Polymorphism in Python

1. What is Polymorphism

Polymorphism allows the same interface (method or operator) to behave differently based on the object or context.

print(len("Python"))   # String length
print(len([1, 2, 3]))  # List length

The same function works for multiple data types.

2. Function Polymorphism

def add(a, b, c=0):
    return a + b + c

print(add(2, 3))        # 5
print(add(2, 3, 4))     # 9

A single function adapts behavior based on arguments.

3. Built-in Polymorphism

print(5 + 10)          # Integer addition
print("Hello " + "AI") # String concatenation

The + operator behaves differently based on operand types.

4. Method Overriding (Runtime Polymorphism)

class Animal:
    def speak(self):
        print("Animal sound")

class Dog(Animal):
    def speak(self):
        print("Dog barks")

pet = Dog()
pet.speak()

Child class alters the behavior of a parent method.

5. Operator Overloading

class Vector:
    def __init__(self, x):
        self.x = x

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

v1 = Vector(10)
v2 = Vector(20)
v3 = v1 + v2

print(v3.x)  # Output: 30

Custom behavior for operators using magic methods.

6. Polymorphism with Different Classes

class Cat:
    def sound(self):
        print("Meow")

class Dog:
    def sound(self):
        print("Bark")

def make_sound(animal):
    animal.sound()

make_sound(Cat())
make_sound(Dog())

Different objects responding to the same method call.

7. Duck Typing

class Car:
    def move(self):
        print("Car moving")

class Boat:
    def move(self):
        print("Boat sailing")

def start(vehicle):
    vehicle.move()

start(Car())
start(Boat())

Behavior is determined by method presence, not class type.

8. Method Overloading via Default Arguments

class Calculator:
    def multiply(self, a, b=1):
        return a * b

calc = Calculator()
print(calc.multiply(5))     # 5
print(calc.multiply(5, 3))  # 15

Python simulates overloading using default parameters.

9. Abstract Base Class Polymorphism

from abc import ABC, abstractmethod

class Shape(ABC):
    @abstractmethod
    def area(self):
        pass

class Rectangle(Shape):
    def area(self):
        return 10 * 5

shape = Rectangle()
print(shape.area())

Ensures consistent interface across implementations.

10. Real-World Polymorphism Example

class Notification:
    def send(self):
        print("Sending notification")

class Email(Notification):
    def send(self):
        print("Sending Email")

class SMS(Notification):
    def send(self):
        print("Sending SMS")

def notify(service):
    service.send()

notify(Email())
notify(SMS())

Multiple behaviors implemented under a unified interface.

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