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Python wrapper around rapidjson

Project description

Authors:Ken Robbins <>; Lele Gaifax <>
License:MIT License
Status: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


The --recursive option is needed because we use a submodule to include RapidJSON sources. Alternatively you can do a plain clone immediately followed by a git submodule update --init.

Alternatively, if you already have (a compatible version of) RapidJSON includes around, you can compile the module specifying their location with the option --rj-include-dir, for example:

$ python3 build --rj-include-dir=/usr/include/rapidjson

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.


Here are things in the standard json library supports that we have decided not to support:

separators argument
This is mostly used for pretty printing and not supported by RapidJSON so it isn’t a high priority. We do support indent kwarg that would get you nice looking JSON anyways.
Coercing keys when dumping
json will stringify a True dictionary key as "true" if you dump it out but when you load it back in it’ll still be a string. We want the dump and load to return the exact same objects so we have decided not to do this coercion.
Arbitrary encodings
json.loads() accepts an encoding kwarg determining the encoding of its input, when that is a bytes or bytearray instance. Although RapidJSON is able to cope with several different encodings, we currently support only the recommended one, UTF-8.


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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