cpython/Lib/json/decoder.py at 3.15 · python/cpython · GitHub

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"""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')

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 = frozendict({

'-Infinity': NegInf,

'Infinity': PosInf,

'NaN': NaN,

})

HEXDIGITS = re.compile(r'[0-9A-Fa-f]{4}', FLAGS)

STRINGCHUNK = re.compile(r'(.*?)(["\\\x00-\x1f])', FLAGS)

BACKSLASH = {

'"': '"', '\\': '\\', '/': '/',

'b': '\b', 'f': '\f', 'n': '\n', 'r': '\r', 't': '\t',

}

def _decode_uXXXX(s, pos, _m=HEXDIGITS.match):

esc = _m(s, pos + 1)

if esc is not None:

try:

return int(esc.group(), 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 - 1)

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)

comma_idx = end - 1

end = _w(s, end).end()

nextchar = s[end:end + 1]

end += 1

if nextchar != '"':

if nextchar == '}':

raise JSONDecodeError("Illegal trailing comma before end of object", s, comma_idx)

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, array_hook, _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 == ']':

if array_hook is not None:

values = array_hook(values)

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)

comma_idx = end - 1

try:

if s[end] in _ws:

end += 1

if s[end] in _ws:

end = _w(s, end + 1).end()

nextchar = s[end:end + 1]

except IndexError:

pass

if nextchar == ']':

raise JSONDecodeError("Illegal trailing comma before end of array", s, comma_idx)

if array_hook is not None:

values = array_hook(values)

return values, end

class JSONDecoder(object):

"""Simple JSON <https://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, array_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.

``array_hook`` is an optional function that will be called with the

result of any literal array decode (a ``list``). The return value of

this function will be used instead of the ``list``. This feature can

be used along ``object_pairs_hook`` to customize the resulting data

structure - for example, by setting that to ``frozendict`` and

``array_hook`` to ``tuple``, one can get a deep immutable data

structute from any JSON data.

``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.array_hook = array_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

cpython/Lib/json/decoder.py at 3.15 · python/cpython · GitHub

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