On Fri, Sep 27, 2019 at 9:14 AM Steven D'Aprano <st...@pearwood.info> wrote:
> But doing it correctly is too painful: > > if any(getattr(T, '__getitem__', None) is not None for T in > type(obj).mro()) > For what it's worth, walking the MRO isn't necessary, and the None trick is only necessary if you want to support people that reuse the __getitem__ name for something else. (And it's often reasonable to say "nope, I don't support that.") >>> class A(object): ... def __getitem__(self, i): return i >>> class B(A): pass ... >>> hasattr(B, '__getitem__') True So for a given object, one could check hasattr(type(obj), '__getitem__'). Or do the None trick with it, but without checking the MRO. (Or replace None with a sentinel object()...) -- Devin
_______________________________________________ Python-ideas mailing list -- python-ideas@python.org To unsubscribe send an email to python-ideas-le...@python.org https://mail.python.org/mailman3/lists/python-ideas.python.org/ Message archived at https://mail.python.org/archives/list/python-ideas@python.org/message/AFJISUYDKGGOLL7ZCOWNNBVTAGXJPFXX/ Code of Conduct: http://python.org/psf/codeofconduct/
