Python Radix Sort, Bucket Sort

#!/usr/bin/env python3

RADIX = 10


# radix sort that works for non negative integers
def radix_sort_nonneg(lst):
    last_iteration = False
    radix_power = 1
    while not last_iteration:
        # split into buckets
        buckets = [[] for _ in range(RADIX)]
        last_iteration = True  # unless we find it isn't
        for el in lst:
            # find the digit corresponding to radix_power
            #  example with radix_power = 1000; el = 123456
            #  el % (radix_power*RADIX) == 123456 % 10000 == 3456
            #  3456 // radix_power == 3456 // 1000 == 3
            digit = el % (radix_power*RADIX) // radix_power
            buckets[digit].append(el)
            if el >= radix_power*RADIX:
                last_iteration = False

        # flatten
        lst = [el for bucket in buckets for el in bucket]
        radix_power *= RADIX
    return lst


def radix_sort(lst):
    positive_ints = radix_sort_nonneg( x for x in lst if x >= 0)
    negative_ints = radix_sort_nonneg(-x for x in lst if x <  0)
    return [-x for x in reversed(negative_ints)] + positive_ints


print(radix_sort([1, 2, 3, -3, -10, 332, 123, 124, 122, 2, 321, 3, 0]))