How to find the index of n largest elements in a list or np.array, Python

Question

Is there a built-in function or a very simple way of finding the index of n largest elements in a list or a numpy array?

K = [1,2,2,4,5,5,6,10]

Answer 1

Consider the following code,

 N=5
 K = [1,10,2,4,5,5,6,2]
 #store list in tmp to retrieve index
 tmp=list(K)
 #sort list so that largest elements are on the far right
 K.sort()
 #To get the 5 largest elements
 print K[-N:]
 #To get the 5th largest element
 print K[-N]
 #get index of the 5th largest element
 print tmp.index(K[-N])

If you wish to ignore duplicates, then use set() as follows,

 N=5
 K = [1,10,2,4,5,5,6,2]
 #store list in tmp to retrieve index
 tmp=list(K)
 #sort list so that largest elements are on the far right
 K.sort()
 #Putting the list to a set removes duplicates
 K=set(K)
 #change K back to list since set does not support indexing
 K=list(K)
 #To get the 5 largest elements
 print K[-N:]
 #To get the 5th largest element
 print K[-N]
 #get index of the 5th largest element
 print tmp.index(K[-N])

Hopefully one of them covers your question :)