Source code for json.decoder

"""Implementation of JSONDecoder
"""
import re

from json import scanner
try:
    from _json import scanstring as c_scanstring
except ImportError:
    c_scanstring = None

__all__ = ['JSONDecoder', 'JSONDecodeError']

FLAGS = re.VERBOSE | re.MULTILINE | re.DOTALL

NaN = float('nan')
PosInf = float('inf')
NegInf = float('-inf')


[docs]class JSONDecodeError(ValueError): """Subclass of ValueError with the following additional properties: msg: The unformatted error message doc: The JSON document being parsed pos: The start index of doc where parsing failed lineno: The line corresponding to pos colno: The column corresponding to pos """ # Note that this exception is used from _json def __init__(self, msg, doc, pos): lineno = doc.count('\n', 0, pos) + 1 colno = pos - doc.rfind('\n', 0, pos) errmsg = '%s: line %d column %d (char %d)' % (msg, lineno, colno, pos) ValueError.__init__(self, errmsg) self.msg = msg self.doc = doc self.pos = pos self.lineno = lineno self.colno = colno def __reduce__(self): return self.__class__, (self.msg, self.doc, self.pos)
_CONSTANTS = { '-Infinity': NegInf, 'Infinity': PosInf, 'NaN': NaN, } STRINGCHUNK = re.compile(r'(.*?)(["\\\x00-\x1f])', FLAGS) BACKSLASH = { '"': '"', '\\': '\\', '/': '/', 'b': '\b', 'f': '\f', 'n': '\n', 'r': '\r', 't': '\t', } def _decode_uXXXX(s, pos): esc = s[pos + 1:pos + 5] if len(esc) == 4 and esc[1] not in 'xX': try: return int(esc, 16) except ValueError: pass msg = "Invalid \\uXXXX escape" raise JSONDecodeError(msg, s, pos) def py_scanstring(s, end, strict=True, _b=BACKSLASH, _m=STRINGCHUNK.match): """Scan the string s for a JSON string. End is the index of the character in s after the quote that started the JSON string. Unescapes all valid JSON string escape sequences and raises ValueError on attempt to decode an invalid string. If strict is False then literal control characters are allowed in the string. Returns a tuple of the decoded string and the index of the character in s after the end quote.""" chunks = [] _append = chunks.append begin = end - 1 while 1: chunk = _m(s, end) if chunk is None: raise JSONDecodeError("Unterminated string starting at", s, begin) end = chunk.end() content, terminator = chunk.groups() # Content is contains zero or more unescaped string characters if content: _append(content) # Terminator is the end of string, a literal control character, # or a backslash denoting that an escape sequence follows if terminator == '"': break elif terminator != '\\': if strict: #msg = "Invalid control character %r at" % (terminator,) msg = "Invalid control character {0!r} at".format(terminator) raise JSONDecodeError(msg, s, end) else: _append(terminator) continue try: esc = s[end] except IndexError: raise JSONDecodeError("Unterminated string starting at", s, begin) from None # If not a unicode escape sequence, must be in the lookup table if esc != 'u': try: char = _b[esc] except KeyError: msg = "Invalid \\escape: {0!r}".format(esc) raise JSONDecodeError(msg, s, end) end += 1 else: uni = _decode_uXXXX(s, end) end += 5 if 0xd800 <= uni <= 0xdbff and s[end:end + 2] == '\\u': uni2 = _decode_uXXXX(s, end + 1) if 0xdc00 <= uni2 <= 0xdfff: uni = 0x10000 + (((uni - 0xd800) << 10) | (uni2 - 0xdc00)) end += 6 char = chr(uni) _append(char) return ''.join(chunks), end # Use speedup if available scanstring = c_scanstring or py_scanstring WHITESPACE = re.compile(r'[ \t\n\r]*', FLAGS) WHITESPACE_STR = ' \t\n\r' def JSONObject(s_and_end, strict, scan_once, object_hook, object_pairs_hook, memo=None, _w=WHITESPACE.match, _ws=WHITESPACE_STR): s, end = s_and_end pairs = [] pairs_append = pairs.append # Backwards compatibility if memo is None: memo = {} memo_get = memo.setdefault # Use a slice to prevent IndexError from being raised, the following # check will raise a more specific ValueError if the string is empty nextchar = s[end:end + 1] # Normally we expect nextchar == '"' if nextchar != '"': if nextchar in _ws: end = _w(s, end).end() nextchar = s[end:end + 1] # Trivial empty object if nextchar == '}': if object_pairs_hook is not None: result = object_pairs_hook(pairs) return result, end + 1 pairs = {} if object_hook is not None: pairs = object_hook(pairs) return pairs, end + 1 elif nextchar != '"': raise JSONDecodeError( "Expecting property name enclosed in double quotes", s, end) end += 1 while True: key, end = scanstring(s, end, strict) key = memo_get(key, key) # To skip some function call overhead we optimize the fast paths where # the JSON key separator is ": " or just ":". if s[end:end + 1] != ':': end = _w(s, end).end() if s[end:end + 1] != ':': raise JSONDecodeError("Expecting ':' delimiter", s, end) end += 1 try: if s[end] in _ws: end += 1 if s[end] in _ws: end = _w(s, end + 1).end() except IndexError: pass try: value, end = scan_once(s, end) except StopIteration as err: raise JSONDecodeError("Expecting value", s, err.value) from None pairs_append((key, value)) try: nextchar = s[end] if nextchar in _ws: end = _w(s, end + 1).end() nextchar = s[end] except IndexError: nextchar = '' end += 1 if nextchar == '}': break elif nextchar != ',': raise JSONDecodeError("Expecting ',' delimiter", s, end - 1) end = _w(s, end).end() nextchar = s[end:end + 1] end += 1 if nextchar != '"': raise JSONDecodeError( "Expecting property name enclosed in double quotes", s, end - 1) if object_pairs_hook is not None: result = object_pairs_hook(pairs) return result, end pairs = dict(pairs) if object_hook is not None: pairs = object_hook(pairs) return pairs, end def JSONArray(s_and_end, scan_once, _w=WHITESPACE.match, _ws=WHITESPACE_STR): s, end = s_and_end values = [] nextchar = s[end:end + 1] if nextchar in _ws: end = _w(s, end + 1).end() nextchar = s[end:end + 1] # Look-ahead for trivial empty array if nextchar == ']': return values, end + 1 _append = values.append while True: try: value, end = scan_once(s, end) except StopIteration as err: raise JSONDecodeError("Expecting value", s, err.value) from None _append(value) nextchar = s[end:end + 1] if nextchar in _ws: end = _w(s, end + 1).end() nextchar = s[end:end + 1] end += 1 if nextchar == ']': break elif nextchar != ',': raise JSONDecodeError("Expecting ',' delimiter", s, end - 1) try: if s[end] in _ws: end += 1 if s[end] in _ws: end = _w(s, end + 1).end() except IndexError: pass return values, end class JSONDecoder(object): """Simple JSON <http://json.org> decoder Performs the following translations in decoding by default: +---------------+-------------------+ | JSON | Python | +===============+===================+ | object | dict | +---------------+-------------------+ | array | list | +---------------+-------------------+ | string | str | +---------------+-------------------+ | number (int) | int | +---------------+-------------------+ | number (real) | float | +---------------+-------------------+ | true | True | +---------------+-------------------+ | false | False | +---------------+-------------------+ | null | None | +---------------+-------------------+ It also understands ``NaN``, ``Infinity``, and ``-Infinity`` as their corresponding ``float`` values, which is outside the JSON spec. """ def __init__(self, *, object_hook=None, parse_float=None, parse_int=None, parse_constant=None, strict=True, object_pairs_hook=None): """``object_hook``, if specified, will be called with the result of every JSON object decoded and its return value will be used in place of the given ``dict``. This can be used to provide custom deserializations (e.g. to support JSON-RPC class hinting). ``object_pairs_hook``, if specified will be called with the result of every JSON object decoded with an ordered list of pairs. The return value of ``object_pairs_hook`` will be used instead of the ``dict``. This feature can be used to implement custom decoders. If ``object_hook`` is also defined, the ``object_pairs_hook`` takes priority. ``parse_float``, if specified, will be called with the string of every JSON float to be decoded. By default this is equivalent to float(num_str). This can be used to use another datatype or parser for JSON floats (e.g. decimal.Decimal). ``parse_int``, if specified, will be called with the string of every JSON int to be decoded. By default this is equivalent to int(num_str). This can be used to use another datatype or parser for JSON integers (e.g. float). ``parse_constant``, if specified, will be called with one of the following strings: -Infinity, Infinity, NaN. This can be used to raise an exception if invalid JSON numbers are encountered. If ``strict`` is false (true is the default), then control characters will be allowed inside strings. Control characters in this context are those with character codes in the 0-31 range, including ``'\\t'`` (tab), ``'\\n'``, ``'\\r'`` and ``'\\0'``. """ self.object_hook = object_hook self.parse_float = parse_float or float self.parse_int = parse_int or int self.parse_constant = parse_constant or _CONSTANTS.__getitem__ self.strict = strict self.object_pairs_hook = object_pairs_hook self.parse_object = JSONObject self.parse_array = JSONArray self.parse_string = scanstring self.memo = {} self.scan_once = scanner.make_scanner(self) def decode(self, s, _w=WHITESPACE.match): """Return the Python representation of ``s`` (a ``str`` instance containing a JSON document). """ obj, end = self.raw_decode(s, idx=_w(s, 0).end()) end = _w(s, end).end() if end != len(s): raise JSONDecodeError("Extra data", s, end) return obj def raw_decode(self, s, idx=0): """Decode a JSON document from ``s`` (a ``str`` beginning with a JSON document) and return a 2-tuple of the Python representation and the index in ``s`` where the document ended. This can be used to decode a JSON document from a string that may have extraneous data at the end. """ try: obj, end = self.scan_once(s, idx) except StopIteration as err: raise JSONDecodeError("Expecting value", s, err.value) from None return obj, end