📘 PAPER 2: OBJECT ORIENTED PROGRAMMING WITH PYTHON UNIT 3 – Classes, Objects & OOP Concepts (university of allahabad)

 

🔴 UNIT 3 – Classes, Objects & OOP Concepts

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1️⃣ Class and Object

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✅ Class

A class is a blueprint or template used to create objects.

📌 It defines:

• Data members (variables)

• Member functions (methods)

Example:

class Student:
    def show(self):
        print("This is a student")

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✅ Object

An object is an instance of a class.

s1 = Student()
s1.show()

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🔹 Key Difference

Class	Object
Blueprint	Real-world entity
Logical	Physical
No memory	Uses memory

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2️⃣ Abstract Data Type (ADT)

✅ Definition

An ADT defines:

• What operations are to be performed

• Not how they are implemented

It focuses on behavior, not implementation.

Example:

• Stack

• Queue

• List

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3️⃣ Classes and Objects in Python

Example Program:

class Person:
    def __init__(self, name):
        self.name = name

    def display(self):
        print("Name:", self.name)

p = Person("Rahul")
p.display()

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4️⃣ Constructor (__init__)

Definition:

A constructor is a special method used to initialize objects.

Example:

class Student:
    def __init__(self, roll):
        self.roll = roll

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5️⃣ Features of OOP in Python

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🔹 1. Encapsulation

Binding data and methods together.

class Bank:
    def __init__(self):
        self.__balance = 5000

✔ Data hiding
✔ Security

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🔹 2. Abstraction

Showing essential features and hiding internal details.

Achieved using:

• Abstract classes

• Interfaces

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🔹 3. Inheritance

Child class inherits properties of parent class.

class Parent:
    def show(self):
        print("Parent")

class Child(Parent):
    pass

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Types of Inheritance:

1. Single

2. Multiple

3. Multilevel

4. Hierarchical

5. Hybrid

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🔹 4. Polymorphism

Same function behaves differently.

Example:

print(len("Python"))
print(len([1,2,3]))

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6️⃣ Abstract Class

Definition:

An abstract class contains abstract methods (methods without body).

Using abc module:

from abc import ABC, abstractmethod

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

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7️⃣ Scope in Python

Types of Scope:

1. Local

2. Global

3. Non-local

4. Built-in

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Example:

x = 10  # global

def fun():
    x = 5  # local
    print(x)

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8️⃣ Multithreading in Python

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✅ Definition

Multithreading means executing multiple threads simultaneously.

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Is Multithreading Supported in Python?

✔ Yes
❌ But limited due to GIL (Global Interpreter Lock)

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Example:

import threading

def display():
    print("Hello")

t = threading.Thread(target=display)
t.start()

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Advantages:

• Faster execution

• Better CPU utilization

• Useful in I/O operations

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Disadvantages:

• Complex debugging

• GIL limits performance