Python urllib2 automatic form filling and retrieval of results

I'm looking to be able to query a site for warranty information on a machine that this script would be running on. It should be able to fill out a form if needed ( like in the case of say HP's service site) and would then be able to retrieve the resulting web page.

I already have the bits in place to parse the resulting html that is reported back I'm just having trouble with what needs to be done in order to do a POST of data that needs to be put in the fields and then being able to retrieve the resulting page.