This paper was written in DocBook XML using Emacs, and converted to HTML using the SAXON XSLT processor from Michael Kay of ICL with a customized version of Norman Walsh's XSL stylesheets. From there, it was converted to PDF using HTMLDoc, and to plain text using w3m

It simply copies the physical layout (entity structure) of the "Dive Into Python" book

If you're interested in learning more about DocBook for technical writing, you should read the canonical book, DocBook: The Definitive Guide. If you're going to do any serious writing in DocBook, I would recommend subscribing to the DocBook mailing lists.