[Python-Dev] Examples for PEP 572 (original) (raw)

Tim Peters tim.peters at gmail.com
Wed Jul 4 14:16:00 EDT 2018

[Yury Selivanov]

Wow, I gave up on this example before figuring this out (and I also

> stared at it for a good couple of minutes). Now it makes sense. It's

> funny that this super convoluted snippet is shown as a good example

> for PEP 572. Although almost all PEP 572 examples are questionable.

And another who didn't actually read the PEP Appendix. See my reply just before this one: yes, the Appendix gave that as a good example, but as a good example of assignment-expression ABUSE. The opposite of something desirable.

I've never insisted there's only one side to this, and when staring at code was equally interested in cases where assignment expressions would hurt as where they would help. I ended up giving more examples where they would help, because after writing up the first two bad examples in the Appendix figured it was clear enough that "it's a bad idea except in cases where it obviously helps".

Same way, e.g., as when list comprehensions were new, I focused much more on cases where they might help after convincing myself that a great many nested loops building lists were much better left as nested loops. So I looked instead for real-code cases where they would obviously help, and found plenty.

And I'm really glad Python added listcomps too, despite the possibility of gross abuse ;-) -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://mail.python.org/pipermail/python-dev/attachments/20180704/e92ce29e/attachment.html>

More information about the Python-Dev mailing list