boolean methods in python object destruction__del__ destructor usage notes summary test your knowledgequiz test your knowledgeanswers designing with classes python and oop polymorphism means interfacesnot call signatures oop and inheritance"is-arelationships oop and composition"has-arelationships stream processors revisited oop and delegation"wrapperproxy objects pseudoprivate class attributes name mangling overview why use pseudoprivate attributesmethods are objectsbound or unbound unbound methods are functions in bound methods and other callable objects classes are objectsgeneric object factories why factoriesmultiple inheritance"mix-inclasses coding mix-in display classes other design-related topics summary test your knowledgequiz test your knowledgeanswers advanced class topics extending built-in types extending types by embedding extending types by subclassing the "new styleclass model just how new is new-stylenew-style class changes attribute fetch for built-ins skips instances type model changes all classes derive from "objectdiamond inheritance change more on the mromethod resolution order examplemapping attributes to inheritance sources table of contents xxiii