Beginner - Traffic Lights - micro:bit

"""
filename:gpio_mb_TrafficLights.py
Beginner Project - Traffic Lights
written by Trevor Olsson
© GPIO Support Services LTD MMXVII
More info here: http://www.gpio.co.uk/traffic-lights/
"""
from microbit import *
while True:
    pin8.write_digital(1)
    sleep(2000)
    pin12.write_digital(1)
    sleep(2000)
    pin8.write_digital(0)
    pin12.write_digital(0)
    pin0.write_digital(1)
    sleep(2000)
    pin0.write_digital(0)
    pin12.write_digital(1)
    sleep(2000)
    pin12.write_digital(0)