TruncatedDivision.qhelp

<!DOCTYPE qhelp PUBLIC
  "-//Semmle//qhelp//EN"
  "qhelp.dtd">
<qhelp>
<overview>
<p>
  In Python 2, the result of dividing two integers is silently truncated into an integer. This may lead to unexpected behavior.
</p>

</overview>
<recommendation>

  <p>
    If the division should never be truncated, add
    <code>from __future__ import division</code>
    to the beginning of the file. If the division should always
    be truncated, replace the division operator <code>/</code> with the
    truncated division operator <code>//</code>.
  </p>

</recommendation>
<example>
<p>
  The first example shows a function for calculating the average of a sequence
  of numbers. When the function runs under Python 2, and the sequence contains
  only integers, an incorrect result may be returned because the result is
  truncated. The second example corrects this error by following the
  recommendation listed above.
</p>

<sample src="TruncatedDivision.py" />
<sample src="TruncatedDivisionCorrect.py" />


</example>
<references>

  <li>Python Language Reference: <a href="https://docs.python.org/2/reference/expressions.html#binary-arithmetic-operations">Binary arithmetic operations</a>.</li>
  <li>PEP 238: <a href="https://www.python.org/dev/peps/pep-0238/">Changing the Division Operator</a>.</li>
  <li>PEP 236: <a href="https://www.python.org/dev/peps/pep-0236/">Back to the __future__</a>.</li>
</references>
</qhelp>