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(0.2)
        1.on()
        sleep(0.2)
        1.off()