Classes and objects are the basis of object-oriented programming (OOP) 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
What Are Classes and Objects?
Classes 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 defines the housing for creating multiple objects, where the objects are similar in functions and properties.
Steps to create a class:
- Define it using the class keyword.
- It can contain attributes (variables) and methods (functions).
Example:
Output:
Objects in Python
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:
- Define a class using the class keyword.
- Create an object by calling the class as a function.
- Access attributes and methods of the object using the dot (.) notation.
Example:
Output:
Advantages of Using Classes and Objects in Python:
- Organised Code: Class helps in grouping related data and functions, which makes the Python code more readable and efficient.
- Reusable: Once a class has been created, it may be used to create multiple objects with less time and effort.
- Data Protection: Classes help in hiding certain details to secure the important information which are private.
- Inheritance: Classes can be created from existing classes, which is done by inheriting and adding new features to the existing class without the need to create a new one.
- Flexibility: Various classes may have the same method names. Makes code more flexible and also increases efficiency
- Scalability: Classes help to add new features or objects without modifying existing code.
Magic Method 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.
The __init__ Method in Python
It 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 __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.
The __str__ Method in Python
The __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 Python
Python Class Variables
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 are often used for attributes or properties that should be consistent across all instances.
Example:
Output:
Explanation: Here, the platform variable is a class attribute shared by all instances, and modifying it at the class level changes it for all objects.
Python Instance Variables
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 (course_name and instructor), which can be modified individually and do not affect other objects.
Accessing Class Attributes Using Objects
The 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 Python
A 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 (OOP).
1. Encapsulation in Python
Encapsulation 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 Python
Inheritance 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 Python
Polymorphism 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 Python
Abstraction 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 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. |
Best Practices for Working with Classes and Objects in Python
By applying best practices when using classes and objects, you can create well-written, efficient, maintainable code in Python.
- Use clear naming: Class and variable naming should be clear in the purpose of the class or variable.
- Keep methods focused and simple: Each method should perform only one task, which helps in improving the reusability and maintainability.
- Use instance variables appropriately: Always lace object-specific data in instance variables in addition to reading. Otherwise, there will be no object-specific attributes that can differ, and the data will collide.
- Follow encapsulation for data security: Use underscore ‘ _’ or double underscore ‘ __’ for private attributes to restrict direct access to the data and manage the safety of the data.
- Avoid deep inheritance: Use inheritance only when it is necessary, and prefer using composition, where the class contains the objects of the other class, which helps in keeping the code easy to manage.
Real-World Applications of Classes and Objects in Python
Classes 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.
- Web Development: Frameworks such as Django and Flask utilise classes in defining the models for handling sessions, user authentication, and database timing of information, providing structure to web apps, if utilised properly.
- Game Development: Objects represent representations of game executable components, such as enemies, weapons, and so on, that allow the developers to manage and handle interactions in a structured manner.
- Data Science and AI: Class and instance variables, along with magic methods, help with the representation of machine learning models, datasets, and preprocessing.
- Banking Systems: Classes are often used in representing customers, accounts, transactions, and loans, which are all part of data security and financial operations in a structured way.
- E-Commerce Applications: Objects could also represent products, users, orders, and payment methods, which helps the developer to manage large-scale online products in an organised way.
Conclusion
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.
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Python Classes and Objects – FAQs
Frequently Asked Questions
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.