def alst(L):
    return alst4r([L])

def alst4r(L):
    head,tail = L[0],L[1:]
    if type(head) != list and tail == []:
        return L
    if type(head) == list:
        return head + [alst4r(head)]
    return alst4r(tail)


print alst([1,2,3,[4,5,[6,7,[9]]]])