Class in Python: What is Python Class?

Introduction to Classes in Python

In Python, we have classes to help us bring all the related objects and functionality together so that it helps us to manage our code easily.

Unlike other programming languages, Python revolves around the concept of objects. Hence, it is an Object-Oriented Programming Language(OOPs).

Classes and objects are two main aspects of OOPs.

Class in python are the user-defined blueprints that help us create an object. Objects are the instances of a particular class. Every other element in Python will be an object of some class, such as the string, dictionary, number(20,30), etc. will be an object of some corresponding built-in class(int, str) in Python.

Let’s take an example to understand this concept better.

Here, we have the blueprint of a car on the left side. This is known as the class while on the right side we have some of the models of the cars based on that blueprint, which are known as the objects of the particular class.

Refer to the following image below:

Creating a Class in Python

Creating a class is as easy as creating a function in Python. In function, we start with the def keyword while class definitions begin with the keyword class.

Following the keyword class, we have the class identifier(i.e. the name of the class we created) and then the : (colon) operator after the class name.

In the next indented lines(statement 1..n) are the members of the class. Also, the variables inside the class are known as attributes. The attributes can be accessed later on in the program using the dot(.) operator.

The syntax for creating a Class in Python is as follows:

Let’s take a simple example of a class named Scaler.

Note: The keyword pass denotes an empty class. It is written just to avoid any errors in the console while running the above code.

Python Class Attributes and Methods

To make the most of Python Classes, we also need to add some functionality to the classes. We can make this possible with the help of attributes and methods.

We need to set some attributes which would contain some functions and data. These would add some functionality to our code.

Those functions which we define inside the class are known as methods.

Let’s take a look at these additional functionalities in brief.

Python Class Attributes

These are the variables that are defined inside the particular class and can be used by all the objects. These attributes can, later on, be called by using the class and attribute name with the dot(.) operator.

Let’s take a look at an example for further understanding.

Here we have a class named Scaler, with a class attribute named Course with a fixed value (ie ‘Python’).

Note: The value of any attributes will remain the same for all objects until and unless it is changed explicitly later on in the code.

Let’s continue with the above example to define some attributes and access it.

Output:

Here we have defined several attributes inside the Scaler Class. Also, we have shown two ways of accessing the values of those attributes. One, by directly using the class name and the other by using an object(class instance). Assigning a class to a variable is known as object instantiation.

Note: If we change the value of the attribute using the class name(the first method in the above example), then it would change across all the instances of that class. While if we change the value of an attribute using class instance(object instantiation), it would only change the value of the attribute in that instance only.

Let’s show an example to have clarity on this concept:

Output:

Python Class Methods

Once we have defined the class attributes, we can even define some functions inside the particular class that can access the class attribute and can add more functionality to the existing code.

These defined functions inside a class are known as methods. We can define as many methods as we want inside a single class.

Syntax:

We define a method(function) inside a class using the def keyword, followed by the method name. We then pass some arguments through the method.

Note: When we define a method, it must at least pass a single parameter which is generally named as self. It refers to the current instance of the class.

We can call this parameter by any name, other than self if we want.

Let’s take a look at an example of the same.

We can also pass other arguments inside the CourseDetails function if we want.

For example, let’s say we have a class Scaler, in which we have an attribute named “name” and a method named CourseDetails. The method would take the argument name along with self. We can also pass multiple arguments as per our requirements in the code.

Instance Attributes (_init_method) in Python:

We can also provide the values of the attributes during the time of object creation. Instance attributes are attached to the instance of a class. Whenever a new object of the class is created, this method is called.

This is done by defining the attributes under the _init_method. The init method is similar to the constructors as in other programming languages(C++, Java). Such a method contains statements that would be executed during the run time(time of object creation).

Let’s take an example to have more clarity on this particular method. This method begins with a double underscore(__).

Output:

Note: We can define separate attribute values for different objects(study1, study2) of a class.

Python Class Properties

In Python, with the property() function inside the class, we can define some additional functionalities.

The property() function, just like Java and other languages, takes the set, get and delete methods as arguments and returns an object. These functionalities can be easily incorporated into the code with property() function.

Let’s look at an example to understand the property() function –

Output:

Here the property(getCourseName, setCourseName) returns the property object and then assigns it to the parameter name.

Note: Using a property decorator (@property) is recommended, instead of the property() method, though both work well.

See Also:

• Python Decorators.
• What is python ?