Artem Krylysov


Benchmark of Python JSON libraries

This post was updated on 2016/08/13: added python-rapidjson; updated simplejson and ujson.

A couple of weeks ago after spending some time with Python profiler, I discovered that Python’s json module is not as fast as I expected. I decided to benchmark alternative JSON libraries.

Libraries

python-cjson, yajl-py and jsonlib are not included in the benchmark, they are not in active development and don’t support Python 3.

simplejson and ujson may be used as a drop-in replacement for the standard json module, but ujson doesn’t support advanced features like hooks, custom encoders and decoders.

You can change your imports this way to use an alternative library:

import ujson as json

Interpreters

  • Python (CPython) 2.7.12

  • Python (CPython) 3.5.2

  • PyPy 5.3.0

Note

ujson is not compatible with PyPy; python-rapidjson is compatible only with Python 3.

Methodology

The tests were performed on MacBook Pro Late 2013 (2.6 GHz Intel Core i5, 8 GB 1600 MHz DDR3, Mac OS 10.11.6). Every test runs 100 times.

Test data

File name

File size

Description

twitter.json

632 KB

Single large JSON (source)

one-json-per-line.jsons.txt

176 KB

Collection of 1000 JSON objects (source)

I published the source code of the benchmark on GitHub. You can clone it and rerun if you want to check it by yourself or if a new version of an alternative JSON library is released.

Results

Python 2.7

json

simplejson

ujson

loads (large obj)

1.140

0.441

0.448

dumps (large obj)

0.564

0.630

0.459

loads (small objs)

1.190

0.579

0.195

dumps (small objs)

0.910

1.641

0.304

Python 3.5

json

simplejson

ujson

rapidjson

loads (large obj)

0.600

0.698

0.605

0.634

dumps (large obj)

0.673

0.629

0.381

0.365

loads (small objs)

0.801

1.091

0.322

0.531

dumps (small objs)

1.213

2.038

0.285

0.234

PyPy 5.3

json

simplejson

loads (large obj)

0.545

1.876

dumps (large obj)

0.632

3.974

loads (small objs)

0.271

1.651

dumps (small objs)

0.719

2.404

Note

Results are in seconds.

Conclusion

The numbers speak for themselves. If your application is dealing with a big amount of JSON data and doesn't use any advanced features of built-in json module, you should probably consider switching to ujson.

I'm not a native English speaker and I'm trying to improve my language skills. Feel free to correct me if you spot any spelling or grammatical error!