OverlyComplexDelMethod.qhelp

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

<overview>
<p>The <code>__del__</code> method exists to release any resources held by an object when that object is deleted.
The <code>__del__</code> is called only by the garbage collector which may call it after an indefinite delay or
never.
</p>

<p>
Consequently,  <code>__del__</code> method should not be relied on to release resources, such as file descriptors.
Rather, these resources should be released explicitly.
</p>

<p>The existence of a complex <code>__del__</code> method suggests that this is the main or only way to release resources
associated with the object.</p>

</overview>
<recommendation>

<p>In order to ensure correct cleanup of the object add an explicit close(), or similar,
method. Possibly make the object a context manager.</p>

<p>The __del__ method should just call close()</p>


</recommendation>
<example>
<p>The first example below shows a class which relies on <code>__del__</code> to release resources. 
The second example shows an improved version of the class where <code>__del__</code> simply calls close.</p>

<sample src="OverlyComplexDelMethod.py" />

</example>
<references>

  <li>Python Standard Library: <a href="http://docs.python.org/library/stdtypes.html#context-manager-types">Context manager</a>.</li>

</references>
</qhelp>