This page has two purposes: to describe how to implement computer language interpreters in general, and in particular to build an interpreter for most of the Scheme dialect of Lisp using Python 3 as the implementation language. I call my language and interpreter Lispy (lis.py). Years ago, I showed how to write a semi-practical Scheme interpreter Java and in in Common Lisp). This time around the goal is to demonstrate, as concisely and simply as possible, what Alan Kay called "Maxwell's Equatio...