On Tue, May 28, 2019 at 5:25 PM Greg Ewing <greg.ew...@canterbury.ac.nz> wrote:
> Terry Reedy wrote: > > I believe that the situation is or can be thought of as this: there is > > exactly 1 function locals dict. Initially, it is empty and inaccessible > > (unusable) from code. Each locals() call updates the dict to a current > > snapshot and returns it. > > Yes, I understand *what's* happening, but not *why* it was designed > that way. Would it really be prohibitively expensive to create a > fresh dict each time? > No. But it would be inconsistent with the behavior at module level. FWIW I am leaning more and more to the [proxy] model, where locals() and frame.f_locals are the same object, which *proxies* the fast locals and cells. That only has one downside: it no longer returns a dict, but merely a MutableMapping. But why would code care about the difference? (There used to be some relevant builtins that took dicts but not general MutableMappings -- but that has been fixed long ago.) -- --Guido van Rossum (python.org/~guido) *Pronouns: he/him/his **(why is my pronoun here?)* <http://feministing.com/2015/02/03/how-using-they-as-a-singular-pronoun-can-change-the-world/>
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