>>> json.dumps(False)
'false'
>>> d = {'a': True,
...   'b': 'Hello',
...   'c': None}
>>> json.dumps(d)
'{"b": "Hello", "c": null, "a": true}'
>>>

>>> from urllib.request import urlopen
>>> import json
>>> u = urlopen('http://search.twitter.com/search.json?q=python&rpp=5')
>>> resp = json.loads(u.read().decode('utf-8'))
>>> from pprint import pprint
>>> pprint(resp)
{'completed_in': 0.074,
'max_id': 264043230692245504,
'max_id_str': '264043230692245504',
'next_page': '?page=2&max_id=264043230692245504&q=python&rpp=5',
'page': 1,
'query': 'python',
'refresh_url': '?since_id=264043230692245504&q=python',
'results': [{'created_at': 'Thu, 01 Nov 2012 16:36:26 +0000',
      'from_user': ...
      },
      {'created_at': 'Thu, 01 Nov 2012 16:36:14 +0000',
      'from_user': ...
      },
      {'created_at': 'Thu, 01 Nov 2012 16:36:13 +0000',
      'from_user': ...
      },
      {'created_at': 'Thu, 01 Nov 2012 16:36:07 +0000',
      'from_user': ...
      }
      {'created_at': 'Thu, 01 Nov 2012 16:36:04 +0000',
      'from_user': ...
      }],
'results_per_page': 5,
'since_id': 0,
'since_id_str': '0'}
>>>

>>> s = '{"name": "ACME", "shares": 50, "price": 490.1}'
>>> from collections import OrderedDict
>>> data = json.loads(s, object_pairs_hook=OrderedDict)
>>> data
OrderedDict([('name', 'ACME'), ('shares', 50), ('price', 490.1)])
>>>

>>> class JSONObject:
...   def __init__(self, d):
...     self.__dict__ = d
...
>>>
>>> data = json.loads(s, object_hook=JSONObject)
>>> data.name
'ACME'
>>> data.shares
50
>>> data.price
490.1
>>>

>>> print(json.dumps(data))
{"price": 542.23, "name": "ACME", "shares": 100}
>>> print(json.dumps(data, indent=4))
{
  "price": 542.23,
  "name": "ACME",
  "shares": 100
}
>>>

>>> class Point:
...   def __init__(self, x, y):
...     self.x = x
...     self.y = y
...
>>> p = Point(2, 3)
>>> json.dumps(p)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python3.3/json/__init__.py", line 226, in dumps
    return _default_encoder.encode(obj)
  File "/usr/local/lib/python3.3/json/encoder.py", line 187, in encode
    chunks = self.iterencode(o, _one_shot=True)
  File "/usr/local/lib/python3.3/json/encoder.py", line 245, in iterencode
    return _iterencode(o, 0)
  File "/usr/local/lib/python3.3/json/encoder.py", line 169, in default
    raise TypeError(repr(o) + " is not JSON serializable")
TypeError: <__main__.Point object at 0x1006f2650> is not JSON serializable
>>>

def serialize_instance(obj):
  d = { '__classname__' : type(obj).__name__ }
  d.update(vars(obj))
  return d

# Dictionary mapping names to known classes
classes = {
  'Point' : Point
}

def unserialize_object(d):
  clsname = d.pop('__classname__', None)
  if clsname:
    cls = classes[clsname]
    obj = cls.__new__(cls) # Make instance without calling __init__
    for key, value in d.items():
      setattr(obj, key, value)
      return obj
  else:
    return d

>>> p = Point(2,3)
>>> s = json.dumps(p, default=serialize_instance)
>>> s
'{"__classname__": "Point", "y": 3, "x": 2}'
>>> a = json.loads(s, object_hook=unserialize_object)
>>> a
<__main__.Point object at 0x1017577d0>
>>> a.x
2
>>> a.y
3
>>>