from machine import pin
from time import sleep

led1 = pin(2, pin.out)
led2 = pin(4, pin.out)
led3 = pin(17, pin.out)

while True:
    led1.on()
    led3.on()
    led2.off()
    sleep(1)
    led1.off()
    led3.off()
    led2.on()
    sleep(1)