What are Class Variables in Python OOP?

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user1 and user2:

class User:
 # Class Variables 
 max_login_attempts = 5 
 password_min_length = 8
 system_name = "hasabTech Portal"
 def __init__(self, username): 
 # Instance Variable 
 self.username = username 
# Creating two different user instances from this class:

user1 = User("Shameel")
user2 = User("Ammad") 
# Print the value of all class variables using user1 instance:
print(f"User 1 Max Login Attempts: {user1.max_login_attempts}")
print(f"User 1 Min Pass Length: {user1.password_min_length}")
print(f"User 1 System Name: {user1.system_name}")
# Print the value of all class variables using user2 instance:
print(f"User 2 Max Login Attempts: {user2.max_login_attempts}")
print(f"User 2 Min Pass Length: {user2.password_min_length}")
print(f"User 2 System Name: {user2.system_name}")

In the case of an instance variable, you are bound to access it using the instance name. However, in case of accessing class variables, it's a matter of choice how one wants to access a class variable. As a general rule of thumb, it is preferred to use pattern # 1 i.e., access class variable using Class name.

Summary

What are Class Variables?

Class variables (also known as class attributes) are shared across all instances (objects) of a class. They belong to the class itself, not to any specific instance.

Two ways of accessing the values of a Class Variable

Access by Class name: Class.classVariableName
Access by Instance name: Instance.classVariableName