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UltraJSON is an ultra fast JSON encoder and decoder written in pure C with bindings for Python 2.5+ and 3.

For a more painless day to day C/C++ JSON decoder experience please checkout ujson4c, based on UltraJSON.

Please checkout the rest of the projects in the Ultra series:

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"'

double_precision

Controls how many decimals to encode for double or decimal values. Default is 9:

>>> ujson.dumps(math.pi)
'3.1415926536'
>>> ujson.dumps(math.pi, double_precision=1)
'3.1'
>>> ujson.dumps(math.pi, double_precision=0)
'3'
>>> ujson.dumps(math.pi, double_precision=4)
'3.1416'

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"
}

Decoders options

precise_float

Set to enable usage of higher precision (strtod) function when decoding string to double values. Default is to use fast but less precise builtin functionality:

>>> ujson.loads("4.56")
4.5600000000000005
>>> ujson.loads("4.56", precise_float=True)
4.5599999999999996

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

Metadata

Release files for ujson 1.35

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