Easy To Learn Operator Overloading Tutorial in Python

Python Operator Overloading

Python operators work for built-in classes. But same operator behaves differently with different types.

This feature in Python, that allows same operator to have different meaning according to the context is called operator overloading.

You have already seen you can use + (addition ) arithmetic operator for adding numbers and at the same time to concatenate strings. It is possible because + operator is overloaded by both int class and str class. The operators are actually methods defined in respective classes. Defining methods for operators is known as operator overloading. For e.g. To use + operator with custom objects you need to define a method called __add__ .

>>> class GridPoint:
    def __init__(self, x, y):  
        self.x = x  
        self.y = y
    def __add__(self, other):
        return GridPoint(self.x + other.x, self.y + other.y)
    def __str__(self):
        string = str(self.x)  
        string = string + ", " + str(self.y)  
        return string

>>> point1 = GridPoint(18, 25)
>>> point2 = GridPoint(-7, 13)
>>> point3 = point1 + point2
>>> print(point3)
11, 38
>>>

Operator	Description	Method
+	Addition	__add__(self, other)
–	Subtraction	__sub__(self, other)
*	Multiplication	__mul__(self, other)
/	True Division	__truediv__(self, other)
//	Floor Division	__floordiv__(self, other)
%	Remainder	__mod__(self, other)
**	Power	__pow__(self, other)
&	Bitwise AND	__and__(self, other)
\|	Bitwise OR	__or__(self, other)
^	Bitwise XOR	__xor__(self, other)
~	Bitwise NOT	__not__(self, other)

Relational Operators in python

Relational operators are overloaded in a very similar way in python. But the difference is, those operators often return true/false instead of another instance of the object. Let’s work with an example..

>>> class My_Sample:
	def __init__(self, x, y):
		self.x = x
		self.y = y
	def __gt__(self, other):
		return self.x > other.x
	def __str__(self):
		string = str(self.x)
		string = string + ", " + str(self.y)
		return string

	
>>> point1 = My_Sample(18, 25)
>>> point2 = My_Sample(-7, 13)
>>> if point1 > point2:
	print('point1 is greater than point2')
else:
	print('point1 is not greater than point2')

	
point1 is greater than point2
>>>

The conventional ‘>’ operator returns true if the operand in the left side of it is greater than the right one. We are going to use this property to compare two instances of class My_Sample.

Operator	Description	Method
>	Greater than	__gt__(self, other)
>=	Greater than or equal to	__ge__(self, other)
<	Less than	__lt__(self, other)
<=	Less than or equal to	__le__(self, other)
==	Equal to	__eq__(self, other)
!=	Not equal to	__ne__(self, other)

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