from random import random

class WeightedChoice(object):
    def __init__(self, weights):
        """Pick items with weighted probabilities.

            weights
                a sequence of tuples of item and it's weight.
        """
        self._total_weight = 0.
        self._item_levels = []
        for item, weight in weights:
            self._total_weight += weight
            self._item_levels.append((self._total_weight, item))

    def pick(self):
        pick = self._total_weight * random()
        for level, item in self._item_levels:
            if level >= pick:
                return item

import csv

weighed_items = [(item,float(weight)) for item,weight in csv.reader(open('file.csv'))]
picker = WeightedChoice(weighed_items)
print(picker.pick())

lst = [ ('Orange', 0.10), ('Apple', 0.05), ('Mango', 0.15), ('etc', 0.69) ]

x = 0.0
lst2 = []
for fruit, chance in lst:
    tup = (x, fruit)
    lst2.append(tup)
    x += chance

tup = (x, None)
lst2.append(tup)

import random

def pick_one(lst2):
    if lst2[0][1] is None:
        raise ValueError, "no valid values to choose"
    while True:
        r = random.random()
        for x, fruit in reversed(lst2):
            if x <= r:
                if fruit is None:
                    break  # try again with a different random value
                else:
                    return fruit

pick_one(lst2)

def choose(items,chances):
    import random
    p = chances[0]
    x = random.random()
    i = 0
    while x > p :
    	i = i + 1
    	p = p + chances[i]
    return items[i]

lst = [ ('Orange', 0.10), ('Apple', 0.05), ('Mango', 0.15), ('etc', 0.69) ]

x = 0.0
lst2 = []
for fruit, chance in lst:
    low = x
    high = x + chance
    tup = (low, high, fruit)
    lst2.append(tup)
    x += chance

if x > 1.0:
    raise ValueError, "chances add up to more than 100%"

low = x
high = 1.0
tup = (low, high, None)
lst2.append(tup)

import random

def pick_one(lst2):
    if lst2[0][2] is None:
        raise ValueError, "no valid values to choose"
    while True:
        r = random.random()
        for low, high, fruit in lst2:
            if low <= r < high:
                if fruit is None:
                    break  # try again with a different random value
                else:
                    return fruit

pick_one(lst2)


# test it 10,000 times
d = {}
for i in xrange(10000):
    x = pick_one(lst2)
    if x in d:
        d[x] += 1
    else:
        d[x] = 1

import random
d= {'orange': 0.10, 'mango': 0.15, 'apple': 0.05}
weightedArray = []
for k in d:
  weightedArray+=[k]*int(d[k]*100)
random.choice(weightedArray)