def _radix_sort(L, i=0):
  if len(L) <= 1: 
    return L
  done_bucket = []
  buckets = [ [] for x in range(255) ]
  for s in L:
    if i >= len(s):
      done_bucket.append(s)
    else:
      buckets[ ord(s[i]) ].append(s)
  buckets = [ _radix_sort(b, i + 1) for b in buckets ]
  return done_bucket + [ b for blist in buckets for b in blist ]