Operator Overloading in Python

Operator overloading in Python allows same operator to work in different ways depending on data type.

• Python built-in data types allow + operator can add numbers, join strings or merge lists and * operator can be used to repeat instances of a string.
• Python also allows to do operator overloading for user defined classes by writing methods like __add__(), __mul__(), __sub__(),, __lt__(), __gt__() and __eq__() to make objects work for operators like +, *, -, <, > and == respectively.
• We cannot override or change the operator behavior of built-in types (like int, str, list) globally; but we can subclass them (or define your own class) and implement the special methods

This example shows how built-in operators like + and * work differently depending on the data type.

# + operator for integers
print(1 + 2)

# + operator for strings (concatenation)
print("Geeks" + "For")

# * operator for numbers
print(3 * 4)

# * operator for strings (repetition)
print("Geeks" * 4)

3
GeeksFor
12
GeeksGeeksGeeksGeeks

Operator Overloading for User Defined Types

When we use an operator on user-defined objects, Python doesn’t know how to handle it. To make operators work with custom classes, Python provides special methods (also called magic methods).

+ operator -> calls __add__(self, other)
- operator -> calls __sub__(self, other)
== operator -> calls __eq__(self, other)

So, when we write obj1 + obj2, internally Python calls:

obj1.__add__(obj2)

If this method is defined in the class, operator overloading works.

Example 1: This code shows how to overload the + operator for integers and strings inside a custom class.

class A:
    def __init__(self, a):
        self.a = a

    # define behavior of +
    def __add__(self, o):
        return self.a + o.a 

ob1 = A(1)
ob2 = A(2)
ob3 = A("Geeks")
ob4 = A("For")

print(ob1 + ob2)   # integer addition
print(ob3 + ob4)   # string concatenation

# actual working (internally)
print(A.__add__(ob1, ob2))
print(ob1.__add__(ob2))

3
GeeksFor
3
3

Explanation:

• ob1 + ob2 automatically calls ob1.__add__(ob2).
• Python translates it into A.__add__(ob1, ob2).
• first operand (ob1) becomes self and second operand (ob2) becomes other.

Example 2: This code shows how to overload + operator for a custom Complex class so that it adds real and imaginary parts separately.

class Complex:
    def __init__(self, a, b):
        self.a = a
        self.b = b

    def __add__(self, other):
        return self.a + other.a, self.b + other.b

Ob1 = Complex(1, 2)
Ob2 = Complex(2, 3)
Ob3 = Ob1 + Ob2
print(Ob3)

(3, 5)

Explanation: Here, Ob1 + Ob2 adds the real parts (1+2) and imaginary parts (2+3) separately.

Overloading Comparison Operators

Operators like >, <, and == can also be overloaded.

Example 1: This code shows how to overload > operator to compare two objects based on their stored values.

class A:
    def __init__(self, a):
        self.a = a
    
    def __gt__(self, other):
        return self.a > other.a

ob1 = A(2)
ob2 = A(3)
if ob1 > ob2:
    print("ob1 is greater than ob2")
else:
    print("ob2 is greater than ob1")

ob2 is greater than ob1

Example 2: This code shows how to overload both < and == operators for custom comparisons.

class A:
    def __init__(self, a):
        self.a = a
    
    def __lt__(self, other):
        return "ob1 is less than ob2" if self.a < other.a else "ob2 is less than ob1"
    
    def __eq__(self, other):
        return "Both are equal" if self.a == other.a else "Not equal"

ob1 = A(2)
ob2 = A(3)
print(ob1 < ob2)

ob3 = A(4)
ob4 = A(4)
print(ob3 == ob4)

ob1 is less than ob2
Both are equal

Non-Associative Operators

Not all operators can be chained. Some are non-associative. For example, = and += cannot be combined in one statement.

a = 5
b = 10
c = 15

# Invalid: mixing assignment (=) and +=
# a = b = (a < b) += (b < c)

Explanation: In Python, = (assignment) and += (augmented assignment) cannot be mixed in same expression because they are non-associative.

Overloading Boolean Operators

We can also overload Boolean operators using magic methods:

• and: __and__(self, other)
• or: __or__(self, other)
• not: __not__(self)

Example: This code shows how to overload & operator so it works like logical AND on custom objects.

class MyClass:
    def __init__(self, value):
        self.value = value

    def __and__(self, other):
        return MyClass(self.value and other.value)

a = MyClass(True)
b = MyClass(False)
c = a & b  
print(c.value)

False

Explanation: Here, we redefined & so it works like logical AND for custom objects.

Special (Magic) Methods for Operator Overloading

Python provides specific magic methods for each operator.

Binary Operators

Comparison Operators

Assignment Operators

Unary Operators

Advantages

Overloading operators in custom classes provides several benefits:

• Improved readability: code looks natural (e.g., ob1 + ob2 instead of ob1.add(ob2)).
• Consistency with built-in types: custom objects behave like integers, strings, etc.
• Conciseness: less boilerplate code.
• Custom behavior: extend operators to user-defined classes (e.g., vectors, matrices).
• Enhanced functionality: enable operators to work meaningfully with new data types.

Operator Overloading in Python

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