Assign variable in while loop condition in Python?

Try this one, works for files opened with open('filename')

for line in iter(data.readline, b''):

Starting Python 3.8, and the introduction of assignment expressions (PEP 572) (:= operator), it's now possible to capture the condition value (data.readline()) of the while loop as a variable (line) in order to re-use it within the body of the loop:

while line := data.readline():
  do_smthg(line)