from time import sleep

while True:

    print("red light on")
    sleep(1)
    print("red light off")
    print("red light on")
    sleep(0.5)
    print("red light off")
    print("red light on")
    sleep(0.5)
    print("red light off")
    print("red light on")
    sleep(0.5)
    print("red light off")
    print("green light on")
    sleep(1)
    print("green light off")
    print("green light on")
    sleep(1)
    print("green light off")
    print("green light on")
    sleep(1)
    print("green light off")
    print("yellow light on")
    sleep(1)
    print("yellow light off")
    print("yellow light on")
    sleep(1)
    print("yellow light off")
    print("yellow light on")
    sleep(1)
    print("yellow light off")