random.sample with large weighted sample-sets?

Terry Reedy tjreedy at udel.edu
Sun Feb 16 10:12:22 CET 2014


On 2/15/2014 11:41 PM, Tim Chase wrote:
> I'm not coming up with the right keywords to find what I'm hunting.
> I'd like to randomly sample a modestly compact list with weighted
> distributions, so I might have
>
>    data = (
>      ("apple", 20),
>      ("orange", 50),
>      ("grape", 30),
>      )

If you actually start with date in this form, write the few lines needed 
to produce the form below.

import bisect
import random

data = [
   (0, 'apple'),
   (20, 'orange'),
   (70, 'grape'),
]

for i in range(10):
     r = random.randrange(0, 100)
     i = bisect.bisect(data, (r, 'zzzzz')) - 1
     print(data[i][1])
 >>>
apple
orange
orange
grape
orange
apple
grape
orange
grape
orange

It is just coincidence that the sample has exactly the expected 
distribution.

-- 
Terry Jan Reedy




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