🔒 Encapsulation in Python — Keeping Your Data Safe!

 Have you ever saved a secret in your diary with a lock? Or kept your chocolate hidden in a secret drawer? 🍫

That’s Encapsulation in real life!

In Python, Encapsulation is a way to hide or protect data so only certain parts of your code can use or change it. It helps kyour programs safe and organized — just like putting your stuff in a locker with a key!

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🧠 What is Encapsulation?

Encapsulation means bundling data and the methods that work on that data into one unit — a class.

But more importantly:

• It hides private data

• It only allows controlled access

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📦 Real-life Analogy

Think of a mobile phone:

• You can use it (call, play games)

• But you can’t open it and change the battery or circuit

That’s encapsulation — some parts are visible, and some are hidden to protect the system!

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🐍 Let’s Learn with Python!

🎒 Class with Protected Data

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

    def show_info(self):
        print(f"Name: {self.name}, Marks: {self.__marks}")

    def update_marks(self, new_marks):
        if new_marks >= 0:
            self.__marks = new_marks
        else:
            print("Marks can't be negative!")

📚 Try it Out:

s1 = Student("Aryan", 85)
s1.show_info()
s1.update_marks(90)
s1.show_info()

# Let's try to change marks directly
s1.__marks = 30
s1.show_info()  # Still shows 90!

💬 Output:

Name: Aryan, Marks: 85
Name: Aryan, Marks: 90
Name: Aryan, Marks: 90

Why didn't s1.__marks = 30 work?

Because __marks is private — only accessible inside the class!

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🕵️‍♂️ Accessing Private Data (Not Recommended)

You can access private data using a special trick, but it’s not safe and not advised:

print(s1._Student__marks)

This works, but we should avoid it. Instead, use getter/setter methods like update_marks().

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✅ Why Use Encapsulation?

Advantage	What it Means
🎯 Controlled Access	Only allow safe changes to data
🔒 Data Protection	Hide sensitive data from outside access
📦 Clean Organization	Keep code tidy and manageable
🚫 Prevent Misuse	Stop users from breaking your class logic

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🎮 Challenge for You!

Create a class BankAccount with:

• Private balance

• Method to show balance

• Method to deposit and withdraw money

• Prevent withdrawal if not enough money

Can you do it? Try it in your Python editor!

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🧠 In Short

• Encapsulation = Wrapping data and methods into a class

• Use __variable to make it private

• Control access with functions inside the class

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📘 Exercise 

1. Private Attribute Creation

Create a BankAccount class with:

• A private attribute __balance

• A method deposit(amount) to increase balance

• A method get_balance() to return the balance
  Task: Create an object, deposit ₹1000, and print the balance.

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2. Name Mangling Access

Using the BankAccount class from Q1, try accessing the __balance attribute directly from outside the class using name mangling.
Task: Demonstrate how to read and modify it without using getter/setter.

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3. Private Method

Create a Car class with:

• A private method __engine_start() that prints "Engine started"

• A public method start() that calls the private method
  Task: Create an object and start the car.

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4. Getter & Setter Methods

Create a Student class with a private attribute __marks.

• Write getter and setter methods for marks.

• The setter should validate that marks are between 0 and 100, otherwise reject.
  Task: Test with valid and invalid marks.

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5. Property Decorator

Rewrite Q4 using @property and @marks.setter instead of getter/setter methods.
Task: Show that student.marks = 85 works directly.

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6. Encapsulation for Read-Only Attribute

Create a Book class with:

• A private attribute __isbn

• A read-only property isbn
  Task: Try changing ISBN from outside and show it fails.

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7. Encapsulation in Inheritance

Create a Person class with a private attribute __age.
Create a Teacher class that inherits from Person.
Task: Show that Teacher objects cannot access __age directly.

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8. Encapsulation with Method Overriding

Create a Device class with:

• A private attribute __status

• A public method turn_on() that sets status to "ON"

• A public method turn_off() that sets status to "OFF"
  Create a subclass SmartDevice that overrides turn_on() to print "Smart device starting..." before turning on.
  Task: Demonstrate usage.

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9. Encapsulation with List of Objects

Create a Library class with:

• A private list __books

• Methods add_book(title) and get_books()
  Task: Add books and print them without directly accessing __books.

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10. Secure Attribute Access

Create a User class with:

• Private attribute __password

• Method set_password(pwd) that stores password only if it meets certain criteria (min 8 chars, contains number & letter)

• Method check_password(pwd) to verify if entered password matches stored one
  Task: Test with valid and invalid passwords.