On Fri, Nov 16, 2018 at 8:01 AM Steve Keller <keller@no.invalid> wrote: > > I wonder why iterators do have an __iter__() method? I thought > iterable objects would have an __iter__() method (but no __next__()) > to create an iterator for it, and that would have the __next__() > method but no __iter__(). > > $ python3 > Python 3.5.2 (default, Nov 12 2018, 13:43:14) > [GCC 5.4.0 20160609] on linux > Type "help", "copyright", "credits" or "license" for more information. > >>> l = [1,2,3] > >>> next(l) > Traceback (most recent call last): > File "<stdin>", line 1, in <module> > TypeError: 'list' object is not an iterator > > This is expected, of course. > > >>> iter(l) > <list_iterator object at 0x7f2e271d1fd0> > >>> iter(iter(l)) > <list_iterator object at 0x7f2e278f5978> > >>> iter(iter(iter(l))) > <list_iterator object at 0x7f2e271d1fd0> > >>> i = iter(iter(iter(l))) > >>> list(i) > [1, 2, 3] > > Is there any reason or usage for this?
Iterators are required to have an __iter__ method that just returns self. The reason is so that iterators can be used in places where an iterable is required; e.g. so that code that is handed an iterator can loop over it. -- https://mail.python.org/mailman/listinfo/python-list
