Python examples to find the largest (or the smallest) N elements from a collection of elements using nlargest() and nsmallest() functions from heapq library.
1. Using heapq module’s nlargest() and nsmallest()
Python heapq
module can be used to find N largest or smallest items from collections. It has two functions to help with –
nlargest()
nsmallest()
1.1. Find items in simple iterables
>>> import heapq >>> nums = [1, 8, 2, 23, 7, -4, 18, 23, 42, 37, 2] print(heapq.nlargest(3, nums)) >>> [42, 37, 23] print(heapq.nsmallest(3, nums)) >>> [-4, 1, 2]
1.2. Find items in complex iterables
>>> portfolio = [ {'name': 'IBM', 'shares': 100, 'price': 91.1}, {'name': 'AAPL', 'shares': 50, 'price': 543.22}, {'name': 'FB', 'shares': 200, 'price': 21.09}, {'name': 'HPQ', 'shares': 35, 'price': 31.75}, {'name': 'YHOO', 'shares': 45, 'price': 16.35}, {'name': 'ACME', 'shares': 75, 'price': 115.65} ] >>> cheap = heapq.nsmallest(3, portfolio, key=lambda s: s['price']) >> cheap >>> [ {'price': 16.35, 'name': 'YHOO', 'shares': 45}, {'price': 21.09, 'name': 'FB', 'shares': 200}, {'price': 31.75, 'name': 'HPQ', 'shares': 35} ] >>> expensive = heapq.nlargest(3, portfolio, key=lambda s: s['price']) >>> expensive >>> [ {'price': 543.22, 'name': 'AAPL', 'shares': 50}, {'price': 115.65, 'name': 'ACME', 'shares': 75}, {'price': 91.1, 'name': 'IBM', 'shares': 100} ]
If you are simply trying to find the single smallest or largest item (
N=1
), it is faster to use min()
and max()
functions.Happy Learning !!
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