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"""Implementation of JSONEncoder
"""
import re
import math
try:
from _json import encode_basestring_ascii as c_encode_basestring_ascii
except ImportError:
c_encode_basestring_ascii = None
__all__ = ['JSONEncoder']
ESCAPE = re.compile(r'[\x00-\x1f\\"\b\f\n\r\t]')
ESCAPE_ASCII = re.compile(r'([\\"]|[^\ -~])')
HAS_UTF8 = re.compile(r'[\x80-\xff]')
ESCAPE_DCT = {
'\\': '\\\\',
'"': '\\"',
'\b': '\\b',
'\f': '\\f',
'\n': '\\n',
'\r': '\\r',
'\t': '\\t',
}
for i in range(0x20):
ESCAPE_DCT.setdefault(chr(i), '\\u{0:04x}'.format(i))
FLOAT_REPR = repr
def floatstr(o, allow_nan=True):
# Check for specials. Note that this type of test is processor- and/or
# platform-specific, so do tests which don't depend on the internals.
if math.isnan(o):
text = 'NaN'
elif math.isinf(o):
if math.copysign(1., o) == 1.:
text = 'Infinity'
else:
text = '-Infinity'
else:
return FLOAT_REPR(o)
if not allow_nan:
msg = "Out of range float values are not JSON compliant: " + repr(o)
raise ValueError(msg)
return text
def encode_basestring(s):
"""Return a JSON representation of a Python string
"""
def replace(match):
return ESCAPE_DCT[match.group(0)]
return '"' + ESCAPE.sub(replace, s) + '"'
def py_encode_basestring_ascii(s):
if isinstance(s, str) and HAS_UTF8.search(s) is not None:
s = s.decode('utf-8')
def replace(match):
s = match.group(0)
try:
return ESCAPE_DCT[s]
except KeyError:
n = ord(s)
if n < 0x10000:
return '\\u{0:04x}'.format(n)
else:
# surrogate pair
n -= 0x10000
s1 = 0xd800 | ((n >> 10) & 0x3ff)
s2 = 0xdc00 | (n & 0x3ff)
return '\\u{0:04x}\\u{1:04x}'.format(s1, s2)
return '"' + str(ESCAPE_ASCII.sub(replace, s)) + '"'
if c_encode_basestring_ascii is not None:
encode_basestring_ascii = c_encode_basestring_ascii
else:
encode_basestring_ascii = py_encode_basestring_ascii
class JSONEncoder(object):
"""Extensible JSON <http://json.org> encoder for Python data structures.
Supports the following objects and types by default:
+-------------------+---------------+
| Python | JSON |
+===================+===============+
| dict | object |
+-------------------+---------------+
| list, tuple | array |
+-------------------+---------------+
| str, unicode | string |
+-------------------+---------------+
| int, long, float | number |
+-------------------+---------------+
| True | true |
+-------------------+---------------+
| False | false |
+-------------------+---------------+
| None | null |
+-------------------+---------------+
To extend this to recognize other objects, subclass and implement a
``.default()`` method with another method that returns a serializable
object for ``o`` if possible, otherwise it should call the superclass
implementation (to raise ``TypeError``).
"""
__all__ = ['__init__', 'default', 'encode', 'iterencode']
item_separator = ', '
key_separator = ': '
def __init__(self, skipkeys=False, ensure_ascii=True,
check_circular=True, allow_nan=True, sort_keys=False,
indent=None, separators=None, encoding='utf-8', default=None):
"""Constructor for JSONEncoder, with sensible defaults.
If skipkeys is False, then it is a TypeError to attempt
encoding of keys that are not str, int, long, float or None. If
skipkeys is True, such items are simply skipped.
If ensure_ascii is True, the output is guaranteed to be str
objects with all incoming unicode characters escaped. If
ensure_ascii is false, the output will be unicode object.
If check_circular is True, then lists, dicts, and custom encoded
objects will be checked for circular references during encoding to
prevent an infinite recursion (which would cause an OverflowError).
Otherwise, no such check takes place.
If allow_nan is True, then NaN, Infinity, and -Infinity will be
encoded as such. This behavior is not JSON specification compliant,
but is consistent with most JavaScript based encoders and decoders.
Otherwise, it will be a ValueError to encode such floats.
If sort_keys is True, then the output of dictionaries will be
sorted by key; this is useful for regression tests to ensure
that JSON serializations can be compared on a day-to-day basis.
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 specified, separators should be a (item_separator, key_separator)
tuple. The default is (', ', ': '). To get the most compact JSON
representation you should specify (',', ':') to eliminate whitespace.
If specified, default is a function that gets called for objects
that can't otherwise be serialized. It should return a JSON encodable
version of the object or raise a ``TypeError``.
If encoding is not None, then all input strings will be
transformed into unicode using that encoding prior to JSON-encoding.
The default is UTF-8.
"""
self.skipkeys = skipkeys
self.ensure_ascii = ensure_ascii
self.check_circular = check_circular
self.allow_nan = allow_nan
self.sort_keys = sort_keys
self.indent = indent
self.current_indent_level = 0
if separators is not None:
self.item_separator, self.key_separator = separators
if default is not None:
self.default = default
self.encoding = encoding
def _newline_indent(self):
return '\n' + (' ' * (self.indent * self.current_indent_level))
def _iterencode_list(self, lst, markers=None):
if not lst:
yield '[]'
return
if markers is not None:
markerid = id(lst)
if markerid in markers:
raise ValueError("Circular reference detected")
markers[markerid] = lst
yield '['
if self.indent is not None:
self.current_indent_level += 1
newline_indent = self._newline_indent()
separator = self.item_separator + newline_indent
yield newline_indent
else:
newline_indent = None
separator = self.item_separator
first = True
for value in lst:
if first:
first = False
else:
yield separator
for chunk in self._iterencode(value, markers):
yield chunk
if newline_indent is not None:
self.current_indent_level -= 1
yield self._newline_indent()
yield ']'
if markers is not None:
del markers[markerid]
def _iterencode_dict(self, dct, markers=None):
if not dct:
yield '{}'
return
if markers is not None:
markerid = id(dct)
if markerid in markers:
raise ValueError("Circular reference detected")
markers[markerid] = dct
yield '{'
key_separator = self.key_separator
if self.indent is not None:
self.current_indent_level += 1
newline_indent = self._newline_indent()
item_separator = self.item_separator + newline_indent
yield newline_indent
else:
newline_indent = None
item_separator = self.item_separator
first = True
if self.ensure_ascii:
encoder = encode_basestring_ascii
else:
encoder = encode_basestring
allow_nan = self.allow_nan
if self.sort_keys:
keys = dct.keys()
keys.sort()
items = [(k, dct[k]) for k in keys]
else:
items = dct.iteritems()
_encoding = self.encoding
_do_decode = (_encoding is not None
and not (_encoding == 'utf-8'))
for key, value in items:
if isinstance(key, str):
if _do_decode:
key = key.decode(_encoding)
elif isinstance(key, basestring):
pass
# JavaScript is weakly typed for these, so it makes sense to
# also allow them. Many encoders seem to do something like this.
elif isinstance(key, float):
key = floatstr(key, allow_nan)
elif isinstance(key, (int, long)):
key = str(key)
elif key is True:
key = 'true'
elif key is False:
key = 'false'
elif key is None:
key = 'null'
elif self.skipkeys:
continue
else:
raise TypeError("key {0!r} is not a string".format(key))
if first:
first = False
else:
yield item_separator
yield encoder(key)
yield key_separator
for chunk in self._iterencode(value, markers):
yield chunk
if newline_indent is not None:
self.current_indent_level -= 1
yield self._newline_indent()
yield '}'
if markers is not None:
del markers[markerid]
def _iterencode(self, o, markers=None):
if isinstance(o, basestring):
if self.ensure_ascii:
encoder = encode_basestring_ascii
else:
encoder = encode_basestring
_encoding = self.encoding
if (_encoding is not None and isinstance(o, str)
and not (_encoding == 'utf-8')):
o = o.decode(_encoding)
yield encoder(o)
elif o is None:
yield 'null'
elif o is True:
yield 'true'
elif o is False:
yield 'false'
elif isinstance(o, (int, long)):
yield str(o)
elif isinstance(o, float):
yield floatstr(o, self.allow_nan)
elif isinstance(o, (list, tuple)):
for chunk in self._iterencode_list(o, markers):
yield chunk
elif isinstance(o, dict):
for chunk in self._iterencode_dict(o, markers):
yield chunk
else:
if markers is not None:
markerid = id(o)
if markerid in markers:
raise ValueError("Circular reference detected")
markers[markerid] = o
for chunk in self._iterencode_default(o, markers):
yield chunk
if markers is not None:
del markers[markerid]
def _iterencode_default(self, o, markers=None):
newobj = self.default(o)
return self._iterencode(newobj, markers)
def default(self, o):
"""Implement this method in a subclass such that it returns a serializable
object for ``o``, or calls the base implementation (to raise a
``TypeError``).
For example, to support arbitrary iterators, you could implement
default like this::
def default(self, o):
try:
iterable = iter(o)
except TypeError:
pass
else:
return list(iterable)
return JSONEncoder.default(self, o)
"""
raise TypeError(repr(o) + " is not JSON serializable")
def encode(self, o):
"""Return a JSON string representation of a Python data structure.
>>> JSONEncoder().encode({"foo": ["bar", "baz"]})
'{"foo": ["bar", "baz"]}'
"""
# This is for extremely simple cases and benchmarks.
if isinstance(o, basestring):
if isinstance(o, str):
_encoding = self.encoding
if (_encoding is not None
and not (_encoding == 'utf-8')):
o = o.decode(_encoding)
if self.ensure_ascii:
return encode_basestring_ascii(o)
else:
return encode_basestring(o)
# This doesn't pass the iterator directly to ''.join() because the
# exceptions aren't as detailed. The list call should be roughly
# equivalent to the PySequence_Fast that ''.join() would do.
chunks = list(self.iterencode(o))
return ''.join(chunks)
def iterencode(self, o):
"""Encode the given object and yield each string representation as
available.
For example::
for chunk in JSONEncoder().iterencode(bigobject):
mysocket.write(chunk)
"""
if self.check_circular:
markers = {}
else:
markers = None
return self._iterencode(o, markers)
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