import machine
import time

LEDs = [machine.Pin(2, machine.Pin.OUT),
        machine.Pin(3, machine.Pin.OUT),
        machine.Pin(4, machine.Pin.OUT),
        machine.Pin(5, machine.Pin.OUT),
        machine.Pin(6, machine.Pin.OUT),
        machine.Pin(7, machine.Pin.OUT),
        machine.Pin(8, machine.Pin.OUT),
        machine.Pin(9, machine.Pin.OUT)]

while True:
    for i in range(len(LEDs)):
        LEDs[i].value(1)
        time.sleep(1)
        LEDs[i].value(0)
        time.sleep(1)
    for i in range(len(LEDs) - 2, 0, -1):
        LEDs[i].value(1)
        time.sleep(1)
        LEDs[i].value(0)
        time.sleep(1)