Christian Heimes | 9054000 | 2008-05-08 14:29:10 +0000 | [diff] [blame^] | 1 | r"""A simple, fast, extensible JSON encoder and decoder |
| 2 | |
| 3 | JSON (JavaScript Object Notation) <http://json.org> is a subset of |
| 4 | JavaScript syntax (ECMA-262 3rd edition) used as a lightweight data |
| 5 | interchange format. |
| 6 | |
| 7 | json exposes an API familiar to uses of the standard library |
| 8 | marshal and pickle modules. |
| 9 | |
| 10 | Encoding basic Python object hierarchies:: |
| 11 | |
| 12 | >>> import json |
| 13 | >>> json.dumps(['foo', {'bar': ('baz', None, 1.0, 2)}]) |
| 14 | '["foo", {"bar": ["baz", null, 1.0, 2]}]' |
| 15 | >>> print(json.dumps("\"foo\bar")) |
| 16 | "\"foo\bar" |
| 17 | >>> print(json.dumps('\u1234')) |
| 18 | "\u1234" |
| 19 | >>> print(json.dumps('\\')) |
| 20 | "\\" |
| 21 | >>> print(json.dumps({"c": 0, "b": 0, "a": 0}, sort_keys=True)) |
| 22 | {"a": 0, "b": 0, "c": 0} |
| 23 | >>> from io import StringIO |
| 24 | >>> io = StringIO() |
| 25 | >>> json.dump(['streaming API'], io) |
| 26 | >>> io.getvalue() |
| 27 | '["streaming API"]' |
| 28 | |
| 29 | Compact encoding:: |
| 30 | |
| 31 | >>> import json |
| 32 | >>> json.dumps([1,2,3,{'4': 5, '6': 7}], separators=(',',':')) |
| 33 | '[1,2,3,{"4":5,"6":7}]' |
| 34 | |
| 35 | Pretty printing (using repr() because of extraneous whitespace in the output):: |
| 36 | |
| 37 | >>> import json |
| 38 | >>> print(repr(json.dumps({'4': 5, '6': 7}, sort_keys=True, indent=4))) |
| 39 | '{\n "4": 5, \n "6": 7\n}' |
| 40 | |
| 41 | Decoding JSON:: |
| 42 | |
| 43 | >>> import json |
| 44 | >>> json.loads('["foo", {"bar":["baz", null, 1.0, 2]}]') |
| 45 | ['foo', {'bar': ['baz', None, 1.0, 2]}] |
| 46 | >>> json.loads('"\\"foo\\bar"') |
| 47 | '"foo\x08ar' |
| 48 | >>> from io import StringIO |
| 49 | >>> io = StringIO('["streaming API"]') |
| 50 | >>> json.load(io) |
| 51 | ['streaming API'] |
| 52 | |
| 53 | Specializing JSON object decoding:: |
| 54 | |
| 55 | >>> import json |
| 56 | >>> def as_complex(dct): |
| 57 | ... if '__complex__' in dct: |
| 58 | ... return complex(dct['real'], dct['imag']) |
| 59 | ... return dct |
| 60 | ... |
| 61 | >>> json.loads('{"__complex__": true, "real": 1, "imag": 2}', |
| 62 | ... object_hook=as_complex) |
| 63 | (1+2j) |
| 64 | >>> import decimal |
| 65 | >>> json.loads('1.1', parse_float=decimal.Decimal) |
| 66 | Decimal('1.1') |
| 67 | |
| 68 | Extending JSONEncoder:: |
| 69 | |
| 70 | >>> import json |
| 71 | >>> class ComplexEncoder(json.JSONEncoder): |
| 72 | ... def default(self, obj): |
| 73 | ... if isinstance(obj, complex): |
| 74 | ... return [obj.real, obj.imag] |
| 75 | ... return json.JSONEncoder.default(self, obj) |
| 76 | ... |
| 77 | >>> dumps(2 + 1j, cls=ComplexEncoder) |
| 78 | '[2.0, 1.0]' |
| 79 | >>> ComplexEncoder().encode(2 + 1j) |
| 80 | '[2.0, 1.0]' |
| 81 | >>> list(ComplexEncoder().iterencode(2 + 1j)) |
| 82 | ['[', '2.0', ', ', '1.0', ']'] |
| 83 | |
| 84 | |
| 85 | Using json.tool from the shell to validate and |
| 86 | pretty-print:: |
| 87 | |
| 88 | $ echo '{"json":"obj"}' | python -mjson.tool |
| 89 | { |
| 90 | "json": "obj" |
| 91 | } |
| 92 | $ echo '{ 1.2:3.4}' | python -mjson.tool |
| 93 | Expecting property name: line 1 column 2 (char 2) |
| 94 | |
| 95 | Note that the JSON produced by this module's default settings |
| 96 | is a subset of YAML, so it may be used as a serializer for that as well. |
| 97 | |
| 98 | """ |
| 99 | |
| 100 | __version__ = '1.9' |
| 101 | __all__ = [ |
| 102 | 'dump', 'dumps', 'load', 'loads', |
| 103 | 'JSONDecoder', 'JSONEncoder', |
| 104 | ] |
| 105 | |
| 106 | __author__ = 'Bob Ippolito <bob@redivi.com>' |
| 107 | |
| 108 | from .decoder import JSONDecoder |
| 109 | from .encoder import JSONEncoder |
| 110 | |
| 111 | _default_encoder = JSONEncoder( |
| 112 | skipkeys=False, |
| 113 | ensure_ascii=True, |
| 114 | check_circular=True, |
| 115 | allow_nan=True, |
| 116 | indent=None, |
| 117 | separators=None, |
| 118 | encoding='utf-8', |
| 119 | default=None, |
| 120 | ) |
| 121 | |
| 122 | def dump(obj, fp, skipkeys=False, ensure_ascii=True, check_circular=True, |
| 123 | allow_nan=True, cls=None, indent=None, separators=None, |
| 124 | encoding='utf-8', default=None, **kw): |
| 125 | """Serialize ``obj`` as a JSON formatted stream to ``fp`` (a |
| 126 | ``.write()``-supporting file-like object). |
| 127 | |
| 128 | If ``skipkeys`` is ``True`` then ``dict`` keys that are not basic types |
| 129 | (``str``, ``unicode``, ``int``, ``long``, ``float``, ``bool``, ``None``) |
| 130 | will be skipped instead of raising a ``TypeError``. |
| 131 | |
| 132 | If ``ensure_ascii`` is ``False``, then the some chunks written to ``fp`` |
| 133 | may be ``unicode`` instances, subject to normal Python ``str`` to |
| 134 | ``unicode`` coercion rules. Unless ``fp.write()`` explicitly |
| 135 | understands ``unicode`` (as in ``codecs.getwriter()``) this is likely |
| 136 | to cause an error. |
| 137 | |
| 138 | If ``check_circular`` is ``False``, then the circular reference check |
| 139 | for container types will be skipped and a circular reference will |
| 140 | result in an ``OverflowError`` (or worse). |
| 141 | |
| 142 | If ``allow_nan`` is ``False``, then it will be a ``ValueError`` to |
| 143 | serialize out of range ``float`` values (``nan``, ``inf``, ``-inf``) |
| 144 | in strict compliance of the JSON specification, instead of using the |
| 145 | JavaScript equivalents (``NaN``, ``Infinity``, ``-Infinity``). |
| 146 | |
| 147 | If ``indent`` is a non-negative integer, then JSON array elements and object |
| 148 | members will be pretty-printed with that indent level. An indent level |
| 149 | of 0 will only insert newlines. ``None`` is the most compact representation. |
| 150 | |
| 151 | If ``separators`` is an ``(item_separator, dict_separator)`` tuple |
| 152 | then it will be used instead of the default ``(', ', ': ')`` separators. |
| 153 | ``(',', ':')`` is the most compact JSON representation. |
| 154 | |
| 155 | ``encoding`` is the character encoding for str instances, default is UTF-8. |
| 156 | |
| 157 | ``default(obj)`` is a function that should return a serializable version |
| 158 | of obj or raise TypeError. The default simply raises TypeError. |
| 159 | |
| 160 | To use a custom ``JSONEncoder`` subclass (e.g. one that overrides the |
| 161 | ``.default()`` method to serialize additional types), specify it with |
| 162 | the ``cls`` kwarg. |
| 163 | |
| 164 | """ |
| 165 | # cached encoder |
| 166 | if (skipkeys is False and ensure_ascii is True and |
| 167 | check_circular is True and allow_nan is True and |
| 168 | cls is None and indent is None and separators is None and |
| 169 | encoding == 'utf-8' and default is None and not kw): |
| 170 | iterable = _default_encoder.iterencode(obj) |
| 171 | else: |
| 172 | if cls is None: |
| 173 | cls = JSONEncoder |
| 174 | iterable = cls(skipkeys=skipkeys, ensure_ascii=ensure_ascii, |
| 175 | check_circular=check_circular, allow_nan=allow_nan, indent=indent, |
| 176 | separators=separators, encoding=encoding, |
| 177 | default=default, **kw).iterencode(obj) |
| 178 | # could accelerate with writelines in some versions of Python, at |
| 179 | # a debuggability cost |
| 180 | for chunk in iterable: |
| 181 | fp.write(chunk) |
| 182 | |
| 183 | |
| 184 | def dumps(obj, skipkeys=False, ensure_ascii=True, check_circular=True, |
| 185 | allow_nan=True, cls=None, indent=None, separators=None, |
| 186 | encoding='utf-8', default=None, **kw): |
| 187 | """Serialize ``obj`` to a JSON formatted ``str``. |
| 188 | |
| 189 | If ``skipkeys`` is ``True`` then ``dict`` keys that are not basic types |
| 190 | (``str``, ``unicode``, ``int``, ``long``, ``float``, ``bool``, ``None``) |
| 191 | will be skipped instead of raising a ``TypeError``. |
| 192 | |
| 193 | If ``ensure_ascii`` is ``False``, then the return value will be a |
| 194 | ``unicode`` instance subject to normal Python ``str`` to ``unicode`` |
| 195 | coercion rules instead of being escaped to an ASCII ``str``. |
| 196 | |
| 197 | If ``check_circular`` is ``False``, then the circular reference check |
| 198 | for container types will be skipped and a circular reference will |
| 199 | result in an ``OverflowError`` (or worse). |
| 200 | |
| 201 | If ``allow_nan`` is ``False``, then it will be a ``ValueError`` to |
| 202 | serialize out of range ``float`` values (``nan``, ``inf``, ``-inf``) in |
| 203 | strict compliance of the JSON specification, instead of using the |
| 204 | JavaScript equivalents (``NaN``, ``Infinity``, ``-Infinity``). |
| 205 | |
| 206 | If ``indent`` is a non-negative integer, then JSON array elements and |
| 207 | object members will be pretty-printed with that indent level. An indent |
| 208 | level of 0 will only insert newlines. ``None`` is the most compact |
| 209 | representation. |
| 210 | |
| 211 | If ``separators`` is an ``(item_separator, dict_separator)`` tuple |
| 212 | then it will be used instead of the default ``(', ', ': ')`` separators. |
| 213 | ``(',', ':')`` is the most compact JSON representation. |
| 214 | |
| 215 | ``encoding`` is the character encoding for str instances, default is UTF-8. |
| 216 | |
| 217 | ``default(obj)`` is a function that should return a serializable version |
| 218 | of obj or raise TypeError. The default simply raises TypeError. |
| 219 | |
| 220 | To use a custom ``JSONEncoder`` subclass (e.g. one that overrides the |
| 221 | ``.default()`` method to serialize additional types), specify it with |
| 222 | the ``cls`` kwarg. |
| 223 | |
| 224 | """ |
| 225 | # cached encoder |
| 226 | if (skipkeys is False and ensure_ascii is True and |
| 227 | check_circular is True and allow_nan is True and |
| 228 | cls is None and indent is None and separators is None and |
| 229 | encoding == 'utf-8' and default is None and not kw): |
| 230 | return _default_encoder.encode(obj) |
| 231 | if cls is None: |
| 232 | cls = JSONEncoder |
| 233 | return cls( |
| 234 | skipkeys=skipkeys, ensure_ascii=ensure_ascii, |
| 235 | check_circular=check_circular, allow_nan=allow_nan, indent=indent, |
| 236 | separators=separators, encoding=encoding, default=default, |
| 237 | **kw).encode(obj) |
| 238 | |
| 239 | |
| 240 | _default_decoder = JSONDecoder(encoding=None, object_hook=None) |
| 241 | |
| 242 | |
| 243 | def load(fp, encoding=None, cls=None, object_hook=None, parse_float=None, |
| 244 | parse_int=None, parse_constant=None, **kw): |
| 245 | """Deserialize ``fp`` (a ``.read()``-supporting file-like object |
| 246 | containing a JSON document) to a Python object. |
| 247 | |
| 248 | If the contents of ``fp`` is encoded with an ASCII based encoding other |
| 249 | than utf-8 (e.g. latin-1), then an appropriate ``encoding`` name must |
| 250 | be specified. Encodings that are not ASCII based (such as UCS-2) are |
| 251 | not allowed, and should be wrapped with |
| 252 | ``codecs.getreader(fp)(encoding)``, or simply decoded to a ``unicode`` |
| 253 | object and passed to ``loads()`` |
| 254 | |
| 255 | ``object_hook`` is an optional function that will be called with the |
| 256 | result of any object literal decode (a ``dict``). The return value of |
| 257 | ``object_hook`` will be used instead of the ``dict``. This feature |
| 258 | can be used to implement custom decoders (e.g. JSON-RPC class hinting). |
| 259 | |
| 260 | To use a custom ``JSONDecoder`` subclass, specify it with the ``cls`` |
| 261 | kwarg. |
| 262 | |
| 263 | """ |
| 264 | return loads(fp.read(), |
| 265 | encoding=encoding, cls=cls, object_hook=object_hook, |
| 266 | parse_float=parse_float, parse_int=parse_int, |
| 267 | parse_constant=parse_constant, **kw) |
| 268 | |
| 269 | |
| 270 | def loads(s, encoding=None, cls=None, object_hook=None, parse_float=None, |
| 271 | parse_int=None, parse_constant=None, **kw): |
| 272 | """Deserialize ``s`` (a ``str`` or ``unicode`` instance containing a JSON |
| 273 | document) to a Python object. |
| 274 | |
| 275 | If ``s`` is a ``str`` instance and is encoded with an ASCII based encoding |
| 276 | other than utf-8 (e.g. latin-1) then an appropriate ``encoding`` name |
| 277 | must be specified. Encodings that are not ASCII based (such as UCS-2) |
| 278 | are not allowed and should be decoded to ``unicode`` first. |
| 279 | |
| 280 | ``object_hook`` is an optional function that will be called with the |
| 281 | result of any object literal decode (a ``dict``). The return value of |
| 282 | ``object_hook`` will be used instead of the ``dict``. This feature |
| 283 | can be used to implement custom decoders (e.g. JSON-RPC class hinting). |
| 284 | |
| 285 | ``parse_float``, if specified, will be called with the string |
| 286 | of every JSON float to be decoded. By default this is equivalent to |
| 287 | float(num_str). This can be used to use another datatype or parser |
| 288 | for JSON floats (e.g. decimal.Decimal). |
| 289 | |
| 290 | ``parse_int``, if specified, will be called with the string |
| 291 | of every JSON int to be decoded. By default this is equivalent to |
| 292 | int(num_str). This can be used to use another datatype or parser |
| 293 | for JSON integers (e.g. float). |
| 294 | |
| 295 | ``parse_constant``, if specified, will be called with one of the |
| 296 | following strings: -Infinity, Infinity, NaN, null, true, false. |
| 297 | This can be used to raise an exception if invalid JSON numbers |
| 298 | are encountered. |
| 299 | |
| 300 | To use a custom ``JSONDecoder`` subclass, specify it with the ``cls`` |
| 301 | kwarg. |
| 302 | |
| 303 | """ |
| 304 | if (cls is None and encoding is None and object_hook is None and |
| 305 | parse_int is None and parse_float is None and |
| 306 | parse_constant is None and not kw): |
| 307 | return _default_decoder.decode(s) |
| 308 | if cls is None: |
| 309 | cls = JSONDecoder |
| 310 | if object_hook is not None: |
| 311 | kw['object_hook'] = object_hook |
| 312 | if parse_float is not None: |
| 313 | kw['parse_float'] = parse_float |
| 314 | if parse_int is not None: |
| 315 | kw['parse_int'] = parse_int |
| 316 | if parse_constant is not None: |
| 317 | kw['parse_constant'] = parse_constant |
| 318 | return cls(encoding=encoding, **kw).decode(s) |