Identity Operator in Python

Last Updated on April 19, 2023 by Prepbytes

Python language supports various operators for different purposes. One of these operators is the identity operator. The identity operator in Python is used to compare two objects to see if they are the same object, as opposed to having the same value. This article will explain the concept of the identity operator in Python, its types, differences between is operator and == operator, the benefits of the identity operator in Python, and the limitations of the identity operator in Python. So, without any delays, let’s move on to our next section.

What is the Identity Operator in Python?

The Identity Operator in Python is a comparison operator that is used to check whether two objects are pointing to the same memory location in the computer’s memory or not.

When we create an object in Python, it is stored in a specific memory location in the computer’s memory. The identity operator in Python compares the memory addresses of two objects and returns True if they are pointing to the same memory location, and False otherwise.

It’s important to note that the identity operators are not the same as the equality operators (== and !=), which compare the values of two variables.

Types of Identity Operator in Python

There are two types of identity operator in Python:

• is
• is not.

The is operator checks whether two variables refer to the same object in memory, returning True if they do, and False otherwise. The is not operator checks whether two variables refer to different objects in memory, returning True if they do, and False otherwise. These operators are useful for testing whether two variables point to the same object, rather than just having the same value. It’s important to note that the identity operators are not the same as the equality operators (== and !=), which compare the values of two variables.

is Operator

The "is" operator is one of the identity operator in Python. It is used to check whether two variables refer to the same object in memory, returning True if they do, and False otherwise.

Syntax of is Identity Operator in Python

The syntax of the "is" identity operator in Python is:

object1 is object2

Here, "object1" and "object2" are the two objects that we want to compare. The "is" operator returns True if "object1" and "object2" are the same object in memory, and False otherwise.

Example of is identity operator in Python
Below is an example of the 1st type of identity operator in python i.e, is operator.

Code Implementation

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

print(a is b)  
print(a is c)

Output

True
False

Explanation of the above example
In the example above, a and b both refer to the same list object, so a is b evaluates to True. On the other hand, a and c have the same values, but they refer to different list objects, so a is c evaluates to False.

is not Operator

The is not operator is also an identity operator in Python. It is used to check whether two variables refer to different objects in memory, returning True if they do, and False otherwise.

Syntax is not Identity Operator in Python
The syntax for the is not identity operator in Python looks something like this:

object1 is not object2

Here, object1 and object2 are two objects that are being compared. The is not operator checks whether object1 and object2 have different identities, i.e., they refer to different objects in memory. If object1 and object2 have different identities, then the is not operator returns True. If they have the same identity, then the is not operator returns False.

Note that is not is a single operator, not two separate operators (is and not). The is not operator is used to test for inequality of object identity, and it’s the opposite of the is operator, which tests for equality of object identity.

Example of is not identity operator in Python
Below is an example of the second type of identity operator in Python i.e, is not operator.

Code Implementation

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

print(a is not b)  
print(a is not c)

Output

True
Flase

Explanation of th above example
In the above example, we define two lists a and b that contain the same values. Since a and b are two different list objects, the is not operator returns True. We also define a variable c that refers to the same object as a. Since a and c have the same identity, the is not operator returns False.

Difference between is Operator and == Operator

The "is" operator and "==" operator are both comparison operators in Python but they have different functionalities.

The "is" operator checks if two objects have the same identity, i.e., if they are the same object in memory. On the other hand, the "==" operator checks if two objects have the same value.

Here’s an example that illustrates the difference between the is and == operators:

Code Implementation

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

print(a == b)    
print(a is b)

Output

True
Flase

Explanation of the above example
In this example, we define two lists a and b with identical values. The == operator compares the values of a and b and returns True since they are equal. However, because a and b are two distinct objects in memory, the is operator returns False.

Therefore, based on what you want to compare, you must choose the appropriate operator. If you want to find out if two variables relate to the same object in memory, use is identity operator, and if you want to determine whether two variables have the same values, use the == operator.

Benefits of Identity Operator in Python

The Identity Operator in Python provides several benefits, including:

1. Faster Execution: The Identity Operator only checks the memory address of the objects, making it faster than the "==" operator that compares the values of the objects.
2. Guarantees Object Identity: The Identity Operator checks if two objects are the same object in memory, which can be useful in certain scenarios.
3. Avoids Unexpected Bugs: When dealing with mutable objects, the Identity Operator can help avoid unexpected bugs. For example, when modifying a list, the Identity Operator can be used to check if the original list has been modified or a new list has been created.

Limitations of Identity Operator in Python

Although the Identity Operator in Python has several benefits, it also has some limitations. These include:

1. Limited Use: The Identity Operator is only useful when comparing object identity, and cannot be used to compare the values of objects.
2. Limited to a single instance: The Identity Operator can only compare two objects at a time. It cannot compare a list of objects or check if an object is in a set of objects.
3. Inconsistent results: The Identity Operator may return inconsistent results when used with certain types of objects, such as NaN values or non-hashable objects.
4. Limited scope: The is operator is only useful for comparing objects within the same program. If you have two different Python programs running, you cannot use the is operator to compare objects between them since each program has its own memory space.
5. Not suitable for numeric values: The is operator is not suitable for comparing numeric values in Python since small integers and some commonly used strings are stored in a shared memory pool, so they may share the same memory address. Therefore, it’s not always safe to assume that two integers with the same value will have the same identity using the is operator.

Conclusion
In conclusion, the Identity Operator in Python is a useful tool for checking object identity and improving the performance of Python code. It provides several benefits, including faster execution, guaranteed object identity, and the ability to avoid unexpected bugs when dealing with mutable objects. However, it also has some limitations, such as its limited use, false negatives, limited application, and potential lack of intuitiveness. Overall, understanding the Identity Operator and its limitations can help developers write more efficient and reliable Python code.

Frequently Asked Questions

Here are some frequently asked questions regarding the Identity Operator in Python:

Q1: When should I use the Identity Operator in Python?
Answer: You should use the Identity Operator when you want to check if two objects are the same object in memory.

Q2: What types of objects can be compared using the Identity Operator in Python?
Answer: The Identity Operator in Python can be used to compare mutable objects that are stored in memory, such as lists, dictionaries, and instances of classes.

Q3: Can the Identity Operator be used to compare integers or strings?
Answer: No, the Identity Operator in Python cannot be used to compare immutable objects like integers or strings.

Q4: Can I use the Identity Operator in Python to compare a list of objects?
Answer: No, the Identity Operator in Python can only compare two objects at a time.

Q5: What is the difference between "is not" and "not is" in Python?
Answer: There is no difference, "is not" and "not is" are equivalent and both can be used to negate the Identity Operator.

Q6: Can I use the Identity Operator with NaN values?
Answer: The Identity Operator in Python may return inconsistent results when used with NaN values.