How to *Search* with google from inside my programme and get the search result?

[Frank Potter]

I want to search something by a key word from inside my py script.
The using google idea comes to my mind first because write a search
programme from scratch is not so easy.

I want to take advantage of goolge results, but I don't know how.
To extract the result from html of google can get the result, but it's not
reliable and stable because the html structure my be changed any time.

Does google supply some webservice to programmers? I did see
some a tool use google to search and use it's result from the programme very
well. Its name is "Email catcher&sender 2.10", which can be download
at http://www.worldminer.com/download.htm. Windows users can take a
look at it. It supports more than google, but yahoo and some other search
engines. How does it do it? I really need some hints.