NotImplemented is like a pure virtual function; failing to implement it tells you that you forgot part of the contract, except at runtime instead of compile time. So if you never need them, you're free to elide them, but if you want full compatibility, you need to implement every part of it.
If someone tried to Obj + Obj and that's just completely nonsensical for the type, then NotImplemented is a reasonable message, as opposed to NameError which can be rather confusing. Alternately, you can implement it and tell the caller exactly why it's not implemented. It's also useful for anyone looking to subclass by immediately showing them every base method they might need to implement. -Em
_______________________________________________ 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/VPARRUAONYWMKELECKVAC4HP7AI23W2W/ Code of Conduct: http://python.org/psf/codeofconduct/
