text: # 首先获得Iterator对象:
  it = iter([1, 2, 3, 4, 5])
  # 循环:
  while True:
      try:
          # 获得下一个值:
          x = next(it)
      except StopIteration:
          # 遇到StopIteration就退出循环
          break
      print("x-=>", x)
  a = (x + 2 for x in range(1))
  print("type--?", type(it))
  print("a--?", a)
  