[Python-Dev] Tricky way of of creating a generator via a comprehension expression (original) (raw)

Ivan Levkivskyi levkivskyi at gmail.com
Wed Nov 22 10:00:05 EST 2017

On 22 November 2017 at 15:46, Antoine Pitrou <solipsis at pitrou.net> wrote:

On Wed, 22 Nov 2017 15:15:49 +0100 Ivan Levkivskyi <levkivskyi at gmail.com> wrote: > There are many things that I would reject in code review, but they are > still allowed in Python, > this is one of the reasons why code reviews exist. Also I am not sure how > yield in a comprehension > is more tricky than await in a comprehension.

I am not sure either, but do note that "yield" and "await" are two different things with different semantics, so allowing "await" while disallowing "yield" wouldn't strike me as inconsistent. The exact semantics of "yield" inside a comprehension is a common source of surprise or bewilderment, and the only actual use I've seen of it is to show it off as a "clever trick". So instead of fixing (and perhaps complicating) the implementation to try and make it do the supposedly right thing, I am proposing to simply disallow it so that we are done with the controversy :-) Actually, I am not sure there is really a controversy, I have not yet met a person who expects yield in a comprehension to work as it works now, instead everyone thinks it is just equivalent to a for-loop.

Anyway, I have some compromise idea, will send it in a separate e-mail.

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