cpython/Doc/c-api/reflection.rst
Neil Schemenauer cdba68e563
[3.15] gh-159136: Avoid stop-the-world when setting function name attributes (gh-159269) (gh-159725)
Setting __name__, __qualname__, __doc__ or __module__ on a function
stopped the world in the free-threaded build since gh-154826 and
gh-154851, making functools.wraps() orders of magnitude slower with
multiple threads.

Use the per-object critical section and _PyObject_XSetRefDelayed()
instead, as gen_set_name() already does.  Use acquire loads in the
readers and hold strong references across error reporting, tracing, and
eval-frame recording that may execute Python or detach the thread.  The
__code__, __defaults__, __kwdefaults__ and __closure__ setters still
stop the world to clear func_version.

Document synchronization requirements for direct field access and the
lifetime of borrowed function attributes.

(cherry picked from commit 010bebbf9f)
2026-10-29 15:17:50 -07:00

112 lines
4 KiB
ReStructuredText

.. highlight:: c
.. _reflection:
Reflection
==========
.. c:function:: PyObject* PyEval_GetBuiltins(void)
.. deprecated:: 3.13
Use :c:func:`PyEval_GetFrameBuiltins` instead.
Return a dictionary of the builtins in the current execution frame,
or the interpreter of the thread state if no frame is currently executing.
.. c:function:: PyObject* PyEval_GetLocals(void)
.. deprecated:: 3.13
Use either :c:func:`PyEval_GetFrameLocals` to obtain the same behaviour as calling
:func:`locals` in Python code, or else call :c:func:`PyFrame_GetLocals` on the result
of :c:func:`PyEval_GetFrame` to access the :attr:`~frame.f_locals` attribute of the
currently executing frame.
Return a mapping providing access to the local variables in the current execution frame,
or ``NULL`` if no frame is currently executing.
Refer to :func:`locals` for details of the mapping returned at different scopes.
As this function returns a :term:`borrowed reference`, the dictionary returned for
:term:`optimized scopes <optimized scope>` is cached on the frame object and will remain
alive as long as the frame object does. Unlike :c:func:`PyEval_GetFrameLocals` and
:func:`locals`, subsequent calls to this function in the same frame will update the
contents of the cached dictionary to reflect changes in the state of the local variables
rather than returning a new snapshot.
.. versionchanged:: 3.13
As part of :pep:`667`, :c:func:`PyFrame_GetLocals`, :func:`locals`, and
:attr:`FrameType.f_locals <frame.f_locals>` no longer make use of the shared cache
dictionary. Refer to the :ref:`What's New entry <whatsnew313-locals-semantics>` for
additional details.
.. c:function:: PyObject* PyEval_GetGlobals(void)
.. deprecated:: 3.13
Use :c:func:`PyEval_GetFrameGlobals` instead.
Return a dictionary of the global variables in the current execution frame,
or ``NULL`` if no frame is currently executing.
.. c:function:: PyFrameObject* PyEval_GetFrame(void)
Return the :term:`attached thread state`'s frame, which is ``NULL`` if no frame is
currently executing.
See also :c:func:`PyThreadState_GetFrame`.
.. c:function:: PyObject* PyEval_GetFrameBuiltins(void)
Return a dictionary of the builtins in the current execution frame,
or the interpreter of the thread state if no frame is currently executing.
.. versionadded:: 3.13
.. c:function:: PyObject* PyEval_GetFrameLocals(void)
Return a dictionary of the local variables in the current execution frame,
or ``NULL`` if no frame is currently executing. Equivalent to calling
:func:`locals` in Python code.
To access :attr:`~frame.f_locals` on the current frame without making an independent
snapshot in :term:`optimized scopes <optimized scope>`, call :c:func:`PyFrame_GetLocals`
on the result of :c:func:`PyEval_GetFrame`.
.. versionadded:: 3.13
.. c:function:: PyObject* PyEval_GetFrameGlobals(void)
Return a dictionary of the global variables in the current execution frame,
or ``NULL`` if no frame is currently executing. Equivalent to calling
:func:`globals` in Python code.
.. versionadded:: 3.13
.. c:function:: const char* PyEval_GetFuncName(PyObject *func)
Return the name of *func* if it is a function, class or instance object, else the
name of *func*\s type.
For a Python function or method, the returned pointer refers to the
function's name and must not be retained across operations that may change
that name. In the free-threaded build, copy the string before detaching
the thread state or executing Python code if the name may be modified
concurrently.
.. c:function:: const char* PyEval_GetFuncDesc(PyObject *func)
Return a description string, depending on the type of *func*.
Return values include "()" for functions and methods, " constructor",
" instance", and " object". Concatenated with the result of
:c:func:`PyEval_GetFuncName`, the result will be a description of
*func*.