But Point(x as a) already has a meaning in PEP 634; it’s a positional argument captured in x *and* in a. (Previously spelled as Point(a := x). The phrase ‘as a’ can be added after any pattern to *also* capture it in ‘a’. More typically used as e.g.‘Pattern(x, y) as p’, which captures the first two fields in x and y, and the whole Point in p.
On Sat, Nov 14, 2020 at 23:06 Kyle Stanley <aeros...@gmail.com> wrote: > On Sun, Nov 15, 2020 at 1:56 AM Chris Angelico <ros...@gmail.com> wrote: > >> On Sun, Nov 15, 2020 at 4:28 PM Kyle Stanley <aeros...@gmail.com> wrote: >> > >> > FWIW, I'd like to add my +1 to usage of "as" for spelling class capture >> patterns. This is by far the clearest and easiest to read form I've seen >> thus far, and I suspect that it would be the easiest to explain to users >> already familiar with usage of "as" from other areas in Python. A new >> feature being as distinguishable as possible and easy to explain to >> existing users is very important in my book, and based on the responses, I >> think that the current "=" form used in PEP 634 for matching class patterns >> would be substantially more difficult for users to mentally parse and >> understand compared to "as". >> > >> > It's also worth considering new Python users that might have general OO >> experience but not with robust pattern matching (e.g. Java-heavy >> backgrounds). I could definitely see "case Point(x=a, y=b):" being confused >> for instantiation, whereas usage of "as" makes it more clear that something >> else is happening (hopefully leading them to search around for more info >> about Python pattern matching). >> > >> >> case Point(x=as a, y=as b): >> >> That doesn't read well to me. >> >> Or is there some other spelling of 'as' that makes better sense to you? >> > > The post from Nick that I was primarily replying to used the following > spelling: "case Point(x as a, y as b):". > _______________________________________________ > Python-Dev mailing list -- python-dev@python.org > To unsubscribe send an email to python-dev-le...@python.org > https://mail.python.org/mailman3/lists/python-dev.python.org/ > Message archived at > https://mail.python.org/archives/list/python-dev@python.org/message/JBSWERRHKBYAB7OW5HS3E4FGVTXDTJUP/ > Code of Conduct: http://python.org/psf/codeofconduct/ > -- --Guido (mobile)
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