from machine import Pin
from time import sleep

banks = [
    [Pin(15, Pin.OUT), Pin(14, Pin.OUT), Pin(13, Pin.OUT)],
    [Pin(12, Pin.OUT), Pin(11, Pin.OUT), Pin(10, Pin.OUT)],
    [Pin(9, Pin.OUT), Pin(8, Pin.OUT), Pin(7, Pin.OUT)]
]

while True:
    for bank in banks:
        for led in bank:
            led.on()
            sleep(0.5)
            led.off()