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 (Mar 31, 2025)

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

encode	json	jsonyx	msgspec	orjson	fastest time
List of 256 booleans	4.56x	5.33x	1.00x	1.06x	1.90 μs
List of 256 ASCII strings	12.12x	13.65x	1.50x	1.00x	3.95 μs
List of 256 floats	23.41x	25.95x	1.30x	1.00x	8.03 μs
List of 256 dicts with 1 int	11.10x	13.61x	1.32x	1.00x	7.75 μs
Medium complex object	10.76x	11.80x	1.16x	1.00x	13.30 μs
List of 256 strings	23.08x	19.66x	2.04x	1.00x	14.42 μs
Complex object	7.36x	7.95x	1.00x	DNF	209.74 μs
Dict with 256 lists of 256 dicts with 1 int	9.23x	11.34x	1.21x	1.00x	2361.90 μs

decode	json	jsonyx	msgspec	orjson	simdjson	fastest time
List of 256 booleans	4.40x	6.26x	2.60x	1.28x	1.00x	1.54 μs
List of 256 ASCII strings	9.08x	12.57x	5.43x	5.03x	1.00x	2.89 μs
List of 256 floats	10.99x	12.47x	2.32x	1.78x	1.00x	6.14 μs
List of 256 dicts with 1 int	12.11x	15.16x	6.87x	5.08x	1.00x	6.17 μs
Medium complex object	12.65x	17.63x	5.26x	4.40x	1.00x	7.62 μs
List of 256 strings	5.68x	4.38x	9.92x	8.00x	1.00x	16.76 μs
Complex object	8.58x	7.54x	8.32x	7.56x	1.00x	136.79 μs
Dict with 256 lists of 256 dicts with 1 int	17.65x	19.13x	12.07x	10.78x	1.00x	1658.37 μs