Create a new population with a weighted list of parents

exact-weight-random-population.py

scores = [(0.4, "a"), (0.5, "b"), (0.1, "c")]

# Calculate the sum of all scores.
# 
# Will probably be 1 since the bots are scored with a percentage,
# but just in case...
denominator = 0
for score in scores:
    denominator += score[0]

new_population = []
POPULATION_SIZE = 100
for i in range(POPULATION_SIZE):
    rand_num = random.random() * denominator
    # Loop through the scores, seeing which score the random number
    # "landed" on.
    #
    # This could be made (algorithmically) faster by changing the
    # scores into a cumulative value, and then doing a binary search
    # on it, but I doubt speed will be an issue here.
    for score in scores:
        if score[0] > rand_num:
            new_population.append(score[1])
            break
         rand_num -= score[0]