json

JSON (JavaScript Object Notation) <http://json.org> is a subset of JavaScript syntax (ECMA-262 3rd edition) used as a lightweight data interchange format.

json exposes an API familiar to users of the standard library marshal and pickle modules. It is the externally maintained version of the json library contained in Python 2.6, but maintains compatibility with Python 2.4 and Python 2.5 and (currently) has significant performance advantages, even without using the optional C extension for speedups.

Encoding basic Python object hierarchies:

>>> import json
>>> json.dumps(['foo', {'bar': ('baz', None, 1.0, 2)}])
'["foo", {"bar": ["baz", null, 1.0, 2]}]'
>>> print json.dumps("\"foo\bar")
"\"foo\bar"
>>> print json.dumps(u'\u1234')
"\u1234"
>>> print json.dumps('\\')
"\\"
>>> print json.dumps({"c": 0, "b": 0, "a": 0}, sort_keys=True)
{"a": 0, "b": 0, "c": 0}
>>> from StringIO import StringIO
>>> io = StringIO()
>>> json.dump(['streaming API'], io)
>>> io.getvalue()
'["streaming API"]'

Compact encoding:

>>> import json
>>> json.dumps([1,2,3,{'4': 5, '6': 7}], sort_keys=True, separators=(',',':'))
'[1,2,3,{"4":5,"6":7}]'

Pretty printing:

>>> import json
>>> print json.dumps({'4': 5, '6': 7}, sort_keys=True,
...                  indent=4, separators=(',', ': '))
{
    "4": 5,
    "6": 7
}

Decoding JSON:

>>> import json
>>> obj = [u'foo', {u'bar': [u'baz', None, 1.0, 2]}]
>>> json.loads('["foo", {"bar":["baz", null, 1.0, 2]}]') == obj
True
>>> json.loads('"\\"foo\\bar"') == u'"foo\x08ar'
True
>>> from StringIO import StringIO
>>> io = StringIO('["streaming API"]')
>>> json.load(io)[0] == 'streaming API'
True

Specializing JSON object decoding:

>>> import json
>>> def as_complex(dct):
...     if '__complex__' in dct:
...         return complex(dct['real'], dct['imag'])
...     return dct
...
>>> json.loads('{"__complex__": true, "real": 1, "imag": 2}',
...     object_hook=as_complex)
(1+2j)
>>> from decimal import Decimal
>>> json.loads('1.1', parse_float=Decimal) == Decimal('1.1')
True

Specializing JSON object encoding:

>>> import json
>>> def encode_complex(obj):
...     if isinstance(obj, complex):
...         return [obj.real, obj.imag]
...     raise TypeError(repr(o) + " is not JSON serializable")
...
>>> json.dumps(2 + 1j, default=encode_complex)
'[2.0, 1.0]'
>>> json.JSONEncoder(default=encode_complex).encode(2 + 1j)
'[2.0, 1.0]'
>>> ''.join(json.JSONEncoder(default=encode_complex).iterencode(2 + 1j))
'[2.0, 1.0]'

Using json.tool from the shell to validate and pretty-print:

$ echo '{"json":"obj"}' | python -m json.tool
{
    "json": "obj"
}
$ echo '{ 1.2:3.4}' | python -m json.tool
Expecting property name enclosed in double quotes: line 1 column 3 (char 2)

Functions

dump(obj, fp[, skipkeys, ensure_ascii, ...]) Serialize obj as a JSON formatted stream to fp (a .write()-supporting file-like object).
dumps(obj[, skipkeys, ensure_ascii, ...]) Serialize obj to a JSON formatted str.
load(fp[, encoding, cls, object_hook, ...]) Deserialize fp (a .read()-supporting file-like object containing a JSON document) to a Python object.
loads(s[, encoding, cls, object_hook, ...]) Deserialize s (a str or unicode instance containing a JSON document) to a Python object.

Classes

JSONDecoder([encoding, object_hook, ...]) Simple JSON <http://json.org> decoder
JSONEncoder([skipkeys, ensure_ascii, ...]) Extensible JSON <http://json.org> encoder for Python data structures.