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Decoding JSON to a Python Object

May 16, 2013

I recently had the opportunity to work on a Python project that involved pulling data from a JSON API. Python’s JSON module makes serializing and deserializing a breeze but for this project I also wanted to be able to call some custom methods on the dictionary returned after deserializing. The solution turned out to be pretty strait forward so I thought I would share what I came up with in case it is useful to anyone with a similar issue.

Create a new parent class which can get and set the attributes from the deserialized JSON dictionary.

class MyObject(dict):
    def __init__(self, dict_):
        super(MyObject, self).__init__(dict_)
        for key in self:
            item = self[key]
            if isinstance(item, list):
                for id, it in enumerate(item):
                    if isinstance(it, dict):
                        item[id] = self.__class__(it)
            elif isinstance(item, dict):
                self[key] = self.__class__(item)

    def __getattr__(self, key):
        return self[key]

Then just create a subclass where you will call your custom methods for that object.

class Tweets(MyObject):
    def __init__(self, dict_):
        super(self.__class__, self).__init__(dict_)

Now you can just initialize a new instance of the subclass with the deserialized JSON dictionary and all of your custom methods will be available.

Example using Twitter’s JSON API

import urllib
import urllib2
import json


class MyObject(dict):
    def __init__(self, dict_):
        super(MyObject, self).__init__(dict_)
        for key in self:
            item = self[key]
            if isinstance(item, list):
                for id, it in enumerate(item):
                    if isinstance(it, dict):
                        item[id] = self.__class__(it)
            elif isinstance(item, dict):
                self[key] = self.__class__(item)

    def __getattr__(self, key):
        return self[key]


class Tweets(MyObject):
    def __init__(self, dict_):
        super(self.__class__, self).__init__(dict_)

    @classmethod
    def search(cls):
        req = urllib2.Request('http://search.twitter.com/search.json?q=%40twitterapi')
        result = urllib2.urlopen(req).read()
        return Tweets(json.loads(result))

    def get_tweets(self):
        tweet_data = dict()
        for tweet in self.results:
            tweet_data[tweet.created_at] = tweet.text
        return tweet_data


# get all tweet data
query = Tweets.search()

# create a new dictionary using the tweet time and text
tweets = query.get_tweets()

# pretty print 
print(json.dumps(tweets, indent=4))

Result

{
    "Thu, 16 May 2013 21:14:02 +0000": "Download GrassHeads - Once In A LifeTime ft. Gill.mp3 | Limelinx http://t.co/gQ91Lib6EN via @twitterapi", 
    "Thu, 16 May 2013 21:17:14 +0000": "RT @SaskiaWaterland: Een bloemlezing van VPRO's seksuele hoogtepunten: de vpro.nl seksavond - VPRO http://t.co/aavuKweaAn via @twitterapi", 
    "Thu, 16 May 2013 21:14:44 +0000": "Download Tom Arts - Dont Blame Me.mp3 | Limelinx http://t.co/CeQIl9PW0W via @twitterapi", 
    "Thu, 16 May 2013 21:15:33 +0000": "Whatcom Locavore: Women becoming a major force in sustainable agriculture http://t.co/FGB8psGTGJ via @twitterapi", 
    "Thu, 16 May 2013 21:09:02 +0000": "YANGON, Myanmar: Myanmar says Shan rebels attack oil company office | World | http://t.co/C9KZPeHEQF http://t.co/y4HFNRaMSt via @twitterapi", 
    "Thu, 16 May 2013 21:16:52 +0000": "RALEIGH: Raleigh police get homicide victim\u2019s deleted Facebook page in seeking leads | Crime | http://t.co/pIJZsxrAPs via @twitterapi", 
    "Thu, 16 May 2013 21:15:23 +0000": "RT @TheOnlyPilot: Download Nick - Chopped and Screwed.mp3 | Limelinx http://t.co/XTK87Hy7cL via @twitterapi", 
    "Thu, 16 May 2013 21:13:10 +0000": "Kad ortak odvali nesto, a smeh jaci od tebe | Smesne reakcije @VladoGeorgiev http://t.co/h7bQHrKhmz via @twitterapi", 
    "Thu, 16 May 2013 21:09:04 +0000": ":)) Adam Lambert's fans land him an O Awards nomination: Pressparty http://t.co/dEjjs28gWa via @twitterapi", 
    "Thu, 16 May 2013 21:18:30 +0000": "\u00bb Rene Rancourt Visits Barstool HQ\u2019s To Get Us Ready for B\u2019s Vs. Rangers Barstool Sports: Boston via @twitterapi", 
    "Thu, 16 May 2013 21:09:28 +0000": "Download Nick - Chopped and Screwed.mp3 | Limelinx http://t.co/XTK87Hy7cL via @twitterapi", 
    "Thu, 16 May 2013 21:16:27 +0000": "Yaa check m\u011b Out Go Download Transformer- Akrshome Foe.mp3 | Limelinx http://t.co/zvvWy20HuG via @twitterapi", 
    "Thu, 16 May 2013 21:13:57 +0000": "(1) Valores Habbid - F\u00f3rum \u00b7 Habbid http://t.co/JL02isdniq via @twitterapi", 
    "Thu, 16 May 2013 21:14:17 +0000": "Washington, D.C.: B Reactor park bill passes Senate committee | Hanford news | http://t.co/9Kcvgf3PrY http://t.co/1SDhZPLT8A via @twitterapi", 
    "Thu, 16 May 2013 21:10:13 +0000": "RT @GlamPimpLinda: Adam Lambert's fans land him an O Awards nomination: Pressparty http://t.co/xgJODYkYPK via @twitterapi"
}

Hopefully this little tutorial helps if you run into the same issue.

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