jsonpath.py

"""
An XPath for JSON, modified by Drew Raines

A port of the Perl, and JavaScript versions of JSONPath
see http://goessner.net/articles/JsonPath/

Based on on JavaScript version by Stefan Goessner at:
        http://code.google.com/p/jsonpath/
and Perl version by Kate Rhodes at:
        http://github.com/masukomi/jsonpath-perl/tree/master
"""

__author__ = "Phil Budne"
__revision__ = "$Revision: 1.10 $"
__version__ = '0.52'

#	Copyright (c) 2007 Stefan Goessner (goessner.net)
#       Copyright (c) 2008 Kate Rhodes (masukomi.org)
#       Copyright (c) 2008 Philip Budne (ultimate.com)
#	Licensed under the MIT licence: 
#	
#	Permission is hereby granted, free of charge, to any person
#	obtaining a copy of this software and associated documentation
#	files (the "Software"), to deal in the Software without
#	restriction, including without limitation the rights to use,
#	copy, modify, merge, publish, distribute, sublicense, and/or sell
#	copies of the Software, and to permit persons to whom the
#	Software is furnished to do so, subject to the following
#	conditions:
#	
#	The above copyright notice and this permission notice shall be
#	included in all copies or substantial portions of the Software.
#	
#	THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
#	EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
#	OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
#	NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
#	HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
#	WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
#	FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
#	OTHER DEALINGS IN THE SOFTWARE.

import re
import sys

# XXX BUGS:
# evalx is generally a crock:
#       handle [email protected]???
# there are probably myriad unexpected ways to get an exception:
#       wrap initial "trace" call in jsonpath body in a try/except??

# XXX TODO:
# internally keep paths as lists to preserve integer types
#       (instead of as ';' delimited strings)

__all__ = [ 'jsonpath' ]

# XXX precompile RE objects on load???
# re_1 = re.compile(.....)
# re_2 = re.compile(.....)

def normalize(x):
    """normalize the path expression; outside jsonpath to allow testing"""
    subx = []

    # replace index/filter expressions with placeholders
    # Python anonymous functions (lambdas) are cryptic, hard to debug
    def f1(m):
        n = len(subx)   # before append
        g1 = m.group(1)
        subx.append(g1)
        ret = "[#%d]" % n
#       print "f1:", g1, ret
        return ret
    x = re.sub(r"[\['](\??\(.*?\))[\]']", f1, x)

    # added the negative lookbehind -krhodes
    x = re.sub(r"'?(?<!@)\.'?|\['?", ";", x)

    x = re.sub(r";;;|;;", ";..;", x)

    x = re.sub(r";$|'?\]|'$", "", x)

    # put expressions back
    def f2(m):
        g1 = m.group(1)
#       print "f2:", g1
        return subx[int(g1)]

    x = re.sub(r"#([0-9]+)", f2, x)

    return x

def jsonpath(obj, expr, result_type='VALUE', debug=0):
    """traverse JSON object using jsonpath expr, returning values or paths"""

    def s(x,y):
        """concatenate path elements"""
        return str(x) + ';' + str(y)

    def isint(x):
        """check if argument represents a decimal integer"""
        return x.isdigit()

    def as_path(path):
        """convert internal path representation to
           "full bracket notation" for PATH output"""
        p = '$'
        for piece in path.split(';')[1:]:
            # make a guess on how to index
            # XXX need to apply \ quoting on '!!
            if isint(piece):
                p += "[%s]" % piece
            else:
                p += "['%s']" % piece
        return p

    def store(path, object):
        if result_type == 'VALUE':
            result.append(object)
        elif result_type == 'IPATH': # Index format path (Python ext)
            # return list of list of indices -- can be used w/o "eval" or split
            result.append(path.split(';')[1:])
        else: # PATH
            result.append(as_path(path))
        return path

    def trace(expr, obj, path):
        if debug: print "trace", expr, "/", path
        if expr:
            x = expr.split(';')
            loc = x[0]
            x = ';'.join(x[1:])
            if debug: print "\t", loc, type(obj)
            if loc == "*":
                def f03(key, loc, expr, obj, path):
                    if debug > 1: print "\tf03", key, loc, expr, path
                    trace(s(key, expr), obj, path)
                walk(loc, x, obj, path, f03)
            elif loc == "..":
                trace(x, obj, path)
                def f04(key, loc, expr, obj, path):
                    if debug > 1: print "\tf04", key, loc, expr, path
                    if isinstance(obj, dict):
                        if key in obj:
                            trace(s('..', expr), obj[key], s(path, key))
                    else:
                        if key < len(obj):
                            trace(s('..', expr), obj[key], s(path, key))
                walk(loc, x, obj, path, f04)
            elif loc == "!":
                # Perl jsonpath extension: return keys
                def f06(key, loc, expr, obj, path):
                    if isinstance(obj, dict):
                        trace(expr, key, path)
                walk(loc, x, obj, path, f06)
            elif isinstance(obj, dict) and loc in obj:
                trace(x, obj[loc], s(path, loc))
            elif isinstance(obj, list) and isint(loc):
                iloc = int(loc)
                if len(obj) >= iloc:
                    trace(x, obj[iloc], s(path, loc))
            else:
                # [(index_expression)]
                if loc.startswith("(") and loc.endswith(")"):
                    if debug > 1: print "index", loc
                    e = evalx(loc, obj)
                    trace(s(e,x), obj, path)
                    return

                # ?(filter_expression)
                if loc.startswith("?(") and loc.endswith(")"):
                    if debug > 1: print "filter", loc
                    def f05(key, loc, expr, obj, path):
                        if debug > 1: print "f05", key, loc, expr, path
                        if isinstance(obj, dict):
                            eval_result = evalx(loc, obj[key])
                        else:
                            eval_result = evalx(loc, obj[int(key)])
                        if eval_result:
                            trace(s(key, expr), obj, path)

                    loc = loc[2:-1]
                    walk(loc, x, obj, path, f05)
                    return

                m = re.match(r'(-?[0-9]*):(-?[0-9]*):?(-?[0-9]*)$', loc)
                if m:
                    if isinstance(obj, (dict, list)):
                        def max(x,y):
                            if x > y:
                                return x
                            return y

                        def min(x,y):
                            if x < y:
                                return x
                            return y

                        objlen = len(obj)
                        s0 = m.group(1)
                        s1 = m.group(2)
                        s2 = m.group(3)

                        # XXX int("badstr") raises exception
                        start = int(s0) if s0 else 0
                        end = int(s1) if s1 else objlen
                        step = int(s2) if s2 else 1

                        if start < 0:
                            start = max(0, start+objlen)
                        else:
                            start = min(objlen, start)
                        if end < 0:
                            end = max(0, end+objlen)
                        else:
                            end = min(objlen, end)

                        for i in xrange(start, end, step):
                            trace(s(i, x), obj, path)
                    return

                # after (expr) & ?(expr)
                if loc.find(",") >= 0:
                    # [index,index....]
                    for piece in re.split(r"'?,'?", loc):
                        if debug > 1: print "piece", piece
                        trace(s(piece, x), obj, path)
        else:
            store(path, obj)

    def walk(loc, expr, obj, path, funct):
        if isinstance(obj, list):
            for i in xrange(0, len(obj)):
                funct(i, loc, expr, obj, path)
        elif isinstance(obj, dict):
            for key in obj:
                funct(key, loc, expr, obj, path)

    def evalx(loc, obj):
        """eval expression"""

        if debug: print "evalx", loc

        # a nod to JavaScript. doesn't work for @.name.name.length
        # Write len(@.name.name) instead!!!
        loc = loc.replace("@.length", "len(__obj)")

        loc = loc.replace("&&", " and ").replace("||", " or ")

        # replace [email protected] with 'name' not in obj
        # XXX handle [email protected]....
        def notvar(m):
            return "'%s' not in __obj" % m.group(1)
        loc = re.sub("!@\.([a-zA-Z@_]+)", notvar, loc)

        # replace @.name.... with __obj['name']....
        # handle @.name[.name...].length
        def varmatch(m):
            def brackets(elts):
                ret = "__obj"
                for e in elts:
                    if isint(e):
                        ret += "[%s]" % e # ain't necessarily so
                    else:
                        ret += "['%s']" % e # XXX beware quotes!!!!
                return ret
            g1 = m.group(1)
            elts = g1.split('.')
            if elts[-1] == "length":
                return "len(%s)" % brackets(elts[1:-1])
            return brackets(elts[1:])

        loc = re.sub(r'(?<!\\)(@\.[a-zA-Z@_.]+)', varmatch, loc)

        # replace = w/ ==
        loc = re.sub(r'(?<!=)(=)(?!=)', '==', loc)

        # replace @  w/ "__obj", but \@ means a literal @
        loc = re.sub(r'(?<!\\)@', "__obj", loc).replace(r'\@', '@')
        if debug: print "eval", loc
        try:
            # eval w/ caller globals, w/ local "__obj"!
            v = eval(loc, caller_globals, {'__obj': obj})
        except Exception, e:
            if debug: print e
            return False

        if debug: print "->", v
        return v

    # body of jsonpath()

    # Get caller globals so eval can pick up user functions!!!
    caller_globals = sys._getframe(1).f_globals
    result = []
    if expr and obj:
        cleaned_expr = normalize(expr)
        if cleaned_expr.startswith("$;"):
            cleaned_expr = cleaned_expr[2:]

        # XXX wrap this in a try??
        trace(cleaned_expr, obj, '$')

        if len(result) > 0:
            return result
    return False

if __name__ == '__main__':
    try:
        import json        # v2.6
    except ImportError:
        import simplejson as json

    import sys

    try:
        path = sys.argv[1]
    except IndexError:
        path = None

    try:
        object = json.loads(sys.stdin.read())
    except ValueError:
        print "no json object"
        sys.exit(1)

    f = sys.stdout
    if path:
        json.dump(jsonpath(object, path, 'VALUE'), f, sort_keys=True, indent=1)
    else:
        json.dump(object, f, sort_keys=True, indent=2)
    f.write("\n")

    sys.exit(0)