借用
collections.Counter.most_common并适当地反转：
from operator import itemgetterimport heapqimport collectionsdef least_common_values(array, to_find=None): counter = collections.Counter(array) if to_find is None: return sorted(counter.items(), key=itemgetter(1), reverse=False) return heapq.nsmallest(to_find, counter.items(), key=itemgetter(1))>>> data = [1,1,2,2,2,2,3,3,3,3,3,3,3,4,4,4,4,4,4,4]>>> least_common_values(data, 2)[(1, 2), (2, 4)]>>> least_common_values([1,1,2,3,3])[(2, 1), (1, 2), (3, 2)]>>>
