Binary Counter Using a Shift Register

import RPi.GPIO as IO
import time

IO.setwarnings(False)
IO.setmode(IO.BCM)
IO.setup(18,IO.OUT)     #data pin on the shift register
IO.setup(23,IO.OUT)     #push pin on the shift register
IO.setup(24,IO.OUT)     #display pin on the shift register

#function to convert decimal number to an array of integers representing the binary equivalent of the decimal
def convert_to_binary(decimal):

    #convert decimal number to binary number
    passthrough = format(decimal, 'b')

    #convert the binary number into an array of strings
    binary = list(passthrough)

    #pad the array to be 8 digits if necessary. now array is a mix of integers and strings
    while len(binary)< 8:
        binary.insert(0,0)

    #convert all array items to integers
    for i in range(8):
        binary[i] = int(binary[i])

    #output the array of integers
    return binary

#function to output binary array to the LEDs
def led_output(bin_arr):
    flip = bin_arr[::-1]            #because of how a shift register works, we need to reverse the array then
                                   #send it to the register

    for x in flip:     #iterate through the array and turn on/off an LED depending on the value of the item
        if x == 1:
            IO.output(18,1)
        IO.output(23,1)
        IO.output(23,0)
        IO.output(18,0)

    IO.output(24,1)
    IO.output(24,0)

#function to clear the LEDs
def led_clear():
    for z in range (8):
        IO.output(18,0)
        IO.output(23,1)
        IO.output(23,0)

    IO.output(24,1)
    IO.output(24,0)

#count from 0 to 255 and output the binary number to the LEDs
for num in range(256):
    led_output(convert_to_binary(num))
    time.sleep(0.2)
    led_clear()

#count from 254 to 0 and output the binary number to the LEDs
for num in range(254,-1,-1):
    led_output(convert_to_binary(num))
    time.sleep(0.2)
    led_clear()