python stdout to file does not respond in real time

Question

Write a simple python script test.py:

  import time
  print "begin"
  time.sleep(10)
  print "stop"

In bash, run

python test.py > log.txt

What I observe is that both "begin" and "stop" appear in log.txt at the same time, after 10 seconds.

Is this expected behavior?

Answer 1

Have you tried calling python with the -u option, which "forces stdin, stdout and stderr to be totally unbuffered" =>

python -u test.py > log.txt