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<qhelp>

<overview>

<p>The <code>__iter__</code> method of an iterator should return self.

This is important so that iterators can be used as sequences in any context

that expect a sequence. To do so requires that <code>__iter__</code> is

idempotent on iterators.</p>

<p>

Note that sequences and mapping should return a new iterator, it is just the returned

iterator that must obey this constraint.

</p>

</overview>

<recommendation>

<p>Make the <code>__iter__</code> return self unless the class should not be an iterator,

in which case rename the <code>next</code> (Python 2) or <code>__next__</code> (Python 3)

to something else.</p>

</recommendation>

<example>

<p>In this example the <code>Counter</code> class's <code>__iter__</code> method does not

return self (or even an iterator). This will cause the program to fail when anyone attempts

to use the iterator in a <code>for</code> loop or <code>in</code> statement.</p>

<sample src="IterReturnsNonSelf.py" />

</example>

<references>

<li>Python Language Reference: <a href="http://docs.python.org/2.7/reference/datamodel.html#object.__iter__">object.__iter__</a>.</li>

<li>Python Standard Library: <a href="http://docs.python.org/2/library/stdtypes.html#typeiter">Iterators</a>.</li>

</references>

</qhelp>