Write to a Python subprocess's stdin without communicate()'s blocking behavior

Question

How do I make this a non-blocking call? osd_cat accepts input only as a PIPE which need p.communicate() call making the process to block. Is there any other way to set stdin in Popen?

p = subprocess.Popen(('osd_cat',
                      '-d',
                      '{}'.format(interval)),
                     stdin=subprocess.PIPE)
p.communicate(message)

Answer 1

The p.communicate method is a one-shot deal in terms of sending data to the process.

Instead, write directly to p.stdin. If you want to get output, you can read lines from p.stdout. Make sure you pass stdout=subprocess.PIPE to the constructor before attempting to read.