Welcome to jsonyx’s Documentation!

jsonyx is a customizable JSON library for Python 3.8+. It is written in pure Python with an optional C extension for better performance and no dependencies.

Key Features

  • JSON decoding, encoding and patching

  • Pretty-printing:

    {
    "foo": [1, 2, 3],
    "bar": {"a": 1, "b": 2, "c": 3}
}

  • Optionally supports these JSON deviations (according to this specification):

    {
    /* Block */ // and line comments
    "Missing commas": [1 2 3],
    "NaN and infinity": [NaN, Infinity, -Infinity],
    "Surrogates": "\ud800",
    "Trailing comma": [0,],
    "Unquoted keys": {key: "value"}
}

  • Detailed error messages:

    Traceback (most recent call last):
  File "/Users/wannes/Downloads/broken.json", line 1, column 99-381
    ...sList": {"GlossEntry": {"ID": "SGM..."GML", "XML"]}, "GlossSee": "markup"
                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
jsonyx.JSONSyntaxError: Unterminated object

  • Dedicated functions for reading and writing files and pretty printing

Benchmark (Apr 30, 2025)

We recommend to use orjson, msgspec or pysimdjson for performance critical applications:

encode

json

jsonyx

msgspec

orjson

fastest time

List of 256 booleans

4.62x

4.17x

1.06x

1.00x

1.82 μs

List of 256 ASCII strings

14.09x

8.10x

1.66x

1.00x

3.66 μs

List of 256 floats

25.20x

25.18x

1.33x

1.00x

8.07 μs

List of 256 dicts with 1 int

11.24x

9.89x

1.34x

1.00x

7.87 μs

Medium complex object

10.21x

8.85x

1.17x

1.00x

13.87 μs

List of 256 strings

26.46x

15.18x

2.23x

1.00x

13.37 μs

Complex object

7.86x

7.41x

1.00x

DNF [1]

207.83 μs

Dict with 256 lists of 256 dicts with 1 int

9.87x

8.72x

1.24x

1.00x

2295.24 μs

encode

json

jsonyx

msgspec

orjson

fastest time

List of 256 booleans

4.57x

3.99x

1.00x

1.06x

1.91 μs

List of 256 ASCII strings

10.98x

6.89x

1.38x

1.00x

4.27 μs

List of 256 floats

23.85x

23.59x

1.35x

1.00x

8.04 μs

List of 256 dicts with 1 int

10.75x

9.66x

1.25x

1.00x

8.23 μs

Medium complex object

9.89x

8.93x

1.12x

1.00x

13.77 μs

List of 256 strings

20.65x

11.83x

1.83x

1.00x

16.02 μs

Complex object

7.26x

7.34x

1.00x

DNF [1]

210.00 μs

Dict with 256 lists of 256 dicts with 1 int

9.51x

9.02x

1.22x

1.00x

2381.95 μs

encode

json

jsonyx

msgspec

orjson

fastest time

List of 256 booleans

6.14x

3.71x

1.00x

1.01x

1.90 μs

List of 256 ASCII strings

15.50x

8.85x

1.61x

1.00x

3.56 μs

List of 256 floats

23.09x

22.28x

1.26x

1.00x

8.04 μs

List of 256 dicts with 1 int

14.50x

9.35x

1.36x

1.00x

7.75 μs

Medium complex object

11.33x

8.35x

1.15x

1.00x

13.35 μs

List of 256 strings

22.60x

11.32x

2.24x

1.00x

15.51 μs

Complex object

8.25x

6.92x

1.00x

DNF [1]

209.85 μs

Dict with 256 lists of 256 dicts with 1 int

13.66x

7.91x

1.23x

1.00x

2364.31 μs

encode

json

jsonyx

msgspec

orjson

fastest time

List of 256 booleans

6.26x

4.12x

1.00x

1.03x

1.88 μs

List of 256 ASCII strings

11.68x

8.62x

1.46x

1.00x

4.06 μs

List of 256 floats

22.07x

22.12x

1.25x

1.00x

8.22 μs

List of 256 dicts with 1 int

13.21x

8.93x

1.32x

1.00x

8.23 μs

Medium complex object

10.62x

8.20x

1.18x

1.00x

13.99 μs

List of 256 strings

24.94x

13.48x

2.09x

1.00x

14.21 μs

Complex object

8.12x

6.90x

1.00x

DNF [1]

215.91 μs

Dict with 256 lists of 256 dicts with 1 int

12.15x

8.06x

1.18x

1.00x

2585.56 μs

encode

json

jsonyx

msgspec

orjson

fastest time

List of 256 booleans

7.51x

4.63x

1.01x

1.00x

1.67 μs

List of 256 ASCII strings

11.36x

8.94x

1.53x

1.00x

3.76 μs

List of 256 floats

23.27x

22.77x

1.35x

1.00x

8.03 μs

List of 256 dicts with 1 int

13.68x

8.89x

1.26x

1.00x

8.06 μs

Medium complex object

10.91x

8.41x

1.08x

1.00x

13.98 μs

List of 256 strings

21.19x

11.98x

2.13x

1.00x

15.38 μs

Complex object

7.60x

7.02x

1.00x

DNF [1]

210.12 μs

Dict with 256 lists of 256 dicts with 1 int

12.34x

7.56x

1.16x

1.00x

2519.36 μs

decode

json

jsonyx

msgspec

orjson

simdjson [2]

fastest time

List of 256 booleans

4.70x

5.22x

2.92x

1.41x

1.00x

1.45 μs

List of 256 ASCII strings

9.04x

7.05x

4.85x

4.43x

1.00x

3.15 μs

List of 256 floats

10.91x

11.22x

2.24x

1.73x

1.00x

6.14 μs

List of 256 dicts with 1 int

12.99x

11.65x

7.35x

5.30x

1.00x

6.11 μs

Medium complex object

13.41x

12.94x

5.44x

4.67x

1.00x

7.65 μs

List of 256 strings

6.85x

3.75x

9.56x

7.85x

1.00x

16.78 μs

Complex object

9.36x

7.63x

8.55x

7.67x

1.00x

136.11 μs

Dict with 256 lists of 256 dicts with 1 int

19.03x

15.62x

11.58x

9.87x

1.00x

1640.77 μs

decode

json

jsonyx

msgspec

orjson

simdjson [2]

fastest time

List of 256 booleans

4.25x

4.76x

2.64x

1.26x

1.00x

1.57 μs

List of 256 ASCII strings

7.44x

7.04x

4.98x

4.57x

1.00x

2.91 μs

List of 256 floats

10.41x

10.29x

2.02x

1.52x

1.00x

6.66 μs

List of 256 dicts with 1 int

12.29x

11.26x

7.19x

5.24x

1.00x

6.02 μs

Medium complex object

12.12x

11.74x

4.84x

4.09x

1.00x

8.00 μs

List of 256 strings

5.36x

3.59x

9.36x

7.26x

1.00x

17.53 μs

Complex object

8.70x

7.38x

8.43x

7.65x

1.00x

136.18 μs

Dict with 256 lists of 256 dicts with 1 int

17.61x

15.44x

11.45x

9.84x

1.00x

1647.79 μs

decode

json

jsonyx

msgspec

orjson

simdjson [2]

fastest time

List of 256 booleans

4.77x

5.19x

3.00x

1.57x

1.00x

1.46 μs

List of 256 ASCII strings

7.55x

8.52x

4.69x

4.49x

1.00x

2.83 μs

List of 256 floats

10.08x

10.95x

2.22x

1.70x

1.00x

5.94 μs

List of 256 dicts with 1 int

10.83x

10.31x

6.27x

4.52x

1.00x

6.17 μs

Medium complex object

11.92x

11.56x

4.91x

3.92x

1.00x

7.90 μs

List of 256 strings

4.04x

2.87x

7.65x

5.58x

1.00x

21.49 μs

Complex object

9.10x

7.38x

8.51x

7.84x

1.00x

128.91 μs

Dict with 256 lists of 256 dicts with 1 int

17.45x

15.26x

11.81x

9.74x

1.00x

1602.67 μs

decode

json

jsonyx

msgspec

orjson

simdjson [2]

fastest time

List of 256 booleans

4.46x

5.23x

3.30x

1.59x

1.00x

1.39 μs

List of 256 ASCII strings

9.39x

5.60x

4.33x

4.05x

1.00x

3.30 μs

List of 256 floats

9.68x

9.14x

2.14x

1.63x

1.00x

6.14 μs

List of 256 dicts with 1 int

10.25x

9.64x

6.93x

5.62x

1.00x

7.03 μs

Medium complex object

13.11x

10.90x

4.80x

4.00x

1.00x

8.19 μs

List of 256 strings

4.77x

3.20x

7.17x

6.34x

1.00x

19.28 μs

Complex object

8.16x

8.01x

8.57x

7.70x

1.00x

131.47 μs

Dict with 256 lists of 256 dicts with 1 int

17.06x

15.47x

12.44x

10.46x

1.00x

1643.52 μs

decode

json

jsonyx

msgspec

orjson

simdjson [2]

fastest time

List of 256 booleans

3.95x

4.71x

2.33x

1.41x

1.00x

1.55 μs

List of 256 ASCII strings

10.23x

7.18x

4.42x

4.29x

1.00x

2.94 μs

List of 256 floats

8.53x

7.72x

1.75x

1.23x

1.00x

7.14 μs

List of 256 dicts with 1 int

11.40x

10.61x

6.14x

4.26x

1.00x

6.23 μs

Medium complex object

11.20x

11.02x

4.34x

3.84x

1.00x

8.20 μs

List of 256 strings

10.64x

4.34x

10.13x

8.59x

1.00x

17.99 μs

Complex object

8.86x

7.89x

9.05x

7.80x

1.00x

133.17 μs

Dict with 256 lists of 256 dicts with 1 int

18.23x

16.57x

13.60x

12.13x

1.00x

1662.84 μs

Warning

The Python version of jsonyx is up to 8.03x slower for encoding and up to 46.71x slower for decoding, so make sure you have a C compiler installed on Windows.

Check out the Getting Started section for further information, including how to install the project.

Footnotes