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<overview>

<p>Python 2.3 introduced new-style classes (classes inheriting from object). New-style classes use

the C3 linearization method to determine a method resolution ordering (MRO) for each class. The C3

linearization method ensures that for a class C, if a class C1 precedes a class C2 in the MRO of C

then C1 should also precede C2 in the MRO of all subclasses of C. It is possible to create a

situation where it is impossible to achieve this consistency and this will guarantee that a <code>

TypeError</code> will be raised at runtime.</p>

</overview>

<recommendation>

<p>Use a class hierarchy that is not ambiguous.</p>

</recommendation>

<example>

<p>The MRO of class <code>X</code> is just <code>X, object</code>. The program will fail when the MRO

of class <code>Y</code> needs to be calculated because <code>object</code> precedes <code>X</code> in

the definition of <code>Y</code> but the opposite is true in the MRO of <code>X</code>.</p>

<sample src="InconsistentMRO.py" />

</example>

<references>

<li>Python: <a href="http://www.python.org/download/releases/2.3/mro/">The Python 2.3 Method Resolution Order</a>.</li>

</references>

</qhelp>