And the second link? On Mon, 2021-11-29 at 00:11 -0500, David Mertz, Ph.D. wrote: > 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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