""" Compare passing a dict to passing a dict as kwargs to a stupid transformation Last results (1 mill calls): j1 1.5026444319955772 k1 1.8377482700016117 j2 1.1962292949901894 k2 1.5545833489886718 j3 1.0014333260041894 k3 1.353256585993222 """ import json import timeit def j1(d): return {"prepend": "foo", **d, "append": "bar"} def k1(**d): return {"prepend": "foo", **d, "append": "bar"} def j2(d): return {**d} def k2(**d): return {**d} def j3(d): return None def k3(**d): return None if __name__ == "__main__": import timeit with open("person.json") as f: json_data = json.load(f) for i in 1, 2, 3: print( "j{}".format(i), timeit.timeit("j{}({!r})".format(i, json_data), setup="from __main__ import j{}".format(i)) ) print( "k{}".format(i), timeit.timeit("k{}(**{!r})".format(i, json_data), setup="from __main__ import k{}".format(i)), )