Python - How to check active domain

This is python and libvirt related post, beware!!

Ok now I want to check from my script, let's say :

bash> xencheck.py nameofvps

So I want the script to check if the vps name is available and active. This is what I done :

#!/usr/bin/python -u

import libvirt
import sys
import os

def Startup():
if not os.access("/proc/xen", os.R_OK):
   print "System is not running Xen kernel!"
   sys.exit(1)

#connect to hypervisor
conn = libvirt.open("xen:///default")

if conn == None:
   print 'Failed to connect to hypervisor'
   sys.exit(1)

dom0 = conn.listDomainsID()
for id in dom0:
dom1 = conn.lookupByID(id)
if dom1.name() == sys.argv[1]:
  print dom1.name()

#main function to execute
def main():
Startup()

if __name__ == "__main__":
main()