19.2. `json` JSON

JSON (JavaScript Object Notation) RFC 7159 (RFC 4627 obsolete) ECMA-404 JavaScript (JavaScript [1])

json API marshal pickle

Python :

>>> import json
>>> json.dumps(['foo', {'bar': ('baz', None, 1.0, 2)}])
'["foo", {"bar": ["baz", null, 1.0, 2]}]'
>>> print(json.dumps("\"foo\bar"))
"\"foo\bar"
>>> print(json.dumps('\u1234'))
"\u1234"
>>> print(json.dumps('\\'))
"\\"
>>> print(json.dumps({"c": 0, "b": 0, "a": 0}, sort_keys=True))
{"a": 0, "b": 0, "c": 0}
>>> from io import StringIO
>>> io = StringIO()
>>> json.dump(['streaming API'], io)
>>> io.getvalue()
'["streaming API"]'

:

>>> import json
>>> json.dumps([1, 2, 3, {'4': 5, '6': 7}], separators=(',', ':'))
'[1,2,3,{"4":5,"6":7}]'

:

>>> import json
>>> print(json.dumps({'4': 5, '6': 7}, sort_keys=True, indent=4))
{
    "4": 5,
    "6": 7
}

JSON :

>>> import json
>>> json.loads('["foo", {"bar":["baz", null, 1.0, 2]}]')
['foo', {'bar': ['baz', None, 1.0, 2]}]
>>> json.loads('"\\"foo\\bar"')
'"foo\x08ar'
>>> from io import StringIO
>>> io = StringIO('["streaming API"]')
>>> json.load(io)
['streaming API']

JSON :

>>> import json
>>> def as_complex(dct):
...     if '__complex__' in dct:
...         return complex(dct['real'], dct['imag'])
...     return dct
...
>>> json.loads('{"__complex__": true, "real": 1, "imag": 2}',
...     object_hook=as_complex)
(1+2j)
>>> import decimal
>>> json.loads('1.1', parse_float=decimal.Decimal)
Decimal('1.1')

JSONEncoder :

>>> import json
>>> class ComplexEncoder(json.JSONEncoder):
...     def default(self, obj):
...         if isinstance(obj, complex):
...             return [obj.real, obj.imag]
...         # Let the base class default method raise the TypeError
...         return json.JSONEncoder.default(self, obj)
...
>>> json.dumps(2 + 1j, cls=ComplexEncoder)
'[2.0, 1.0]'
>>> ComplexEncoder().encode(2 + 1j)
'[2.0, 1.0]'
>>> list(ComplexEncoder().iterencode(2 + 1j))
['[2.0', ', 1.0', ']']

json.tool :

$ echo '{"json":"obj"}' | python -m json.tool
{
    "json": "obj"
}
$ echo '{1.2:3.4}' | python -m json.tool
Expecting property name enclosed in double quotes: line 1 column 2 (char 1)

JSON YAML 1.2 ( ) JSON YAML 1.0 1.1 YAML

19.2.1.

json.dump(obj, fp, *, skipkeys=False, ensure_ascii=True, check_circular=True, allow_nan=True, cls=None, indent=None, separators=None, default=None, sort_keys=False, **kw)

obj JSON fp (.write() file-like object)

skipkeys true ( False) (str, int, float, bool, None) TypeError

json bytes str fp.write() str

ensure_ascii () true ASCII ensure_ascii false

check_circular false ( True) OverflowError ()

allow_nan ( True) float (nan, inf, -inf) JSON ValueError allow_non JavaScript (NaN, Infinity, -Infinity)

indent JSON 0 "" None () indent indent ("\t" )

3.2 : indent

separators (item_separator, key_separator) indent None (', ', ': ') (',', ': ') JSON (',', ':')

3.4 : indent None (',', ': ')

default JSON TypeError TypeError

sort_keys true ( False )

JSONEncoder ( default() ) cls ; JSONEncoder

3.6 :

json.dumps(obj, *, skipkeys=False, ensure_ascii=True, check_circular=True, allow_nan=True, cls=None, indent=None, separators=None, default=None, sort_keys=False, **kw): obj JSON str dump()

pickle marshal JSON fp dump() JSON

JSON str JSON JSON loads(dumps(x)) != x

json.load(fp, *, cls=None, object_hook=None, parse_float=None, parse_int=None, parse_constant=None, object_pairs_hook=None, **kw)

Deserialize fp (a .read()-supporting file-like object containing a JSON document) to a Python object using this conversion table.

object_hook (dict) object_hook dict ( JSON-RPC )

object_pairs_hook object_pairs_hook dict ( collections.OrderedDict() ) object_hook object_pairs_hook

3.1 : object_pairs_hook

parse_float JSON float(num_str) JSON ( decimal.Decimal)

parse_int JSON int(num_str) JSON ( float)

parse_constant : '-Infinity', 'Infinity', 'NaN', 'null', 'true', 'false' JSON

3.1 : 'null', 'true', 'false' parse_constant

JSONDecoder cls ; JSONDecoder

JSON JSONDecodeError

3.6 :

json.loads(s, *, encoding=None, cls=None, object_hook=None, parse_float=None, parse_int=None, parse_constant=None, object_pairs_hook=None, **kw)

s (JSON str, bytes, bytearray ) Python

encoding load()

JSON JSONDecodeError

3.6 : s bytes bytearray UTF-8, UTF-16, UTF-32

19.2.2.

class json.JSONDecoder(*, object_hook=None, parse_float=None, parse_int=None, parse_constant=None, strict=True, object_pairs_hook=None)

JSON

:

JSON	Python
object	dict
array	list
string	str
number (int)	int
number (real)
true	True
false	False
null	None

NaN, Infinity, -Infinity float JSON

object_hook JSON dict ( JSON-RPC )

object_pairs_hook JSON object_pairs_hook dict ( collections.OrderedDict() ) object_hook object_pairs_hook

3.1 : object_pairs_hook

parse_float JSON float(num_str) JSON ( decimal.Decimal)

parse_int JSON int(num_str) JSON ( float)

parse_constant : '-Infinity', 'Infinity', 'NaN', 'null', 'true', 'false' JSON

strict false ( True) '\t' ()'\n''\r''\0' 0-31

JSON JSONDecodeError

3.6 :

decode(s)

s (str JSON ) Python

JSON JSONDecodeError

raw_decode(s)

s (str JSON ) JSON Python s 2

JSON

class json.JSONEncoder(*, skipkeys=False, ensure_ascii=True, check_circular=True, allow_nan=True, sort_keys=False, indent=None, separators=None, default=None)

Python JSON

:

Python	JSON
dict	object
list, tuple	array
str	string
intfloat int float	number
True	true
False	false
None	null

3.4 : int float

default() o (TypeError )

skipkeys false () str, int, float, None TypeError skipkeys true

ensure_ascii () true ASCII ensure_ascii false

check_circular true () ( OverflowError ) True

allow_nan true () NaN, Infinity, -Infinity JSON JavaScript True ValueError

sort_keys true ( False) JSON

indent JSON 0 "" None () indent indent ("\t" )

3.2 : indent

separators (item_separator, key_separator) indent None (', ', ': ') (',', ': ') JSON (',', ':')

3.4 : indent None (',', ': ')

default JSON TypeError TypeError

3.6 :

default(o)

o (TypeError )

:

def default(self, o):
   try:
       iterable = iter(o)
   except TypeError:
       pass
   else:
       return list(iterable)
   # Let the base class default method raise the TypeError
   return json.JSONEncoder.default(self, o)

encode(o)

Python o JSON :

>>> json.JSONEncoder().encode({"foo": ["bar", "baz"]})
'{"foo": ["bar", "baz"]}'

iterencode(o)

o yield :

for chunk in json.JSONEncoder().iterencode(bigobject):
    mysocket.write(chunk)

19.2.3.

exception json.JSONDecodeError(msg, doc, pos)

ValueError :

msg

doc: JSON

pos: doc

lineno: pos

colno: pos

3.5 .

19.2.4.

JSON RFC 7159 ECMA-404 RFC JSONEncoder JSONDecoder

JavaScript JSON RFC :

NaN ;

RFC RFC RFC RFC

19.2.4.1.

RFC UTF-8UTF-16UTF-32JSONUTF-8

RFC ensure_ascii=True ASCII

ensure_ascii Python Unicode

RFC JSON (BOM) BOM RFC JSON BOM BOM ValueError

RFC JSON Unicode ( UTF-16 )( str )

19.2.4.2. NaN

RFC NaN Infinity-InfinityNaN JSON :

>>> # Neither of these calls raises an exception, but the results are not valid JSON
>>> json.dumps(float('-inf'))
'-Infinity'
>>> json.dumps(float('nan'))
'NaN'
>>> # Same when deserializing
>>> json.loads('-Infinity')
-inf
>>> json.loads('NaN')
nan

allow_nan parse_constant

19.2.4.3.

RFC JSON JSON

>>> weird_json = '{"x": 1, "x": 2, "x": 3}'
>>> json.loads(weird_json)
{'x': 3}

object_pairs_hook

19.2.4.4.

RFC 4627 JSON JSON JSON (Python dict list)JSON null, boolean, number, string RFC 7159

19.2.4.5.

JSON

JSON
JSON
JSON
JSON

Python Python

JSON JSON JSON IEEE 754 Python int decimal.Decimal ""

19.2.5.

: Lib/json/tool.py

json.tool JSON

infile outfile sys.stdin sys.stdout :

$ echo '{"json": "obj"}' | python -m json.tool
{
    "json": "obj"
}
$ echo '{1.2:3.4}' | python -m json.tool
Expecting property name enclosed in double quotes: line 1 column 2 (char 1)

3.5 : --sort-keys

19.2.5.1.

infile

JSON :

$ python -m json.tool mp_films.json
[
    {
        "title": "And Now for Something Completely Different",
        "year": 1971
    },
    {
        "title": "Monty Python and the Holy Grail",
        "year": 1975
    }
]

infile sys.stdin

outfile: infile outfile sys.stdout

--sort-keys: 3.5 .

-h, --help

[1]	RFC 7159 JSON (ECMAScript Edition 5.1 ) JavaScript U+2028 (LINE SEPARATOR) U+2029 (PARAGRAPH SEPARATOR)

19.2. json JSON

19.2.1.

19.2.2.

19.2.3.

19.2.4.

19.2.4.1.

19.2.4.2. NaN

19.2.4.3.

19.2.4.4.

19.2.4.5.

19.2.5.

19.2.5.1.

19.2. `json` JSON