diff options
| -rw-r--r-- | Doc/c-api/reflection.rst | 27 | ||||
| -rw-r--r-- | Doc/reference/datamodel.rst | 4 | ||||
| -rw-r--r-- | Doc/whatsnew/3.13.rst | 36 |
3 files changed, 46 insertions, 21 deletions
diff --git a/Doc/c-api/reflection.rst b/Doc/c-api/reflection.rst index af9a1a7..038e697 100644 --- a/Doc/c-api/reflection.rst +++ b/Doc/c-api/reflection.rst @@ -19,23 +19,28 @@ Reflection .. deprecated:: 3.13 - To avoid creating a reference cycle in :term:`optimized scopes <optimized scope>`, - use either :c:func:`PyEval_GetFrameLocals` to obtain the same behaviour as calling + 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 get the same result as this function without having to - cache the proxy instance on the underlying frame. + of :c:func:`PyEval_GetFrame` to access the :attr:`~frame.f_locals` attribute of the + currently executing frame. - Return 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. - If the frame refers to an :term:`optimized scope`, this returns a - write-through proxy object that allows modifying the locals. - In all other cases (classes, modules, :func:`exec`, :func:`eval`) it returns - the mapping representing the frame locals directly (as described for - :func:`locals`). + 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`, return a proxy object for optimized scopes. + 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) diff --git a/Doc/reference/datamodel.rst b/Doc/reference/datamodel.rst index 134385e..9110060 100644 --- a/Doc/reference/datamodel.rst +++ b/Doc/reference/datamodel.rst @@ -1347,13 +1347,13 @@ Special read-only attributes ``object.__getattr__`` with arguments ``obj`` and ``"f_code"``. * - .. attribute:: frame.f_locals - - The dictionary used by the frame to look up + - The mapping used by the frame to look up :ref:`local variables <naming>`. If the frame refers to an :term:`optimized scope`, this may return a write-through proxy object. .. versionchanged:: 3.13 - Return a proxy for functions and comprehensions. + Return a proxy for optimized scopes. * - .. attribute:: frame.f_globals - The dictionary used by the frame to look up diff --git a/Doc/whatsnew/3.13.rst b/Doc/whatsnew/3.13.rst index ab260bf..66626ac 100644 --- a/Doc/whatsnew/3.13.rst +++ b/Doc/whatsnew/3.13.rst @@ -287,8 +287,9 @@ returns a write-through proxy to the frame's local and locally referenced nonlocal variables in these scopes, rather than returning an inconsistently updated shared ``dict`` instance with undefined runtime semantics. -See :pep:`667` for more details, including related C API changes and -deprecations. +See :pep:`667` for more details, including related C API changes and deprecations. Porting +notes are also provided below for the affected :ref:`Python APIs <pep667-porting-notes-py>` +and :ref:`C APIs <pep667-porting-notes-c>`. (PEP and implementation contributed by Mark Shannon and Tian Gao in :gh:`74929`. Documentation updates provided by Guido van Rossum and @@ -2246,6 +2247,8 @@ Changes in the Python API returned by :meth:`zipfile.ZipFile.open` was changed from ``'r'`` to ``'rb'``. (Contributed by Serhiy Storchaka in :gh:`115961`.) +.. _pep667-porting-notes-py: + * Calling :func:`locals` in an :term:`optimized scope` now produces an independent snapshot on each call, and hence no longer implicitly updates previously returned references. Obtaining the legacy CPython behaviour now @@ -2341,15 +2344,27 @@ Changes in the C API to :c:func:`PyUnstable_Code_GetFirstFree`. (Contributed by Bogdan Romanyuk in :gh:`115781`.) -* Calling :c:func:`PyFrame_GetLocals` or :c:func:`PyEval_GetLocals` in an - :term:`optimized scope` now returns a write-through proxy rather than a - snapshot that gets updated at ill-specified times. If a snapshot is desired, - it must be created explicitly (e.g. with :c:func:`PyDict_Copy`) or by calling - the new :c:func:`PyEval_GetFrameLocals` API. (Changed as part of :pep:`667`.) +.. _pep667-porting-notes-c: + +* The effects of mutating the dictionary returned from :c:func:`PyEval_GetLocals` in an + :term:`optimized scope` have changed. New dict entries added this way will now *only* be + visible to subsequent :c:func:`PyEval_GetLocals` calls in that frame, as + :c:func:`PyFrame_GetLocals`, :func:`locals`, and + :attr:`FrameType.f_locals <frame.f_locals>` no longer access the same underlying cached + dictionary. Changes made to entries for actual variable names and names added via the + write-through proxy interfaces will be overwritten on subsequent calls to + :c:func:`PyEval_GetLocals` in that frame. The recommended code update depends on how the + function was being used, so refer to the deprecation notice on the function for details. + (Changed as part of :pep:`667`.) + +* Calling :c:func:`PyFrame_GetLocals` in an :term:`optimized scope` now returns a + write-through proxy rather than a snapshot that gets updated at ill-specified times. + If a snapshot is desired, it must be created explicitly (e.g. with :c:func:`PyDict_Copy`) + or by calling the new :c:func:`PyEval_GetFrameLocals` API. (Changed as part of :pep:`667`.) * :c:func:`!PyFrame_FastToLocals` and :c:func:`!PyFrame_FastToLocalsWithError` no longer have any effect. Calling these functions has been redundant since - Python 3.11, when :c:func:`PyFrame_GetLocals` was first introduced. + Python 3.11, when :c:func:`PyFrame_GetLocals` was first introduced. (Changed as part of :pep:`667`.) * :c:func:`!PyFrame_LocalsToFast` no longer has any effect. Calling this function @@ -2509,6 +2524,11 @@ Deprecated C APIs :c:func:`PyWeakref_GetRef` on Python 3.12 and older. (Contributed by Victor Stinner in :gh:`105927`.) +* Deprecate the :c:func:`PyEval_GetBuiltins`, :c:func:`PyEval_GetGlobals`, and + :c:func:`PyEval_GetLocals` functions, which return a :term:`borrowed reference`. + Refer to the deprecation notices on each function for their recommended replacements. + (Soft deprecated as part of :pep:`667`.) + Pending Removal in Python 3.14 ------------------------------ |