Class or Static Variables in Python?

In this article we are going to learn about class or static variables on python. The class variables or static variables that are used to share across all the instances of a class. Unlike the instance variables which are specific to each object, Class variables maintain the common value for all the objects of the class.

They are defined within the class but outside any instance methods, making them accessible to all the instances. These variables are used when we want to have a single shared state or value among all instance.

Example 1

Let's look at the following example, where we are going to demonstrate how class variable can be used to count the objects created.

class demo:
    count = 0
    def __init__(self, name):
        self.name = name
        demo.count += 1
x1 = demo("Ravi")
x2 = demo("Suresh")
print("Result :", demo.count)

Following is the output of the above program -

Result : 2

Example 2

Consider the following example, where we are going to illustrate how class variable provides a shared configuration value across different objects.

class demo:
    studying = "B.tech"
    def __init__(self, user):
        self.user = user
x1 = demo("Sunil")
x2 = demo("Poorna")
print(x1.studying)
print(x2.studying)

The output of the above program is -

B.tech
B.tech

Example 3

In the following example, we are going to modify the class variables from outside the class.

class demo:
    drive = "2stroke"
    def __init__(self, model):
        self.model = model
print("Initial drive:", demo.drive)
demo.drive = "4stroke"
x1 = demo("Ciaz")
print("After Modification :", x1.drive)

Following is the output of the above program -

Initial drive: 2stroke
After Modification : 4stroke