from subprocess import Popen, PIPE, STDOUT
from sys import argv, stdin, stdout, executable

def writeRead(process, text):
    data = text.encode("ASCII")
    print(">> write: %s" % repr(data))
    stdout.flush()
    process.stdin.write(data)
    process.stdin.flush()

    line = process.stdout.readline()
    line = line.rstrip()
    print("<< read: %s" % line)
    stdout.flush()

def parent():
    process = Popen([executable, "-u", __file__, "child"], stdin=PIPE, stdout=PIPE, stderr=STDOUT)
    writeRead(process, "aaa")
    writeRead(process, "bb\n")

    print("Close"); stdout.flush()
    stdout.flush()
    process.stdin.close()

    print("Wait"); stdout.flush()
    process.wait()

    print("Exit code: %s" % process.returncode)

def child():
    while True:
        data = stdin.read(3)
        print("data: [%s] %s" % (len(data), repr(data)))
        if not data:
            break

if __name__ == "__main__":
    if len(argv) == 2 and argv[1] == "child":
        child()
    else:
        parent()