finding top k largest keys in a dictionary python

Question

Lets say I have a dictionary:

{key1:value1........... keyn:valuen}

So lets say I want to write a function

def return_top_k(dictionary, k):

    return list_of_keys_sorted   

What is the most efficient way (in terms of big O) to get the keys which have the top k values (maintaining the order i.e the highest value key is present in the beginning.. and so on.)

Answer 1

O(n log k):

import heapq

k_keys_sorted = heapq.nlargest(k, dictionary)

You could use key keyword parameter to specify what should be used as a sorting key e.g.:

k_keys_sorted_by_values = heapq.nlargest(k, dictionary, key=dictionary.get)