isinstance() to check if object argument is an instance of input classinfo in Python

Check if the input object is instance of input classinfo.

object : Object to be checked for instance against classinfo
classinfo : object to be checked against this classinfo. Can be a tuple of more than one class

isinstance returns True if object is instance of given classinfo, False otherwise.

isinstance(ojbect,classinfo)

built in types

We have built in types in Python. We can check the object against built in types like string, integer, float, list ,tuple, set , dictionary etc.

my_number=34
my_str='plus2net'
my_list=['a','b','c']
my_tuple=('x','y','z')
my_dict={1:'One',2:'Two',3:'Three'}
my_set={'one','two','three'}

print(isinstance(my_number,int))  # True
print(isinstance(my_str,str))     # True
print(isinstance(my_list,list))   # True
print(isinstance(my_tuple,tuple)) # True
print(isinstance(my_dict,dict))   # True
print(isinstance(my_set,set))     # True

Using tuple

We can check against more than one classinfo by using a tuple

my_str='plus2net'
print(isinstance(my_str,int))        # False 
print(isinstance(my_str,(int,str)))  # True

In last line we used a tuple of ( int,str). As our string object my_str is an instance of string ( str ) class so it returns True. However in previous line we checked against integer ( int ) so we got False as output.

Using user defined class

animals() is or base or parent class. wild() is out derived or child class.

class animals():
    home='Jungle' #class attribute
#instance attributes
    def __init__(self,name,height):
        self.name= name
        self.height=height
class wild(animals):
    weight=2
class birds(wild):
    name='Eagle'
    
tiger=animals('Alex',4) # object of animal class created

print(isinstance(tiger,animals))  # True
print(isinstance(tiger,wild)) # False 
print(isinstance(tiger,birds)) # False

lion=wild('Tom',3)      # object of wild class created
print(isinstance(lion,animals))  # True
print(isinstance(lion,wild)) # True 
print(isinstance(lion,birds)) # False

An object of child class is also instance of parent class.

tiger is an object of animals() class so isinstance() returns False when we checked against child class wild().

In case of object lion ( an object of wild() ) the line print(isinstance(lion,animals)) returns True as wild() is child class of base class animals()

All Built in Functions in Python locals() dir() classmethod issubclass

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Subhendu Mohapatra

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I write and maintain practical tutorials on Python, PHP, SQL, JavaScript, HTML, jQuery, and web development at plus2net. The tutorials focus on clear explanations, working examples, and code that readers can test and adapt while learning.

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