280 lines
8.0 KiB
Python
280 lines
8.0 KiB
Python
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#!/usr/bin/env python
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#
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# Copyright (C) 2010 Google Inc.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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# This module is used for version 2 of the Google Data APIs.
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__author__ = 'j.s@google.com (Jeff Scudder)'
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"""Provides classes and methods for working with JSON-C.
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This module is experimental and subject to backwards incompatible changes.
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Jsonc: Class which represents JSON-C data and provides pythonic member
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access which is a bit cleaner than working with plain old dicts.
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parse_json: Converts a JSON-C string into a Jsonc object.
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jsonc_to_string: Converts a Jsonc object into a string of JSON-C.
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"""
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try:
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import simplejson
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except ImportError:
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try:
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# Try to import from django, should work on App Engine
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from django.utils import simplejson
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except ImportError:
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# Should work for Python2.6 and higher.
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import json as simplejson
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def _convert_to_jsonc(x):
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"""Builds a Jsonc objects which wraps the argument's members."""
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if isinstance(x, dict):
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jsonc_obj = Jsonc()
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# Recursively transform all members of the dict.
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# When converting a dict, we do not convert _name items into private
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# Jsonc members.
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for key, value in x.iteritems():
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jsonc_obj._dict[key] = _convert_to_jsonc(value)
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return jsonc_obj
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elif isinstance(x, list):
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# Recursively transform all members of the list.
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members = []
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for item in x:
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members.append(_convert_to_jsonc(item))
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return members
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else:
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# Return the base object.
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return x
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def parse_json(json_string):
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"""Converts a JSON-C string into a Jsonc object.
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Args:
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json_string: str or unicode The JSON to be parsed.
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Returns:
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A new Jsonc object.
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"""
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return _convert_to_jsonc(simplejson.loads(json_string))
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def parse_json_file(json_file):
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return _convert_to_jsonc(simplejson.load(json_file))
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def jsonc_to_string(jsonc_obj):
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"""Converts a Jsonc object into a string of JSON-C."""
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return simplejson.dumps(_convert_to_object(jsonc_obj))
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def prettify_jsonc(jsonc_obj, indentation=2):
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"""Converts a Jsonc object to a pretified (intented) JSON string."""
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return simplejson.dumps(_convert_to_object(jsonc_obj), indent=indentation)
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def _convert_to_object(jsonc_obj):
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"""Creates a new dict or list which has the data in the Jsonc object.
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Used to convert the Jsonc object to a plain old Python object to simplify
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conversion to a JSON-C string.
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Args:
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jsonc_obj: A Jsonc object to be converted into simple Python objects
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(dicts, lists, etc.)
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Returns:
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Either a dict, list, or other object with members converted from Jsonc
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objects to the corresponding simple Python object.
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"""
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if isinstance(jsonc_obj, Jsonc):
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plain = {}
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for key, value in jsonc_obj._dict.iteritems():
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plain[key] = _convert_to_object(value)
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return plain
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elif isinstance(jsonc_obj, list):
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plain = []
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for item in jsonc_obj:
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plain.append(_convert_to_object(item))
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return plain
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else:
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return jsonc_obj
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def _to_jsonc_name(member_name):
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"""Converts a Python style member name to a JSON-C style name.
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JSON-C uses camelCaseWithLower while Python tends to use
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lower_with_underscores so this method converts as follows:
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spam becomes spam
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spam_and_eggs becomes spamAndEggs
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Args:
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member_name: str or unicode The Python syle name which should be
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converted to JSON-C style.
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Returns:
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The JSON-C style name as a str or unicode.
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"""
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characters = []
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uppercase_next = False
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for character in member_name:
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if character == '_':
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uppercase_next = True
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elif uppercase_next:
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characters.append(character.upper())
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uppercase_next = False
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else:
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characters.append(character)
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return ''.join(characters)
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class Jsonc(object):
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"""Represents JSON-C data in an easy to access object format.
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To access the members of a JSON structure which looks like this:
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{
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"data": {
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"totalItems": 800,
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"items": [
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{
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"content": {
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"1": "rtsp://v5.cache3.c.youtube.com/CiILENy.../0/0/0/video.3gp"
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},
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"viewCount": 220101,
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"commentCount": 22,
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"favoriteCount": 201
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}
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]
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},
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"apiVersion": "2.0"
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}
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You would do the following:
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x = gdata.core.parse_json(the_above_string)
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# Gives you 800
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x.data.total_items
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# Should be 22
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x.data.items[0].comment_count
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# The apiVersion is '2.0'
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x.api_version
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To create a Jsonc object which would produce the above JSON, you would do:
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gdata.core.Jsonc(
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api_version='2.0',
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data=gdata.core.Jsonc(
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total_items=800,
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items=[
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gdata.core.Jsonc(
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view_count=220101,
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comment_count=22,
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favorite_count=201,
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content={
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'1': ('rtsp://v5.cache3.c.youtube.com'
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'/CiILENy.../0/0/0/video.3gp')})]))
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or
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x = gdata.core.Jsonc()
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x.api_version = '2.0'
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x.data = gdata.core.Jsonc()
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x.data.total_items = 800
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x.data.items = []
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# etc.
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How it works:
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The JSON-C data is stored in an internal dictionary (._dict) and the
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getattr, setattr, and delattr methods rewrite the name which you provide
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to mirror the expected format in JSON-C. (For more details on name
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conversion see _to_jsonc_name.) You may also access members using
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getitem, setitem, delitem as you would for a dictionary. For example
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x.data.total_items is equivalent to x['data']['totalItems']
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(Not all dict methods are supported so if you need something other than
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the item operations, then you will want to use the ._dict member).
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You may need to use getitem or the _dict member to access certain
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properties in cases where the JSON-C syntax does not map neatly to Python
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objects. For example the YouTube Video feed has some JSON like this:
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"content": {"1": "rtsp://v5.cache3.c.youtube.com..."...}
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You cannot do x.content.1 in Python, so you would use the getitem as
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follows:
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x.content['1']
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or you could use the _dict member as follows:
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x.content._dict['1']
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If you need to create a new object with such a mapping you could use.
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x.content = gdata.core.Jsonc(_dict={'1': 'rtsp://cache3.c.youtube.com...'})
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"""
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def __init__(self, _dict=None, **kwargs):
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json = _dict or {}
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for key, value in kwargs.iteritems():
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if key.startswith('_'):
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object.__setattr__(self, key, value)
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else:
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json[_to_jsonc_name(key)] = _convert_to_jsonc(value)
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object.__setattr__(self, '_dict', json)
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def __setattr__(self, name, value):
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if name.startswith('_'):
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object.__setattr__(self, name, value)
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else:
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object.__getattribute__(
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self, '_dict')[_to_jsonc_name(name)] = _convert_to_jsonc(value)
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def __getattr__(self, name):
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if name.startswith('_'):
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object.__getattribute__(self, name)
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else:
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try:
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return object.__getattribute__(self, '_dict')[_to_jsonc_name(name)]
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except KeyError:
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raise AttributeError(
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'No member for %s or [\'%s\']' % (name, _to_jsonc_name(name)))
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def __delattr__(self, name):
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if name.startswith('_'):
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object.__delattr__(self, name)
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else:
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try:
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del object.__getattribute__(self, '_dict')[_to_jsonc_name(name)]
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except KeyError:
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raise AttributeError(
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'No member for %s (or [\'%s\'])' % (name, _to_jsonc_name(name)))
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# For container methods pass-through to the underlying dict.
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def __getitem__(self, key):
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return self._dict[key]
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def __setitem__(self, key, value):
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self._dict[key] = value
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def __delitem__(self, key):
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del self._dict[key]
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