Method resolution order (MRO)

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Python's MRO uses the C3 linearization algorithm. You can inspect it with ClassName.__mro__ or ClassName.mro(). For class D(B, C) where both B and C inherit from A: the MRO is D -> B -> C -> A -> object. B is checked before C, and A appears only once at the end. Understanding MRO matters when using mixins - a common pattern in Django, Flask, and test frameworks where you compose behavior from multiple small classes.