import serial
import time
import sys
import os

def main():
    s = serial.Serial("/dev/ttyUSB0", 9600) // the second serial should be capitalized
    while 1:
        s.write("lon1\n".encode()) // Need .encode() on each of them
        time.sleep(1) // time.sleep is in seconds, not milliseconds so it should be 1
        s.write("lof1\n".encode())
        s.write("lon2\n".encode())
        time.sleep(1)
        s.write("lof2\n".encode())
        s.write("lon3\n".encode())
        time.sleep(1)
        s.write("lof3\n".encode())

if __name__ == '__main__':
    try:
        main()
    except KeyboardInterrupt:
        print ("Interrupted")
        try:
            sys.exit(0)
        except SystemExit:
            os._exit(0)