mirror of
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319 lines
12 KiB
Python
319 lines
12 KiB
Python
r"""A simple, fast, extensible JSON encoder and decoder
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JSON (JavaScript Object Notation) <http://json.org> is a subset of
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JavaScript syntax (ECMA-262 3rd edition) used as a lightweight data
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interchange format.
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json exposes an API familiar to uses of the standard library
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marshal and pickle modules.
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Encoding basic Python object hierarchies::
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>>> import json
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>>> json.dumps(['foo', {'bar': ('baz', None, 1.0, 2)}])
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'["foo", {"bar": ["baz", null, 1.0, 2]}]'
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>>> print json.dumps("\"foo\bar")
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"\"foo\bar"
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>>> print json.dumps(u'\u1234')
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"\u1234"
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>>> print json.dumps('\\')
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"\\"
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>>> print json.dumps({"c": 0, "b": 0, "a": 0}, sort_keys=True)
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{"a": 0, "b": 0, "c": 0}
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>>> from StringIO import StringIO
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>>> io = StringIO()
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>>> json.dump(['streaming API'], io)
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>>> io.getvalue()
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'["streaming API"]'
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Compact encoding::
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>>> import json
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>>> json.dumps([1,2,3,{'4': 5, '6': 7}], separators=(',',':'))
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'[1,2,3,{"4":5,"6":7}]'
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Pretty printing (using repr() because of extraneous whitespace in the output)::
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>>> import json
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>>> print repr(json.dumps({'4': 5, '6': 7}, sort_keys=True, indent=4))
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'{\n "4": 5, \n "6": 7\n}'
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Decoding JSON::
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>>> import json
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>>> json.loads('["foo", {"bar":["baz", null, 1.0, 2]}]')
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[u'foo', {u'bar': [u'baz', None, 1.0, 2]}]
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>>> json.loads('"\\"foo\\bar"')
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u'"foo\x08ar'
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>>> from StringIO import StringIO
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>>> io = StringIO('["streaming API"]')
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>>> json.load(io)
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[u'streaming API']
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Specializing JSON object decoding::
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>>> import json
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>>> def as_complex(dct):
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... if '__complex__' in dct:
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... return complex(dct['real'], dct['imag'])
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... return dct
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...
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>>> json.loads('{"__complex__": true, "real": 1, "imag": 2}',
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... object_hook=as_complex)
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(1+2j)
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>>> import decimal
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>>> json.loads('1.1', parse_float=decimal.Decimal)
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Decimal('1.1')
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Extending JSONEncoder::
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>>> import json
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>>> class ComplexEncoder(json.JSONEncoder):
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... def default(self, obj):
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... if isinstance(obj, complex):
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... return [obj.real, obj.imag]
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... return json.JSONEncoder.default(self, obj)
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...
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>>> dumps(2 + 1j, cls=ComplexEncoder)
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'[2.0, 1.0]'
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>>> ComplexEncoder().encode(2 + 1j)
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'[2.0, 1.0]'
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>>> list(ComplexEncoder().iterencode(2 + 1j))
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['[', '2.0', ', ', '1.0', ']']
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Using json.tool from the shell to validate and
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pretty-print::
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$ echo '{"json":"obj"}' | python -mjson.tool
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{
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"json": "obj"
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}
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$ echo '{ 1.2:3.4}' | python -mjson.tool
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Expecting property name: line 1 column 2 (char 2)
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Note that the JSON produced by this module's default settings
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is a subset of YAML, so it may be used as a serializer for that as well.
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"""
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__version__ = '1.9'
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__all__ = [
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'dump', 'dumps', 'load', 'loads',
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'JSONDecoder', 'JSONEncoder',
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]
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__author__ = 'Bob Ippolito <bob@redivi.com>'
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from .decoder import JSONDecoder
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from .encoder import JSONEncoder
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_default_encoder = JSONEncoder(
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skipkeys=False,
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ensure_ascii=True,
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check_circular=True,
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allow_nan=True,
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indent=None,
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separators=None,
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encoding='utf-8',
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default=None,
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)
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def dump(obj, fp, skipkeys=False, ensure_ascii=True, check_circular=True,
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allow_nan=True, cls=None, indent=None, separators=None,
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encoding='utf-8', default=None, **kw):
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"""Serialize ``obj`` as a JSON formatted stream to ``fp`` (a
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``.write()``-supporting file-like object).
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If ``skipkeys`` is ``True`` then ``dict`` keys that are not basic types
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(``str``, ``unicode``, ``int``, ``long``, ``float``, ``bool``, ``None``)
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will be skipped instead of raising a ``TypeError``.
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If ``ensure_ascii`` is ``False``, then the some chunks written to ``fp``
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may be ``unicode`` instances, subject to normal Python ``str`` to
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``unicode`` coercion rules. Unless ``fp.write()`` explicitly
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understands ``unicode`` (as in ``codecs.getwriter()``) this is likely
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to cause an error.
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If ``check_circular`` is ``False``, then the circular reference check
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for container types will be skipped and a circular reference will
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result in an ``OverflowError`` (or worse).
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If ``allow_nan`` is ``False``, then it will be a ``ValueError`` to
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serialize out of range ``float`` values (``nan``, ``inf``, ``-inf``)
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in strict compliance of the JSON specification, instead of using the
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JavaScript equivalents (``NaN``, ``Infinity``, ``-Infinity``).
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If ``indent`` is a non-negative integer, then JSON array elements and object
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members will be pretty-printed with that indent level. An indent level
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of 0 will only insert newlines. ``None`` is the most compact representation.
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If ``separators`` is an ``(item_separator, dict_separator)`` tuple
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then it will be used instead of the default ``(', ', ': ')`` separators.
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``(',', ':')`` is the most compact JSON representation.
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``encoding`` is the character encoding for str instances, default is UTF-8.
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``default(obj)`` is a function that should return a serializable version
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of obj or raise TypeError. The default simply raises TypeError.
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To use a custom ``JSONEncoder`` subclass (e.g. one that overrides the
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``.default()`` method to serialize additional types), specify it with
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the ``cls`` kwarg.
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"""
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# cached encoder
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if (skipkeys is False and ensure_ascii is True and
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check_circular is True and allow_nan is True and
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cls is None and indent is None and separators is None and
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encoding == 'utf-8' and default is None and not kw):
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iterable = _default_encoder.iterencode(obj)
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else:
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if cls is None:
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cls = JSONEncoder
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iterable = cls(skipkeys=skipkeys, ensure_ascii=ensure_ascii,
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check_circular=check_circular, allow_nan=allow_nan, indent=indent,
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separators=separators, encoding=encoding,
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default=default, **kw).iterencode(obj)
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# could accelerate with writelines in some versions of Python, at
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# a debuggability cost
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for chunk in iterable:
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fp.write(chunk)
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def dumps(obj, skipkeys=False, ensure_ascii=True, check_circular=True,
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allow_nan=True, cls=None, indent=None, separators=None,
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encoding='utf-8', default=None, **kw):
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"""Serialize ``obj`` to a JSON formatted ``str``.
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If ``skipkeys`` is ``True`` then ``dict`` keys that are not basic types
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(``str``, ``unicode``, ``int``, ``long``, ``float``, ``bool``, ``None``)
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will be skipped instead of raising a ``TypeError``.
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If ``ensure_ascii`` is ``False``, then the return value will be a
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``unicode`` instance subject to normal Python ``str`` to ``unicode``
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coercion rules instead of being escaped to an ASCII ``str``.
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If ``check_circular`` is ``False``, then the circular reference check
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for container types will be skipped and a circular reference will
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result in an ``OverflowError`` (or worse).
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If ``allow_nan`` is ``False``, then it will be a ``ValueError`` to
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serialize out of range ``float`` values (``nan``, ``inf``, ``-inf``) in
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strict compliance of the JSON specification, instead of using the
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JavaScript equivalents (``NaN``, ``Infinity``, ``-Infinity``).
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If ``indent`` is a non-negative integer, then JSON array elements and
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object members will be pretty-printed with that indent level. An indent
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level of 0 will only insert newlines. ``None`` is the most compact
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representation.
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If ``separators`` is an ``(item_separator, dict_separator)`` tuple
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then it will be used instead of the default ``(', ', ': ')`` separators.
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``(',', ':')`` is the most compact JSON representation.
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``encoding`` is the character encoding for str instances, default is UTF-8.
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``default(obj)`` is a function that should return a serializable version
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of obj or raise TypeError. The default simply raises TypeError.
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To use a custom ``JSONEncoder`` subclass (e.g. one that overrides the
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``.default()`` method to serialize additional types), specify it with
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the ``cls`` kwarg.
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"""
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# cached encoder
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if (skipkeys is False and ensure_ascii is True and
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check_circular is True and allow_nan is True and
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cls is None and indent is None and separators is None and
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encoding == 'utf-8' and default is None and not kw):
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return _default_encoder.encode(obj)
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if cls is None:
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cls = JSONEncoder
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return cls(
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skipkeys=skipkeys, ensure_ascii=ensure_ascii,
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check_circular=check_circular, allow_nan=allow_nan, indent=indent,
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separators=separators, encoding=encoding, default=default,
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**kw).encode(obj)
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_default_decoder = JSONDecoder(encoding=None, object_hook=None)
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def load(fp, encoding=None, cls=None, object_hook=None, parse_float=None,
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parse_int=None, parse_constant=None, **kw):
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"""Deserialize ``fp`` (a ``.read()``-supporting file-like object
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containing a JSON document) to a Python object.
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If the contents of ``fp`` is encoded with an ASCII based encoding other
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than utf-8 (e.g. latin-1), then an appropriate ``encoding`` name must
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be specified. Encodings that are not ASCII based (such as UCS-2) are
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not allowed, and should be wrapped with
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``codecs.getreader(fp)(encoding)``, or simply decoded to a ``unicode``
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object and passed to ``loads()``
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``object_hook`` is an optional function that will be called with the
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result of any object literal decode (a ``dict``). The return value of
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``object_hook`` will be used instead of the ``dict``. This feature
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can be used to implement custom decoders (e.g. JSON-RPC class hinting).
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To use a custom ``JSONDecoder`` subclass, specify it with the ``cls``
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kwarg.
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"""
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return loads(fp.read(),
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encoding=encoding, cls=cls, object_hook=object_hook,
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parse_float=parse_float, parse_int=parse_int,
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parse_constant=parse_constant, **kw)
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def loads(s, encoding=None, cls=None, object_hook=None, parse_float=None,
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parse_int=None, parse_constant=None, **kw):
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"""Deserialize ``s`` (a ``str`` or ``unicode`` instance containing a JSON
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document) to a Python object.
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If ``s`` is a ``str`` instance and is encoded with an ASCII based encoding
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other than utf-8 (e.g. latin-1) then an appropriate ``encoding`` name
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must be specified. Encodings that are not ASCII based (such as UCS-2)
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are not allowed and should be decoded to ``unicode`` first.
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``object_hook`` is an optional function that will be called with the
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result of any object literal decode (a ``dict``). The return value of
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``object_hook`` will be used instead of the ``dict``. This feature
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can be used to implement custom decoders (e.g. JSON-RPC class hinting).
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``parse_float``, if specified, will be called with the string
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of every JSON float to be decoded. By default this is equivalent to
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float(num_str). This can be used to use another datatype or parser
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for JSON floats (e.g. decimal.Decimal).
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``parse_int``, if specified, will be called with the string
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of every JSON int to be decoded. By default this is equivalent to
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int(num_str). This can be used to use another datatype or parser
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for JSON integers (e.g. float).
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``parse_constant``, if specified, will be called with one of the
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following strings: -Infinity, Infinity, NaN, null, true, false.
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This can be used to raise an exception if invalid JSON numbers
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are encountered.
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To use a custom ``JSONDecoder`` subclass, specify it with the ``cls``
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kwarg.
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"""
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if (cls is None and encoding is None and object_hook is None and
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parse_int is None and parse_float is None and
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parse_constant is None and not kw):
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return _default_decoder.decode(s)
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if cls is None:
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cls = JSONDecoder
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if object_hook is not None:
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kw['object_hook'] = object_hook
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if parse_float is not None:
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kw['parse_float'] = parse_float
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if parse_int is not None:
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kw['parse_int'] = parse_int
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if parse_constant is not None:
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kw['parse_constant'] = parse_constant
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return cls(encoding=encoding, **kw).decode(s)
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