Multiple dispatch

When Python executes a method call, say a.f(b, c, d), it should first select the right f function. Due to polymorphism, it depends on the type of a. The process of choosing the method is usually called dynamic dispatch.

Python supports only single-dispatch polymorphism because a single object alone (a in the example) affects the method selection. Some other languages, however, may also consider a type of b, c and d. This mechanism is called multiple disaptch. C# is a notable example of languages that support that technique.

However, multiple dispatch can be emulated via single-dispatch. The visitor design pattern is created exactly for this. What visitor do is essentially calling single-dispatch twice to imitate double-dispatch.

Mind, that the ability to overload methods (like in Java and C++) is not the same as multiple dispatch. Dynamic dispatch works in runtime while overloading solely affects compile time.