UltraJSON

UltraJSON is an ultra fast JSON encoder and decoder written in pure C with bindings for Python 3.7+.

Install with pip:

python -m 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]""")
[{'key': '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("åäö")
'"\\u00e5\\u00e4\\u00f6"'
>>> ujson.dumps("åäö", ensure_ascii=False)
'"åäö"'

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 indentation ("pretty output") is enabled. Default is 0 (disabled):

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

Benchmarks

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

Test machine

Linux 5.0.0-1032-azure x86_64 #34-Ubuntu SMP Mon Feb 10 19:37:25 UTC 2020

Versions

• CPython 3.8.2 (default, Feb 28 2020, 14:28:43) [GCC 7.4.0]
• nujson : 1.35.2
• orjson : 2.6.1
• simplejson: 3.17.0
• ujson : 2.0.2

	ujson	nujson	orjson	simplejson	json
Array with 256 doubles
encode	22,082	4,282	76,975	5,328	5,436
decode	24,127	34,349	29,059	14,174	13,822
Array with 256 UTF-8 strings
encode	3,557	2,528	24,300	3,061	2,068
decode	2,030	2,490	931	406	358
Array with 256 strings
encode	39,041	31,769	76,403	16,615	16,910
decode	25,185	24,287	34,437	32,388	27,999
Medium complex object
encode	10,382	11,427	32,995	3,959	5,275
decode	9,785	9,796	11,515	5,898	7,200
Array with 256 True values
encode	114,341	101,039	344,256	62,382	72,872
decode	149,367	151,615	181,123	114,597	130,392
Array with 256 dict{string, int} pairs
encode	13,715	14,420	51,942	3,271	6,584
decode	12,670	11,788	12,176	6,743	8,278
Dict with 256 arrays with 256 dict{string, int} pairs
encode	50	54	216	10	23
decode	32	32	30	20	23
Dict with 256 arrays with 256 dict{string, int} pairs, outputting sorted keys
encode	46	41		8	24
Complex object
encode	533	582		408	431
decode	466	454		154	164

Build options

For those with particular needs, such as Linux distribution packagers, several build options are provided in the form of environment variables.

Debugging symbols

UJSON_BUILD_NO_STRIP

By default, debugging symbols are stripped on Linux platforms. Setting this environment variable with a value of 1 or True disables this behavior.

Using an external or system copy of the double-conversion library

These two environment variables are typically used together, something like:

export UJSON_BUILD_DC_INCLUDES='/usr/include/double-conversion'
export UJSON_BUILD_DC_LIBS='-ldouble-conversion'

Users planning to link against an external shared library should be aware of the ABI-compatibility requirements this introduces when upgrading system libraries or copying compiled wheels to other machines.

UJSON_BUILD_DC_INCLUDES

One or more directories, delimited by os.pathsep (same as the PATH environment variable), in which to look for double-conversion header files; the default is to use the bundled copy.

UJSON_BUILD_DC_LIBS

Compiler flags needed to link the double-conversion library; the default is to use the bundled copy.