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| Educational infographic showing Python OOP concepts like Class, Constructor, Inheritance, Polymorphism and Encapsulation in simple way. |
🔹 1. Class & Object
A class is a blueprint. An object is created from a class.
class MyCar:
wheels = 4 # class attribute
def display_info(self):
print(f"This car runs on {self.wheels} wheels")
car_1 = MyCar()
car_1.display_info()
🔹 2. Constructor (__init__)
__init__ is used to initialize values when creating an object.
class MyCar:
wheels = 4
def __init__(self, brand, color):
self.brand = brand
self.color = color
def display_info(self):
print(f"{self.color} {self.brand} drives on {self.wheels} wheels")
car_1 = MyCar("BMW", "Red")
car_1.display_info()
🔹 3. Rectangle Example
Demonstrating methods inside methods.
class Rectangle:
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)
def describe(self):
print(f"Area is {self.area()} and Perimeter is {self.perimeter()}")
rectangle = Rectangle(10, 5)
rectangle.describe()
🔹 4. Inheritance
Inheritance allows a child class to use parent class properties.
class Animal:
def speak(self):
print("Animal speaks")
class Dog(Animal):
def speak(self):
print("Dog barks")
dog_1 = Dog()
dog_1.speak()
🔹 Method Overriding
Overriding means a child class changes the method of the parent class.
The method name must be the same in both classes.
✅ Example 1: Basic Overriding
class Animal: # Parent class
age = 0
def speak(self):
print("Animal speak")
class Dog(Animal): # Child class
def speak(self): # Overriding parent method
print("Dog bark")
dog_1 = Dog()
print(dog_1.age) # Inherited attribute
dog_1.speak() # Calls overridden method
✔ The Dog class overrides the speak() method of Animal.
⚠ Constructor Inheritance Problem
If the parent class has a constructor, the child must pass required arguments.
class Animal:
def __init__(self, color):
self.color = color
class Dog(Animal):
def speak(self):
print("Dog bark")
# dog_1 = Dog() ❌ Error (missing color argument)
✔ Fix using super() to call parent constructor.
class Animal:
def __init__(self, name):
self.name = name
class Dog(Animal):
def __init__(self, name, color):
super().__init__(name) # Call parent constructor
self.color = color
def speak(self):
print(f"{self.name} barks")
dog_1 = Dog("Buddy", "Brown")
print(dog_1.name)
print(dog_1.color)
✅ Real World Example (Employee & Manager)
class Employee:
def __init__(self, name, salary):
self.name = name
self.salary = salary
def display_info(self):
print(f"Name: {self.name}, Salary: {self.salary}", end="")
class Manager(Employee):
def __init__(self, name, salary, department):
super().__init__(name, salary)
self.department = department
def display_info(self): # Overriding method
super().display_info()
print(f", Department: {self.department}")
manager_1 = Manager("Sherul", "2000.00", "Academic")
manager_1.display_info()
✔ Manager class overrides display_info() and adds department.
🔹 Method Overloading
Overloading means using the same method name but with different parameters.
⚠ Python does not support traditional overloading like Java. We simulate it using default arguments.
✅ Example: Simulated Overloading
class Animal:
age = 0
def speak(self):
print("Animal speak")
class Dog(Animal):
def speak(self, bark=None): # Overloading style
if bark is None:
print("Dog barks loudly!")
else:
print(f"Dog barks: {bark}")
dog_1 = Dog()
print(dog_1.age)
dog_1.speak() # Without argument
dog_1.speak("woof woof") # With argument
✔ Same method name speak() works in two different ways.
🔹 6. Polymorphism
Same method name behaves differently in different classes.
class Dog:
def speak(self):
print("Dog barks")
class Cat:
def speak(self):
print("Cat meows")
🔹 7. Encapsulation
Encapsulation means hiding data using private attributes.
class Car:
def __init__(self, brand):
self.__brand = brand # private
def get_brand(self):
return self.__brand
car = Car("Toyota")
print(car.get_brand())
🔹 8. BankAccount Example (Encapsulation)
class BankAccount:
def __init__(self, account_number, owner_name):
self.__account_number = account_number
self.__owner_name = owner_name
self.__balance = 0.0
def __valid_amount(self, amount):
return amount > 0
def deposit(self, amount):
if self.__valid_amount(amount):
self.__balance += amount
def withdraw(self, amount):
if self.__valid_amount(amount) and self.__balance >= amount:
self.__balance -= amount
def get_balance(self):
return self.__balance
account = BankAccount("213", "Sherul")
account.deposit(1000)
print(account.get_balance())
🎯 These OOP concepts are very important for real-world Python projects.