In [1]: import json
 
In [2]: a = {'name': 'wang', 'age': 29}
 
In [3]: b = json.dumps(a)
 
In [4]: print b, type(b)
{"age": 29, "name": "wang"} <type 'str'>
 
In [11]: json.loads(b)
Out[11]: {u'age': 29, u'name': u'wang'}
 
In [12]: print type(json.loads(b))
<type 'dict'>

In [1]: import json
 
In [2]: a = {'name': 'wang', 'age': 29}
 
In [3]: b = json.dumps(a)
 
In [4]: print b, type(b)
{"age": 29, "name": "wang"} <type 'str'>
 
In [5]: c = json.dump(a)
---------------------------------------------------------------------------
TypeError                 Traceback (most recent call last)
<ipython-input-5-92dc0d929363> in <module>()
----> 1 c = json.dump(a)
 
TypeError: dump() takes at least 2 arguments (1 given)

In [1]: import json
 
In [2]: a = {'name': 'wang'}
 
In [3]: fp = file('test.txt', 'w')
 
In [4]: type(fp)
Out[4]: file
 
In [5]: json.dump(a, fp)
 
In [6]: cat test.txt
 
In [7]: fp.close()
 
In [8]: cat test.txt
{"name": "wang"}
In [9]: json.load(fp)
---------------------------------------------------------------------------
ValueError                Traceback (most recent call last)
<ipython-input-9-0064dabedb17> in <module>()
----> 1 json.load(fp)
 
/usr/local/Cellar/python/2.7.11/Frameworks/Python.framework/Versions/2.7/lib/python2.7/json/__init__.pyc in load(fp, encoding, cls, object_hook, parse_float, parse_int, parse_constant, object_pairs_hook, **kw)
  285
  286   """
--> 287   return loads(fp.read(),
  288     encoding=encoding, cls=cls, object_hook=object_hook,
  289     parse_float=parse_float, parse_int=parse_int,
 
ValueError: I/O operation on closed file
 
In [10]: fp = file('test.txt', 'r')
 
In [11]: json.load(fp)
Out[11]: {u'name': u'wang'}