I have a set of html files, I need to translate their content. On the way out to get the same set of html but translated. All this is handled locally.
Parse them with BeautifulSoup, get the strings in the markup, and then use the Rest API provided by Google to translate them. Put them back in your html files using BeautifulSoup one more time.
This is just the general algorithm, look at the two documentation, and come back if you have any more questions