assignment expression

In Python, an assignment expression is an assignment that returns a value. You perform this type of assignment using the walrus operator (:=), which allows you to assign a value to a variable as part of an expression.

Assignment expressions can make your code more concise and readable. They’re particularly useful in situations where you want to assign a value to a variable and then immediately use that value, such as in loops or conditional statements.

Example

Here’s an example of an assignment expression in a while loop:

Python 
>>> values = [10, 20, 0, 30]

>>> while (n := len(values)) > 0:
...     print(f"Current list length: {n}")
...     values.pop()
...
Current list length: 4
30
Current list length: 3
0
Current list length: 2
20
Current list length: 1
10

In this example, the assignment expression n := len(values) assigns the length of values to n and immediately uses it in the condition of the while loop. This eliminates the need for a separate line to assign the length to n, making the code more concise.

The Walrus Operator: Python's Assignment Expressions

Tutorial

The Walrus Operator: Python's Assignment Expressions

In this tutorial, you'll learn about assignment expressions and the walrus operator. The biggest change back in Python 3.8 was the inclusion of the := operator, which you can use to assign variables in the middle of expressions. You'll see several examples of how to take advantage of this feature.

intermediate best-practices

For additional information on related topics, take a look at the following resources:

By Leodanis Pozo Ramos • Updated June 20, 2025
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