<!DOCTYPE qhelp PUBLIC

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<qhelp>

<overview>

<p>

In Python, assertions are not executed when optimizations are enabled.

This may lead to unexpected behavior when assertions are used to the check

validity of a piece of input.

</p>

</overview>

<recommendation>

<p>

If the value being tested is false, replace the <code>assert</code>

statement with a <code>raise</code> statement that raises an appropriate

exception. If the value being tested is true, delete the <code>assert</code>

statement or replace it with a <code>pass</code> statement.

</p>

</recommendation>

<example>

<p>

This example shows a function <code>buy_bananas</code> that takes a

number <code>n</code> as input. The function checks that this number is not too big

before sending off an order for that number of bananas. Because this is done

using an <code>assert</code> statement, the check disappears when

optimizations are enabled. The second function corrects this error by

explicitly raising an <code>AssertionError</code>, and checks the value even

when optimizations are enabled.

</p>

<sample src="AssertLiteralConstant.py" />

</example>

<references>

<li>Python Language Reference: <a href="https://docs.python.org/2/reference/simple_stmts.html#the-assert-statement">The assert statement</a>.</li>

<li>The Python Tutorial: <a href="https://docs.python.org/2.7/tutorial/modules.html#compiled-python-files">“Compiled” Python files</a>.</li>

</references>

</qhelp>