I guess a native Python implementation would be too slow. However, there is a fantastic libtorrent library that has Python bindings and allows to implement a torrent client in Python relatively easily.

BTW, regarding the original article, there is also a MonoTorrent library for .NET. Despite the name it can be compiled by Visual Studio. The original library was abandoned a while ago and seems to be buggy, but I was able to make a very simple .NET client with WinForms UI using this fork: https://github.com/ErtyHackward/monotorrent