“is” Keyword in Python: Comparing Object Identity

"is" Keyword in Python: Comparing Object Identity

Python provides a number of comparison operators. One such operator is the “is” keyword. This operator compares the object identity in Python. Unlike the “==” operator, which compares the values of the objects, the “is” keyword compares the identity of the two objects. In this article, we’ll explore the use cases of the “is” keyword in Python, as well as its differences with the “==” operator.

Comparing Object Identity

Let’s first understand the concept of object identity. When an object is created in Python, it is assigned a unique identifier, which is generated by the Python interpreter. This identifier is unique for each object and can be obtained using the built-in function id(). The identity of the object is based on the memory address where it is stored. If two objects are located in different memory addresses, then they have different identities, even if they have the same value.

The “is” keyword in Python is used to determine whether two objects have the same identity. If two objects are the same, then they also have the same identity. Let’s have a look at an example:

a = 5
b = 5
if a is b:
    print("a and b have the same identity")
else:
    print("a and b do not have the same identity")

In this example, the integer 5 is assigned to the variables a and b. Since integers in Python are immutable objects, they are assigned a unique identifier when they are created. When a and b are assigned the value 5, they both reference the same memory location, hence they share the same identity. Therefore, when we run this code, it will output:

a and b have the same identity

Now let’s see an example where two lists having the same values do not have the same identity.

list1 = [1, 2, 3]
list2 = [1, 2, 3]
if list1 is list2:
    print("list1 and list2 have the same identity")
else:
    print("list1 and list2 do not have the same identity")

In this example, two lists are created, having the same values. Since lists are mutable objects, they are assigned a unique identifier when they are created. When list1 and list2 are created, they are stored in different memory locations, hence they have different identities. Therefore, when we run this code, it will output:

list1 and list2 do not have the same identity

Now let’s see an example where the objects have the same value as well as the same identity.

c = "Hello, World!"
d = "Hello, World!"
if c is d:
    print("c and d have the same identity")
else:
    print("c and d do not have the same identity")

In this example, two strings are created, having the same value. Since strings in Python are immutable objects, they are assigned a unique identifier when they are created. When c and d are assigned the same value, they both reference the same memory location, hence they share the same identity. Therefore, when we run this code, it will output:

c and d have the same identity

Differences between “is” and “==”

In Python, there are two operators for equality comparison- the “is” keyword and the “==” operator. Although they may seem similar, there is a subtle difference in how they compare objects. As we’ve seen earlier, the “is” keyword compares the object identity, whereas the “==” operator compares the objects’ values.

Let’s understand the difference by taking an example:

e = [1, 2, 3]
f = [1, 2, 3]
if e == f:
    print("e and f are equal")
else:
    print("e and f are not equal")
if e is f:
    print("e and f have the same identity")
else:
    print("e and f do not have the same identity")

In this example, two lists are created with the same values. When we use the “==” operator, e and f are equal since they have the same values. However, when we use the “is” keyword, e and f do not share the same identity since they are stored in different memory locations. Therefore, when we run this code, it will output:

e and f are equal
e and f do not have the same identity

The “is” keyword should be used to compare object identity, while the “==” operator should be used to compare object values.

Conclusion

In summary, the “is” keyword in Python is used to compare object identity rather than the values of the objects. It is useful when comparing mutable objects that may have the same values but different identities. The “==” operator, on the other hand, compares the values of the objects. It is important to understand the differences between the two operators and to use them appropriately.

Leave a Reply

Your email address will not be published. Required fields are marked *