Sometimes, you want to run a subprocess with Python and stream/print its output live to the calling process' terminal, and at the same time save the output to a variable. Here's how:

proc = subprocess.Popen(cmd, stdout=subprocess.PIPE)
for line in proc.stdout:
    sys.stdout.buffer.write(line)
    sys.stdout.buffer.flush()
    # do stuff with the line variable here
proc.wait()