Cheapest k

Write cheapest(prices, k) that returns the k smallest numbers in prices, smallest first. If k is larger than the list, return everything sorted; if k is 0, return an empty list. Do not change prices.

cheapest([40, 25, 2.5, 60, 15], 2)  ->  [2.5, 15]
cheapest([40, 25], 5)               ->  [25, 40]
cheapest([40, 25], 0)               ->  []

import heapq

def cheapest(prices, k):
    ...