A weighted version of random.choice

Question

I needed to write a weighted version of random.choice (each element in the list has a different probability for being selected). This is what I came up with:

Answer 1

One way is to randomize on the total of all the weights and then use the values as the limit points for each var. Here is a crude implementation as a generator.

def rand_weighted(weights):
    """
    Generator which uses the weights to generate a
    weighted random values
    """
    sum_weights = sum(weights.values())
    cum_weights = {}
    current_weight = 0
    for key, value in sorted(weights.iteritems()):
        current_weight += value
        cum_weights[key] = current_weight
    while True:
        sel = int(random.uniform(0, 1) * sum_weights)
        for key, value in sorted(cum_weights.iteritems()):
            if sel < value:
                break
        yield key