This is a tutorial about Downloading and Parsing possibilities of Python.
As an example website was taken http://xkcd.com/
Check the blog post on this topic - http://code-speculations.herokuapp.co...
To execute the script you will need:
lxml
xpath helper extensions/plugin in your browser
DOM inspector (built-in in the most modern browsers)
Script code here - http://pastebin.com/JcUn9Qui