Technology for ponies

Mar 18, 2015

Python JSON modules benchmark

We are currently working on a project that loads and dumps very big JSON objects. We recently had some slowness issues and though giving a try to some C compiled JSON modules could give a boost to our API.

After some googling we found out a few exsting modules and decided to setup a benchmark to decide which one to use. The selected modules are:

We wrote a little code snippet to automate our benchmark. It is using the timeit standard module.

from timeit import timeit

modules = ['json', 'cjson', 'jsonlib', 'simplejson', 'ujson', 'yajl']

for module in modules:
        loads = "loads"
        dumps = "dumps"
        if module == "cjson":
                loads = "decode"
                dumps = "encode"

        print "[%s]" % module
        load_time = timeit("obj = json.%s(data)" % loads, setup="import %s as json; data = open('file.json').read()" % module, number=NUMBER)
        dump_time = timeit("json.%s(obj)" % dumps, setup="import %s as json; obj = json.%s(open('file.json').read())" % (module, loads), number=NUMBER)

        print "Load time: ", load_time
        print "Dump time: ", dump_time


  • The file.json is 15Mb.
  • cjson is not a drop-in replacement of the standard json module. We have to patch the loads and dumps functions.
  • Loading and dumping are done 20 times for a better accuracy

And the winners are:

Load time:  12.7440698147
Dump time:  6.37574481964
Load time:  6.24644708633
Dump time:  11.6356570721
Load time:  13.1087989807
Dump time:  15.4686369896
Load time:  4.67061305046
Dump time:  6.65470814705
Load time:  5.84970593452
Dump time:  5.00060105324
Load time:  6.7509560585
Dump time:  16.4374480247

simplejson for loading and ujson for dumping. Choose one or the other depending if your program is more loading or dumping data.