timeout on os.popen3?

[selwyn]

hi all,

I would like some advice on how I can include a timeout for a scanning 
operation using unzip on linux and os.popen3.

I am scanning through about 30g of rescued zip files, looking for xml 
extensions within those files.  What I have put together 'works', but 
only for what appears to be properly reconstructed files. 
Unfortunately, some aren't AND for some reason no standard error 
messages are being triggered. This causes my script to hang indefinitely.

What I would like is for the script to move on to the next file, after 
say a 10sec period of inactivity, but am unsure how this could be 
included. I have googled around and think the select module may be 
helpful, but after reading the docs I am still confused :-(

Here is what I have so far:

#!/usr/bin/python
import os,sys, time, string

filesscanned=0
possibles=0
nonzips=0
files=[]
a = os.listdir(sys.argv[1])

for i in a:
     print i
     stdin, stdout, stderr = os.popen3('unzip -l %s%s' % (sys.argv[1], i))
     if stderr.read()=='':
         zippedfiles = string.lower(stdout.read())
         if zippedfiles.find('xml')!= -1:
             os.system("""cp '%s%s' candidates"""% (sys.argv[1], i))
             possibles +=1
             print 'found a candidate:- %s%s'% (sys.argv[1],i)
             files.append(i)
     else:
         os.system("""cp '%s%s' nonzips"""% (sys.argv[1], i))
         nonzips +=1
         print 'found nonzip or broken file:- %s' %i

     filesscanned +=1

Any help gratefully received.
cheers,
Selwyn.