python3: signal.signal/singal.alarm not working as expected

Alan alanwilter at
Mon Aug 2 12:37:05 CEST 2010

Hi there,

I have this example code to illustrate a problem I am having with python3.
It works fine with python 2.6 and 2.7 but does not with python 3.1.

Please, can someone tell me why or how to fix this example?

from __future__ import print_function
import os, subprocess, signal

def signal_handler( signum, frame ):

    print( "PID: %s" % pid )
    print( "Timed out! Process %s killed, max exec time (%ss) exceeded" %
(pid, timeTol ) )
    os.kill( int( pid ), 15 )
    raise Exception( "Taking too long to finish... aborting!" )

if __name__ == '__main__':

    timeTol = 5

    cmd = 'find /'

    signal.signal(signal.SIGALRM, signal_handler)

    p = subprocess.Popen(cmd, shell=True, stderr = subprocess.STDOUT, stdout
= subprocess.PIPE)
    pid =

    out = str( p.communicate()[0].decode() )

Many thanks,


Alan Wilter S. da Silva, D.Sc. - CCPN Research Associate
Department of Biochemistry, University of Cambridge.
80 Tennis Court Road, Cambridge CB2 1GA, UK.
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