Difference Between is and == in Python

While working on a Python project for US clients, I often come across two operators, is and ==, that seem similar but have distinct purposes. In this tutorial, I will explain the difference between is and == in Python. Let us understand more about the topic with examples and screenshots of executed example code.

‘==’ in Python

The == operator is used to compare the values of two objects. It checks whether the values are equivalent, regardless of whether they are the same object in memory.

Example

a = [1, 2, 3]
b = [1, 2, 3]
print(a == b)
print(a is b) 

Output:

True
False

I have executed the above example code and added the screenshot below.

In the example above, a and b are two different lists that contain the same values. The == operator returns True because the values are the same. However, the is operator returns False because a and b are different objects in memory.

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‘is’ in Python

The is operator checks for object identity. It returns True if two references point to the same object in memory.

Example

a = [1, 2, 3]
b = a
print(a == b) 
print(a is b)  

Output:

True
True

I have executed the above example code and added the screenshot below.

In this example, a and b are references to the same list object. Both == and is return True because they refer to the same object in memory.

Check out Difference Between “is None” and “== None” in Python

Key Differences

1. Purpose: == checks for value equality, while is checks for identity.
2. Usage: Use == when you need to compare the values of objects. Use is when you need to check if two references point to the same object.
3. Behavior with Immutable Types: Immutable types like integers and strings, is might seem to behave like == due to Python’s internal optimizations, but this is not guaranteed.

Examples

1. Compare Strings

a = "hello"
b = "hello"
print(a == b)  
print(a is b)  

Output:

True 
True

I have executed the above example code and added the screenshot below.

For small strings, Python may use a technique called interning, where it reuses objects for efficiency. This can make is return True for small strings with the same value. However, this behavior should not be relied upon.

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2. Compare Lists

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

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

Output:

True
False

Lists are mutable, so a and b are different objects even if they contain the same values. Thus, == returns True, but is returns False.

Check out Difference Between = and == in Python

3. Compare Integers

a = 1000
b = 1000
print(a == b) 
print(a is b)  

Output:

True
False

Here, a and b have the same value, so == returns True. However, they are different objects in memory, so is returns False.

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3. Use is with None

A common use case for is is to check if a variable is None.

a = None

if a is None:
    print("a is None") 

Output:

a is None

Here, is is used to check if a is None, which is more efficient and idiomatic than using ==.

Read Is Python an Interpreted Language

Summary Table

Conclusion

In this tutorial, I explained the difference between is and == in Python. We discussed what are “==” and ‘is‘ in Python with examples some key differences. I gave examples by comparing strings, lists, and integers, by using 'is' with None and given a summary for reference.

You may also like to read:

• Is Python a Compiled Language?
• Difference Between {} and [] in Python
• How to Comment Out a Block of Code in Python?

Bijay Kumar

I am Bijay Kumar, a Microsoft MVP in SharePoint. Apart from SharePoint, I started working on Python, Machine learning, and artificial intelligence for the last 5 years. During this time I got expertise in various Python libraries also like Tkinter, Pandas, NumPy, Turtle, Django, Matplotlib, Tensorflow, Scipy, Scikit-Learn, etc… for various clients in the United States, Canada, the United Kingdom, Australia, New Zealand, etc. Check out my profile.

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