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<qhelp>

<overview>

<p>When a file is opened, it should always be closed.

</p>

<p>A file opened for writing that is not closed when the application exits may result in data loss, where not all of the data written may be saved to the file.

A file opened for reading or writing that is not closed may also use up file descriptors, which is a resource leak that in long running applications could lead to a failure to open additional files.

</p>

</overview>

<recommendation>

<p>Ensure that opened files are always closed, including when an exception could be raised.

The best practice is often to use a <code>with</code> statement to automatically clean up resources.

Otherwise, ensure that <code>.close()</code> is called in a <code>try...except</code> or <code>try...finally</code>

block to handle any possible exceptions.

</p>

</recommendation>

<example>

<p>In the following examples, in the case marked BAD, the file may not be closed if an exception is raised. In the cases marked GOOD, the file is always closed.</p>

<sample src="examples/FileNotAlwaysClosed.py" />

</example>

<references>

<li>Python Documentation: <a href="https://docs.python.org/3/tutorial/inputoutput.html#reading-and-writing-files">Reading and writing files</a>.</li>

<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>