Mark Shannon wrote: > On 02/04/2021 7:19 am, Brandt Bucher wrote: > > I agree that self-matching classes should absolutely allow keyword matches. > > I had no idea the PEP forbade it. > PEP 634 allows it.
PEP 634 says: > For a number of built-in types (specified below), a single positional > subpattern is accepted which will match the entire subject; for these types > no keyword patterns are accepted. (https://www.python.org/dev/peps/pep-0634/#class-patterns) > Most checks are cheap though. > Checking for duplicates in `__match_args__` can be done at class creation > time, and checking for duplicates in the pattern can be done at compile time. I assume the compile-time check only works for named keyword attributes. The current implementation already does this. -1 on checking `__match_args__` anywhere other than the match block itself. Guido van Rossum wrote: > On Fri, Apr 2, 2021 at 3:38 AM Mark Shannon m...@hotpy.org wrote: > > Are there are any use-cases? > > The test-case `int(real=0+0j, imag=0-0j)` is contrived, but I'm struggling > > to come up with less contrived examples for any of float, list, dict, > > tuple, str. > There could be a subclass that adds an attribute. That's still contrived > though. I could see the case for something like `case defaultdict({"Spam": s}, default_factory=f)`. I certainly don't think it should be forbidden. _______________________________________________ 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/L2RB6WYAOSLZECG4N2JTYMAAQX3U64GA/ Code of Conduct: http://python.org/psf/codeofconduct/
