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How does super() work in the context of multiple inheritance, and why is it more than just 'call the parent class'? What is a mixin class, and how does it differ from a typical base class in multiple inheritance? How do you call a specific ancestor's method explicitly, bypassing the normal MRO-based super() resolution? How does the built-in `object` class relate to every class's MRO, and why does it always appear last? What's the difference between mixing in an abstract base class (using abc.ABC) versus a plain mixin class? How does the C3 linearization algorithm compute a class's MRO? Why does the convention of listing mixins before the primary base class matter for MRO and method overriding? Why does Python sometimes raise 'TypeError: Cannot create a consistent method resolution order'? How does cooperative multiple inheritance require every class in the hierarchy to call super() consistently, even in __init__? How would you design a mixin to be safely combinable with any base class's __init__ signature using **kwargs?
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How can you use isinstance() and issubclass() to check relationships in a multiple-inheritance hierarchy?

Intermediate

Answer

isinstance(obj, cls) checks if obj's class is cls or any of its ancestors per the full inheritance graph (not just direct parents), and issubclass(cls1, cls2) checks the same relationship between two classes. In multiple inheritance, both correctly consider all branches of the inheritance tree, so an instance of a class combining multiple mixins returns True for isinstance checks against any of those mixins.
class Flyer: pass
class Swimmer: pass
class Duck(Flyer, Swimmer): pass

d = Duck()
print(isinstance(d, Flyer))    # True
print(isinstance(d, Swimmer))  # True
print(issubclass(Duck, Flyer)) # True
Real-world example A plugin system checks `isinstance(plugin, Cacheable)` to decide whether to wrap a plugin's results in a caching layer, working correctly regardless of how deep Cacheable sits in the plugin's multiple-inheritance chain.

Common follow-ups: How does this interact with virtual subclasses registered via ABCs?;What's the performance cost of isinstance checks in a deep hierarchy?

Multiple Inheritance & MRO;Metaclasses & Class Customization
All 15 Multiple Inheritance & MRO questions