fiddling with subprocess piping

dumper.py

import time
import sys

DELAY = 0.2

for i in range(10):
    sys.stdout.write("1")
    time.sleep(DELAY)
sys.stdout.write("\r\n")

for i in range(10):
    sys.stdout.write("2")
    time.sleep(DELAY)
sys.stdout.write("\r")

for i in range(10):
    sys.stdout.write("3")
    time.sleep(DELAY)
sys.stdout.write("\n")

sys.stdout.write("done!\n")

spawner.py

import subprocess
import select
import io

def main():
    args = (
        "python",
        "-u",
        "dumper.py",
    )
    proc = subprocess.Popen(args,
                            stdout=subprocess.PIPE,
                            #encoding="utf8",
                            #universal_newlines=True,
                            #bufsize = 0,
                            )
    reader = io.TextIOWrapper(proc.stdout,
                              encoding='utf8',
                             )
    print("starting")
    for line in reader:
        line=line.replace("\r", "\\r")
        line=line.replace("\n", "\\n")
        print("foo: " + line.strip())

main()