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<qhelp>

<overview>

<p>When a function returns a non-trivial value, that value should not be ignored. Doing so may result in errors being ignored or

information being thrown away.</p>

<p>A return value is considered to be trivial if it is <code>None</code> or it is a parameter (parameters, usually <code>self</code> are often

returned to assist with method chaining, but can be ignored).

A return value is also assumed to be trivial if it is ignored for more than 25% of calls.

</p>

</overview>

<recommendation>

<p>Act upon all non-trivial return values, either propagating each value or recording it.

If a return value should be ignored, then ensure that it is ignored consistently.

</p>

<p>

If you have access to the source code of the called function, then consider modifying it so that it does not return pointless values.

</p>

</recommendation>

<example>

<p>

In the <code>ignore_error</code> function the error condition is ignored.

Ideally the <code>Resource.initialize()</code> function would raise an exception if it failed, but as it does not, the caller must deal with the error.

The <code>do_not_ignore_error</code> function checks the error condition and raises an exception if <code>Resource.initialize()</code> fails.

</p>

<sample src="ReturnValueIgnored.py" />

</example>

<references>

<li>Python Language Reference: <a href="http://docs.python.org/2/reference/compound_stmts.html#function">Function definitions</a>.

</li>

</references>

</qhelp>