On Thu, Dec 13, 2018 at 3:07 PM Chris Barker - NOAA Federal via Python-ideas <python-ideas@python.org> wrote: > > >>> and the test for an iterator is: > >>> > >>> obj is iter(obj) > > Is that a hard and fast rule? I know it’s the vast majority of cases, > but I imagine you could make an object that behaved exactly like an > iterator, but returned some proxy object rather that itself. > > Not sure why one would do that, but it should be possible.
Yes, it is. https://docs.python.org/3/library/stdtypes.html#iterator-types For an iterable, __iter__ needs to return an appropriate iterator. For an iterator, __iter__ needs to return self (which is, by definition, the "appropriate iterator"). Note also that the behaviour around StopIteration is laid out there, including that an iterator whose __next__ has raised SI but then subsequently doesn't continue to raise SI is broken. (Though it *is* legit to raise StopIteration with a value the first time, and then raise a vanilla SI subsequently. Generators do this, rather than retain the return value indefinitely.) ChrisA _______________________________________________ Python-ideas mailing list Python-ideas@python.org https://mail.python.org/mailman/listinfo/python-ideas Code of Conduct: http://python.org/psf/codeofconduct/
