Roulette_wheel_select base on Python

Roulette_wheel_select.py

def roulette_wheel_select(groups):
    """
    Groups should format in list:
    (weigth (positive), content)
    More weight more chance that we pick this content
    BUT not every time

    i.e.

    [(1, '1'),
     (2, '2')]
    """
    total_p = reduce(lambda s, x: s+x,
                     [x[0] for x in groups])

    assert total_p > 0, "Total percent %d <= 0" % total_p

    seed = random.uniform(0, total_p)
    upto = 0

    for weight, content in groups:

        upto += weight

        if upto >= seed:
            return content

total_p = sum(map(lambda x: x[0], groups))

how about it?