https://docs.python.org/3.6/tutorial/classes.html#multiple-inheritance Hello. There is a phrase about searching in base classes in text on link above: Thus, if an attribute is not found in DerivedClassName, it is searched for in Base1, then (recursively) in the base classes of Base1, and if it was not found there, it was searched for in Base2, and so on. I think it's a bug in a documentation and newer version of Python search methods in other way, using c3-linearization method. -- Onufriev Anton