Keyboard input with timeout?

Question

How would you prompt the user for some input but timing out after N seconds?

Google is pointing to a mail thread about it at http://mail.python.org/pipermail/python-list/2006-January/533215.html but it seems not to work. The statement in which the timeout happens, no matter whether it is a sys.input.readline or timer.sleep(), I always get:

<type 'exceptions.TypeError'>: [raw_]input expected at most 1 arguments, got 2

which somehow the except fails to catch.

Answer 1

The example you have linked to is wrong and the exception is actually occuring when calling alarm handler instead of when read blocks. Better try this:

import signal
TIMEOUT = 5 # number of seconds your want for timeout

def interrupted(signum, frame):
    "called when read times out"
    print 'interrupted!'
signal.signal(signal.SIGALRM, interrupted)

def input():
    try:
            print 'You have 5 seconds to type in your stuff...'
            foo = raw_input()
            return foo
    except:
            # timeout
            return

# set alarm
signal.alarm(TIMEOUT)
s = input()
# disable the alarm after success
signal.alarm(0)
print 'You typed', s