python while循环

循环打印1~5

i = 1
while i <= 5:
    print(i)
    i += 1

输出

1
2
3
4
5

循环执行判断用户输入，若输入quit就退出循环

prompt = "Please enter 'quit' to logoff program: "
message = ""
while message != 'quit':
    message = input(prompt)
    print(message)

输出

Please enter 'quit' to logoff program: exit
exit
Please enter 'quit' to logoff program: byebye
byebye
Please enter 'quit' to logoff program: quit
quit

 使用循环标志

active = True
prompt = "Please enter 'quit' to logoff program: "
message = ""
while active:
    if message != 'quit':
        message = input(prompt)
        print(message)
    else:
        active = False

输出

Please enter 'quit' to logoff program: byebye
byebye
Please enter 'quit' to logoff program: exit
exit
Please enter 'quit' to logoff program: quit
quit

使用break退出循环

prompt = "Please enter 'quit' to logoff program: "
message = ""
while True:
    if message != 'quit':
        message = input(prompt)
        print(message)
    else:
        break

 输出

Please enter 'quit' to logoff program: bye
bye
Please enter 'quit' to logoff program: exit
exit
Please enter 'quit' to logoff program: quit
quit