itemgetter_vs_lambda.py

import timeit
import operator

def time_func(f, N, k=3):
    """Basic version of IPython's %timeit magic"""
    t = min(timeit.timeit(f, number=N) for _ in range(k))

    t_per = t / N
    if t_per < 1e-6:
        units = 'ns'
        t_per *= 1e9
    elif t_per < 1e-3:
        units = 'µs'
        t_per *= 1e6
    else:
        units = 'ms'
        t_per *= 1e3

    print(f'{N} loops, best of {k}: {t_per:0.4} {units}')


def xform_by_getter(l, getter):
    return [getter(k) for k in l]

ig = operator.itemgetter(0)
igl = lambda x: x[0]

l = [(i,) * 5 for i in range(1000)]

time_func(lambda: xform_by_getter(l, ig), 5000)
# 5000 loops, best of 3: 110.3 µs

time_func(lambda: xform_by_getter(l, igl), 5000)
# 5000 loops, best of 3: 129.1 µs


class ArbGet:
    def __getitem__(self, idx):
        return idx * 9

la = [ArbGet() for _ in range(1000)]

time_func(lambda: xform_by_getter(la, ig), 5000)
# 5000 loops, best of 3: 307.3 µs

time_func(lambda: xform_by_getter(la, igl), 5000)
# 5000 loops, best of 3: 326.7 µs