use bisect to random get items with weighted probability, the weight field can be specified

weighted_random_choice.py

import random
import collections
import bisect

def weighted_random_choice(candidates, field='weight'):
    '''
    use bisect to random get items with weighted probability, the weight field can be specified
    '''
    prepared_candidates = {}
    total_weight = 0
    for candidate in candidates:
        total_weight+= candidate[field]
        prepared_candidates[total_weight]=candidate
    od = collections.OrderedDict(sorted(prepared_candidates.items(), key=lambda t: t[0]))
    idx = bisect.bisect(od.keys(), random.randint(0, total_weight-1))
    print idx
    return od.values()[idx]

if __name__=='__main__':
    weighted_things = [
        {'weight':18, 'name': 'A', 'event':'Meet a Bomb',},
        {'weight':16, 'name': 'B', 'event':'Meet a beast',},
        {'weight':14, 'name': 'C', 'event':'Meet a love',},
        {'weight':30, 'name': 'D', 'event':'Meet a hate',},
    ]
    for i in range(1, 100):
        print weighted_random_choice(weighted_things)