Python Polymorphism

Polymorphism is an essential concept in object-oriented programming (OOP) that allows objects of different classes to be treated as objects of a common superclass. It promotes code flexibility and reusability.

In Python, polymorphism is achieved through method overriding, operator overloading, and built-in functions that work with different types of objects.

What is Polymorphism?

The word Polymorphism is derived from the Greek words “poly” (meaning many) and “morph” (meaning forms). It allows a single method or operator to behave differently based on the object it is acting upon.

Types of Polymorphism

• Method Overriding: Redefining a method in a child class that already exists in the parent class.
• Operator Overloading: Defining custom behavior for standard operators.

1. Method Overriding

Method overriding occurs when a child class provides a specific implementation of a method already defined in its parent class.

Example:

class Animal:
    def sound(self):
        return "Animal makes a sound"

class Dog(Animal):
    def sound(self):  # Method overriding
        return "Dog barks"

class Cat(Animal):
    def sound(self):  # Method overriding
        return "Cat meows"

# Using polymorphism
animals = [Dog(), Cat()]

for animal in animals:
    print(animal.sound())

# Output:
# Dog barks
# Cat meows

2. Operator Overloading

Operator overloading allows you to redefine the behavior of operators for custom objects.

Example:

class Point:
    def __init__(self, x, y):
        self.x = x
        self.y = y

    def __add__(self, other):
        return Point(self.x + other.x, self.y + other.y)

    def __str__(self):
        return f"({self.x}, {self.y})"

p1 = Point(2, 3)
p2 = Point(4, 5)
p3 = p1 + p2  # Operator overloading for '+'
print(p3)  # Output: (6, 8)

Polymorphism with Built-in Functions

Many built-in Python functions, like len(), exhibit polymorphism by working with different types of objects.

Example:

print(len("Hello"))  # Output: 5 (string length)
print(len([1, 2, 3, 4]))  # Output: 4 (list length)

Real-world Example of Polymorphism

Polymorphism is widely used in real-world applications to create flexible and reusable code.

Example – Payment System:

class Payment:
    def pay(self):
        pass

class CreditCardPayment(Payment):
    def pay(self):
        return "Payment made with Credit Card"

class PayPalPayment(Payment):
    def pay(self):
        return "Payment made with PayPal"

def process_payment(payment):
    print(payment.pay())

# Using polymorphism
credit = CreditCardPayment()
paypal = PayPalPayment()

process_payment(credit)  # Output: Payment made with Credit Card
process_payment(paypal)  # Output: Payment made with PayPal

Conclusion

Polymorphism is a key feature of Python that enhances code reusability and flexibility. By understanding and applying method overriding, operator overloading, and polymorphic behavior in built-in functions, you can write cleaner and more maintainable code.