pastebin - collaborative debugging

import random


def ShuffleBag(items, seed=None):
    """Create a new shuffled bag using the elements in items.

    Items can be a dict of (item : frequency) pairs, or an iterable.
    """
    try:
        items = sum(([item] * freq for (item, freq) in items.items()), [])
    except AttributeError:
        items = list(items)
    random.seed(seed)
    while True:
        n = len(items)
        for i in range(n):
            grab = random.randint(i, n-1)
            items[i], items[grab] = items[grab], items[i]
            yield items[i]


sb = ShuffleBag([1, 2, 2, 2])
print sb.next() # 1 - 25%, 2 - 75%

sb = ShuffleBag({1:1, 2:3})
print sb.next() #1 - 25%, 2 - 75%