I've (finally) gotten the book content upgraded to Python 3.7.
I've also deleted all the previous versions of the book. I had been keeping them on my web server because -- well -- because I don't know why. They go back to at least 2011, some of the content may be even older than that.
I've also deleted some previous self-published content.
(I started writing about Python almost 20 years ago. Some of the content could have been that old. It deserves to be deleted.)