# [Numpy-discussion] is there an efficient way to get a random set of subsets/combinations?

Val Kalatsky kalatsky@gmail....
Tue Feb 21 00:57:11 CST 2012

```Hi Slava,

Since your k is only 10, here is a quickie:

import numpy as np
arr = np.arange(n)
for i in range(k):
np.random.shuffle(arr)
print np.sort(arr[:p])

If your ever get non-unique entries in a set of k=10 for your n and p,
consider yourself lucky:)
Val

On Mon, Feb 20, 2012 at 10:35 PM, Yaroslav Halchenko
<lists@onerussian.com>wrote:

> Hi to all Numeric  Python experts,
>
> could not think of a mailing list with better fit to my question which
> might
>
> straightforward (naive) Python code to answer my question would be
> something like
>
> import random, itertools
> n,p,k=100,50,10  # don't try to run with this numbers! ;)
> print random.sample(list(itertools.combinations(range(n), p)), k)
>
> so the goal is to get k (non-repeating) p-subsets of n, where n and p
> prohibitively large to first populate the full set of combinations.
>
> Thank you in advance ;-)
> --
> =------------------------------------------------------------------=
> Keep in touch                                     www.onerussian.com
> Yaroslav Halchenko                 www.ohloh.net/accounts/yarikoptic
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