__mro__ stands for method resolution order. It is a tuple whose elements correspond to the types from which a type is derived (and hence, this dunder is found in type objects). class A: pass class B: pass class C(A, B): pass print(A.__mro__) # # (<class '__main__.A'>, <class 'object'>) print(B.__mro__) # # (<class '__main__.B'>, <class 'object'>) print(C.__mro__) # # (<class '__main__.C'>, <class '__main__.A'>, <class '__main__.B'>, <class 'object'>) a = A() b = B() c = C() assert not hasattr(a, '__mro__') assert not hasattr(b, '__mro__') assert not hasattr(c, '__mro__')
type(). __bases__ which returns a class's immediate super classes).