Class Variable and Instance Variable

Python classes can hold two kinds of variables: class variables, which are shared across every object of that class, and instance variables, which hold unique data for each individual object.

Instance Variables

Instance variables are typically defined inside the __init__ method using self, and each object gets its own separate copy.

class Student:
    def __init__(self, name):
        self.name = name   # instance variable

s1 = Student("Abhay")
s2 = Student("Priya")
print(s1.name, s2.name)   # Abhay Priya (different for each object)

Class Variables

Class variables are defined directly inside the class body, outside any method, and their value is shared by every instance of the class unless explicitly overridden.

class Student:
    institute = "Uncodemy"   # class variable, shared by all students

    def __init__(self, name):
        self.name = name   # instance variable, unique per student

s1 = Student("Abhay")
s2 = Student("Priya")
print(s1.institute, s2.institute)   # Uncodemy Uncodemy

Coming Up Next

Next, you'll learn about constructors and destructors - the special methods that run automatically when an object is created and destroyed.