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