Source: 📖 Effective Python item 10

Assignment expressions explained

An assignment expression := (also known as the walrus operator) allows you to assign variables in places where you normally wouldn't be able to (such as within an if statement) which can then be used in the proceeding code block.

from random import randint

if result := randint(0, 2):	# result being assigned a value 0, 1 or 2
	print(10 / result)	# randint didn't evaluate to 0, we can divide
else:
	print("Can't divide because randint is {result}")

In the above example, the assignment expression first assigns a value to the result variable (a random integer between 0 and 2), and then evaluates it within the context of the if statement. If randint evaluated to 1 or 2 then the if statement evaluates to True. If randint evaluated to 0 then the if statement evaluates to false and the else block is called.

This can be clearer than assigning the variable before a code block:

from random import randint

result = randint(0, 2)

if result:
	print(10/ result)
else:
	print("Cant divide becuase randint is {result}")

Proper use of the walrus operator can streamline code and improve readability as it keep variables embedded within the code blocks where they'll be used.