How can I parse JSON in Google App Engine?

Consider using Django's json lib, which is included with GAE.

from django.utils import simplejson as json

# load the object from a string
obj = json.loads( string )

The link above has examples of Django's serializer, and here's the link for simplejson's documentation.

If you're looking at storing Python class instances or objects (as opposed to compositions of lists, strings, numbers, and dictionaries), you probably want to look at pickle.

I hope that helps.

Incidentally, to get Django 1.0 (instead of Django 0.96) running on GAE, you can use the following call in your main.py, per this article:

from google.appengine.dist import use_library
use_library('django', '1.0')

Edit: Native JSON support in Google App Engine 1.6.0 with Python 2.7

As of Google App Engine 1.6.0, you can use the Python 2.7 runtime by adding runtime: python27 in app.yaml, and then you can import the native JSON library with import json.

Google App Engine now supports python 2.7. If using python 2.7, you can do the following:

import json
structured_dictionary = json.loads(string_received)

Include the simplejson library with your app?