Read streaming input from subprocess.communicate()

Question

I\'m using Python\'s subprocess.communicate() to read stdout from a process that runs for about a minute.

How can I print out each line of that process

Answer 1

If you're simply trying to pass the output through in realtime, it's hard to get simpler than this:

import subprocess

# This will raise a CalledProcessError if the program return a nonzero code.
# You can use call() instead if you don't care about that case.
subprocess.check_call(['ls', '-l'])

See the docs for subprocess.check_call().

If you need to process the output, sure, loop on it. But if you don't, just keep it simple.

Edit: J.F. Sebastian points out both that the defaults for the stdout and stderr parameters pass through to sys.stdout and sys.stderr, and that this will fail if sys.stdout and sys.stderr have been replaced (say, for capturing output in tests).