Python: Essential Reference, Third Edition

Operator Overloading

User-defined objects can be made to work with all of Python’s built-in operators by adding implementations of the special methods described in Chapter 3 to a class. For example, if you wanted to add a new kind of number to Python, you could define a class in which special methods such as __add__() were defined to make instances work with the standard mathematical operators.

The following example shows how this works by defining a class that implements the complex numbers with some of the standard mathematical operators and type-coercion methods to allow complex numbers to be mixed with integers and floats. Note that because Python already provides a complex number type, this class is only provided for the purpose of illustration. ...