On Wed, Apr 11, 2018 at 6:55 PM, Paul Moore <p.f.mo...@gmail.com> wrote: > On 11 April 2018 at 06:32, Chris Angelico <ros...@gmail.com> wrote: >> The name ``prefix`` is thus searched for at global scope, ignoring the class >> name. Under the proposed semantics, this name will be eagerly bound, being >> approximately equivalent to:: >> >> class X: >> names = ["Fred", "Barney", "Joe"] >> prefix = "> " >> def <listcomp>(prefix=prefix): >> result =  >> for name in names: >> result.append(prefix + name) >> return result >> prefixed_names = <listcomp>() > > Surely "names" would also be eagerly bound, for use in the "for" loop?
Yep, exactly. Have corrected the example, thanks. >> This could be used to create ugly code! >> --------------------------------------- >> >> So can anything else. This is a tool, and it is up to the programmer to use >> it >> where it makes sense, and not use it where superior constructs can be used. > > Related objection - when used to name subexpressions in a > comprehension (one of the original motivating use cases for this > proposal), this introduces an asymmetry which actually makes the > comprehension harder to read. As a result, it's quite possible that > people won't want to use assignment expressions in this case, and the > use case of precalculating expensive but multiply used results in > comprehensions will remain unanswered. > > I think the response here is basically the same as the above - if you > don't like them, don't use them. But I do think the additional nuance > of "we might not have solved the original motivating use case" is > worth a specific response. The PEP has kinda pivoted a bit since its inception, so I'm honestly not sure what "original motivating use case" matters. :D I'm just lumping all the use-cases together at the same priority now. > Overall, I like this much better than the previous proposal. I'm now > +1 on the semantic changes to comprehensions, and barely +0 on the > assignment expression itself (I still don't think assignment > expressions are worth it, and I worry about the confusion they may > cause for beginners in particular). Now that they have the same semantics as any other form of assignment, they're a bit less useful in some cases, a bit more useful in others, and a lot easier to explain. The most confusing part, honestly, is "why do we have two ways to do assignment", which is why that is specifically answered in the PEP. ChrisA _______________________________________________ Python-ideas mailing list Pythonfirstname.lastname@example.org https://mail.python.org/mailman/listinfo/python-ideas Code of Conduct: http://python.org/psf/codeofconduct/