What Is Isinstance in Python And How To Implement It?

Isinstance Python

Python isinstance() function returns True if the object is specified types, and it will not match then return False. 

Syntax: isinstance(obj, class)

Parameters : 

• obj : The object that need to be checked as a part of class or not.
• class : class/type/tuple of class or type, against which object is needed to be checked.

Returns : True, if object belongs to the given class/type if single class is passed or any of the class/type if tuple of class/type is passed, else returns False. Raises

TypeError: if anything other than mentioned valid class type. 

Example for Python isinstance() :

Example 1: Python isinstance with int and list

• Python3

# Python 3 code to demonstrate
# working of isinstance()
# with native types
 
# initializing native types
test_int = 5
test_list = [1, 2, 3]
 
# testing with isinstance
print("Is test_int integer? : " + str(isinstance(test_int, int)))
print("Is test_int string? : " + str(isinstance(test_int, str)))
print("Is test_list integer? : " + str(isinstance(test_list, int)))
print("Is test_list list? : " + str(isinstance(test_list, list)))
 
# testing with tuple
print("Is test_int integer or list or string? : "
      + str(isinstance(test_int, (int, list, str))))

Output:

Is test_int integer? : True
Is test_int string? : False
Is test_list integer? : False
Is test_list list? : True
Is test_int integer or list or string? : True

Example 2: Demonstrating the use of isinstance() with objects 

• Python3

# Python 3 code to demonstrate
# working of isinstance()
# with objects
 
# declaring classes
class gfg1:
    a = 10
 
# inherited class
class gfg2(gfg1):
    string = 'GeeksforGeeks'
 
 
# initializing objects
obj1 = gfg1()
obj2 = gfg2()
 
# checking instances
print("Is obj1 instance of gfg1? : " + str(isinstance(obj1, gfg1)))
print("Is obj2 instance of gfg2? : " + str(isinstance(obj2, gfg2)))
print("Is obj1 instance of gfg2? : " + str(isinstance(obj1, gfg2)))
 
 
# check inheritance case
# return true
print("Is obj2 instance of gfg1? : " + str(isinstance(obj2, gfg1)))

Output:

Is obj1 instance of gfg1? : True
Is obj2 instance of gfg2? : True
Is obj1 instance of gfg2? : False
Is obj2 instance of gfg1? : True

Example 3: Python isinstance array

• Python3

test_list = [1, 2, 3]
print ("Is test_list list? : " + str(isinstance(test_list, list)))

Output:

Is test_list list? : True

Example 4: Python isinstance string

• Python3

test_str = "GeeksforGeeks"
print ("Is test_str string? : " + str(isinstance(test_str, str)))

Output:

Is test_str string? : True

Example 5: Python isinstance dict

• Python3

test_dict = {"apple" : 1, "Ball" : 2 }
print ("Is test_str dictionary? : " + str(isinstance(test_dict, dict)))

Output:

Is test_str dictionary? : True

Example 6: Python isinstace class methods 

• Python

class geeks:
    course = 'DSA'
   
    def purchase(obj):
        return obj.course
   
   
geeks.purchase = classmethod(geeks.purchase)
str(isinstance(geeks.purchase(), str ))

Output:

True