Learning Python Classes and Objects Step by Step

As Python programs grow, writing everything as separate variables and functions quickly gets messy. Classes solve this problem by grouping data and behavior together.

Thinking in Terms of Blueprints

Classes act as blueprints for creating Objects.

A class defines what something should look like and what it should be able to do. The class itself is not a tangible entity that you interact with. Instead, it describes how objects created from it should behave.

Here is a simple class definition:

Python class Dog with a bark method that prints the word “Woof”.

This class describes a dog. It says that every dog object should be able to bark.

Creating Objects From a Class

An object is an instance of a class. It is the real usable thing created from the blueprint.

Full Python example showing a Dog class with a name property, a bark method, two objects, and printed output.

Here, both dog1 and dog2 are objects. They were created using the Dog class. This class defines both data and behavior for dog objects. The object can call the bark method (line 5) because that behavior was defined in the class.

Let’s dissect the example:

1. The Class Definition

class Dog:

This line creates a new class named Dog.

class is the keyword that tells Python you are defining a class.
Dog is the class name, written in capitalized form by convention.

At this point, nothing is created yet. You are only defining a blueprint.

2. The __init__Method

Python constructor definition def __init__(self, name): for initializing object data.

This method runs automatically when a new object is created from the class.

__init__ is called the initializer
It prepares the object for use.
self refers to the current object instance (we could use any keyword but self is a common approach).
name is data passed in during creation

3. Storing Data With self

Python line assigning a parameter to an object property using self.name = name.

This line attaches data to the object.

self.name creates an attribute called name.
name on the right is the value passed in.

Each object gets its own name value.

Example:

Python code creating two Dog objects named Max and Bella using Dog(

dog1.name is “Max”

dog2.name is “Bella”

The objects share the same structure but hold different data.

4. The bark Method

Python method definition showing def bark(self): inside a class.

This defines a method that belongs to the class.

Methods describe what an object can do.
self gives the method access to the object’s data.

5. Using Object Data Inside a Method

Python print statement that outputs the dog’s name followed by the text “says woof” using self.name.

This line uses the object’s stored data.

self.name retrieves the name of the current object.
The output changes depending on which object calls the method.

Example:

Python console output showing two method calls, printing “Max says woof” and “Bella says woof”.

Key Takeaways

The class defines structure and behavior.
__init__ prepares each object.
self refers to the current object instance.
Attributes store data.
Methods act on that data.

Class Versus Object

The difference between a class and an object is simple once you see it in action.

A class serves to define the structure and behavior of object instances.
An object holds actual data and uses that behavior.

By writing just one class (one blueprint) you can create many objects. This keeps code organized and avoids repetition.

Wrapping It Up

Classes are the manifestation of real ideas into blueprints. Users, products, files, or messages are some of these ideas and all can all be represented as objects following the structure dictated by the class.

Each object maintains its own state while adhering to rules defined by the class. This approach keeps programs readable and easy to extend.

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