Classes and objects are the basis of object-oriented programming in Python. Knowing them will help you in writing organised, efficient, reusable code. The key to understanding classes and objects in Python is that the objects get their functionality from classes when they store data and include actions. In this article, you will learn about classes and objects in Python, along with the practical examples and best practices in detail.
Table of Contents:
Classes and objects are the building blocks of object-oriented programming in Python, where classes and objects are the actual instances created from them.
How to Define a Class in Python?A class in Python is a blueprint for creating objects. It assists in defining the properties(data) and actions (methods, which are the functions) that objects will have, much like the building plans that guide the construction of a home. A class in Python defines the housing for creating multiple objects, where the objects are similar in functions and properties.
Steps to create a class in Python:
Example: Python init method
Output:
Creating Objects in Python (Step-by-Step)In Python, an object is a specific instance of a class that holds data (attributes) and performs the same actions (methods) that are specified by the class. Each object has its own data, but uses the same method defined in the class.
Steps to create an object:
Example:
Output:
Advantages of Using Classes and Objects in Python:Magic methods in Python are special functions that start and end with double underscores (__). They allow the class objects to make actions automatic, including setting values as they are created, printing output, or comparing with other objects. It gives us the ability to modify the functionality and behaviour of classes without additional programming.
Understanding Python’s init Constructor MethodIt is a special constructor method inside a class that gets called automatically when a new object is created. It helps initialize the object’s attributes. In the example below, the keyword self refers to the current instance (like course1, course2). Each object created using the class will have its own set of attributes and methods.
Example:
Explanation: Here, the Python init method automatically sets the course_name and duration attributes for the object when it is created.
Initiate Object with __init__
The __init__ method in Python automatically initialises an attribute of the object when the object is created.
Example:
Output:
Explanation: Here, the __init__ method automatically initialises the object’s course_name and duration attributes when created.
Python str Method – Custom String Output for ObjectsThe __str__ method in Python allows you to define a custom string for the objects created, which helps in making the object more meaningful and readable. By default, when we print an object or convert it to a string using str(), Python uses the default implementation, which returns a string like <__main__.ClassName object at 0x…>. With the help of __str__, the object that is displayed can be controlled.
Example:
Output:
Explanation: Here, the __str__ method customises how the IntellipaatCourse object is displayed, which makes it more readable.
Class and Instance Variables in PythonClass Variables in Python
The class variables in Python are shared among all instances of a class.. Unless explicitly overridden at the instance level, this Python variable holds the same value for all instances. Class variables in Python are often used for attributes or properties that should be consistent across all instances.
Example:
Output:
Explanation: Here, the platform variable is a class variables in Python attribute shared by all instances, and modifying it at the class level changes it for all objects.
Instance Variables in Python
An instance variable in Python is a variable that belongs to specific objects which is created from a class. Every object has a copy of its variable, which allows the object to store unique data. These variables are normally defined within the methods like __init__ using a self keyword. This helps in ensuring that each object maintains its state independently of the other objects.
Example:
Output:
Explanation: Here, each object has its own instance variables in Python (course_name and instructor), which can be modified individually and do not affect other objects.
Accessing Python Class Attributes Using Object InstancesThe class variable in Python can be accessed with an object by using the dot notation object_name.attribute_name. This will help you to retrieve the value of the class attribute that is associated with the specific object. As the class attributes are shared among all the objects, accessing them with the object gives the same value, which means that if any change is made to the class attribute, the same will be reflected across all the objects.
Example:
Output:
Explanation: Here, the class attribute platform is accessed directly using the class name and also using the instances, showing that the class attributes remain the same for all objects.
Key Concepts of Classes in PythonA class is a blueprint for making an object. They help in organising data and functions together efficiently. There are four key concepts of classes are Encapsulation, Inheritance, Polymorphism, and Abstraction, which are the foundation of object-oriented programming in Python (OOP).
1. Encapsulation in PythonEncapsulation is a technique of restricting direct access to some properties of an object, while still giving controlled access through methods. This is essential because encapsulation allows you to save sensitive information and prevents modification of the information. When using encapsulation, with private variables, you get to prevent direct access to the variable by the outside world. This ensures that all access to the variable provides the functionality you want, while hiding as many details as you choose.
Example:
Output:
Explanation: Here, the price variable is private, meaning no direct access to the variable from outside the class will be allowed.
2. Inheritance in PythonInheritance allows a child class to acquire the properties and methods of a parent class. This enables code reuse and reduces repetition. The child class can also override or extend the functionalities of the parent class. It is helpful when creating a hierarchy of related classes, so that the shared attributes and behaviours can be managed effectively.
Example:
Output:
Explanation: Here, the AdvancedCourse class inherits from the Course class and reuses its properties.
3. Polymorphism in PythonPolymorphism allows different classes to define the same method name, but perform different actions. This makes your code more flexible and scalable because, while working with objects, those objects could be treated interchangeably. Polymorphism enables developers to code many versions of one method in different classes and still have polymorphism.
Example:
Output:
Explanation: Here, both classes have a show_details() method, but they behave differently based on the class.
4. Abstraction in PythonAbstraction is the method of hiding complex data and only presenting the necessary information. It uses the abstract classes and methods, which serve as blueprints for other classes. Abstraction helps in reducing the complexity of the code and improving the readability by showing only the data that is essential.
Example:
Output:
Explanation: Here, Course is an abstract class that defines a structure, and DataScience implements the method.
Class vs Object in PythonBelow is the comparison table between class vs object in Python.
Feature Class Object Definition A class is a blueprint or template that is used to create objects. An object is a specific instance of a class. Memory A class does not take memory space until objects are created. Each object takes up memory because it holds data. Stores Data A class only defines variables but does not store any real values. Objects store actual values in variables, unique to each object. Uses Methods A class contains functions (methods) that define behavior but do not run by themselves. An object calls these methods to perform actions using its data. Changes Changing something in the class affects all future objects created from it. Changing one object’s data does not affect other objects. Example class Course: it defines how the course has to be structured.course1 = Course() (Creates a real course with details). Purpose A class is used to define multiple objects with the same structure and behavior. An object represents one specific item with its data and behavior. Composition vs Inheritance in Python Feature Composition Inheritance Relationship Type “Has-a” “Is-a” Flexibility More flexible, loosely coupled Less flexible, tightly coupled Reusability Achieved by using components Achieved by extending base classes Change Impact Localized changes Changes in parent affect child classes Use Case Preferred for code maintainability Preferred when subclassing makes sense Class Methods vs Static Methods Feature Class Method Static Method Decorator Used @classmethod @staticmethod First Argument cls (refers to the class) No default first argument Access to Class State Yes, the class method can access to class state No, a static method cannot access class state Use Case Modify the class state or the alternative constructor Utility functions related to the class Access Instance (‘self’) No No Best Practices for Writing Python Classes and Objects
By applying best practices when using classes and objects, you can create well-written, efficient, maintainable code in Python.
Python allows the creation of custom exceptions using classes, which is a powerful way to handle specific error conditions with clarity.
To define a custom exception, create a new class that inherits from Python’s built-in Exception class. This is especially useful in large applications where predefined exceptions do not provide enough context.
Using custom exception handling with classes improves error reporting, making code easier to debug and maintain.
Real-World Use Cases of Python Classes and ObjectsClasses and objects in Python are frequently used in practical scenarios that help in organising a program. It helps to manage information, encourages code reuse, and simplifies the development process as a whole across different sectors.
Classes and objects are very important for Object-Oriented programming in Python, which gives us a way to write code in a more efficient and organised manner. Instead of storing the data, we can use classes and the objects along with the magic methods to manipulate information within objects. Knowing the difference between classes and objects, along with some best practices, will help you write clean and error-free code. All the key concepts of the classes are applied in real-world scenarios, which are used for structuring the code. Mastering these concepts helps in writing a simple and organised code.
Further, check out our Python Certification course and get ready to excel in your career with our Basic Python Interview Questions prepared by experts.
Python Classes and Objects - FAQs
Q1. What is a class in Python?
A class is a template for creating objects. It defines the attributes (variables) and behaviours (methods) that objects created from the class will have.
Q2. How do you create an object in Python?
You can create an object by calling the name of the class like a function, for example: obj = ClassName() creates an instance of ClassName.
Q3. What is the purpose of the __init__ method in Python?
The __init__ method is a special class method that is run automatically when an object of the class is created. It initializes instance variables.
Q4. What is the difference between class variables and instance variables?
Class variables are accessible by all instances of the class (every individual object created from the class), and instance variables are unique to each instance of the class.
Q5. Why should we use classes and objects in Python?
Classes and objects help to structure code, increase reuse, and follow the principles of OOP like encapsulation and inheritance to structure the code.
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