[Typing-sig] Re: PEP 591 discussion: final

On Tue, May 7, 2019 at 12:54 PM Guido van Rossum wrote:

On Tue, May 7, 2019 at 2:30 PM Dominik Gabi wrote:

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I would simply remove the loop example from the PEP.

OK, but words should be added that a compliant type checker need not allow Final declarations in loops (with the explanation that the Python runtime sees this as multiple assignments to a single variable).

That sounds reasonable to me.

...

I agree with the general definition that

...

There must be exactly one assignment to a final name.

In Pyre this is guaranteed to hold even if you have a final in a loop. In Mypy it’s not and therefore the error from the example makes sense for your particular implementation but not for ours.

Agreed.

-- --Guido van Rossum (python.org/~guido) Pronouns: he/him/his (why is my pronoun here?)