How to Use Walrus Operator in Python: Syntax and Examples

The walrus operator := in Python allows you to assign a value to a variable as part of an expression. It helps reduce code repetition by combining assignment and condition checks in one line.

Syntax

The walrus operator uses the syntax variable := expression. It assigns the result of expression to variable and returns that value immediately.

This lets you use the assigned value right away in the same expression, such as inside an if or while condition.

python

if (n := len('hello')) > 3:
    print(f"Length is {n}")

Output

Length is 5

Example

This example shows how to read user input and check it in one line using the walrus operator. It assigns the input to user_input and tests if it is not empty.

python

while (user_input := input('Enter text (empty to quit): ')) != '':
    print(f'You entered: {user_input}')
print('Done')

Output

Enter text (empty to quit): hello
You entered: hello
Enter text (empty to quit): world
You entered: world
Enter text (empty to quit): 
Done

Common Pitfalls

One common mistake is using the walrus operator where a simple assignment would be clearer or where it reduces readability.

Another is forgetting that the walrus operator returns the assigned value, so it must be used in an expression context.

python

count = 0
# Wrong: using walrus outside expression context
# count := 5  # SyntaxError

# Right: use walrus inside an expression
if (count := 5) > 3:
    print(f'Count is {count}')

Output

Count is 5

Quick Reference

Use the walrus operator to:

• Assign and use a value in the same expression
• Reduce repeated function calls or computations
• Make loops and conditions more concise

Remember it works only in Python 3.8 and later.

Use Case	Example
Assign in condition	if (n := len(data)) > 0:
Assign in loop	while (line := file.readline()) != '':
Avoid repeated calls	if (result := expensive_func()) is not None:

Key Takeaways

The walrus operator := assigns and returns a value in one expression.

Use it to simplify code by combining assignment and condition checks.

It works only in Python 3.8 and newer versions.

Avoid overusing it where it hurts readability.

It must be used inside an expression, not as a standalone statement.