LEARN COMPLETE PYTHON IN 24 HOURS

5. Polymorphism – One Name, Different Behavior

Polymorphism (from Greek: "many forms") means that the same method name can behave differently depending on the object calling it. In simple words: "One interface, multiple implementations".

Python achieves polymorphism very naturally through duck typing and method overriding — no need for interfaces like in Java/C#.

5.1 Method Overriding in Detail

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

The child version replaces (overrides) the parent version when called on a child object.

Example – Animal hierarchy

Python

class Animal: def speak(self): return "Some generic animal sound..." class Dog(Animal): def speak(self): return "Woof! Woof!" class Cat(Animal): def speak(self): return "Meow!" class Cow(Animal): def speak(self): return "Moo!" # Polymorphism in action animals = [Dog(), Cat(), Cow(), Animal()] for animal in animals: print(animal.speak())

Output:

text

Woof! Woof! Meow! Moo! Some generic animal sound...

Key points:

• Same method name speak() — different behavior

• Python decides at runtime which version to call (based on the actual object type)

• This is called dynamic polymorphism (or runtime polymorphism)

When to override:

• When child needs specialized behavior

• When you want to extend (not completely replace) → call super()

With super()

Python

class SmartDog(Dog): def speak(self): parent_sound = super().speak() return f"{parent_sound} I'm a smart dog!"

5.2 Operator Overloading (add, eq, lt, etc.)

Operator overloading lets you define how operators (+, ==, <, etc.) work with your custom objects.

These are called dunder (double underscore) methods — also known as magic methods.

Common operators and their methods:

OperatorMethodDescriptionExample Usage+__add__Additiona + b-__sub__Subtractiona - b*__mul__Multiplicationa * b==__eq__Equality comparisona == b!=__ne__Not equala != b<__lt__Less thana < b<=__le__Less than or equala <= b>__gt__Greater thana > b>=__ge__Greater than or equala >= blen()__len__Length of objectlen(obj)str()__str__String representation (print)print(obj)repr()__repr__Developer string representationrepr(obj)

Real example – Vector class

Python

class Vector: def init(self, x, y): self.x = x self.y = y def add(self, other): return Vector(self.x + other.x, self.y + other.y) def eq(self, other): return self.x == other.x and self.y == other.y def str(self): return f"Vector({self.x}, {self.y})" v1 = Vector(2, 3) v2 = Vector(1, 4) print(v1 + v2) # Vector(3, 7) print(v1 == v2) # False

Tip: Always implement eq when you define add or similar — consistency matters.

5.3 Duck Typing – “If it walks like a duck…”

Duck typing is Python's philosophy: "If it looks like a duck, swims like a duck, and quacks like a duck, then it probably is a duck."

Instead of checking the class/type, Python checks whether the object has the required methods/attributes.

Example – Polymorphism without inheritance

Python

class Bird: def quack(self): return "Quack!" class RubberDuck: def quack(self): # no inheritance! return "Squeak!" class Person: def quack(self): return "I can quack too!" def make_it_quack(thing): print(thing.quack()) make_it_quack(Bird()) # Quack! make_it_quack(RubberDuck()) # Squeak! make_it_quack(Person()) # I can quack too!

Power of duck typing:

• No need for inheritance or interfaces

• Very flexible and Pythonic

• Works with any object that has the required method

5.4 Abstract Base Classes (abc module)

Abstract Base Class (ABC) forces subclasses to implement certain methods — like an interface.

Use the abc module to create abstract classes.

Example – Shape hierarchy

Python

from abc import ABC, abstractmethod class Shape(ABC): @abstractmethod def area(self): """Must be implemented by all subclasses""" pass @abstractmethod def perimeter(self): pass class Rectangle(Shape): def init(self, length, width): self.length = length self.width = width def area(self): return self.length self.width def perimeter(self): return 2 (self.length + self.width) # r = Shape() # TypeError: Can't instantiate abstract class rect = Rectangle(10, 5) print(rect.area()) # 50 print(rect.perimeter()) # 30

Key points:

• @abstractmethod → must be overridden in child class

• Cannot create instance of abstract class

• Useful for defining interfaces/contracts

Mini Summary Project – Animal Sound Simulator

Python

from abc import ABC, abstractmethod class Animal(ABC): @abstractmethod def speak(self): pass class Dog(Animal): def speak(self): return "Woof!" class Cat(Animal): def speak(self): return "Meow!" class Robot(Animal): # must implement speak() def speak(self): return "Beep boop!" animals = [Dog(), Cat(), Robot()] for a in animals: print(a.speak())

This completes the full Polymorphism – One Name, Different Behavior section — now you understand how Python achieves flexible, reusable, and elegant code through overriding, overloading, duck typing, and abstract classes!

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