Read realtime output with python subprocess

caller.py

import os
import subprocess
import fcntl
import time

def non_block_read(output):
    fd = output.fileno()
    fl = fcntl.fcntl(fd, fcntl.F_GETFL)
    fcntl.fcntl(fd, fcntl.F_SETFL, fl | os.O_NONBLOCK)
    try:
        return output.readline()
    except:
        return ""

def run_process(cmd):
    with subprocess.Popen(cmd, shell=False, universal_newlines=True, encoding='utf-8', bufsize=1, stdout=subprocess.PIPE, stderr=subprocess.PIPE) as p:
        while True:
            out = non_block_read(p.stdout)
            err = non_block_read(p.stderr)
            if out:
                print(out, end='')
                # this is for socket broadcasting
                # socketio.emit('console-response', out)
            if err:
                # this is for socket broadcasting
                # socketio.emit('console-response', err)
                print('E: ' + err, end='')
            if p.poll() is not None:
                break

            time.sleep(0.0001)

if __name__ == "__main__":
    path = os.path.dirname(os.path.abspath(__file__))
    script = path + "/debug.py"
    cmd = ['/usr/bin/python3', script, 'ORD-', '6']
    run_process(cmd)

process.py

import sys
import time
import random

def run(startWith, howManyTimes):
    for i in range(0, howManyTimes):
        randomString = ''.join(random.choice('0123456789') for i in range(10))
        sys.stdout.write(startWith + randomString + '\n')
        sys.stdout.flush()

        time.sleep(1)

if __name__ == '__main__':
    startWith = "ORDER-"
    howManyTimes = 10

    if len(sys.argv) > 1:
        startWith = sys.argv[1]

    if len(sys.argv) > 2:
        howManyTimes = int(sys.argv[2])

    run(startWith, howManyTimes)