[Python-Dev] [PEP 558] thinking through locals() semantics (original) (raw)

Greg Ewing greg.ewing at canterbury.ac.nz
Tue May 28 21:45:41 EDT 2019

Nathaniel Smith wrote:

- [proxy]: Simply return the .flocals object, so in all contexts locals() returns a live mutable view of the actual environment:

def locals(): return getcallerframe().flocals

Not sure I quite follow this -- as far as I can see, f_locals currently has the same snapshot behaviour as locals().

I'm assuming you mean to change things so that locals() returns a mutable view tracking the environment in both directions. That sounds like a much better idea all round to me. No weird shared-snapshot behaviour, and no need for anything to behave differently when tracing.

If the change to the behaviour of exec() and eval() is a concern, then perhaps there should be a new localsview() function that returns a mutable view, with locals() redefined as dict(localsview()).

-- Greg

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