Let's say that I have a class Suit and four subclasses of suit: Heart, Spade, Diamond, Club. class Suit: ... class Heart(Suit): ... class Spade(Suit): ... class Diamond(Suit): ... class Club(Suit): ... I have a method which receives a suit as a parameter, which is a class object, not an instance. More precisely, it may receive only one of the four values: Heart, Spade, Diamond, Club. How can I make an assertion which ensures such a thing? Something like: def my_method(suit): assert(suit subclass of Suit) ... I'm using Python 3. Continue reading...