On Mon, 24 Feb 2020 at 12:10, Guido van Rossum <gu...@python.org> wrote: > > On Sat, Feb 22, 2020 at 4:45 PM Brandt Bucher <brandtbuc...@gmail.com> wrote: >> >> [quoting Nick] >> > collections.Mapping and collections.MutableMapping could provide concrete >> > method implementations that make subclasses behave in a way that's similar >> > to built-in dicts >> >> Hm, haven't thought too much about this (I don't have much experience with >> the ABCs). Would they return dicts, or call the self.copy and self.update >> methods? >> >> Those are just hypothetical questions for now; I don't necessarily want to >> dig too far into that discussion again. But I agree that it's definitely >> worth considering. ;) > > Mapping and MutableMapping don't have copy() methods -- these are > intentionally narrower interfaces than dict. I think we should leave them > alone. The PEP does *not* propose to add `|` to Mapping, and that's > intentional. Because of this I think we should also not add `|=` to > MutableMapping, even though it does have an update() method. Adding it (even > with a default implementation) could cause discrepancies to virtual > subclasses registered with MutableMapping.register(C).
That's an excellent point regarding virtual subclasses - I was only thinking about concrete subclasses. So if folks want to mimic the full dict API, they can inherit from UserDict, while Mapping and MutableMapping continue with their existing narrower APIs. Cheers, Nick. -- Nick Coghlan | ncogh...@gmail.com | Brisbane, Australia _______________________________________________ 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/E5V4RK4HCLZBKC2Z4HXXO4FZWWKGWZHX/ Code of Conduct: http://python.org/psf/codeofconduct/
