Python JSON module benchmark (3.x)

bench.py

from random import randint, random, choice, uniform, seed
from string import ascii_letters
from timeit import repeat
import json

def rand_string():
    return ''.join(choice(ascii_letters) for _ in range(randint(3, 24)))

def make_test_data(depth=0):
    if random() > 1 - (depth / 9)**3:
        if random() > 0.75:
            return rand_string()
        else:
            return round(uniform(-1e6, 1e6), 4)
    else:
        seq = range(randint(3, 7))
        if randint(0, 1):
            return [make_test_data(depth + 1) for _ in seq]
        else:
            return {rand_string(): make_test_data(depth + 1) for _ in seq}

seed(0xfeedbeef)
data = make_test_data()
data_json = json.dumps(data)
data_len = len(data_json)
prep = 'import json, io; from __main__ import data, data_json; outfile = io.StringIO(); infile = io.StringIO(data_json)'
tests = 'json.dump(data, outfile)', 'outfile.write(json.dumps(data))', 'json.load(infile)', 'json.loads(infile.read())'

for time, test in sorted((min(repeat(test, prep, repeat=5, number=1)), test) for test in tests):
    print('{:40} {:7.3f} MB/s'.format(test, data_len / 1024**2 / time))

output.txt

json.loads(infile.read())                 42.335 MB/s
json.load(infile)                         42.240 MB/s
outfile.write(json.dumps(data))           23.574 MB/s
json.dump(data, outfile)                   5.196 MB/s