How Can I Implement Time-Limited User Input in Programming?

Input with Time Restriction

In programming, it can be beneficial to impose a time limit on user input. For instance, you may wish to ask users a question and provide them with a limited duration to respond, such as:

print('some scenario')
prompt = input("You have 10 seconds to choose the correct answer...\n")

If the user exceeds the time limit, you can display a message like:

print('Sorry, times up.')

Solutions for Time-Limited Input

To implement time-limited input, consider these options:

• Blocking the Main Thread: If it is acceptable to block the execution of your code while the user is providing input, you can use a Timer object:

from threading import Timer

timeout = 10
t = Timer(timeout, print, ['Sorry, times up'])
t.start()
prompt = "You have %d seconds to choose the correct answer...\n" % timeout
answer = input(prompt)
t.cancel()

• Non-Blocking Input (Windows): To avoid blocking the main thread, you can use the following method on Windows (note that this approach is not tested):

import msvcrt
import time

class TimeoutExpired(Exception):
    pass

def input_with_timeout(prompt, timeout, timer=time.monotonic):
    sys.stdout.write(prompt)
    sys.stdout.flush()
    endtime = timer() + timeout
    result = []
    while timer() < endtime:
        if msvcrt.kbhit():
            result.append(msvcrt.getwche())  # XXX can it block on multibyte characters?
            if result[-1] == '\r':
                return ''.join(result[:-1])
        time.sleep(0.04)  # just to yield to other processes/threads
    raise TimeoutExpired

• Non-Blocking Input (Unix): Alternatively, on Unix-based systems, you can use one of the following approaches:

import select
import sys

def input_with_timeout(prompt, timeout):
    sys.stdout.write(prompt)
    sys.stdout.flush()
    ready, _, _ = select.select([sys.stdin], [],[], timeout)
    if ready:
        return sys.stdin.readline().rstrip('\n')  # expect stdin to be line-buffered
    raise TimeoutExpired

import signal

def alarm_handler(signum, frame):
    raise TimeoutExpired

def input_with_timeout(prompt, timeout):
    # set signal handler
    signal.signal(signal.SIGALRM, alarm_handler)
    signal.alarm(timeout)  # produce SIGALRM in `timeout` seconds

    try:
        return input(prompt)
    finally:
        signal.alarm(0)  # cancel alarm

By implementing these methods, you can effectively apply time restrictions to user input, enhancing the user experience and controlling the flow of your program.

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