JSONVisitor

jsonizer.py

import json
from parsimonious import Grammar, NodeVisitor


class JSONVisitor(NodeVisitor):
    """
    A simple JSON serializer for Parsimonious parse trees.

    """
    def generic_visit(self, node, children):
        if node.expr_name:
            out = OrderedDict(expr_name=node.expr_name, text=node.text,
                              start=node.start, end=node.end)
            if children:
                out['children'] = children
        else:
            if children:
                out = children
            else:
                out = None

        return out


if __name__ == '__main__':
    my_grammar = Grammar(r"""
        styled_text = bold_text / italic_text
        bold_text   = "((" text "))"
        italic_text = "''" text "''"
        text        = ~"[A-Z 0-9]*"i
        """)

    tree = my_grammar.parse("((bold stuff))")
    visited = JSONVisitor().visit(tree)
    print(json.dumps(visited, indent=2))

    """ returns:
    {
      "expr_name": "styled_text",
      "text": "((bold stuff))",
      "start": 0,
      "end": 14,
      "children": [
        {
          "expr_name": "bold_text",
          "text": "((bold stuff))",
          "start": 0,
          "end": 14,
          "children": [
            null,
            {
              "expr_name": "text",
              "text": "bold stuff",
              "start": 2,
              "end": 12
            },
            null
          ]
        }
      ]
    }
    """