On Sun, Nov 28, 2021, 11:43 PM Paul Bryan <pbr...@anode.ca> wrote: > According to https://docs.python.org/3/glossary.html#term-iterator and > https://docs.python.org/3/library/stdtypes.html#typeiter, iterators must > implement the __iter__ method.
>From your first link: CPython implementation detail: CPython does not consistently apply the > requirement that an iterator define __iter__(). That said, I don't think the description at the link is very good. Anyway, it's different from what I teach, and also different from how Python actually behaves. E.g.: >>> class Foo: ... def __iter__(self): ... return Bar() ... >>> class Bar: ... def __next__(self): ... if random() > 0.5: ... raise StopIteration ... return "Bar" ... >>> for x in Foo(): ... print(x) ... Bar Bar Bar Or anyway, what would you call `bar := Bar()` if not "an iterator?! On Sun, 2021-11-28 at 22:02 -0500, David Mertz, Ph.D. wrote: > > On Sun, Nov 28, 2021, 8:59 PM Steven D'Aprano > > To be an iterator, your object needs: > > 1. a `__next__` method which returns the next value; > 2. and an `__iter__` method which returns self. > > > That's not quite right. > > An iterator only needs .__next__(), and an iterable only needs > .__iter__(). Returning self is a convenient, and probably the most common, > way of creating an object that is both. But exceptions exist, and remain > iterators and/or iterables. > > >
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