[Python-ideas] PEP 572: Statement-Local Name Bindings, take three!

[Guido van Rossum]

On Sun, Apr 8, 2018 at 8:01 AM, Steven D'Aprano <steve at pearwood.info> wrote:

> If we really wanted to keep the sublocal scoping, we could make
> list/set/dict displays their own scope too.
>
> Personally, that's the only argument for sublocal scoping that I like
> yet: what happens inside a display should remain inside the display, and
> not leak out into the function.
>

That sounds like a reasonable proposal that we could at least consider. But
I think it will not fly. Presumably it doesn't apply to tuple displays,
because of reasonable examples like ((a := f(), a+1), a+2), and because it
would create an ugly discontinuity between (a := f()) and (a := f(),). But
then switching between [a := f(), a] and (a := f(), a) would create a
discontinuity.

For comprehensions and generator expressions there is no such discontinuity
in the new proposal, since these *already* introduce their own scope.

-- 
--Guido van Rossum (python.org/~guido)
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