Add a new Py_TPFLAGS_DISALLOW_INSTANTIATION type flag to disallow
creating type instances: set tp_new to NULL and don't create the
"__new__" key in the type dictionary.
The flag is set automatically on static types if tp_base is NULL or
&PyBaseObject_Type and tp_new is NULL.
Use the flag on the following types:
* _curses.ncurses_version type
* _curses_panel.panel
* _tkinter.Tcl_Obj
* _tkinter.tkapp
* _tkinter.tktimertoken
* _xxsubinterpretersmodule.ChannelID
* sys.flags type
* sys.getwindowsversion() type
* sys.version_info type
Update MyStr example in the C API documentation to use
Py_TPFLAGS_DISALLOW_INSTANTIATION.
Add _PyStructSequence_InitType() function to create a structseq type
with the Py_TPFLAGS_DISALLOW_INSTANTIATION flag set.
type_new() calls _PyType_CheckConsistency() at exit.
The Python C API
================
The C API is divided into three sections:
1. ``Include/``
2. ``Include/cpython/``
3. ``Include/internal/``
Include: Limited API
====================
``Include/``, excluding the ``cpython`` and ``internal`` subdirectories,
contains the public Limited API (Application Programming Interface).
The Limited API is a subset of the C API, designed to guarantee ABI
stability across Python 3 versions, and is defined in :pep:`384`.
Guidelines for expanding the Limited API:
- Functions *must not* steal references
- Functions *must not* return borrowed references
- Functions returning references *must* return a strong reference
- Macros should not expose implementation details
- Please start a public discussion before expanding the API
- Functions or macros with a ``_Py`` prefix do not belong in ``Include/``.
It is possible to add a function or macro to the Limited API from a
given Python version. For example, to add a function to the Limited API
from Python 3.10 and onwards, wrap it with
``#if !defined(Py_LIMITED_API) || Py_LIMITED_API+0 >= 0x030A0000``.
Include/cpython: CPython implementation details
===============================================
``Include/cpython/`` contains the public API that is excluded from the
Limited API and the Stable ABI.
Guidelines for expanding the public API:
- Functions *must not* steal references
- Functions *must not* return borrowed references
- Functions returning references *must* return a strong reference
Include/internal: The internal API
==================================
With PyAPI_FUNC or PyAPI_DATA
-----------------------------
Functions or structures in ``Include/internal/`` defined with
``PyAPI_FUNC`` or ``PyAPI_DATA`` are internal functions which are
exposed only for specific use cases like debuggers and profilers.
With the extern keyword
-----------------------
Functions in ``Include/internal/`` defined with the ``extern`` keyword
*must not and can not* be used outside the CPython code base. Only
built-in stdlib extensions (built with the ``Py_BUILD_CORE_BUILTIN``
macro defined) can use such functions.
When in doubt, new internal C functions should be defined in
``Include/internal`` using the ``extern`` keyword.