from machine import Pin
from utime import sleep

led=[0,1,2,3]
L=[0,0,0,0]

for i in range(0,4):
  L[i]=Pin(led[i],Pin.OUT)

while True:
  for i in range(0,4):
    L[i].value(1)
    sleep(0.5)
    L[i].value(0)