nick at craig-wood
Jul 16, 2009, 6:29 AM
Post #9 of 12
(459 views)
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Re: using timers to force an execution time
[In reply to]
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superpollo <user [at] example> wrote:
> Diez B. Roggisch wrote:
> > superpollo wrote:
> >>am i wrong?
> >
> >
> > No, you are right, for threads that is. You can try & trick around with the
> > trace-functionality of python, and some ctypes-based
> > system-thread-module-tricks that are, as mentioned before, black-magic & a
> > spinning gatling gun pointed to your very own lower extremities.
> >
>
> OUCH.
>
> > The only reliable way of terminating an asynchronous computation is to use
> > processes, since python2.6 that's rather convenient with the
> > multiprocessing-module. However, that imposes some limits to what you can
> > do.
>
> fair enough.
Or if you are on unix you can use signals...
It is probably just about acceptable to raise an exception in a signal
handler like this code does.
import signal, os, time
class TimeOut(Exception):
"""Thrown on alarm"""
pass
def sig_alarm(signum, frame):
raise TimeOut()
def time_out(t, fn, *args, **kwargs):
"""Calls fn with the args and kwargs returning its result or raising a TimeOut exception if it doesn't complete within t seconds"""
# Turn alarm off and read old value
old_alarm = signal.alarm(0)
# Install new handler remembering old
old_handler = signal.signal(signal.SIGALRM, sig_alarm)
# Set the timer going
signal.alarm(t)
try:
rc = fn(*args, **kwargs)
finally:
# Restore the old handler
signal.signal(signal.SIGALRM, old_handler)
signal.alarm(0)
def test():
for repeat in range(10):
print time.time()
time.sleep(0.66)
if __name__ == "__main__":
try:
time_out(3, test)
except TimeOut:
print "timed out"
--
Nick Craig-Wood <nick [at] craig-wood> -- http://www.craig-wood.com/nick
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