module signal

Peter Otten __peter__ at web.de
Tue Oct 26 11:19:06 CEST 2004


Klaus Neuner wrote:

> # (2)
> 
> import sys, signal
> 
> def alarm_handler(signum, frame):
>     raise
> 
> try:
>     signal.signal(signal.SIGALRM, alarm_handler)
>     signal.alarm(3)
>     re.search("a(((.)*c)*d)*e", "abcdf"*20)
> except:
>     print "Time over."
> 
> #############################################################
> 
> (1) behaves the way one would expect it to behave: It stops counting
> after about 3 seconds. (2) will stop trying to match the regexp at
> once. And this behaviour will not change if you give any other
> argument to signal.alarm().
> 
> Why?

To remind you that a bare except is always a bad idea. Modify your program
along these lines

class Timeout(Exception): pass

def alarm_handler(signum, frame):
    raise Timeout

try
    ...
except Timeout:
    print "Time over."

to see that you didn't import the re module which raises a NameError.
Unfortunately the resulting script does not terminate anymore and I cannot
help you with that.

Peter




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