Sort strings using a radix sort

string_radix_sort.py

def order(string, pivot):
    if pivot >= len(string):
        return 0

    return ord(string[pivot]) - ord("a") + 1


def sort_by_order(strings, pivot):
    buckets = [None] * 27
    for i_buckets in range(len(buckets)):
        buckets[i_buckets] = []

    for s in strings:
        key = order(s, pivot)
        buckets[key].append(s)

    for b in buckets:
        for s in b:
            yield s


def sort(strings):
    for p in range(10, -1, -1):
        strings = list(sort_by_order(strings, p))

    return strings


case1 = ["apple", "orange", "banana", "app"]

print(sort(case1))