Python find largest N (top N) or smallest N items

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 –

1. nlargest()
2. 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}	] 

Happy Learning !!