04. Understanding Python Classes: Objects, Blueprints & Methods

Introduction

In Python, classes form the foundation of object-oriented programming (OOP). A class acts as a blueprint for creating objects, bundling data (attributes) and behaviors (methods) together. In this post, you will learn how to define classes, instantiate objects, use constructors, define custom methods, and manage object properties.

What Are Classes and Objects?

A class defines a blueprint for objects. An object (or instance) is a concrete realization of that blueprint—each object has its own attributes and can call methods defined by its class.

For example, you might define a Car class with attributes like make, model, and methods like drive(). Then you can create multiple Car objects using that class blueprint.

Defining a Class

You use the class keyword to define a class. Inside a class you can define attributes and methods.

class MyClass:

x = 5

Here, MyClass has an attribute x with value 5.

To create an object of that class:

p1 = MyClass()

print(p1.x) # outputs 5

The init() Method (Constructor)

To initialize object attributes when an object is created, define the __init__() method inside the class. This is called automatically when you create a new object.

class Person:

def __init__(self, name, age):

self.name = name

self.age = age

p1 = Person("John", 36)

print(p1.name) # John

print(p1.age) # 36

Here, self refers to the instance being created, allowing you to assign values to its attributes.

The str() Method

By default, when you print an object, Python shows a generic representation. You can control how an object is represented as a string by defining __str__() in your class.

class Person:

def __init__(self, name, age):

self.name = name

self.age = age

def __str__(self):

return f"{self.name} ({self.age})"

p1 = Person("John", 36)

print(p1) # outputs: John (36)

If you don’t define __str__(), printing the object shows something like <__main__.Person object at 0x...>.

Defining Methods

Methods are functions defined inside a class that operate on objects. Use self to access object attributes inside methods.

class Person:

def __init__(self, name, age):

self.name = name

self.age = age

def greet(self):

print("Hello, my name is " + self.name)

p1 = Person("John", 36)

p1.greet() # Hello, my name is John

Methods let objects perform actions or compute values based on their state.

The self Parameter

Inside class definitions, self is not a keyword but a naming convention. It refers to the instance of the class and must be the first parameter in methods. You could name it differently (e.g. mysillyobject), but using self is standard and clearer to other developers.

class Person:

def __init__(mysillyobject, name, age):

mysillyobject.name = name

mysillyobject.age = age

def myfunc(abc):

print("Hello, my name is " + abc.name)

Here, mysillyobject and abc replace self. The behavior is the same, but it's less readable.

Modifying and Deleting Object Properties

You can modify object properties outside the class definition:

p1.age = 40

You can also delete attributes or even objects:

del p1.age

del p1

If you delete p1, the object no longer exists.

The pass Statement in Class Definition

If you want to define an empty class (i.e. a class with no methods or attributes yet), you cannot leave it blank. Use the pass statement to avoid syntax errors.

class Person:

pass

This creates a class with no contents; you can fill it later.

Summary

Classes in Python let you encapsulate data and behavior in reusable, modular structures. By defining attributes, constructors (__init__()), methods, and special methods like __str__(), you can create rich object types. Understanding self, modifying or deleting properties, and even defining empty classes with pass are fundamental skills for object-oriented development in Python.

04. Understanding Python Classes Objects Blueprints Methods

coldshadow44 on 2025-10-11

(0)