Python - Comparison Operator Overloading

Comparison operators are those operators which compares two operand, like operators (==, <, >, <=, >=) compares Python data types. Following is the list of comparison operators and corresponding magic methods that can be overloaded in Python.

Python allows us to specify these operators with a special meaning for a class object.

Example: overloading comparison operators

In the example below, comparison operators < and > are overloaded. When it is applied with point objects, it compares its distance from origin and returns true or false based on the comparison result. For example:

• (10, 15) > (5, 25) will compare √10² + 15² > √5² + 25² which is equivalent to √325 > √650, hence returns false.
• (10, 15) < (12, 14) will compare √10² + 15² < √12² + 14² which is equivalent to √325 < √340, hence returns true.

Note: In this example, math module's hypot function is used to calculate distance of a point from the origin.

import math

class point:
  def __init__(self, x, y):
    self.x = x
    self.y = y
  def __str__(self):
    return "({0},{1})".format(self.x, self.y)
  
  #function for operator overloading <
  def __lt__(self, other):
    d1 = math.hypot(self.x, self.y)
    d2 = math.hypot(other.x, other.y)
    res = True if d1 < d2 else False
    return res

  #function for operator overloading >
  def __gt__(self, other):
    d1 = math.hypot(self.x, self.y)
    d2 = math.hypot(other.x, other.y)
    res = True if d1 > d2 else False
    return res

#creating point objects
p1 = point(10, 15)
p2 = point(5, 25)
p3 = point(12, 14)

#using overloaded < and > operators 
#with point objects
print("(p1 > p2) returns:", (p1>p2))
print("(p1 < p3) returns:", (p1<p3))

The output of the above code will be:

(p1 > p2) returns: False
(p1 < p3) returns: True