method to read without advancing position. (Contributed by Marcel Martin in :gh:`90533`.)

• :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`.)

• 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`.)

• 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`.)

• 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`.)

• :mod:`re` now supports set operations and nested sets in character classes, as described in Unicode Technical Standard #18: set difference ([A--B]), intersection ([A&&B]) and union ([A||B]), where an operand may be a nested set written in square brackets. For example, [a-z--[aeiou]] matches an ASCII lowercase consonant. (Contributed by Serhiy Storchaka in :gh:`152100`.)
• Regular expressions now support Unicode property escapes \p{...} and \P{...}, which match a character by a Unicode property -- for example \p{Lu} (an uppercase letter), \p{Cased} or \p{ASCII}. See :ref:`the regular expression syntax <re-syntax>` for the supported properties. (Contributed by Serhiy Storchaka in :gh:`95555`.)

• 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`.)

• :meth:`socket.socket.sendfile` now uses the :c:func:`!TransmitFile` system call on Windows, instead of falling back to a slower :meth:`~socket.socket.send` loop. (Contributed by An Long in :gh:`65920`.)

• 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`.)

• 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`.)

• 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`.)

• Character class escapes (\d, \D, \s, \S, \w and \W) outside a character set, and character sets containing a single such escape (such as [\d] or [^\s]), 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` and Pieter Eendebak in :gh:`152056`.)

• TODO

• 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.

• 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).

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

• Calling the Python implementation of :func:`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.

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

• 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`.)

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

• 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`.)

• 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`.)

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

• :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.

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

• 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`.)

• 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`.)

• TODO

• TODO

• :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.