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PEP 558: Fix mention of old locals() semantics (#1266) 

When updating the PEP to specify independent snapshots for locals()
at function scope, I missed this reference to the old semantics
that returned a direct reference to the dynamic internal snapshot.
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Nick Coghlan 2020-01-02 02:30:39 +10:00 committed by GitHub
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@ -290,11 +290,11 @@ defined ``locals()`` builtin, trace functions necessarily use the implementation
dependent ``frame.f_locals`` interface, as a frame reference is what gets
passed to hook implementations.
Instead of being a direct reference to the dynamic snapshot returned by
``locals()``, ``frame.f_locals`` will be updated to instead return a dedicated
proxy type (implemented as a private subclass of the existing
``types.MappingProxyType``) that has two internal attributes not exposed as
part of either the Python or public C API:
Instead of being a direct reference to the internal dynamic snapshot used to
populate the independent snapshots returned by ``locals()``, ``frame.f_locals``
will be updated to instead return a dedicated proxy type (implemented as a
private subclass of the existing ``types.MappingProxyType``) that has two
internal attributes not exposed as part of the Python runtime API:
* *mapping*: an implicitly updated snapshot of the function local variables
and closure references, as well as any arbitrary items that have been set via
@ -302,6 +302,9 @@ part of either the Python or public C API:
underlying frame
* *frame*: the underlying frame that the snapshot is for
For backwards compatibility, the stored snapshot will continue to be made
available through the public ``PyEval_GetLocals()`` C API.
``__getitem__`` operations on the proxy will read directly from the stored
snapshot.