jsonyx

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.

The documentation for jsonyx is available online at: https://jsonyx.readthedocs.io

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 (specified in the documentation):

  {
      /* 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	207.83 μs
Dict with 256 lists of 256 dicts with 1 int	9.87x	8.72x	1.24x	1.00x	2295.24 μs

decode	json	jsonyx	msgspec	orjson	simdjson	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