如何让 raw_input 重复直到我想退出？

Question

假设我想像这样使用 raw_input：

code = raw_input("请输入您的三字母代码或空行来退出：")

下：

if __name__=="__main__": 

我怎样才能让每次运行程序时它都会重复多次而不是一次？
另一个问题是编写什么代码可以满足“或空行退出（程序）”条件。

Answer 1

最好的：

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

while 1:
    choice=raw_input("Enter: ")
    if choice in ["Q","q"]: break
    print choice
    #do something else

Answer 3

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

for code in iter(myInput, ""):
    if len(code) != 3 or not code.isalpha():
        print 'invalid code'
        continue
    #do something with the code

Answer 4

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: ")