radix sort

from random import randrange

zero = []
one = []
two = []
three = []
four = []
five = []
six = []
seven = []
eight = []
nine = []

array = []
decimal_place = 0

def generate_random_array(size, bound):
    global array
    for i in range(size):
        array.append(randrange(1,bound))

def get_digit(num):
    global decimal_place
    return (num//pow(10,decimal_place)) % 10

def separate():
    global array, decimal_place
    for num in array:
        digit = get_digit(num)

        if digit == 0:
            zero.append(num)
        elif digit == 1:
            one.append(num)
        elif digit == 2:
            two.append(num)
        elif digit == 3:
            three.append(num)
        elif digit == 4:
            four.append(num)
        elif digit == 5:
            five.append(num)
        elif digit == 6:
            six.append(num)
        elif digit == 7:
            seven.append(num)
        elif digit == 8:
            eight.append(num)
        elif digit == 9:
            nine.append(num)

    array = [] # reset

def rebuild():
    global zero, one, two, three, four, five, six, seven, eight, nine, array
    array = zero + one + two + three + four + five + six + seven + eight + nine
    if (len(zero) == len(array)):
        return True
    zero = []
    one = []
    two = []
    zero = []
    three = []
    four = []
    five = []
    six = []
    seven = []
    eight = []
    nine = []
    return False

def solve():
    global array, decimal_place
    while(True):
        separate()
        is_done = rebuild()
        if (is_done):
            break
        else:
            decimal_place += 1

generate_random_array(20, 1000)
solve()
print(array)