Need function like "raw_input", but with time limit

[Radioactive Man]

On Sun, 19 Sep 2004 11:21:49 +0200, aleaxit at yahoo.com (Alex Martelli)
wrote:

>Radioactive Man <rm at rm.rm> wrote:
>
>> anyone know of a function like "raw_input", which collects a string
>> from the user entry, but one where I can set a time limit, as follows:
>> 
>> time_limit = 10    # seconds
>> user_answer = function_xyz("GIVE ME AN ANSWER:  ", time_limit)  
>> 
>> 
>> The problem with "raw_input" is that it will stop unattended script
>> indefinitely.  I'm looking for a function that does the exact same
>> thing, but with a time limit feature, and preferably one that returns
>> an empty string ('') when it gets no response.  Any suggestions?
>
>It depends on what platforms you need to run on.  On any kind of
>Unix-like platform (including Linux, BSD, MacOSX, ...), the function
>select of module select can work on any kind of files, including
>sys.stdin, and it does provide timeout functionality, too.  So, you
>could sys.stdout.write the prompt, then call select.select with
>sys.stdin.fileno as the only file descriptor of interest and whatever
>timeout you wish.  Depending on what select.select returns you can then
>either sys.stdin.readline (and strip the trailing \n) or just return the
>empty string from your function.
>
>Unfortunately, on Windows, select.select works only on sockets, not
>ordinary files nor the console.  So, if you want to run on Windows, you
>need a different approach.  On Windows only, the Python standard library
>has a small module named msvcrt, including functions such as
>msvcrt.kbhit which tells you whether any keystroke is waiting to be
>read.  Here, you might sys.stdout.write the prompt, then enter a small
>loop (including a time.sleep(0.2) or so) which waits to see whether the
>user is pressing any key -- if so then you can sys.stdin.readline etc,
>but if after your desired timeout is over no key has been hit, then just
>return the empty string from your function.

In other words, the user must make any entries while the time.sleep()
statement is running.  If the user has entered data during this time,
it should be indicated by the value of msvcrt.kbhit().  The problem
I've had is that msvcrt.kbhit() returns 0 no matter what I've entered
before the statement is executed and while the sleep statement is
being executed.

>
>All of this assumes that if the user has STARTED typing something then
>you want to wait indefinitely (not timeout in the middle of their
>entering their answer!).  Otherwise, you have more work to do, since you
>must ensure that the user has hit a Return (which means you must peek at
>exactly what's in sys.stdin, resp. use msvcrt.getch, one character at a
>time).  Fortunately, the slightly simpler approach of waiting
>indefinitely if the user has started entering seems to be the preferable
>one from a user interface viewpoint -- it lets you deal with unattended
>consoles as you desire, yet IF the user is around at all it gives the
>user all the time they want to COMPLETE their answer.
>
>
>Alex
> 


Thanks for the info.