Class and Instance Attributes in Python

Class attributes

Class attributes belong to the class itself they will be shared by all the instances. Such attributes are defined in the class body parts usually at the top, for legibility.

# Write Python code here
class sampleclass:
    count = 0     # class attribute

    def increase(self):
        sampleclass.count += 1

# Calling increase() on an object
s1 = sampleclass()
s1.increase()
print(s1.count)

# Calling increase on one more
# object
s2 = sampleclass()
s2.increase()
print(s2.count)

print(sampleclass.count)

Output:

1              
2                           
2

Instance Attributes

Unlike class attributes, instance attributes are not shared by objects. Every object has its own copy of the instance attribute (In case of class attributes all object refer to single copy).

To list the attributes of an instance/object, we have two functions:-
1. vars()– This function displays the attribute of an instance in the form of an dictionary.
2. dir()– This function displays more attributes than vars function,as it is not limited to instance. It displays the class attributes as well. It also displays the attributes of its ancestor classes.

# Python program to demonstrate
# instance attributes.
class emp:
    def __init__(self):
        self.name = 'xyz'
        self.salary = 4000

    def show(self):
        print(self.name)
        print(self.salary)

e1 = emp()
print("Dictionary form :", vars(e1))
print(dir(e1))

Output :

Dictionary form :{'salary': 4000, 'name': 'xyz'}
['__doc__', '__init__', '__module__', 'name', 'salary', 'show']