urllib IOError Exception

[Bart Nessux]

 From the urllib documentation: "If the connection cannot be made, or if 
the server returns an error code, the IOError exception is raised. "

Suppose I have an array of IPs and I want to pass each element of the 
array to urllib. Basically, I'm just trying to see how many hosts are 
serveing-up Web pages in a certain IP range. Is there a way in which I 
can handle the IOError so that the script will continue on to the next 
host in the array if the host before isn't running a Web server? Below 
is my code:

def gen_ip_range():
    import urllib
    n = 0
    hosts = []
    networks = []
    while n < 254:
       n = n + 1
       networks.append("192.168.%s." %(n))
    for network in networks:
       h = 0
       while h < 254:
          h = h + 1
          hosts.append(network+str(h))
    for host in hosts:
        f = urllib.urlopen("http://%s" %host)
        print f.read()
        f.close()
gen_ip_range()

Thanks,
Bart