ultrajson/README.md

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 5.15.0-1037-azure x86_64 #44-Ubuntu SMP Thu Apr 20 13:19:31 UTC 2023

Versions

• CPython 3.11.3 (main, Apr 6 2023, 07:55:46) [GCC 11.3.0]
• ujson : 1.36.dev558
• orjson : 3.9.0
• simplejson : 3.19.1
• json : 2.0.9

	ujson	orjson	simplejson	json
Array with 256 doubles
encode	16,268	67,856	4,113	4,144
decode	20,055	72,031	10,059	10,158
Array with 256 UTF-8 strings
encode	2,468	24,117	2,337	2,437
decode	2,472	2,860	364	1,393
Array with 256 strings
encode	37,144	110,032	15,895	18,304
decode	25,211	59,879	32,200	32,933
Medium complex object
encode	6,501	38,501	3,025	4,415
decode	9,518	18,114	5,901	7,286
Array with 256 True values
encode	83,830	324,140	65,395	66,498
decode	162,760	281,594	118,120	125,927
Array with 256 dict{string, int} pairs
encode	9,265	58,508	2,295	5,504
decode	12,911	20,799	7,110	9,592
Dict with 256 arrays with 256 dict{string, int} pairs
encode	35	232	7	19
decode	31	34	18	22
Dict with 256 arrays with 256 dict{string, int} pairs, outputting sorted keys
encode	27		6	20
Complex object
encode	448		341	396
decode	468	591	162	266

Above metrics are in call/sec, larger is better.

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.