找到最大或者最小的N个元素

heapq模块中的两个函数nlargest()和nsmallest()

import heapq
nums = [1,5,6,458,6,787,5,45,6]
print(heapq.nlargest(3,nums))
[787, 458, 45]
print(heapq.nsmallest(3,nums))
[1, 5, 5]