Data Structures and Algorithms

by Albert Major

Operator Overloading in Python

What Is Operator Overloading?

• Built-in types like integers, strings, lists, etc., already overload operators differently. For example:
  • 1 + 2 → numeric addition
  • 'a' + 'b' → string concatenation
  • [1] + [2] → list concatenation
• You can define what +, ==, etc., should mean for your own class using special methods (called dunder methods).

Example Class: Complex

A simple example is a class for complex numbers. A complex number has:

• A real part (r)
• An imaginary part (c)

class Complex:
    def __init__(self, r, c):
        self.r = r
        self.c = c

This creates an object like Complex(3, 2) representing 3 + 2i.

String Representation: __str__ and __repr__

• __str__ defines what happens when you call str(obj) or use print(obj).
• __repr__ defines what happens in the Python shell (interactive display).

def __str__(self):
    return str(self.r) + "+" + str(self.c) + "i"

Key rules: