Understanding the Identity Operator in Python

Python, a versatile programming language, offers various operators to perform different tasks. One of those operators is the “identity operator in Python.”

This operator allows you to compare the identities (memory locations) of two objects. 

We will explain everything about the identity operator in Python with examples in this blog. We’ll see its usage and significance in Python programming.

What is an Identity Operator in Python?

An identity operator is used to compare the memory locations of two objects in Python. It checks whether the two objects being compared refer to the same location in memory.

Python provides two identity operators:

1. is 
2. is not

“is” operator

The “is” operator checks if the memory address of two objects is the same.

It returns:-

1. True:-  if the two operands have the same object. 
2. False:- if the two do not have the same object.

“is not” Operator

“is not” operator in Python works in the opposite way of the “is” operator.

It returns:-

1. True:- if the two operands do not have the same object. 
2. False:- if the two have the same object.

Understanding Object Identity

Before delving deeper into the identity operator, let’s understand the concept of object identity in Python.

As we know, Python is an object-oriented programming language.

In Python, everything is an object. Each object has a unique identity. This identity is assigned when the object is created. This identity never changes during the object’s lifetime.

Python has a function called “id()”. This function can obtain the unique identifier of an object. This identifier represents the memory address where the object is stored.

Consider the following example:

In this case, both “x” and “y” refer to the same object because integers in Python are immutable. Let’s verify this using the identity operator:

Examples of the Identity Operator in Python

The programmers primarily use the identity operator in situations where you need to compare object identities rather than their values. Here are some basic Python programs where the identity operator can be useful:

Comparing Immutable Objects with Identity Operator in Python

As mentioned earlier, immutable objects like numbers and strings are cached in Python. If you assign the same value to two variables, they point towards the same (memory) location. We can use the identity operator to check if two variables refer to the same object:

Differentiating Mutable Objects with Identity Operator in Python

Unlike immutable objects, mutable objects (like lists & dictionaries) can have multiple references pointing to different memory locations. The identity operator helps in distinguishing between such objects:

Comparing None with Identity Operator in Python

The identity operator is commonly used to check if a variable is “None“. Since “None” is a singleton object in Python, we can use the “is” operator to verify its existence:

Potential Pitfalls

While using the identity operator, it is important to be aware of some potential pitfalls:

Floating Point Numbers

For small integers, Python caches the objects and reuses them. But it’s not the same with floating point (float) numbers. The identity operator may not behave as expected for floating point numbers due to internal caching mechanisms:

Custom Objects

The behavior of the identity operator depends on how we implement the objects. For custom objects, the identity operator may not always work as expected. By default, object identity is based on the memory address. But you can override it by using these functions in Python – “eq()” and “ne()”.

More examples of identity operator in Python

Example 1: Checking List Membership

Identity operators can be used to check if an element exists within a list. The in operator, combined with the is operator, helps us determine if an element is present in the given list.

In the above example, we use the “is not” operator to ensure that the element being checked is not “None” before using the “in” operator.

Example 2: Comparing Boolean Values

Identity operators can also be useful when comparing Boolean values, such as True and False.

In this example, we compare two Boolean (bool values i.e. True & False) variables using the identity operators to determine if they have the same or different truth values.

Example 3: Checking Object Types

Identity operators can help in checking the type of an object in Python. By using the is operator, we can verify if an object belongs to a specific type.

In this scenario, we’re using the “is” operator to compare the type of the variable “x” (type(x)). This will tell us its type from below.

• “int” (integer) 
• “str” (string)
• “float”
• “bool” (Boolean)

Example 4: Comparing Function References

In Python, functions are objects & can be assigned to variables. We can use identity operators to compare function references.

In this example, we assign the same function greet to two different variables func1 and func2. By using the identity operator, we can confirm that both variables reference the same function.

Example 5: Verifying Module Imports

We can use Identity operators to verify if the system has imported a module correctly or not. By comparing module references, we can ensure that the desired module has been successfully imported.

In this example, we use the identity operator to see if the system has imported the “math” successfully. Additionally, we can verify the import of the “random” module by using the “in” operator along with the “is not” operator.

These examples demonstrate different scenarios where identity operators prove useful for comparing objects’ identities, types, and membership, allowing us to write more efficient and reliable code in Python.

Key Points To Take Away

1. The identity operator in Python allows you to compare the memory addresses of objects.
2. It is useful when you need to check if two objects point towards the same (memory) location.
3. Remember: The identity operator compares the identity of objects, not their values.