Help-log in to a web page

[Murugesh]

Hi all,
I'm a newbie to python.I need to login to a webpage after supplying 
usename and password.

import urllib   
sock = urllib.urlopen("http://xop-pc.main.com")
htmlSource = sock.read()                           
sock.close()                                       
print htmlSource        

In the above code how can i supply username and password to that URL.
Thanks for you time.

Thanks
Amen.