is a pile of bits

lisp dialect for python modules

Originally started in 2008 as a followup to the much-maligned spexy, sibilant was meant to be a serious take on a LISP dialect that compiled to a Python module. It fell by the wayside when real life interferred in a big way.

Spexy and Sibilant were both re-discovered in January of 2014, and I’ve been looking over them to see what– if anything– can be salvaged.

I imported sibilant to GitHub in its non-function state, and that’s the starting point for any future hacking.

Sibilant Goals

  • Python 3
  • Scheme-like (LISP1, not LISP2)
  • REPL
  • import support for sibilant source files
    • importing sibilant should enable the import features such that it will begin searching for .pyscm files on further import calls
    • the contents of a .pyscm file should be consumable from other Python modules
    • should support compiling .pyscm into .pyc
    • .pyscm should be able to import native python modules as well as other .pyscm modules
  • should follow a continuation-passing style call conformity after being compiled
  • should support tail-call recursion optimization
  • should support call/cc (even across calls into native Python)
  • should support symbols as a type
  • should support cons cell style lists as a type
  • should support macros
  • should provide a way to write DSL in Python (arguably, this is The Point)
  • should support correctly printing traceback lines
  • should support the with managed interface from Python objects
  • should support generators
  • should support multimethods and CLOS-style class definitions (dispatching to Pythonic classes? Maybe a metaclass?)



There is already a serious and strong LISP that runs on Python, and it is Clojure. If anyone were to ask me, “should I use Sibilant?” I would tell them to look to Python Clojure instead. Clojure has a real community around it, and it is a language that runs on Java as well as Python platforms.

Sibilant Javascript

There is also another project that has come into existence named “sibilant”. What with it being a dictionary word meaning loosely “speaks with a lisp” this is hardly surprising! The other sibilant is a lisp that compiles to Javascript.