Python multithreading interrupt input()

问题:

Hi I am fairly new to python and I am trying to create a program that starts a thread that after five seconds will interrupt the input () function and print the message “Done!”.
Currently it only prints “Done!” after input is given. Even after five seconds has passed, the user must enter input before the message "Done!" is displayed. How can I get the thread to interrupt the input() function?

import time
import threading

def fiveSec():
    time.sleep(5)
    print('Done!')

def main():
    t = threading.Thread(target = fiveSec)
    t.daemond = True
    t.start()
    input('::>')

if __name__ == '__main__':
    main()

(Using Python version 3.4.2)

回答1:

You don't need a thread to do this, use a signal instead:

import signal
def interrupted(signum, frame):
    print "Timeout!"
signal.signal(signal.SIGALRM, interrupted)
signal.alarm(5)
try:
    s = input("::>")
except:
    print "You are interrupted."
signal.alarm(0)

You can read the documentation on signal module: https://docs.python.org/2/library/signal.html

回答2:

As NeoWang shows, you can do it with a signal. You can also do it with a thread and a signal. Here is a slightly more complete example that will let you enter several lines of data, and will exit if it has been more than 5 seconds since you pressed enter:

import time
import threading
import os
import signal

class FiveSec(threading.Thread):
    def restart(self):
        self.my_timer = time.time() + 5
    def run(self, *args):
        self.restart()
        while 1:
            time.sleep(0.1)
            if time.time() >= self.my_timer:
                break
        os.kill(os.getpid(), signal.SIGINT)


def main():
    try:
        t = FiveSec()
        t.daemon = True
        t.start()
        while 1:
            x = input('::> ')
            t.restart()
            print('\nYou entered %r\n' % x)
    except KeyboardInterrupt:
        print("\nDone!")

if __name__ == '__main__':
    main()