Random Python dictionary key, weighted by values

Question

I have a dictionary where each key has a list of variable length, eg:

d = {
 \'a\': [1, 3, 2],
 \'b\': [6],
 \'c\': [0, 0]
}

Is there a cle

Answer 1

Given that your dict fits in memory, the random.choice method should be reasonable. But assuming otherwise, the next technique is to use a list of increasing weights, and use bisect to find a randomly chosen weight.

>>> import random, bisect
>>> items, total = [], 0
>>> for key, value in d.items():
        total += len(value)
        items.append((total, key))


>>> items[bisect.bisect_left(items, (random.randint(1, total),))][1]
'a'
>>> items[bisect.bisect_left(items, (random.randint(1, total),))][1]
'c'