Railroad-diagram Generator is a small library for generating railroad diagrams
(like what JSON.org uses) using SVG, with both JS and Python ports.

Railroad diagrams are a way of visually representing a grammar in a form that is
more readable than using regular expressions or BNF. They can easily represent
any context-free grammar, and some more powerful grammars. There are several
railroad-diagram generators out there, but none of them had the visual appeal I
wanted, so I wrote my own.