Python Classes and Objects

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🔹 Classes and Objects in Python

Python is an object-oriented programming (OOP) language. This means it allows you to create and use classes and objects—which helps you organize and reuse code easily.

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🔸 What is a Class?

A class is like a blueprint for creating objects. Think of a class as a design for a car. It defines what a car is (wheels, engine, doors), but it's not a real car yet.

A class is a code template for creating objects. 

Objects have member variables and have behavior associated with them. 

In python, a class is created by the keyword class.

Example:

class Car:
    # attributes and methods go here
    pass

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🔸 What is an Object?

An object is a real-world instance of a class. If a class is the blueprint, then an object is the actual car built using that blueprint.

Example:

my_car = Car()

Now my_car is an object of the Car class.

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🔸 Let’s Build a Real Example

Let’s create a class that represents a Person with a name and age, and a method to display their info.

✅ Example:

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

    def greet(self):          # method
        print(f"Hello, my name is {self.name} and I am {self.age} years old.")

# Creating objects
person1 = Person("Surya", 25)
person2 = Person("Pawan", 30)

# Calling methods
person1.greet()
person2.greet()

💡 Output:

Hello, my name is Surya and I am 25 years old.
Hello, my name is Pawan and I am 30 years old.

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🔸 Breaking It Down

Part	Description
class Person:	Defines a class called Person
__init__	A special method called a constructor; runs when you create an object
self	Refers to the current object (must be the first parameter in methods)
self.name = name	Assigns the input to the object's attribute
greet()	A method that prints a message using the object’s data

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🔸 Another Example: A Simple Bank Account

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

    def deposit(self, amount):
        self.balance += amount
        print(f"{amount} deposited. New balance: {self.balance}")

    def withdraw(self, amount):
        if amount <= self.balance:
            self.balance -= amount
            print(f"{amount} withdrawn. New balance: {self.balance}")
        else:
            print("Insufficient balance!")

# Create an account
account = BankAccount("John", 1000)

# Use the methods
account.deposit(500)
account.withdraw(300)
account.withdraw(1500)

💡 Output:

500 deposited. New balance: 1500
300 withdrawn. New balance: 1200
Insufficient balance!

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🔚 Summary

• A class defines the structure and behavior (attributes and methods).

• An object is a real example of the class.

• Use __init__ to initialize object attributes.

• Use self to refer to the current object inside the class.

• Classes help keep your code organized, reusable, and clean.

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