python - Python 3 和 Windows 7 的定时输入

Question

我正在寻找一种解决方案，使用户的输入在一段时间后超时。 此代码应在 5 秒后打印“成功...”，无需用户进行任何交互:

def input_with_timeout(timeout):

    print ("Hello, you can type and press enter to change 'ans' variable value or wait "+str(timeout)+" seconds and the program will continue")   
    ans=input()   #pass input after timeout
    return ans


s="mustnotchange"

s=input_with_timeout(5)

if s=="mustnotchange":
    print("Success, if you didn't just cheat by writing mustnotchange")
else:
    print("you answered : "+s+" variable value has changed")

我知道这个问题经常被问到，但以下主题中提供的解决方案均不适用于 WINDOWS 7 和 Python 3(Windows 7“终极”SP1 64 位和 Python 3.6.8 64 位) Python 3 Timed Input

How to set time limit on raw_input

Keyboard input with timeout?

raw_input and timeout

实际上我正在使用一个“技巧”来避免这个问题:我使用 os.startfile() 启动另一个 python 脚本，但它在启动时无法对输入使用react。

如果没有任何可行的答案，那么它一定很难做到(多处理、线程、队列...)，但这在很多情况下肯定会有所帮助。

谢谢。

Answer 1

下面的代码用于使用 input() once 进行跨平台提示 暂停。超时时，它会要求用户按 Enter 键，以便提示器- 线程可以干净地关闭。

删除影响 _prompter_exit 的部分将允许在超时时恢复，而无需用户按 Enter 键，但代价是使提示器线程保持事件状态，直到整个进程退出。

仅仅像 @Mad Physicist 建议的那样加入带有超时的提示线程是行不通的，因为它不会解锁 input() 调用本身。如果不使用特定于操作系统的库，(据我所知)如果不最终提供某种形式的输入，就无法唤醒等待 input() 的线程。

该代码是我的答案的精简版本，允许在给定时间范围内进行多个输入:

Taking in multiple inputs for a fixed time in Python

from threading import Thread, enumerate, Event
from queue import Queue, Empty
import time


SENTINEL = None


class PromptManager(Thread):

    def __init__(self, timeout):
        super().__init__()
        self.timeout = timeout
        self._in_queue = Queue()
        self._out_queue = Queue()
        self.prompter = Thread(target=self._prompter, daemon=True)
        self._prompter_exit = Event()

    def run(self):
        """Run worker-thread. Start prompt-thread, fetch passed
        input from in_queue and forward it to `._poll()` in MainThread.
        If timeout occurs before user-input, enqueue SENTINEL to
        unblock `.get()` in `._poll()`.
        """
        self.prompter.start()
        try:
            txt = self._in_queue.get(timeout=self.timeout)
        except Empty:
            self._out_queue.put(SENTINEL)
            print(f"\n[{time.ctime()}] Please press Enter to continue.")
            # without usage of _prompter_exit() and Enter, the
            # prompt-thread would stay alive until the whole program ends
            self._prompter_exit.wait()
        else:
            self._out_queue.put(txt)

    def start(self):
        """Start manager-thread."""
        super().start()
        return self._poll()

    def _prompter(self):
        """Prompting target function for execution in prompter-thread."""
        self._in_queue.put(input(f"[{time.ctime()}] >$ "))
        self._prompter_exit.set()

    def _poll(self):
        """Get forwarded inputs from the manager-thread executing `run()`
        and process them in the parent-thread.
        """
        msg =  self._out_queue.get()
        self.join()
        return msg

用于演示:

if __name__ == '__main__':

    pm = PromptManager(timeout=5)
    msg = pm.start()
    print(f"User input: {msg}")

    for i in range(3):
        print(f"[{time.ctime()}] Do something else. "
              f"Alive threads:{[t.name for t in enumerate()]}")
        time.sleep(1)

运行时触发超时:

[Tue Nov 26 20:50:47 2019] >$ 
[Tue Nov 26 20:50:52 2019] Please press Enter to continue.

User input: None
[Tue Nov 26 20:50:57 2019] Do something else. Alive threads:['MainThread']
[Tue Nov 26 20:50:58 2019] Do something else. Alive threads:['MainThread']
[Tue Nov 26 20:50:59 2019] Do something else. Alive threads:['MainThread']

Process finished with exit code 0

及时运行用户输入:

[Tue Nov 26 20:51:16 2019] >$ Hello
User input: Hello
[Tue Nov 26 20:51:19 2019] Do something else. Alive threads:['MainThread']
[Tue Nov 26 20:51:20 2019] Do something else. Alive threads:['MainThread']
[Tue Nov 26 20:51:21 2019] Do something else. Alive threads:['MainThread']

Process finished with exit code 0