Python isinstance() Function

The isinstance() function is used to determine whether an object is an instance of a specified class or the object is an instance of one of the classes in a given tuple of classes.

Syntax:

isinstance(object, cls)

    or 

isinstance(object, tuple_of_classes)

The function returns a Boolean value; True if the object is an instance of the specified class or is an instance of one of the given classes( if the second argument is a tuple). It returns  False otherwise.

This function is commonly used to check whether the given object belongs to a certain type.

isinstance('Hello', str)
//True
isinstance(5, int)
//True
isinstance(True, bool)
//True 
isinstance(3.142, int)
//False
isinstance(3.142, float)
//True
isinstance([1, 2, 3,4], list)
//True
isinstance({}, set)
//False
isinstance({}, dict)
//True

The function also returns True if the given class is a base class of the class that the object belongs to. For example calling isinstance(False, int) will return True because the value False belongs to the bool type which is a subclass of the int type.

example:

isinstance(bool, int)
//True
isinstance(True, bool)
//True
isinstance(True, int)
//True

Using a tuple of types

isinstance(1, (list, int, tuple))
//True
isinstance([1, 2, 3], (tuple, set, dict))
//False
isinstance(0j, (int, float, complex))
//True

Using user-defined classes

class MyClass:
    def __init__(self):
        self.name = 'instance'
x = MyClass()
print(isinstance(x, MyClass))