import time
from machine import Pin
leds=[0,1,2,3,4,5,6,7,8,9]
vel=50

for x in range(0,10):
    Pin(leds[x],Pin.OUT)

while True:
    for x in range(0,10):
        Pin(leds[x]).on()
        time.sleep_ms(vel)
        Pin(leds[x]).off()
        time.sleep_ms(vel)
    for x in range(9,0,-1):
        Pin(leds[x]).on()
        time.sleep_ms(vel)
        Pin(leds[x]).off()
        time.sleep_ms(vel)