On 19 April 2018 at 02:38, Brett Cannon <br...@python.org> wrote: > I'm also -1. > > I understand the usefulness of the construct in languages where block scopes > make having this kind of expression assignment in e.g. an 'if' guard useful. > But for Python and it's LGB scoping -- although I think we need to add an > "N" for "non-local" :) -- this is syntactic sugar and I don't see enough > wide benefit on top of the potential ugliness/misuse of it to warrant the > cognitive overhead of adding it. > > Although, as usual, Chris, great PEP! :)
Aye, tremendous work on the PEP Chris - assignment expressions are an idea that has come up many, many times on python-ideas, and it's great to finally have a consolidated proposal that attempts to make the best case it can for the idea. Unfortunately, I still have to admit that even I'm -0 on the idea of actually adding it to the language (despite helping it to reach a plausibly acceptable state), primarily on "more than one way to do it" grounds: * assignment statements and top-level assignment expressions would be syntactically distinct, but semantically identical * for the if statement use case, pre-assignment of the re-used part of the condition expression already works fine * for the while loop use case, I think my discussion with Tim about tuple unpacking shows that the loop-and-a-half construct won't be going anywhere, so users would still end up needing to learn both forms (even for new code) The comprehension/genexp use case still seems like the most promising candidate for a reasonable justification for the extra complexity, but there's also a solid argument that if a comprehension is complex enough that the lack of assignment expressions is causing problems, then it's also complex enough that it's reasonable to require extracting the algorithm into a named generator function in order to access assignment statements. Cheers, Nick. -- Nick Coghlan | ncogh...@gmail.com | Brisbane, Australia _______________________________________________ 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
