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JSON (JavaScript Object Notation) <http://json.org> is a subset of JavaScript syntax (ECMA-262 3rd edition) used as a lightweight data interchange format.
:mod:`simplejson` exposes an API familiar to users of the standard library :mod:`marshal` and :mod:`pickle` modules. It is the externally maintained version of the :mod:`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 simplejson as 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 simplejson as json
>>> json.dumps([1,2,3,{'4': 5, '6': 7}], separators=(',',':'))
'[1,2,3,{"4":5,"6":7}]'
Pretty printing:
>>> import simplejson as json
>>> s = json.dumps({'4': 5, '6': 7}, sort_keys=True, indent=' ')
>>> print '\n'.join([l.rstrip() for l in s.splitlines()])
{
"4": 5,
"6": 7
}
Decoding JSON:
>>> import simplejson as 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 simplejson as 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 simplejson as 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 simplejson.tool from the shell to validate and pretty-print:
$ echo '{"json":"obj"}' | python -m simplejson.tool
{
"json": "obj"
}
$ echo '{ 1.2:3.4}' | python -m simplejson.tool
Expecting property name: line 1 column 2 (char 2)
Version: 2.6.0
Author: Bob Ippolito <bob@redivi.com>
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JSONDecodeError Subclass of ValueError with the following additional properties: |
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JSONDecoder Simple JSON <http://json.org> decoder |
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JSONEncoder Extensible JSON <http://json.org> encoder for Python data structures. |
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OrderedDict Dictionary that remembers insertion order |
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| Function Details |
Serialize ``obj`` as a JSON formatted stream to ``fp`` (a ``.write()``-supporting file-like object). If ``skipkeys`` is true then ``dict`` keys that are not basic types (``str``, ``unicode``, ``int``, ``long``, ``float``, ``bool``, ``None``) will be skipped instead of raising a ``TypeError``. If ``ensure_ascii`` is false, then the some chunks written to ``fp`` may be ``unicode`` instances, subject to normal Python ``str`` to ``unicode`` coercion rules. Unless ``fp.write()`` explicitly understands ``unicode`` (as in ``codecs.getwriter()``) this is likely to cause an error. If ``check_circular`` is false, then the circular reference check for container types will be skipped and a circular reference will result in an ``OverflowError`` (or worse). If ``allow_nan`` is false, then it will be a ``ValueError`` to serialize out of range ``float`` values (``nan``, ``inf``, ``-inf``) in strict compliance of the JSON specification, instead of using the JavaScript equivalents (``NaN``, ``Infinity``, ``-Infinity``). If *indent* is a string, then JSON array elements and object members will be pretty-printed with a newline followed by that string repeated for each level of nesting. ``None`` (the default) selects the most compact representation without any newlines. For backwards compatibility with versions of simplejson earlier than 2.1.0, an integer is also accepted and is converted to a string with that many spaces. If ``separators`` is an ``(item_separator, dict_separator)`` tuple then it will be used instead of the default ``(', ', ': ')`` separators. ``(',', ':')`` is the most compact JSON representation. ``encoding`` is the character encoding for str instances, default is UTF-8. ``default(obj)`` is a function that should return a serializable version of obj or raise TypeError. The default simply raises TypeError. If *use_decimal* is true (default: ``True``) then decimal.Decimal will be natively serialized to JSON with full precision. If *namedtuple_as_object* is true (default: ``True``), :class:`tuple` subclasses with ``_asdict()`` methods will be encoded as JSON objects. If *tuple_as_array* is true (default: ``True``), :class:`tuple` (and subclasses) will be encoded as JSON arrays. If *bigint_as_string* is true (default: ``False``), ints 2**53 and higher or lower than -2**53 will be encoded as strings. This is to avoid the rounding that happens in Javascript otherwise. Note that this is still a lossy operation that will not round-trip correctly and should be used sparingly. If specified, *item_sort_key* is a callable used to sort the items in each dictionary. This is useful if you want to sort items other than in alphabetical order by key. This option takes precedence over *sort_keys*. If *sort_keys* is true (default: ``False``), the output of dictionaries will be sorted by item. To use a custom ``JSONEncoder`` subclass (e.g. one that overrides the ``.default()`` method to serialize additional types), specify it with the ``cls`` kwarg. |
Serialize ``obj`` to a JSON formatted ``str``. If ``skipkeys`` is false then ``dict`` keys that are not basic types (``str``, ``unicode``, ``int``, ``long``, ``float``, ``bool``, ``None``) will be skipped instead of raising a ``TypeError``. If ``ensure_ascii`` is false, then the return value will be a ``unicode`` instance subject to normal Python ``str`` to ``unicode`` coercion rules instead of being escaped to an ASCII ``str``. If ``check_circular`` is false, then the circular reference check for container types will be skipped and a circular reference will result in an ``OverflowError`` (or worse). If ``allow_nan`` is false, then it will be a ``ValueError`` to serialize out of range ``float`` values (``nan``, ``inf``, ``-inf``) in strict compliance of the JSON specification, instead of using the JavaScript equivalents (``NaN``, ``Infinity``, ``-Infinity``). If ``indent`` is a string, then JSON array elements and object members will be pretty-printed with a newline followed by that string repeated for each level of nesting. ``None`` (the default) selects the most compact representation without any newlines. For backwards compatibility with versions of simplejson earlier than 2.1.0, an integer is also accepted and is converted to a string with that many spaces. If ``separators`` is an ``(item_separator, dict_separator)`` tuple then it will be used instead of the default ``(', ', ': ')`` separators. ``(',', ':')`` is the most compact JSON representation. ``encoding`` is the character encoding for str instances, default is UTF-8. ``default(obj)`` is a function that should return a serializable version of obj or raise TypeError. The default simply raises TypeError. If *use_decimal* is true (default: ``True``) then decimal.Decimal will be natively serialized to JSON with full precision. If *namedtuple_as_object* is true (default: ``True``), :class:`tuple` subclasses with ``_asdict()`` methods will be encoded as JSON objects. If *tuple_as_array* is true (default: ``True``), :class:`tuple` (and subclasses) will be encoded as JSON arrays. If *bigint_as_string* is true (not the default), ints 2**53 and higher or lower than -2**53 will be encoded as strings. This is to avoid the rounding that happens in Javascript otherwise. If specified, *item_sort_key* is a callable used to sort the items in each dictionary. This is useful if you want to sort items other than in alphabetical order by key. This option takes precendence over *sort_keys*. If *sort_keys* is true (default: ``False``), the output of dictionaries will be sorted by item. To use a custom ``JSONEncoder`` subclass (e.g. one that overrides the ``.default()`` method to serialize additional types), specify it with the ``cls`` kwarg. |
Deserialize ``fp`` (a ``.read()``-supporting file-like object containing a JSON document) to a Python object. *encoding* determines the encoding used to interpret any :class:`str` objects decoded by this instance (``'utf-8'`` by default). It has no effect when decoding :class:`unicode` objects. Note that currently only encodings that are a superset of ASCII work, strings of other encodings should be passed in as :class:`unicode`. *object_hook*, if specified, will be called with the result of every JSON object decoded and its return value will be used in place of the given :class:`dict`. This can be used to provide custom deserializations (e.g. to support JSON-RPC class hinting). *object_pairs_hook* is an optional function that will be called with the result of any object literal decode with an ordered list of pairs. The return value of *object_pairs_hook* will be used instead of the :class:`dict`. This feature can be used to implement custom decoders that rely on the order that the key and value pairs are decoded (for example, :func:`collections.OrderedDict` will remember the order of insertion). If *object_hook* is also defined, the *object_pairs_hook* takes priority. *parse_float*, if specified, will be called with the string of every JSON float to be decoded. By default, this is equivalent to ``float(num_str)``. This can be used to use another datatype or parser for JSON floats (e.g. :class:`decimal.Decimal`). *parse_int*, if specified, will be called with the string of every JSON int to be decoded. By default, this is equivalent to ``int(num_str)``. This can be used to use another datatype or parser for JSON integers (e.g. :class:`float`). *parse_constant*, if specified, will be called with one of the following strings: ``'-Infinity'``, ``'Infinity'``, ``'NaN'``. This can be used to raise an exception if invalid JSON numbers are encountered. If *use_decimal* is true (default: ``False``) then it implies parse_float=decimal.Decimal for parity with ``dump``. To use a custom ``JSONDecoder`` subclass, specify it with the ``cls`` kwarg. |
Deserialize ``s`` (a ``str`` or ``unicode`` instance containing a JSON document) to a Python object. *encoding* determines the encoding used to interpret any :class:`str` objects decoded by this instance (``'utf-8'`` by default). It has no effect when decoding :class:`unicode` objects. Note that currently only encodings that are a superset of ASCII work, strings of other encodings should be passed in as :class:`unicode`. *object_hook*, if specified, will be called with the result of every JSON object decoded and its return value will be used in place of the given :class:`dict`. This can be used to provide custom deserializations (e.g. to support JSON-RPC class hinting). *object_pairs_hook* is an optional function that will be called with the result of any object literal decode with an ordered list of pairs. The return value of *object_pairs_hook* will be used instead of the :class:`dict`. This feature can be used to implement custom decoders that rely on the order that the key and value pairs are decoded (for example, :func:`collections.OrderedDict` will remember the order of insertion). If *object_hook* is also defined, the *object_pairs_hook* takes priority. *parse_float*, if specified, will be called with the string of every JSON float to be decoded. By default, this is equivalent to ``float(num_str)``. This can be used to use another datatype or parser for JSON floats (e.g. :class:`decimal.Decimal`). *parse_int*, if specified, will be called with the string of every JSON int to be decoded. By default, this is equivalent to ``int(num_str)``. This can be used to use another datatype or parser for JSON integers (e.g. :class:`float`). *parse_constant*, if specified, will be called with one of the following strings: ``'-Infinity'``, ``'Infinity'``, ``'NaN'``. This can be used to raise an exception if invalid JSON numbers are encountered. If *use_decimal* is true (default: ``False``) then it implies parse_float=decimal.Decimal for parity with ``dump``. To use a custom ``JSONDecoder`` subclass, specify it with the ``cls`` kwarg. |
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