22.5. Multiple inheritance

In Python, a class can inherit from more than one parent class. This is called multiple inheritance. Multiple inheritance can be useful when you want to create a class that is a combination of multiple classes. For example, suppose we have a class Swimmer (which represents all of the aspects of a character that can swim) and a class Flyer (for all of the aspects of a character that relate to flying). We can create a class Goose that inherits from both Swimmer and Flyer by putting both these class names in parentheses: class Goose(Swimmer, Flyer). This class will have all the methods and attributes of both Swimmer and Flyer:

class Swimmer: def swim(self): print("Swimming!") class Flyer: def fly(self): print("Flying!") class Goose(Swimmer, Flyer): pass my_goose = Goose() my_goose.swim() # Swimming! my_goose.fly() # Flying!

Multiple inheritance can improve our ability to re-use code and classes. It can be particularly useful if the classes represent “features” that we can selectively apply to subclasses. However, it’s generally a good rule to avoid multiple inheritance unless it provides a clear and significant benefit. Always consider simpler alternatives, such as composition (using an instance of one class as an instance variable inside of another class) or single inheritance, before turning to multiple inheritance.

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