[Matthew Woodcraft] >>> Well, that's a reason to make the example a bit more realistic, then. >>> >>> Say: >>> >>> if match := re.search(pat1, text): >>> do_something_with(match.group(0)) >>> elif match := re.search(pat2, text): >>> do_something_else_with(match.group(0), match.group(1)) >>> elif match := re.search(pat3, text): >>> do_some_other_things_with(match.group(0)) >>> and_also_with(match.group(1), match.group(2))
[Steven D'Aprano <st...@pearwood.info>] >> I don't think that a bunch of generic "do_something_with" functions is >> precisely "realistic". >> >> If I saw something like that, I'd try very hard to find a way to >> refactor it into code like this: >> >> for handler in handlers: >> if handler.match(text): >> handler.process() >> break >> else: >> # handle no-match case here >> >> where the knowledge of what to search for, where to search for it, how >> to search for it, and what to do when found, was encapsulated in the >> handler objects. Your tastes may vary. >> >> But your point is well-taken that the version with binding assignment >> (thanks Tim!) is nicer to read than the current procedural version: >> >> match = re.search(pat1, text) >> if match: >> do_something_with(match.group(0)) >> else: >> match = re.search(pat2, text) >> if match: >> do_something_else_with(match.group(0), match.group(1)) >> else: >> match = = re.search(pat3, text) >> do_some_other_things_with(match.group(0)) >> and_also_with(match.group(1), match.group(2)) >> >> I just don't think it counts as a motivating use-case distinct from the >> single match case. [Guido] > The version of this code found in reality is not as regular as the example > quoted, and the rebuttal "but I would rewrite it with a loop" shoots a straw > man. To me the if-elif-elif portion of the example is very much a separate > motivation, since being able to put the assignment in the elif clause avoids > runaway indentation. I've regretted not being able to use elif in this kind > of situation many times, whereas in the single match case I don't find it a > burden to assign the variable in a separate statement preceding the > if-clause. (I guess this is a case of "flat is better than nested" -- thanks > Tim! :-) Au contraire - thank you for forcing me to channel you succinctly lo those many years ago ;-) And for pointing out this real use case, which I'm not sure has been stressed before. The PEP could clearly use more motivating examples, and this is a fine class of them. Few things are more maddening than runaway cascading indentation :-( And noting again that a simple "binding expression" (my neologism for `identifier ":=" expression`, to break the reflexive horror at imagining the full complexity of assignment statements being allowed everywhere expressions are allowed) is sufficient to address it. _______________________________________________ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
