如何用Python编写"dead man's switch"，在指定时间内监视交互？

Question

我想运行一个 Python 脚本，该脚本在指定的时间段（例如一周）内寻找与之交互的人。如果有人与它互动，它就会继续寻找互动的另一个循环。如果有人不与之交互，则它开始执行某些操作。

我已经使用模块信号（以及 20 秒的示例超时）启动了这样的脚本，但超时似乎不起作用;脚本立即启动到非交互操作。出了什么问题？有没有更好的方法来解决这个问题？

#!/usr/bin/env python
import propyte
import signal
import time
def main():
    response = "yes"
    while response == "yes":
        response = get_input_nonblocking(
            prompt          = "ohai?",
            timeout         = 20 #604800 s (1 week)
        )
    print("start non-response procedures")
    # do things
def alarm_handler(signum, frame):
    raise Exception
def get_input_nonblocking(
    prompt          = "",
    timeout         = 20, # seconds
    message_timeout = "prompt timeout"
    ):
    signal.signal(signal.SIGALRM, alarm_handler)
    signal.alarm(timeout)
    try:
        response = propyte.get_input(prompt)
        signal.alarm(0)
        return response
    except Exception:
        print(message_timeout)
    signal.signal(signal.SIGALRM, signal.SIG_IGN)
    return ""
if __name__ == '__main__':
    main()

Answer 1

你可以简单地写：

import signal
TIMEOUT = 20 * 60 # secs to wait for interaction
def interrupted(signum, frame):
    "called when read times out"
    print('Exiting')
signal.signal(signal.SIGALRM, interrupted)
def i_input():
    try:
            print('You have 20 minutes to interact or this script will cease to execute')
            foo = input()
            return foo
    except:
            # timeout
            return
# set alarm
signal.alarm(TIMEOUT)
inp = i_input()
# disable the alarm if not wanted any longer
# signal.alarm(0)