FileNotAlwaysClosed.qhelp

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

<overview>
<p> If a file is opened then it should always be closed again, even if an
exception is raised.
Failing to ensure that all files are closed may result in failure due to too
many open files.</p>

</overview>
<recommendation>

<p>Ensure that if you open a file it is always closed on exiting the method.
Wrap the code between the <code>open()</code> and <code>close()</code>
functions in a <code>with</code> statement or use a <code>try...finally</code>
statement. Using a <code>with</code> statement is preferred as it is shorter
and more readable.</p>

</recommendation>
<example>
<p>The following code shows examples of different ways of closing a file. In the first example, the
file is closed only if the method is exited successfully. In the other examples, the file is always
closed on exiting the method.</p>

<sample src="FileNotAlwaysClosed.py" />

</example>
<references>


<li>Python Language Reference: <a href="http://docs.python.org/reference/compound_stmts.html#the-with-statement">The with statement</a>,
 <a href="http://docs.python.org/reference/compound_stmts.html#the-try-statement">The try statement</a>.</li>
<li>Python PEP 343: <a href="http://www.python.org/dev/peps/pep-0343">The "with" Statement</a>.</li>



</references>
</qhelp>