json.py

import pyparsing as pp

from bench.helpers import json_unescape


def compile():
    LBRACE, RBRACE, LBRACK, RBRACK, COLON = map(pp.Suppress, '{}[]:')

    value    = pp.Forward()

    true     = pp.Keyword('true').setParseAction(pp.replaceWith(True))
    false    = pp.Keyword('false').setParseAction(pp.replaceWith(False))
    null     = pp.Keyword('null').setParseAction(pp.replaceWith(None))
    number   = (pp.Regex(r'-?(0|[1-9][0-9]*)(\.[0-9]+)?([eE][-+]?[0-9]+)?')
                .setParseAction(pp.tokenMap(float)))
    string   = (pp.Regex(r'"([ !#-\[\]-\U0010ffff]+'
                         r'|\\(?:["\\/bfnrt]|u[0-9A-Fa-f]{4}))*"')
                .setParseAction(pp.tokenMap(json_unescape)))

    items    = pp.delimitedList(value)
    array    = (pp.Group(LBRACK - pp.Optional(items) + RBRACK)
                .setParseAction(lambda t: t.asList()))

    member   = pp.Group(string + COLON + value)
    members  = pp.delimitedList(member)
    object   = (pp.Dict(LBRACE - pp.Optional(members) + RBRACE)
                .setParseAction(lambda t: t.asDict()))

    value   << (object | array | string | number | true | false | null)

    json     = value('top') + pp.StringEnd()
    json.setDefaultWhitespaceChars(' \t\n\r')
    json.parseWithTabs()

    return lambda s: json.parseString(s)['top']


parse = compile()