Cave of Python

The object-oriented concept of a “mixin” is used in Python, as in many programming languages (but not all).

The Python concept of a mixin doesn’t quite literally conform to the Wikipedia definition of a mixin, but it’s close.

Usually a subclass is a version of the superclass. In the example below, a VW literally is a Car, which is why it inherits from Car.

However, sometimes a parent class is added just to provide a bit of functionality. The class providing the functionality is then known as a mixin.

class Car:
    def drive(self):
        print("Vroooom")

class Alarm:
    def sound_alarm(self):
        print("Woo-woo-woo")

class VW(Car, Alarm):
    pass

herbie = VW()

herbie.drive()
herbie.sound_alarm()

Vroooom
Woo-woo-woo

While a VW is a type of Car, it’s not really a type of Alarm. The Alarm class is added as a superclass purely to provide some functionality; it is a mixin.