> I don't understand that list bit -- surely, if I'm bothering to implement > removeprefix and removesuffix in my subclass, I would also want > to > return self to keep my subclass? Why would I want to go through the extra > overhead of either calling my own __getitem__ method, or have the > str.__getitem__ method discard my subclass?
I should clarify: by "when working with subclasses" I meant "when str.removeprefix() is called on a subclass that does not override removeprefix", and in that case it should return a base str. I was not taking a stance on how the methods should be overridden, and I'm not sure there are many use cases where it should be. > However, if you are saying that self[:] will call > self.__class__.__getitem__ > so my subclass only has to override __getitem__ instead of > removeprefix and > removesuffix, that I can be happy with. I was only saying that the new methods should match 20 other methods in the str API by always returning a base str (the exceptions being format, format_map, and (r)partition for some reason). I did not mean to suggest that they should ever call user-supplied ``__getitem__`` code -- I don't think they need to. I haven't found anyone trying to use ``str`` as a mixin class/ABC, and it seems that this would be very difficult to do given that none of its methods currently rely on ``self.__class__.__getitem__``. If ``return self[:]`` in the PEP is too closely linked to "must call user-supplied ``__getitem__`` methods" for it not to be true, and so you're suggesting ``return self`` is more faithful, I can understand. So now if I understand the dilemma up to this point we have: Benefits of writing ``return self`` in the PEP: - Makes it clear that the optimization of not copying is allowed - Makes it clear that ``self.__class__.__getitem__`` isn't used Benefits of writing ``return self[:]`` in the PEP: - Makes it clear that returning self is an implementation detail - For subclasses not overriding ``__getitem__`` (the majority of cases), makes it clear that this method will return a base str like the other str methods. Did I miss anything? All the best, Dennis _______________________________________________ Python-Dev mailing list -- [email protected] To unsubscribe send an email to [email protected] https://mail.python.org/mailman3/lists/python-dev.python.org/ Message archived at https://mail.python.org/archives/list/[email protected]/message/EQVVXMC7XQJSQIHEB7ND2OLWBQLC7QYM/ Code of Conduct: http://python.org/psf/codeofconduct/