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37 lines
1.3 KiB
XML
37 lines
1.3 KiB
XML
<!DOCTYPE qhelp PUBLIC
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"-//Semmle//qhelp//EN"
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"qhelp.dtd">
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<qhelp>
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<overview>
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<p>The <code>for</code> statement is designed to allow you to iterate over the elements of a
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sequence or other iterable object. If a non-iterable object is used in a <code>for</code> statement
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(<code>for var in object:</code>) then a TypeError will be raised.
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</p>
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</overview>
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<recommendation>
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<p>Since this defect usually indicates a logical error, it is not possible to give a general method
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for addressing the defect. </p>
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</recommendation>
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<example>
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<p>
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In this example, the loop may attempt to iterate over <code>None</code>, which is not an iterable.
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It is likely that the programmer forgot to test for <code>None</code> before the loop.
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</p>
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<sample src="NonIteratorInForLoop.py" />
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</example>
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<references>
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<li>Python Language Reference: <a href="http://docs.python.org/reference/compound_stmts.html#the-for-statement">The for statement</a>,
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<a href="http://docs.python.org/2.7/reference/datamodel.html#object.__iter__">object.__iter__</a>.</li>
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<li>Python Standard Library: <a href="http://docs.python.org/dev/library/stdtypes.html#iterator-types">Iterator types</a>.</li>
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<li>Scipy lecture notes: <a href="http://scipy-lectures.github.io/advanced/advanced_python/#iterators">Iterators,
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generator expressions and generators</a>.</li>
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</references>
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</qhelp>
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