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Thu Nov 23 03:21:58 EST 2017 · https://mail.python.org/pipermail/python-dev/2017-November/150752.html

On 23 November 2017 at 09:11, Greg Ewing <greg.ewing at canterbury.ac.nz>
wrote:

> Ivan Levkivskyi wrote:
>
>> "People sometimes want to refactor for-loops containing `yield` into a
>> comprehension but that doesn't work (particularly because of the hidden
>> function scope) - lets make it a SyntaxError"
>>
>
> Personally I'd be fine with removing the implicit function
> scope from comprehensions and allowing yield in them, since
> the semantics of that are clear.
>
> But I don't see a way to do anything equivalent with
> generator expressions. Since the current effect of
> yield in a generator expression is pretty useless,
> it seems best just to disallow it.
>
> That means a list comprehension won't be equivalent
> to list(generator_expression) in all cases, but I
> don't think there's any great need for it to be.
>

I am also fine with this. Generator expressions are indeed less clear.
Also different people have different mental model about them (especially re
implicit scope and equivalence to comprehensions).

On the contrary, vast majority agrees that comprehensions are just
for-loops without leaking variables.

--
Ivan
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[Python-Dev] Tricky way of of creating a generator via a comprehension expression