如何让raw_input重复直到我想退出？

Question

说我想这样使用raw_input:

code = raw_input("Please enter your three-letter code or a blank line to quit: ")

下:

if __name__=="__main__": 

我怎样才能让它重复多次,而不是每次运行程序时都重复一次？
另一个问题是编写什么代码可以满足条件"或空行退出(程序)".

Answer 1

最好:

if __name__ == '__main__':
  while True:
    entered = raw_input("Please enter your three-letter code or leave a blank line to quit: ")
    if not entered: break
    if len(entered) != 3:
      print "%r is NOT three letters, it's %d" % (entered, len(entered))
      continue
    if not entered.isalpha():
      print "%r are NOT all letters -- please enter exactly three letters, nothing else!"
      continue
    process(entered)

Answer 2

if __name__ == '__main__':

    input = raw_input("Please enter your three-letter code or leave a blank line to quit: ")
    while input:
        input = raw_input("Please enter your three-letter code or leave a blank line to quit: ")