python - Finding the nth smallest number in a list?

Question

i need a efficient way of getting the nth smallest number AND its index in a list containing up to 15000 enties (so speed is not super crucial).

I sadly can't use numpy or any other non-standard library.

Im using Python 2.7

Answer 1

use heapq.nsmallest (and enumerate to get the index):

nums = [random.randint(1,1000000) for _ in range(10000)]

import heapq
import operator

heapq.nsmallest(10,enumerate(nums),key=operator.itemgetter(1))
Out[26]: 
[(5544, 35),
 (1702, 43),
 (6547, 227),
 (1540, 253),
 (4919, 360),
 (7993, 445),
 (1608, 495),
 (5832, 505),
 (1388, 716),
 (5103, 814)]