Author: Saravana Kumar

Encapsulation in Python | Easy OOP Explanation for Beginners

🔹 What is Encapsulation?

Encapsulation means hiding data and keeping it safe.
In Python, we use class to keep variables and functions together.
It helps to protect the data from being changed accidentally.

📌 Think of a capsule – it keeps medicine safely inside.
Encapsulation keeps data and code safely inside the class.

🔹 Why Encapsulation?

✅ Easy to use
✅ Protects data
✅ Only allow limited access
✅ Clean and secure code

🔹 Example: Without Encapsulation

class Student:
    def __init__(self, name, marks):
        self.name = name
        self.marks = marks

s1 = Student("Arun", 85)
print(s1.marks)  # Anyone can access and change

s1.marks = 40  # Can be changed easily
print(s1.marks)

🔐 Example: With Encapsulation (using private variable)

class Student:
    def __init__(self, name, marks):
        self.name = name
        self.__marks = marks  # private variable

    def get_marks(self):     # getter
        return self.__marks

    def set_marks(self, value):  # setter
        if value >= 0 and value <= 100:
            self.__marks = value
        else:
            print("Invalid marks!")

s1 = Student("Arun", 85)
print(s1.get_marks())  # Output: 85

s1.set_marks(95)       # Valid update
print(s1.get_marks())  # Output: 95

s1.set_marks(150)      # Invalid update

🔎 What is `__` (double underscore)?

It makes the variable private.
Cannot access it directly like s1.__marks
Must use getter and setter methods.

🧠 Real-Life Example:

ATM Machine:

You can see balance, add money, withdraw money – but you can’t open the system.
That is encapsulation.

📝 Practice Questions with Answers

❓ Q1: Create a class `BankAccount` with private balance. Add `deposit()` and `get_balance()` methods.

✅ Answer:

class BankAccount:
    def __init__(self, balance):
        self.__balance = balance

    def deposit(self, amount):
        if amount > 0:
            self.__balance += amount

    def get_balance(self):
        return self.__balance

acc = BankAccount(1000)
acc.deposit(500)
print("Balance:", acc.get_balance())  # Output: 1500

❓ Q2: Make a class `Person` with private `age`. Use `set_age()` to update age with condition (must be > 0).

✅ Answer:

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

    def get_age(self):
        return self.__age

    def set_age(self, new_age):
        if new_age > 0:
            self.__age = new_age
        else:
            print("Invalid age!")

p1 = Person("Ravi", 25)
print(p1.get_age())
p1.set_age(-10)  # Invalid
p1.set_age(30)   # Valid
print(p1.get_age())  # 30

📘 Summary

Word	Meaning
Encapsulation	Hide data inside class using private vars
`__`	Makes variable private
Getter	Function to get value
Setter	Function to set value safely

📣 Coming Up Next:

➡️ Inheritance in Python | Learn How One Class Can Use Another

July 6, 2025

What is self in Python? | Easy Explanation with Examples

🔹 What is `self` in Python?

self means this object.
It helps Python know which object we are talking about.
It is used inside class functions to access the object’s data and functions.

📌 Important Points:

self is not a keyword. You can name it anything (but using self is the rule).
It is sent automatically when you call a function using an object.

🔹 Example 1: Using `self` to store data

class Student:
    def __init__(self, name, age):
        self.name = name  # save name
        self.age = age    # save age

    def show(self):
        print("Name:", self.name)
        print("Age:", self.age)

s1 = Student("Arun", 18)
s1.show()

✅ Output:

Name: Arun
Age: 18

🔹 How `self` works:

Let’s understand:

self.name = name → store the value in the object.
self.age = age → same for age.
Later, inside the show() function, we again use self.name to get the data back.

🔹 Example 2: Use `self` in multiple objects

class Car:
    def __init__(self, brand):
        self.brand = brand

    def start(self):
        print(self.brand, "is starting...")

c1 = Car("Toyota")
c2 = Car("BMW")

c1.start()  # Toyota is starting...
c2.start()  # BMW is starting...

👉 Here, self.brand is different for each object.

🔹 Example 3: Change values using `self`

class Employee:
    def __init__(self, name, salary):
        self.name = name
        self.salary = salary

    def change_salary(self, new_salary):
        self.salary = new_salary

    def show(self):
        print("Name:", self.name)
        print("Salary:", self.salary)

e1 = Employee("Ravi", 30000)
e1.change_salary(40000)
e1.show()

✅ Output:

Name: Ravi
Salary: 40000

📝 Practice Questions with Answers

❓ Q1: Create a class `Laptop` with `brand` and `price`. Use `self` to store and print data.

✅ Answer:

class Laptop:
    def __init__(self, brand, price):
        self.brand = brand
        self.price = price

    def show(self):
        print("Brand:", self.brand)
        print("Price:", self.price)

l1 = Laptop("HP", 55000)
l1.show()

❓ Q2: Create a class `Circle` with radius. Use a method to calculate area. (Area = 3.14 × radius × radius)

✅ Answer:

class Circle:
    def __init__(self, radius):
        self.radius = radius

    def area(self):
        return 3.14 * self.radius * self.radius

c = Circle(5)
print("Area:", c.area())

🧾 Summary Table

Term	Meaning
`self`	Refers to current object inside a class
Use	To access variables and methods in object

📣 Next:

➡️ “Encapsulation in Python | Easy OOP Explanation for Beginners”

July 6, 2025

What is __init__() in Python? | Constructor Made Simple
🔹 What is __init__()?
- __init__() is a special function in a class.
- It is called automatically when you create an object.
- It is used to give values to the object’s variables.
📌 We also call it a constructor.

🔹 Simple Example:
```
class Person:
    def __init__(self, name):
        self.name = name

p1 = Person("John")
print(p1.name)  # Output: John
```
🧾 What happens here?
1. We created a class called Person.
2. Inside the class, we wrote a __init__() function.
3. self.name = name means we are saving the name in the object.
4. We made an object p1 = Person("John"). It runs the __init__() and stores "John" inside it.
🔹 What is self in __init__()?
- self means this object.
- Python sends it automatically to every function inside a class.
```
class Student:
    def __init__(self, name, age):
        self.name = name
        self.age = age

s1 = Student("Arun", 18)
print(s1.name)  # Arun
print(s1.age)   # 18
```
🔹 You Can Add More Than One Parameter
```
class Car:
    def __init__(self, brand, year):
        self.brand = brand
        self.year = year

c1 = Car("Toyota", 2020)
print(c1.brand)  # Toyota
print(c1.year)   # 2020
```
📝 Practice Questions with Answers

❓ Q1: Create a class Book with title and author. Use __init__() to set values and print them.

✅ Answer:
```
class Book:
    def __init__(self, title, author):
        self.title = title
        self.author = author

b1 = Book("Python Basics", "Ravi")
print("Title:", b1.title)
print("Author:", b1.author)
```
❓ Q2: Create a class Laptop with brand and price. Use __init__() and print details.

✅ Answer:
```
class Laptop:
    def __init__(self, brand, price):
        self.brand = brand
        self.price = price

lap1 = Laptop("Dell", 50000)
print("Brand:", lap1.brand)
print("Price:", lap1.price)
```
🔎 Summary

Keyword Meaning
__init__() Constructor — runs when object created
self Refers to the current object
Object A real item created from a class

📣 Coming Next:

➡️ “What is self in Python? | Easy Explanation with Examples”
July 6, 2025
🧑‍🏫 What is Class and Object in Python? | Simple Explanation for Beginners
🔹 What is a Class?
- A class is a template or design to make things (objects).
- It tells Python what the object has (variables) and what it can do (functions).
✅ Example:
```
class Student:
    def __init__(self, name, age):
        self.name = name
        self.age = age
```
This class is like a student form. It has:
- name
- age
🔹 What is an Object?
- An object is something real made from the class.
- We can make many objects from one class.
✅ Example:
```
s1 = Student("Arun", 18)
print(s1.name)  # Output: Arun
```
➡️ s1 is an object of the class Student.

🔹 __init__() Method
- This is a special function in the class.
- It runs automatically when you make an object.
- It gives values to the object.
✅ Example:
```
class Car:
    def __init__(self, brand):
        self.brand = brand

c1 = Car("Toyota")
print(c1.brand)  # Output: Toyota
```
🔹 What is self?
- self means this object.
- It is used to store data inside the object.
✅ Example:
```
class Example:
    def show(self):
        print("Hello from", self)

obj = Example()
obj.show()
```
🧠 Real-Life Example

Let’s say we want to make details of books.

✅ Example:
```
class Book:
    def __init__(self, title, author):
        self.title = title
        self.author = author

b1 = Book("Python Basics", "Ravi")
print(b1.title)   # Python Basics
print(b1.author)  # Ravi
```
✅ Benefits of Using Class and Object

Why we use OOP? Simple Explanation
Reuse Code Use the same class to make many objects
Clean Code Easy to read and update
Better Structure Keep data and actions together

📝 Practice Questions

Q1. Create a class Employee with name and salary. Show details.

✅ Answer:
```
class Employee:
    def __init__(self, name, salary):
        self.name = name
        self.salary = salary

    def show(self):
        print("Name:", self.name)
        print("Salary:", self.salary)

e1 = Employee("Meena", 25000)
e1.show()
```
🧾 Summary Table

Word Meaning
Class Blueprint for making objects
Object Real item created from class
__init__() Gives values when object is created
self Refers to the current object

🔗 Next Topic:

➡️ __init__() in Python – Constructor Made Simple (Coming up next)
July 6, 2025

Keyword	Meaning
`__init__()`	Constructor — runs when object created
`self`	Refers to the current object
Object	A real item created from a class

Why we use OOP?	Simple Explanation
Reuse Code	Use the same class to make many objects
Clean Code	Easy to read and update
Better Structure	Keep data and actions together

Word	Meaning
Class	Blueprint for making objects
Object	Real item created from class
`__init__()`	Gives values when object is created
`self`	Refers to the current object

What is init.py in Python?

🧩 What is `init.py` in Python?

📘 Definition

__init__.py is a special Python file used to mark a folder as a Python package.
It tells Python: “This folder contains Python code you can import.“

📦 Where is it used?

It is placed inside a package folder like this:

mypackage/
├── __init__.py
├── add.py
├── sub.py

✅ Why `init.py` is Important

Purpose	Explanation
Marks folder as a package	Without it, Python may not treat the folder as a package.
Runs code when imported	You can put code in it that runs automatically.
Helps in organizing imports	Makes it easy to control what’s imported.

✅ Example 1: Simple Empty `init.py`

# __init__.py
# (can be empty)

Usage:

from mypackage import add
print(add.add(2, 3))  # Output: 5

✅ Example 2: With Code in `init.py`

# __init__.py
print("Welcome to mypackage!")

def greet():
    print("Hello from the package!")

Usage:

import mypackage

mypackage.greet()

🖨 Output:

Welcome to mypackage!
Hello from the package!

✅ Example 3: Control Imports

If you want only certain modules to be accessible:

# __init__.py
__all__ = ['add']

Now:

from mypackage import *
# Only add is available, not sub

🔁 Summary

Item	Meaning
`__init__.py`	Makes folder a package
Can be empty	Yes
Can have code	Yes (runs on import)
Can control what to import	Yes with `__all__`

📝 Practice Task

❓ Create a package with:

__init__.py (prints “Package loaded”)
calc.py (function to add numbers)
Then import and use it.

✅ Answer:

Folder: tools/

➡️ __init__.py

print("Package loaded!")

➡️ calc.py

def add(a, b):
    return a + b

➡️ Main file:

from tools import calc
print(calc.add(4, 5))  # Output: 9

July 6, 2025

Author: Saravana Kumar

Encapsulation in Python | Easy OOP Explanation for Beginners

🔹 What is Encapsulation?

🔹 Why Encapsulation?

🔹 Example: Without Encapsulation

🔐 Example: With Encapsulation (using private variable)

🔎 What is __ (double underscore)?

🧠 Real-Life Example:

📝 Practice Questions with Answers

❓ Q1: Create a class BankAccount with private balance. Add deposit() and get_balance() methods.

❓ Q2: Make a class Person with private age. Use set_age() to update age with condition (must be > 0).

📘 Summary

📣 Coming Up Next:

What is self in Python? | Easy Explanation with Examples

🔹 What is self in Python?

📌 Important Points:

🔹 Example 1: Using self to store data

🔹 How self works:

🔹 Example 2: Use self in multiple objects

🔹 Example 3: Change values using self

📝 Practice Questions with Answers

❓ Q1: Create a class Laptop with brand and price. Use self to store and print data.

❓ Q2: Create a class Circle with radius. Use a method to calculate area. (Area = 3.14 × radius × radius)

🧾 Summary Table

📣 Next:

What is __init__() in Python? | Constructor Made Simple

🔹 What is __init__()?

🔹 Simple Example:

🔹 What is self in __init__()?

🔹 You Can Add More Than One Parameter

📝 Practice Questions with Answers

❓ Q1: Create a class Book with title and author. Use __init__() to set values and print them.

❓ Q2: Create a class Laptop with brand and price. Use __init__() and print details.

🔎 Summary

📣 Coming Next:

🧑‍🏫 What is Class and Object in Python? | Simple Explanation for Beginners

🔹 What is a Class?

🔹 What is an Object?

🔹 __init__() Method

🔹 What is self?

🧠 Real-Life Example

✅ Benefits of Using Class and Object

📝 Practice Questions

🧾 Summary Table

🔗 Next Topic:

What is __init__.py in Python?

🧩 What is __init__.py in Python?

📘 Definition

📦 Where is it used?

✅ Why __init__.py is Important

✅ Example 1: Simple Empty __init__.py

Usage:

✅ Example 2: With Code in __init__.py

Usage:

✅ Example 3: Control Imports

🔁 Summary

📝 Practice Task

❓ Create a package with:

🔎 What is `__` (double underscore)?

❓ Q1: Create a class `BankAccount` with private balance. Add `deposit()` and `get_balance()` methods.

❓ Q2: Make a class `Person` with private `age`. Use `set_age()` to update age with condition (must be > 0).

🔹 What is `self` in Python?

🔹 Example 1: Using `self` to store data

🔹 How `self` works:

🔹 Example 2: Use `self` in multiple objects

🔹 Example 3: Change values using `self`

❓ Q1: Create a class `Laptop` with `brand` and `price`. Use `self` to store and print data.

❓ Q2: Create a class `Circle` with radius. Use a method to calculate area. (Area = 3.14 × radius × radius)

What is init() in Python? | Constructor Made Simple

🔹 What is `init()`?

🔹 What is `self` in `init()`?

❓ Q1: Create a class `Book` with `title` and `author`. Use `init()` to set values and print them.

❓ Q2: Create a class `Laptop` with `brand` and `price`. Use `init()` and print details.

🔹 `init()` Method

🔹 What is `self`?

What is init.py in Python?

🧩 What is `init.py` in Python?

✅ Why `init.py` is Important

✅ Example 1: Simple Empty `init.py`

✅ Example 2: With Code in `init.py`