summaryrefslogtreecommitdiffstats
path: root/Lib/json/__init__.py
blob: c419c780e1601f6cd9743034458795850ae4b3dc (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
r"""A simple, fast, extensible JSON encoder and decoder

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 uses of the standard library
marshal and pickle modules.

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('\u1234'))
    "\u1234"
    >>> print(json.dumps('\\'))
    "\\"
    >>> print(json.dumps({"c": 0, "b": 0, "a": 0}, sort_keys=True))
    {"a": 0, "b": 0, "c": 0}
    >>> from io 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}], separators=(',',':'))
    '[1,2,3,{"4":5,"6":7}]'

Pretty printing (using repr() because of extraneous whitespace in the output)::

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

Decoding JSON::

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

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)
    >>> import decimal
    >>> json.loads('1.1', parse_float=decimal.Decimal)
    Decimal('1.1')

Extending JSONEncoder::

    >>> import json
    >>> class ComplexEncoder(json.JSONEncoder):
    ...     def default(self, obj):
    ...         if isinstance(obj, complex):
    ...             return [obj.real, obj.imag]
    ...         return json.JSONEncoder.default(self, obj)
    ...
    >>> dumps(2 + 1j, cls=ComplexEncoder)
    '[2.0, 1.0]'
    >>> ComplexEncoder().encode(2 + 1j)
    '[2.0, 1.0]'
    >>> list(ComplexEncoder().iterencode(2 + 1j))
    ['[', '2.0', ', ', '1.0', ']']


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

    $ echo '{"json":"obj"}' | python -mjson.tool
    {
        "json": "obj"
    }
    $ echo '{ 1.2:3.4}' | python -mjson.tool
    Expecting property name: line 1 column 2 (char 2)

Note that the JSON produced by this module's default settings
is a subset of YAML, so it may be used as a serializer for that as well.

"""

__version__ = '1.9'
__all__ = [
    'dump', 'dumps', 'load', 'loads',
    'JSONDecoder', 'JSONEncoder',
]

__author__ = 'Bob Ippolito <bob@redivi.com>'

from .decoder import JSONDecoder
from .encoder import JSONEncoder

_default_encoder = JSONEncoder(
    skipkeys=False,
    ensure_ascii=True,
    check_circular=True,
    allow_nan=True,
    indent=None,
    separators=None,
    encoding='utf-8',
    default=None,
)

def dump(obj, fp, skipkeys=False, ensure_ascii=True, check_circular=True,
        allow_nan=True, cls=None, indent=None, separators=None,
        encoding='utf-8', default=None, **kw):
    """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 non-negative integer, then JSON array elements and object
    members will be pretty-printed with that indent level. An indent level
    of 0 will only insert newlines. ``None`` is the most compact representation.

    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.

    To use a custom ``JSONEncoder`` subclass (e.g. one that overrides the
    ``.default()`` method to serialize additional types), specify it with
    the ``cls`` kwarg.

    """
    # cached encoder
    if (skipkeys is False and ensure_ascii is True and
        check_circular is True and allow_nan is True and
        cls is None and indent is None and separators is None and
        encoding == 'utf-8' and default is None and not kw):
        iterable = _default_encoder.iterencode(obj)
    else:
        if cls is None:
            cls = JSONEncoder
        iterable = cls(skipkeys=skipkeys, ensure_ascii=ensure_ascii,
            check_circular=check_circular, allow_nan=allow_nan, indent=indent,
            separators=separators, encoding=encoding,
            default=default, **kw).iterencode(obj)
    # could accelerate with writelines in some versions of Python, at
    # a debuggability cost
    for chunk in iterable:
        fp.write(chunk)


def dumps(obj, skipkeys=False, ensure_ascii=True, check_circular=True,
        allow_nan=True, cls=None, indent=None, separators=None,
        encoding='utf-8', default=None, **kw):
    """Serialize ``obj`` to a JSON formatted ``str``.

    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 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 non-negative integer, then JSON array elements and
    object members will be pretty-printed with that indent level. An indent
    level of 0 will only insert newlines. ``None`` is the most compact
    representation.

    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.

    To use a custom ``JSONEncoder`` subclass (e.g. one that overrides the
    ``.default()`` method to serialize additional types), specify it with
    the ``cls`` kwarg.

    """
    # cached encoder
    if (skipkeys is False and ensure_ascii is True and
        check_circular is True and allow_nan is True and
        cls is None and indent is None and separators is None and
        encoding == 'utf-8' and default is None and not kw):
        return _default_encoder.encode(obj)
    if cls is None:
        cls = JSONEncoder
    return cls(
        skipkeys=skipkeys, ensure_ascii=ensure_ascii,
        check_circular=check_circular, allow_nan=allow_nan, indent=indent,
        separators=separators, encoding=encoding, default=default,
        **kw).encode(obj)


_default_decoder = JSONDecoder(encoding=None, object_hook=None)


def load(fp, encoding=None, cls=None, object_hook=None, parse_float=None,
        parse_int=None, parse_constant=None, **kw):
    """Deserialize ``fp`` (a ``.read()``-supporting file-like object
    containing a JSON document) to a Python object.

    If the contents of ``fp`` is encoded with an ASCII based encoding other
    than utf-8 (e.g. latin-1), then an appropriate ``encoding`` name must
    be specified. Encodings that are not ASCII based (such as UCS-2) are
    not allowed, and should be wrapped with
    ``codecs.getreader(fp)(encoding)``, or simply decoded to a ``unicode``
    object and passed to ``loads()``

    ``object_hook`` is an optional function that will be called with the
    result of any object literal decode (a ``dict``). The return value of
    ``object_hook`` will be used instead of the ``dict``. This feature
    can be used to implement custom decoders (e.g. JSON-RPC class hinting).

    To use a custom ``JSONDecoder`` subclass, specify it with the ``cls``
    kwarg.

    """
    return loads(fp.read(),
        encoding=encoding, cls=cls, object_hook=object_hook,
        parse_float=parse_float, parse_int=parse_int,
        parse_constant=parse_constant, **kw)


def loads(s, encoding=None, cls=None, object_hook=None, parse_float=None,
        parse_int=None, parse_constant=None, **kw):
    """Deserialize ``s`` (a ``str`` or ``unicode`` instance containing a JSON
    document) to a Python object.

    If ``s`` is a ``str`` instance and is encoded with an ASCII based encoding
    other than utf-8 (e.g. latin-1) then an appropriate ``encoding`` name
    must be specified. Encodings that are not ASCII based (such as UCS-2)
    are not allowed and should be decoded to ``unicode`` first.

    ``object_hook`` is an optional function that will be called with the
    result of any object literal decode (a ``dict``). The return value of
    ``object_hook`` will be used instead of the ``dict``. This feature
    can be used to implement custom decoders (e.g. JSON-RPC class hinting).

    ``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. 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. float).

    ``parse_constant``, if specified, will be called with one of the
    following strings: -Infinity, Infinity, NaN, null, true, false.
    This can be used to raise an exception if invalid JSON numbers
    are encountered.

    To use a custom ``JSONDecoder`` subclass, specify it with the ``cls``
    kwarg.

    """
    if (cls is None and encoding is None and object_hook is None and
            parse_int is None and parse_float is None and
            parse_constant is None and not kw):
        return _default_decoder.decode(s)
    if cls is None:
        cls = JSONDecoder
    if object_hook is not None:
        kw['object_hook'] = object_hook
    if parse_float is not None:
        kw['parse_float'] = parse_float
    if parse_int is not None:
        kw['parse_int'] = parse_int
    if parse_constant is not None:
        kw['parse_constant'] = parse_constant
    return cls(encoding=encoding, **kw).decode(s)