NonIteratorInForLoop.qhelp

<!DOCTYPE qhelp PUBLIC
  "-//Semmle//qhelp//EN"
  "qhelp.dtd">
<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>