from machine import Pin
import time
from time import sleep
 led1=Pin(18,Pin.OUT)
 led2=Pin(19,Pin.OUT)
 led3=Pin(20,Pin.OUT)
 led4=Pin(21,Pin.OUT)
 leds=[led1,led2,led3,led4]

 while True:
    for 1 in leds:
        sleep(0.6)
        1.on()
        sleep(0.6)
        1.off()