json_vs_ujson_bench.py

import json
import time
import ujson

NUM_OBJ_KEYS = 1000
NUM_RUNS = 1000000

obj = {}
for i in range(NUM_OBJ_KEYS):
    obj[i] = 'foo'

if __name__ == "__main__":
    for json_module in (json, ujson):
        serialized_obj = getattr(json_module, 'dumps')(obj)
        times = []
        num_runs = NUM_RUNS
        for operation in ('dumps', 'loads'):
            print('# keys in object: {}. Runs: {}. json_module: {}. '
                  'Operation: {}'.format(NUM_OBJ_KEYS,
                                          NUM_RUNS,
                                          json_module.__name__,
                                          operation))

            for i in range(num_runs):
                t1 = time.time()
                if operation == 'loads':
                    operand = serialized_obj
                else:
                    operand = obj

                getattr(json_module, operation)(operand)
                times.append(time.time() - t1)

            avg = sum(times)/len(times)
            print('average time:', avg)

Run on MB Pro Yosemite, 2.8 GHz Intel Core i7, 16GB RAM:

Dict with 10 keys, 1MM runs of each operation:
dumps: ujson took ~39% of the time of json
loads: ujson took ~38% of the time of json

Dict with 1000 keys, 1MM runs of each operation:
dumps: ujson took ~77% of the time of json
loads: ujson took 70% of the time of json