Identity operators in Python

Today we’ll be talking about the two identity operators, is and is not.

Here’s the video version of this article:

We use the built-in function id to check the identity of an object. The identities of two objects are different if they have different memory locations.

There are two identity operators which we can use to compare the memory locations of two objects:

is	evaluates to True if the two objects have the same identity, which means we have two references to the same object
is not	evaluates to True if the two objects have different identities, which means we have two distinct objects

Here’s how it works. We have two variables referring to the same number 5:

>>> a = 5
>>> b = 5 

Turns out a and b refer to the same object:

>>> a is b
True
>>> a is not b
False 

Let’s check it out. Indeed, the same identities:

>>> id(a)
1595892064
>>> id(b)
1595892064 

Another example:

>>> x = "hello"
>>> y = "hi" 

x and y refer to different objects:

>>> x is y
False 

From now on y refers to the same object as x:

>>> y = x

So, they have the same identity:

 >>> x is y
 True 

Type Checking

You can also use the identity operators to check whether an object is of a specific type:

>>> type(True) is bool
True
>>> type(7) is not float
True
>>> type("hello") is str
True