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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.

OperatorMagic Method
<__lt__(self, other)
>__gt__(self, other)
<=__le__(self, other)
>=__ge__(self, other)
==__eq__(self, other)
!=__ne__(self, other)

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

p1 = Point(10, 15)
p2 = Point(5, 25)
p3 = Point(12, 14)

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

❮ Python - Operator Overloading

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