UltraJSON

UltraJSON is an ultra fast JSON encoder and decoder written in pure C with bindings for Python 2.7 and 3.5+.

To install it just run pip as usual:

$ pip install ujson

Usage

May be used as a drop in replacement for most other JSON parsers for Python:

>>> import ujson
>>> ujson.dumps([{"key": "value"}, 81, True])
'[{"key":"value"},81,true]'
>>> ujson.loads("""[{"key": "value"}, 81, true]""")
[{u'key': u'value'}, 81, True]

Encoder options

encode_html_chars

Used to enable special encoding of "unsafe" HTML characters into safer Unicode sequences. Default is False:

>>> ujson.dumps("<script>John&Doe", encode_html_chars=True)
'"\\u003cscript\\u003eJohn\\u0026Doe"'

ensure_ascii

Limits output to ASCII and escapes all extended characters above 127. Default is true. If your end format supports UTF-8 setting this option to false is highly recommended to save space:

>>> ujson.dumps(u"\xe5\xe4\xf6")
'"\\u00e5\\u00e4\\u00f6"'
>>> ujson.dumps(u"\xe5\xe4\xf6", ensure_ascii=False)
'"\xc3\xa5\xc3\xa4\xc3\xb6"'

escape_forward_slashes

Controls whether forward slashes (/) are escaped. Default is True:

>>> ujson.dumps("http://esn.me")
'"http:\/\/esn.me"'
>>> ujson.dumps("http://esn.me", escape_forward_slashes=False)
'"http://esn.me"'

indent

Controls whether indention ("pretty output") is enabled. Default is 0 (disabled):

>>> ujson.dumps({"foo": "bar"})
'{"foo":"bar"}'
>>> ujson.dumps({"foo": "bar"}, indent=4)
{
    "foo":"bar"
}

Benchmarks

UltraJSON calls/sec compared to three other popular JSON parsers with performance gain specified below each.

Test machine:

Linux 3.13.0-66-generic x86_64 #108-Ubuntu SMP Wed Oct 7 15:20:27 UTC 2015

Versions:

• CPython 2.7.6 (default, Jun 22 2015, 17:58:13) [GCC 4.8.2]
• blist : 1.3.6
• simplejson: 3.8.1
• ujson : 1.34 (0c52200eb4e2d97e548a765d5f089858c41967b0)
• yajl : 0.3.5

	ujson	yajl	simplejson	json
Array with 256 doubles
encode	3508.19	5742.00	3232.38	3309.09
decode	25103.37	11257.83	11696.26	11871.04
Array with 256 UTF-8 strings
encode	3189.71	2717.14	2006.38	2961.72
decode	1354.94	630.54	356.35	344.05
Array with 256 strings
encode	18127.47	12537.39	12541.23	20001.00
decode	23264.70	12788.85	25427.88	9352.36
Medium complex object
encode	10519.38	5021.29	3686.86	4643.47
decode	9676.53	5326.79	8515.77	3017.30
Array with 256 True values
encode	105998.03	102067.28	44758.51	60424.80
decode	163869.96	78341.57	110859.36	115013.90
Array with 256 dict{string, int} pairs
encode	13471.32	12109.09	3876.40	8833.92
decode	16890.63	8946.07	12218.55	3350.72
Dict with 256 arrays with 256 dict{string, int} pairs
encode	50.25	46.45	13.82	29.28
decode	33.27	22.10	27.91	10.43
Dict with 256 arrays with 256 dict{string, int} pairs, outputting sorted keys
encode	27.19		7.75	2.39
Complex object
encode	577.98		387.81	470.02
decode	496.73	234.44	151.00	145.16

Versions:

• CPython 3.4.3 (default, Oct 14 2015, 20:28:29) [GCC 4.8.4]
• blist : 1.3.6
• simplejson: 3.8.1
• ujson : 1.34 (0c52200eb4e2d97e548a765d5f089858c41967b0)
• yajl : 0.3.5

	ujson	yajl	simplejson	json
Array with 256 doubles
encode	3477.15	5732.24	3016.76	3071.99
decode	23625.20	9731.45	9501.57	9901.92
Array with 256 UTF-8 strings
encode	1995.89	2151.61	1771.98	1817.20
decode	1425.04	625.38	327.14	305.95
Array with 256 strings
encode	25461.75	12188.64	13054.76	14429.81
decode	21981.31	17014.22	23869.48	22483.58
Medium complex object
encode	10821.46	4837.04	3114.04	4254.46
decode	7887.77	5126.67	4934.60	6204.97
Array with 256 True values
encode	100452.86	94639.42	46657.63	60358.63
decode	148312.69	75485.90	88434.91	116395.51
Array with 256 dict{string, int} pairs
encode	11698.13	8886.96	3043.69	6302.35
decode	10686.40	7061.77	5646.80	7702.29
Dict with 256 arrays with 256 dict{string, int} pairs
encode	44.26	34.43	10.40	21.97
decode	28.46	23.95	18.70	22.83
Dict with 256 arrays with 256 dict{string, int} pairs, outputting sorted keys
encode	33.60		6.94	22.34
Complex object
encode	432.30		351.47	379.34
decode	434.40	221.97	149.57	147.79