[Python-Dev] Informal educator feedback on PEP 572 (was Re: 2018 Python Language Summit coverage, last part) (original) (raw)

Ivan Pozdeev vano at mail.mipt.ru
Wed Jun 27 20:10:40 EDT 2018

On 28.06.2018 2:31, Greg Ewing wrote:

Steven D'Aprano wrote:

The very first motivating example for this proposal came from a comprehension.

I think it is both unfortunate and inevitable that the discussion bogged down in comprehension-hell. I think the unfortunateness started when we crossed over from talking about binding a temporary name for use within a comprehension or expression, to binding a name for use outside the comprehension or expression where it's bound. I've shown in <05f368c2-3cd2-d7e0-9f91-27afb40d5b35 at mail.mipt.ru> (27 Jun 2018 17:07:24 +0300) that assignment expressions are fine in most use cases without any changes to scoping whatsoever.

So, as Guido suggested in <CAP7+vJ+xBAT4ZvAo4B7qSqxnnpj8jJ1VZ-Le7EwT8=n-UTjE3Q at mail.gmail.com> (26 Jun 2018 19:36:14 -0700), the scoping matter can be split into a separate PEP and discussion.

As long as it's for internal use, whether it's in a comprehension or not isn't an issue.

Tim Peters has also given a couple of good examples of mathematical code that would benefit strongly from this feature.

Going back a few months now, they were the examples that tipped me over Well, I remain profoundly unconvinced that writing comprehensions with side effects is ever a good idea, and Tim's examples did nothing to change that.

-- Regards, Ivan

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