<!DOCTYPE qhelp PUBLIC

"-//Semmle//qhelp//EN"

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<qhelp>

<overview>

<p>The <code>for</code> statement is designed to allow you to iterate over the elements of a

sequence or other iterable object. If a non-iterable object is used in a <code>for</code> statement

(<code>for var in object:</code>) then a TypeError will be raised.

</p>

</overview>

<recommendation>

<p>Since this defect usually indicates a logical error, it is not possible to give a general method

for addressing the defect. </p>

</recommendation>

<example>

<p>

In this example, the loop may attempt to iterate over <code>None</code>, which is not an iterable.

It is likely that the programmer forgot to test for <code>None</code> before the loop.

</p>

<sample src="NonIteratorInForLoop.py" />

</example>

<references>

<li>Python Language Reference: <a href="http://docs.python.org/reference/compound_stmts.html#the-for-statement">The for statement</a>,

<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/dev/library/stdtypes.html#iterator-types">Iterator types</a>.</li>

<li>Scipy lecture notes: <a href="http://scipy-lectures.github.io/advanced/advanced_python/#iterators">Iterators,

generator expressions and generators</a>.</li>

</references>

</qhelp>