A wee little script to convert the Pigeon User Interface into JSON suitable for graphing with the D3.js visualization kit. See http://thinkpigeon.blogspot.com/2013/01/persistant-binary-tree.html

d2j.py

from pigeon.xerblin.world import ROOT

def trreee(node):
  key, value, lower, higher = node
  it = {'name': key}
  children = []
  if lower:
    children.append(trreee(lower))
  if higher:
    children.append(trreee(higher))
  if children:
    it['children'] = children
  return it

json.dump(trreee(ROOT[1]), open('tree.json','w'), indent=2)