R. David Murray added the comment:
The definition of an Iterable is a class that defines an __iter__ method.
Your class does not, so the behavior you site is correct.
The glossary entry for 'iterable' could use a little clarification. A class
that defines __getitem__ is an iterable if and only if it returns results when
passed integers. Since the documentation for Iterable references that glossary
entry, it should probably also be explicit that defining __getitem__ does not
(because of the forgoing limitation) cause isinstance(x, Iterable) to be True.
For a class that does not define __iter__, you must explicitly register it with
Iterable.
To see why this must be so, consider this:
>>> y = IsIterable({'a': 'b', 'c': 'd'})
>>> [x for x in y]
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "<stdin>", line 1, in <listcomp>
File "<stdin>", line 5, in __getitem__
KeyError: 0
----------
assignee: -> docs@python
components: +Documentation -Library (Lib)
nosy: +docs@python, r.david.murray
stage: -> needs patch
title: Iterables not detected correctly -> Iterable glossary entry needs
clarification
versions: +Python 3.4
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Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue18558>
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