(How to Write a (Lisp) Interpreter (In Python))

This article explains how to build a Lisp interpreter in Python, covering both general interpreter implementation principles and the specific creation of "Lispy," an interpreter for the Scheme dialect of Lisp. The tutorial emphasizes that understanding how interpreters work is fundamental to understanding how computers work, and demonstrates how Scheme's simple syntax—consisting of only 5 keywords and 8 syntactic forms compared to Python's 33 keywords—makes it an ideal language for learning interpreter design. The article begins by contrasting Scheme's consistent list-based syntax with more complex languages like Java, then introduces a simplified "Lispy Calculator" subset before building toward a more complete Scheme implementation.