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Python wrapper around rapidjson

Project description


Ken Robbins <>

Lele Gaifax <>


MIT License

Build status Documentation status

RapidJSON is an extremely fast C++ JSON parser and serialization library: this module wraps it into a Python 3 extension, exposing its serialization/deserialization (to/from either bytes, str or file-like instances) and JSON Schema validation capabilities.

Latest version documentation is automatically rendered by Read the Docs.

Getting Started

First install python-rapidjson:

$ pip install python-rapidjson

or, if you prefer Conda:

$ conda install -c conda-forge python-rapidjson

Basic usage looks like this:

>>> import rapidjson
>>> data = {'foo': 100, 'bar': 'baz'}
>>> rapidjson.dumps(data)
>>> rapidjson.loads('{"bar":"baz","foo":100}')
{'bar': 'baz', 'foo': 100}
>>> class Stream:
...   def write(self, data):
...      print("Chunk:", data)
>>> rapidjson.dump(data, Stream(), chunk_size=5)
Chunk: b'{"foo'
Chunk: b'":100'
Chunk: b',"bar'
Chunk: b'":"ba'
Chunk: b'z"}'


If you want to install the development version (maybe to contribute fixes or enhancements) you may clone the repository:

$ git clone --recursive

A set of makefiles implement most common operations, such as build, check and release; see make help output for a list of available targets.


python-rapidjson tries to be as performant as possible while staying compatible with the json module.

See the this section in the documentation for a comparison with other JSON libraries.


Although we tried to implement an API similar to the standard library json, being a strict drop-in replacement in not our goal and we have decided to depart from there in some aspects. See this section in the documentation for further details.


1.10 (2023-03-15)

1.9 (2022-10-17)

  • Produce Python 3.11 wheels, thanks to cibuildwheel 2.11.1

1.8 (2022-07-07)

1.7 (2022-07-06)

  • Use current master version of rapidjson

  • Update the test suite to work on Pyston, thanks to Kevin Modzelewski (PR #161)

1.6 (2022-02-19)

  • Fix memory leak when using end_array (issue #160)

1.5 (2021-10-16)

  • Fix serialization bug when using DM_UNIX_TIME in a non-C locale context

1.4 (2021-06-25)

  • Build binary wheel for aarch64, thanks to odidev (PR #156)

1.3 (2021-06-25)

  • Yet another attempt to fix automatic wheels upload

1.2 (2021-06-25)

  • Fix automatic wheels upload from GH Actions to PyPI

1.1 (2021-06-25)

  • Reduce decoder memory consumption by uniquifiying keys in the loaded dictionaries

  • Implement an alternative way of transmogrify JSON objects, similar to json‘s object_pairs_hook load option (issue #154)

1.0 (2020-12-13)

  • Require Python 3.6 or greater

  • New serialization options, iterable_mode and mapping_mode, to give some control on how generic iterables and mappings get encoded (fix issue #149 and issue #150)

  • Internal refactorings, folding “skipkeys” and “sort_keys” arguments into the mapping_mode options, respectively as MM_SKIP_NON_STRING_KEYS and MM_SORT_KEYS: “old” arguments kept for backward compatibility

  • Bump major version to 1, tag as “production/stable” and switch to a simpler X.Y versioning schema

0.9.4 (2020-11-16)

  • Fix memory leak loading an invalid JSON (issue #148)

0.9.3 (2020-10-24)

  • Fix access to Encoder instance attributes (issue #147)

0.9.2 (2020-10-24)

  • Use current master version of rapidjson

  • Enable GH Actions-based test workflow, thanks to Martin Thoma (PR #143)

  • Produce Python 3.9 wheels, disable testing under Python < 3.6

  • Make the character used for indentation in pretty mode a parameter (issue #135)

  • Handle wider precision range in timestamps fractional seconds (PR 133), thanks to Karl Seguin

  • Add comparison benchmarks against orjson and hyperjson (issue #130 and PR #131, thanks to Sebastian Pipping)

0.9.1 (2019-11-13)

  • Fix memory leak in case of failed validation (issue #126)

0.9.0 (2019-11-13)

  • Produce Python 3.8 wheels

  • Compatibility fix for Python 3.8 (issue #125)

  • New dump option write_mode, supporting RapidJSON’s kFormatSingleLineArray option (issue #123), thanks to Nguyễn Hồng Quân for the initial implementation (PR #124)

0.8.0 (2019-08-09)

  • New serialization option bytes_mode to control how bytes instances get encoded (issue #122)

0.7.2 (2019-06-09)

  • Hopefully fix the memory leak when loading from a stream (issue #117)

0.7.1 (2019-05-11)

  • Raise a more specific exception on loading errors, JSONDecodeError, instead of generic ValueError (issue #118)

  • Fix optimization path when using OrderedDicts (issue #119)

  • Fix serialization of IntEnums (issue #121)

  • I spent quite a lot of time investigating on the memory leak when loading from a stream (issue #117): as I was not able to fully replicate the problem, I cannot be sure I solved the problem… sorry!

0.7.0 (2019-02-11)

  • Raise correct exception in code samples (PR #109), thanks to Thomas Dähling

  • Fix compilation with system-wide install of rapidjson (issue #110)

  • Use current master version of rapidjson, that includes a fix for its issue #1368 and issue #1336, and cures several compilation warnings as well (issue #112 and issue #107)

  • Fix memory leak when using object_hook (issue #115)

0.6.3 (2018-07-11)

  • No visible changes, but now PyPI carries binary wheels for Python 3.7.

0.6.2 (2018-06-08)

  • Use a more specific ValidationError, to differentiate from invalid JSON

0.6.1 (2018-06-06)

  • Nothing new, attempt to build Python 3.6 binary wheels on Travis CI

0.6.0 (2018-06-06)

  • Add a new comparison table involving ensure_ascii (issue #98)

  • Use Python’s repr() to emit float values instead of rapidjson’s dtoa() (issue #101)

  • Use a newer (although unreleased) version of rapidjson to fix an issue with JSONSchema validation (PR #103), thanks to Anthony Miyaguchi

0.5.2 (2018-03-31)

  • Tiny tweak to restore macOS build on Travis CI

0.5.1 (2018-03-31)

  • Minor tweaks to CI and PyPI deploy configuration

0.5.0 (2018-03-31)

  • New RawJSON class, allowing inclusion of pre-serialized content (PR #95 and PR #96), thanks to Silvio Tomatis

0.4.3 (2018-01-14)

  • Deserialize from bytes and bytearray instances, ensuring they contain valid UTF-8 data

  • Speed up parsing of floating point numbers, avoiding intermediary conversion to a Python string (PR #94)

0.4.2 (2018-01-09)

  • Fix precision handling of DM_UNIX_TIME timestamps

0.4.1 (2018-01-08)

  • Fix memory leaks in Decoder() and Encoder() classes, related to bad handling of PyObject_GetAttr() result value

  • Fix compatibility with Python 3.7a

0.4.0 (2018-01-05)

  • Implemented the streaming interface, see load() and dump() (issue #80)

    Backward incompatibility: now the flags arguments on all the functions are keyword only, to mimic stdlib’s json style

0.3.2 (2017-12-21)

0.3.1 (2017-12-20)

  • Fix Travis CI recipe to accomodate MacOS

0.3.0 (2017-12-20)

  • Fix compilation on MacOS (issue #78)

  • Handle generic iterables (PR #89)

    Backward incompatibility: the dumps() function and the Encoder() constructor used to accept a max_recursion_depth argument, to control the maximum allowed nesting of Python structures; since the underlying function is now effectively recursive, it has been replaced by the generic sys.setrecursionlimit() mechanism

0.2.7 (2017-12-08)

  • Restore compatibility with Python < 3.6

0.2.6 (2017-12-08)

  • Fix memory leaks when using object_hook/start_object/end_object

0.2.5 (2017-09-30)

  • Fix bug where error handling code could raise an exception causing a confusing exception to be returned (PR #82)

  • Fix bug where loads’s object_hook and dumps’s default arguments could not be passed None explicitly (PR #83)

  • Fix crash when dealing with surrogate pairs (issue #81)

0.2.4 (2017-09-17)

  • Fix compatibility with MacOS/clang

0.2.3 (2017-08-24)

  • Limit the precision of DM_UNIX_TIME timestamps to six decimal digits

0.2.2 (2017-08-24)

  • Nothing new, attempt to fix production of Python 3.6 binary wheels

0.2.1 (2017-08-24)

  • Nothing new, attempt to fix production of Python 3.6 binary wheels

0.2.0 (2017-08-24)

  • New parse_mode option, implementing relaxed JSON syntax (issue #73)

  • New Encoder and Decoder, implementing a class-based interface

  • New Validator, exposing the underlying JSON schema validation (issue #71)

0.1.0 (2017-08-16)

  • Remove beta status

0.1.0b4 (2017-08-14)

  • Make execution of the test suite on Appveyor actually happen

0.1.0b3 (2017-08-12)

  • Exclude CI configurations from the source distribution

0.1.0b2 (2017-08-12)

  • Fix Powershell wheel upload script in appveyor configuration

0.1.0b1 (2017-08-12)

  • Compilable with somewhat old g++ (issue #69)

  • Backward incompatibilities:

    • all DATETIME_MODE_XXX constants have been shortened to DM_XXX DATETIME_MODE_ISO8601_UTC has been renamed to DM_SHIFT_TO_UTC

    • all UUID_MODE_XXX constants have been shortened to UM_XXX

  • New option DM_UNIX_TIME to serialize date, datetime and time values as UNIX timestamps targeting issue #61

  • New option DM_NAIVE_IS_UTC to treat naïve datetime and time values as if they were in the UTC timezone (also for issue #61)

  • New keyword argument number_mode to use underlying C library numbers

  • Binary wheels for GNU/Linux and Windows on PyPI (one would hope: this is the reason for the beta1 release)

0.0.11 (2017-03-05)

  • Fix a couple of refcount handling glitches, hopefully targeting issue #48.

0.0.10 (2017-03-02)

  • Fix source distribution to contain all required stuff (PR #64)

0.0.9 (2017-03-02)

0.0.8 (2016-12-09)

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