Exception raised in wrong thread?

Hello.

I have problem and I'm looking for help. Probably there is some quite
easy solution, but I can't see it.

I'm trying to perform some action that have to be timeout safe. So here
is the structure of my program:

\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
def TimeoutHandler():
print '!'
raise Exception

class Active:
def Action:
timer = Timer(1, TimeoutHandler)
print '1'
timer.start()
try:
print '2'
time.sleep(20)
print '3'
except:
print '4'
else:
print '5'
timer.cancel()
print '6'

active = Actice()

///////////////////////////////////////////
The output is:
12!356

My question is, why exception is not raised correctly? Could be the
reason that (probably) timer is another thread and there is no
exception in the main thread? How to solve this problem? [My timeout
should be smaller than one second so I can't use signal.alarm()]

Thanks for your reply,
Krzysztof Nowak