Python - Classes and Objects (Complete Guide for Beginners)

 Python is an object-oriented programming (OOP) language, which means it allows you to organize code using classes and objects. These concepts help you build programs that are more structured, reusable, and easier to manage.

In this tutorial, you will learn what classes and objects are, how to create them, and how to use them in real-world examples.

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What is a Class?

A class is a blueprint or template for creating objects.

It defines:

• Attributes (variables)
• Methods (functions)

Example:

class Car:
    pass

Here, Car is a class, but it does nothing yet.

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What is an Object?

An object is an instance of a class. It represents a real-world entity.

Example:

class Car:
    pass

car1 = Car()

print(car1)

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Class vs Object

Class	Object
Blueprint	Real instance
Defines structure	Uses structure
Example: Car design	Example: Toyota Car

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Creating a Class with Attributes

Attributes are variables inside a class.

Example:

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

car1 = Car("Toyota", "Corolla")

print(car1.brand)
print(car1.model)

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The init Method (Constructor)

The __init__ method is automatically called when an object is created.

Example:

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

s1 = Student("John", 20)

print(s1.name)
print(s1.age)

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Adding Methods in a Class

Methods are functions inside a class.

Example:

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

    def greet(self):
        print("Hello", self.name)

s1 = Student("Alice")
s1.greet()

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Creating Multiple Objects

Each object has its own data.

Example:

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

s1 = Student("John")
s2 = Student("Sara")

print(s1.name)
print(s2.name)

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Modifying Object Values

You can change values after creating objects.

Example:

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

car1 = Car("Toyota")

car1.brand = "Honda"

print(car1.brand)

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Deleting Object Properties

You can delete attributes using del.

Example:

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

s1 = Student("John")

del s1.name

# print(s1.name)  # This will cause error

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Deleting Objects

You can delete objects completely.

Example:

class Car:
    pass

car1 = Car()

del car1

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The self Keyword

self refers to the current object.

Example:

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

    def show(self):
        print(self.name)

s1 = Student("John")
s1.show()

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Real-World Example: Student System

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

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

s1 = Student("John", 85)
s2 = Student("Alice", 90)

s1.display()
s2.display()

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Real-World Example: Car System

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

    def show(self):
        print(self.brand, "runs at", self.speed, "km/h")

car1 = Car("Toyota", 120)
car2 = Car("BMW", 200)

car1.show()
car2.show()

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Key Features of Classes and Objects

• Code reusability
• Easy maintenance
• Real-world modeling
• Data encapsulation
• Scalability

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Common Mistakes

Mistake 1: Forgetting self

❌ Wrong:

def show(name):
    print(name)

✔ Must use self

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Mistake 2: Not creating object

Car.show()

✔ Must create object first

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Mistake 3: Confusing class and object

✔ Class = blueprint, Object = real instance

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Safe Example

class Test:
    def show(self):
        print("Hello OOP")

t = Test()
t.show()

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Conclusion

Classes and objects are the foundation of Python OOP programming.

You learned:

• What classes and objects are
• How to create attributes and methods
• How to use constructors
• Real-world examples
• Key OOP concepts

Mastering classes and objects is the first step to becoming an expert in Python object-oriented programming.