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"""
Implementation of JSONEncoder
"""
# NOTE(kgibbs): This line must be added to make this file work under
# Python 2.2, which is commonly used at Google.
from __future__ import generators
# NOTE(kgibbs): End changes.
import re
# this should match any kind of infinity
INFCHARS = re.compile(r'[infINF]')
ESCAPE = re.compile(r'[\x00-\x19\\"\b\f\n\r\t]')
ESCAPE_ASCII = re.compile(r'([\\"]|[^\ -~])')
ESCAPE_DCT = {
'\\': '\\\\',
'"': '\\"',
'\b': '\\b',
'\f': '\\f',
'\n': '\\n',
'\r': '\\r',
'\t': '\\t',
}
for i in range(0x20):
ESCAPE_DCT.setdefault(chr(i), '\\u%04x' % (i,))
def floatstr(o, allow_nan=True):
s = str(o)
# If the first non-sign is a digit then it's not a special value
if (o < 0.0 and s[1].isdigit()) or s[0].isdigit():
return s
elif not allow_nan:
raise ValueError("Out of range float values are not JSON compliant: %r"
% (o,))
# These are the string representations on the platforms I've tried
if s == 'nan':
return 'NaN'
if s == 'inf':
return 'Infinity'
if s == '-inf':
return '-Infinity'
# NaN should either be inequal to itself, or equal to everything
if o != o or o == 0.0:
return 'NaN'
# Last ditch effort, assume inf
if o < 0:
return '-Infinity'
return 'Infinity'
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 encode_basestring_ascii(s):
def replace(match):
s = match.group(0)
try:
return ESCAPE_DCT[s]
except KeyError:
return '\\u%04x' % (ord(s),)
return '"' + str(ESCAPE_ASCII.sub(replace, s)) + '"'
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']
def __init__(self, skipkeys=False, ensure_ascii=True,
check_circular=True, allow_nan=True, sort_keys=False):
"""
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.
"""
self.skipkeys = skipkeys
self.ensure_ascii = ensure_ascii
self.check_circular = check_circular
self.allow_nan = allow_nan
self.sort_keys = sort_keys
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 '['
first = True
for value in lst:
if first:
first = False
else:
yield ', '
for chunk in self._iterencode(value, markers):
yield chunk
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 '{'
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()
for key, value in items:
# NOTE(kgibbs): This line was modified to replace the use of
# basestring, to make this file work under Python 2.2, which is
# commonly used at Google.
if isinstance(key, (str, unicode)):
# NOTE(kgibbs): End changes.
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 %r is not a string" % (key,))
if first:
first = False
else:
yield ', '
yield encoder(key)
yield ': '
for chunk in self._iterencode(value, markers):
yield chunk
yield '}'
if markers is not None:
del markers[markerid]
def _iterencode(self, o, markers=None):
# NOTE(kgibbs): This line was modified to replace the use of
# basestring, to make this file work under Python 2.2, which is
# commonly used at Google.
if isinstance(o, (str, unicode)):
# NOTE(kgibbs): End changes.
if self.ensure_ascii:
encoder = encode_basestring_ascii
else:
encoder = encode_basestring
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("%r is not JSON serializable" % (o,))
def encode(self, o):
"""
Return a JSON string representation of a Python data structure.
>>> JSONEncoder().encode({"foo": ["bar", "baz"]})
'{"foo":["bar", "baz"]}'
"""
# This doesn't pass the iterator directly to ''.join() because it
# sucks at reporting exceptions. It's going to do this internally
# anyway because it uses PySequence_Fast or similar.
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)
__all__ = ['JSONEncoder']
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