Understanding
Classes and Objects

What are Classes and Objects?

In programming, a class is a blueprint or template that defines the structure and behavior (data and functions) of objects. An object is an actual instance of a class—just like a real-world object with properties and actions.

Imagine a class as a recipe and an object as the actual dish prepared from that recipe.

Real-World Analogy

Consider a "Car" as a class. All cars have certain properties like color, model, and engine type. They also have behaviors like drive, brake, and honk.

• The Car class defines these common properties and actions.
• Your individual car, say a red sedan, is an object (an instance) of that class.

Why Do We Use Classes and Objects?

• To model real-world entities in code.
• To group related data and functions together.
• To reuse code efficiently (you can create many objects from one class).

Basic Class and Object Structure

class Car:
    attribute color
    attribute model

    method drive():
        print "The car is driving."

    method brake():
        print "The car has stopped."

# Creating an object
myCar = new Car()
myCar.color = "Red"
myCar.model = "Sedan"

myCar.drive()
myCar.brake()

Output:

The car is driving.
The car has stopped.

Explanation of the Code

• class Car defines a blueprint for cars.
• attribute defines the properties every car has.
• method represents actions the car can perform.
• myCar is an instance (object) created from the Car class.
• We assign values to its attributes and call its methods.

Question: What happens if you create another car object?

Answer: You can create as many car objects as needed, each with its own unique state (color, model, etc.), but all sharing the same behavior (methods).

Another Example: Class for a Student

Let’s consider modeling a student:

class Student:
    attribute name
    attribute grade

    method introduce():
        print "Hi, my name is " + name + " and I am in grade " + grade

# Creating objects
student1 = new Student()
student1.name = "Alice"
student1.grade = "10"

student2 = new Student()
student2.name = "Bob"
student2.grade = "12"

student1.introduce()
student2.introduce()

Output:

Hi, my name is Alice and I am in grade 10
Hi, my name is Bob and I am in grade 12

Beginner Intuition Check

Q: Can two objects have different values for the same attribute?
A: Yes, even though both are instances of the same class, their properties can have different values.

Key Takeaways

• A class defines a template; an object is an instance of that template.
• Classes help organize code and model real-life entities with attributes and behaviors.
• Objects created from the same class can have different values but share the same structure.

Practice Questions

• What’s the difference between a class and an object?
• How can you create multiple objects from the same class?
• Can objects share methods but have different attribute values?

Next Up

We’ll learn about constructors, the special methods used to initialize objects with default values upon creation.