Getting all combinations of a string and its substrings

Question

I\'ve seen many questions on getting all the possible substrings (i.e., adjacent sets of characters), but none on generating all possible strings including the combinations

Answer 1

def return_substrings(s):
    all_sub = set()
    recent = {s}

    while recent:
        tmp = set()
        for word in recent:
            for i in range(len(word)):
                tmp.add(word[:i] + word[i + 1:])
        all_sub.update(recent)
        recent = tmp

    return all_sub