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

Brett Cannon brett at python.org
Sat Nov 25 12:15:40 EST 2017

On Fri, Nov 24, 2017, 19:32 Guido van Rossum, <guido at python.org> wrote:

> On Fri, Nov 24, 2017 at 4:22 PM, Guido van Rossum <guido at python.org>
> wrote:
>> The more I hear about this topic, the more I think that `await`, `yield`
>> and `yield from` should all be banned from occurring in all comprehensions
>> and generator expressions. That's not much different from disallowing
>> `return` or `break`.
> From the responses it seems that I tried to simplify things too far. Let's
> say that `await` in comprehensions is fine, as long as that comprehension
> is contained in an `async def`. While we *could* save `yield [from]` in
> comprehensions, I still see it as mostly a source of confusion, and the
> fact that the presence of `yield [from]` *implicitly* makes the surrounding
> `def` a generator makes things worse. It just requires too many mental
> contortions to figure out what it does.
> I still propose to rule out all of the above from generator expressions,
> because those can escape from the surrounding scope.

+1 from me.


> --
> --Guido van Rossum (python.org/~guido)
> _______________________________________________
> Python-Dev mailing list
> Python-Dev at python.org
> https://mail.python.org/mailman/listinfo/python-dev
> Unsubscribe:
> https://mail.python.org/mailman/options/python-dev/brett%40python.org
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.python.org/pipermail/python-dev/attachments/20171125/8f861f9e/attachment.html>

More information about the Python-Dev mailing list