from machine import Pin #import Pin module to control GPIO
from time import sleep  #import sleep function to create delays

while True:                 #infinite loop
    #move led foward
    for i in range(1,6,1):  #loop from gp1 to gp5
        led=Pin(i,Pin.OUT)  #define led dynamically
        led.value(1)        #turn on led
        sleep(0.3)          #wait for 0.3 secs
        led.value(0)        #turn off led
    #move led reverse
    for i in range(4,1,-1):  #loop from gp4 to gp2
        led=Pin(i,Pin.OUT)  #define led dynamically
        led.value(1)        #turn on led
        sleep(0.3)          #wait for 0.3 secs
        led.value(0)        #turn off led