Identity Operators in Python

The identity operators allow us to check if two variables refer to the same object in memory. These operators are useful for comparing the identity of objects, that is, if two variables point to the same place in memory.

The is and is not operators are very efficient as they simply compare the memory addresses of two objects. They do not perform any additional operations, making them suitable for checking the identity of objects.

List of identity operators

is Operator

The is operator is used to check if two variables refer to the same object in memory.

a = [1, 2, 3]
b = a

is_equal = (a is b)  # True, since a and b refer to the same object

In this example, both a and b point to the same object in memory, so the expression a is b is True.

is not Operator

The is not operator is used to check if two variables do NOT refer to the same object in memory.

x = 10
y = 10

is_not_equal = (x is not y)  # False, since x and y refer to the same object

In this example, both x and y point to the same object in memory (in Python, small integers are stored in the same location), so the expression x is not y is False.

Usage Examples

Verification of variable identity

x = 100
y = x

are_equal = (x is y)  # True, since x and y are the same object in memory

Verification of list identity

list1 = [1, 2, 3]
list2 = [1, 2, 3]
list3 = list1

are_equal = (list1 is list2)  # False, since list1 and list2 are not the same object
are_equal2 = (list1 is list3)  # True, since list1 and list3 are the same object

Verification of object identity

class MyClass:
    pass

object1 = MyClass()
object2 = MyClass()
object3 = object1

are_equal = (object1 is object2)  # False, since object1 and object2 are not the same object
are_equal2 = (object1 is object3)  # True, since object1 and object3 are the same object