Shuffling an iterator with itertools vs. random.shuffle().

shuffle.py

import itertools as it
import random
import timeit


def shuffle(deck):
    """Return iterator over shuffled deck."""
    deck = list(deck)
    random.shuffle(deck)
    return iter(tuple(deck))


def ishuffle(iterable, n):
    """Return shuffled iterator of an `iterable` with length `n`."""
    pool = iter(iterable)
    for i in range(1, n+1):
        randn = random.randint(0, n-i)
        left, right = it.tee(pool, 2)
        right = it.islice(right, randn, None)
        yield next(right)
        pool = it.chain(it.islice(left, randn), right)


def test_shuffle():
    for _ in shuffle(range(100)):
        pass


print(timeit.timeit('test_shuffle()',
                    setup='from __main__ import test_shuffle',
                    number=10000))

# Output: 1.0292874510050751


def test_ishuffle():
    for _ in ishuffle(range(100), 100):
        pass


print(timeit.timeit('test_ishuffle()',
                    setup='from __main__ import test_ishuffle',
                    number=10000))

# Output: 5.076113043993246