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Identity Operators

Python Identity Operators

Introduction

Identity operators are used to compare the memory locations of two objects in Python. Unlike comparison operators that compare values, identity operators check whether two variables refer to the same object in memory.

Identity operators are particularly useful when working with objects, lists, dictionaries, classes, and special values such as None.

Python provides two identity operators:

  • is

  • is not

In this tutorial, you will learn about Python identity operators, their syntax, examples, practical applications, and best practices.

What are Identity Operators?

Identity operators determine whether two variables point to the same object in memory.

Example

x = [1, 2, 3]
y = x

print(x is y)

Output

True

Both variables reference the same object in memory.

Types of Identity Operators

Python provides two identity operators:

OperatorDescription
isReturns True if both variables refer to the same object
is notReturns True if both variables refer to different objects

The is Operator

The is operator checks whether two variables reference the same object.

Syntax

object1 is object2

If both variables point to the same object, Python returns True.

Example

a = [10, 20, 30]
b = a

print(a is b)

Output

True

Both variables reference the same list object.

Memory Representation

a ──► [10, 20, 30]
       ▲
       │
b ─────┘

Both variables point to the same memory location.

The is not Operator

The is not operator checks whether two variables refer to different objects.

Syntax

object1 is not object2

Example

a = [10, 20, 30]
b = [10, 20, 30]

print(a is not b)

Output

True

Although the values are identical, the objects are different.

Identity Operators vs Comparison Operators

This is one of the most important concepts for beginners.

Comparison Operator (==)

Checks whether values are equal.

Example

a = [10, 20, 30]
b = [10, 20, 30]

print(a == b)

Output

True

The values are equal.

Identity Operator (is)

Checks whether both variables point to the same object.

Example

a = [10, 20, 30]
b = [10, 20, 30]

print(a is b)

Output

False

The objects are different even though the values are the same.

Understanding Object Identity

Every object in Python has:

  • A value

  • A memory location (identity)

The id() function returns the memory identity of an object.

Example

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

print(id(a))
print(id(b))

Output

140252123456
140252123456

Both IDs are the same.

Example

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

print(id(a))
print(id(b))

Output

140252123456
140252123789

The IDs are different.

Identity Operators with Integers

Python sometimes stores small integers in memory for optimization.

Example

a = 10
b = 10

print(a is b)

Output

True

Python may reuse the same memory object.

Example

a = 1000
b = 1000

print(a is b)

Output

May be True or False

This behavior can vary depending on Python implementation.

For numeric value comparison, use == instead of is.

Identity Operators with Strings

Example

name1 = "Python"
name2 = "Python"

print(name1 is name2)

Output

True

Python often stores identical strings efficiently.

Example

name1 = "Python Programming"
name2 = "Python Programming"

print(name1 == name2)

Output

True

Identity Operators with Lists

Lists are commonly used to demonstrate identity.

Example

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

print(list1 is list2)

Output

True

Example

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

print(list1 is list2)

Output

False

Because they are separate objects.

Identity Operators with Dictionaries

Example

student1 = {"name": "John"}
student2 = student1

print(student1 is student2)

Output

True

Example

student1 = {"name": "John"}
student2 = {"name": "John"}

print(student1 is student2)

Output

False

Different dictionary objects.

Using Identity Operators with None

Checking for None is the most common real-world use of identity operators.

Example

value = None

print(value is None)

Output

True

Example

value = "Python"

print(value is not None)

Output

True

Why Use is None Instead of == None?

Recommended

if value is None:
    print("No Value")

Not Recommended

if value == None:
    print("No Value")

Python’s style guide recommends using is None.

Identity Operators in Conditional Statements

Example

user = None

if user is None:
    print("User Not Found")

Output

User Not Found

Example

session = "active"

if session is not None:
    print("Session Running")

Output

Session Running

Real-World Example: Database Record Validation

record = None

if record is None:
    print("Record Not Available")

Output

Record Not Available

Real-World Example: API Response Validation

response = None

if response is None:
    print("API Response Missing")

Output

API Response Missing

Identity Operators in Automation Testing

Identity operators are often used in Selenium and API automation when checking whether objects exist.

Example

element = None

if element is None:
    print("Element Not Found")

Output

Element Not Found

Example

driver = object()

if driver is not None:
    print("Browser Started")

Output

Browser Started

Common Mistakes Beginners Make

Using is Instead of ==

Incorrect

a = 1000
b = 1000

print(a is b)

This checks identity, not value.

Correct

print(a == b)

This checks whether the values are equal.

Assuming Equal Values Mean Same Object

Example

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

print(list1 == list2)

Output:

True

print(list1 is list2)

Output:

False

Equal values do not necessarily mean identical objects.

Best Practices

Use == for Value Comparison

if age == 18:

Use is for Identity Checks

if value is None:

Use is not None

if response is not None:

Avoid Using is with Numbers and Strings

Identity behavior may vary.

Advantages of Identity Operators

  • Compare object identities directly

  • Useful for checking None

  • Helpful when working with objects and references

  • Improve code readability

  • Commonly used in object-oriented programming

Conclusion

Identity operators are used to determine whether two variables reference the same object in memory. Python provides two identity operators: is and is not.

Unlike comparison operators (== and !=), identity operators focus on object identity rather than object value. They are especially useful when working with objects, references, and checking for None.

Understanding the difference between value comparison and identity comparison is an important step toward mastering Python programming.

Frequently Asked Questions (FAQs)

What are identity operators in Python?

Identity operators check whether two variables refer to the same object in memory.

Which identity operators are available in Python?

is
is not

What does the is operator do?

It returns True if both variables reference the same object.

Example:

a = []
b = a

print(a is b)

Output:

True

What does the is not operator do?

It returns True if the variables refer to different objects.

Example:

a = []
b = []

print(a is not b)

Output:

True

What is the difference between == and is?

OperatorPurpose
==Compares values
isCompares object identities

Example:

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

print(a == b)

Output:

True

print(a is b)

Output:

False

Key Takeaways

  • Identity operators compare object memory locations.

  • Python provides two identity operators: is and is not.

  • is returns True when two variables reference the same object.

  • is not returns True when variables reference different objects.

  • Identity operators differ from comparison operators.

  • Use == for value comparison.

  • Use is when checking object identity.

  • Use is None and is not None when working with None.

  • Identity operators are commonly used in object-oriented programming and automation testing.