__bases__ returns a class's immediate base classes. Compare with __mro__. class A : pass class B : pass class C : pass class D : pass class ABD(A, B, D ): pass class BC (B, C ): pass class x(ABD, BC ): pass print([ _.__name__ for _ in x.__bases__]) # # ['ABD', 'BC'] print([ _.__name__ for _ in ABD.__bases__]) # # ['A', 'B', 'D'] print([ _.__name__ for _ in x.__mro__ ]) # # ['x', 'ABD', 'A', 'BC', 'B', 'D', 'C', 'object']