On Sat, Aug 29, 2020, at 20:14, Greg Ewing wrote: > I think this could be done more simply as > > def __getitem__(self, index, **kwds): > self.real_getitem(*index, **kwds) > > def real_getitem(self, x, y): > ... > > The point about obscuring the signature still remains, though. > > Also, this is a hack that we would never be able to get rid of, > whereas new dunders would provide a path to cleaning things up > in the future.
The thing that bothers me with new dunders is - can it be done in such a way that *all* possible ways of calling it with only positional arguments behave the same as presently when the old one is defined, and an intuitive way with the new one, without requiring the calling bytecode to know which signature is going to be used? __getitem__(self, arg) vs __getitem_ex__(self, *args, **kwargs) x[1] - old arg=1; new args=(1,) x[1,] - old arg=(1,); new args=(1,)? x[(1,)] old arg=(1,); new args=((1,),)? x[1,2] old arg=(1,2); new args=(1,2) x[(1,2)] old arg=(1,2); new args=((1,2),)? x[*a] old arg=a new args=a? Also, do we want to walk the MRO looking for both in turn, or look for the new one on the whole chain before then looking for the old one? is there a precedent for two different ways to define a method on a single class? [getattr vs getattribute is not a case of this, and i say "single class" to exclude the complexity of binary operators] Another concern is where a new setitem should put the value argument? i may have missed something mentioning it, but I don't think I've seen a proposal that goes into detail on that? Having the user define a __setitem__ that calls the real_setitem if needed gets around that by leaving the signature up to the user [where they can e.g. put it in a keyword arg with a name they know they won't need] _______________________________________________ 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/IOMTOY43LUFBXJS2PYHR2FMCHFCI2NNK/ Code of Conduct: http://python.org/psf/codeofconduct/
