? Python Classes and Objects

⚡ Quick Overview

A class is a blueprint for creating objects. It defines the attributes (data) and methods (functions) that its objects will have. Objects are instances of a class and can hold their own unique data while sharing the behavior defined by the class.

? Key Concepts

Class: A blueprint or template that describes what data and behavior its objects will have.
Object: A concrete instance created from a class; it has real data stored in its attributes.
__init__(): A special initializer method that runs automatically when an object is created.
self: Refers to the current object instance; used to access attributes and methods.
Attributes: Variables that belong to an object (e.g., name, breed).
Methods: Functions defined inside a class that describe the behavior of its objects (e.g., bark()).

? Syntax and Theory

A basic Python class is defined using the class keyword. The __init__() method initializes the attributes for each new object created from the class.

When you create an object (also called instantiating a class), Python calls __init__() automatically and passes the arguments you provide to it.

? Creating a Class and an Object

Here is a simple Dog class with two attributes (name and breed) and one method (bark()).

? View Code Example – Define Class and Create One Object

class Dog:
    def __init__(self, name, breed):
        self.name = name      # instance attribute
        self.breed = breed    # instance attribute

    def bark(self):
        print(f"{self.name} is barking!")

# Creating an object
dog1 = Dog("Buddy", "Golden Retriever")

? Working with Objects

Once an object is created, you can access its attributes and call its methods using the dot (.) operator.

? View Code Example – Access Attributes and Call Methods

print(dog1.name)   # Buddy
print(dog1.breed)  # Golden Retriever

dog1.bark()        # Buddy is barking!

? Multiple Objects from One Class

You can create many objects from the same class. Each object has its own data but shares the structure and behavior defined by the class.

? View Code Example – Multiple Dog Objects

dog2 = Dog("Charlie", "Beagle")
dog3 = Dog("Max", "German Shepherd")

dog2.bark()  # Charlie is barking!
dog3.bark()  # Max is barking!

⚙️ Class vs Object

You can think of a class as a blueprint and an object as the actual thing built from it:

A class is like a recipe for a cake.
An object is the actual cake you bake using that recipe.
You can use the same recipe (class) to bake many cakes (objects), each with its own decorations (data).

? Live Output

? Expected Output

If you run all of the code examples together, you would see something like:

# Expected output when running all the code above
Buddy
Golden Retriever
Buddy is barking!
Charlie is barking!
Max is barking!

Each call to bark() prints a message that includes the name of the specific dog object. Even though all objects are created from the same Dog class, they carry their own values for name and breed.

? Tips and Best Practices

Think of a class as a recipe and objects as cakes made from that recipe.
You can create as many objects from a class as you need; each object can hold its own data.
Always include self as the first parameter in methods defined inside a class.
Use methods to define what your objects can do (their behavior).
Remember: instance attributes (like self.name) belong to each object separately.

? Try It Yourself

Create a Car class with attributes brand and year. Then make three different car objects.
Write a Student class with a method study() and call it using two different student objects.
Build an Animal class and create different animal objects with their names.
Experiment by adding more methods (like start(), stop(), eat()) to your classes.