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Python通过字典(dict)中value获取前n个最大的元素方法及示例代码

本文主要介绍Python中,根据字典(Dictionary)中value的大小,来获取字典中获取前n个最大的元素的方法,以及相关的示例代码。

1、使用 collections.defaultdict实现

文档:collections.defaultdict

from collections import defaultdictpN ={'dave': 10, 'jacinta': 10, 'james': 8, 'john': 6, 'jack': 3, 'sam': 2}#交换key和valuedct = defaultdict(list)for k, v in pN.items():  dct[v].append(k)#排序for k, v in sorted(dct.items(), reverse=True):  print(k, ', '.join(v))#返回前n个元素def top_n(d, n):  dct = defaultdict(list)   for k, v in d.items():    dct[v].append(k)        return sorted(dct.items())[-n:][::-1]top_n(pN, 3)

输出结果

[(10, ['dave', 'jacinta']), (8, ['james']), (6, ['john'])]

2、使用max来实现

pN ={'dave': 10, 'jacinta': 10, 'james': 8, 'john': 6, 'jack': 3, 'sam': 2}def top_n_scores(n, score_dict):  ''' returns the n scores from a name:score dict'''  lot = [(k,v) for k, v in pN.items()] #make list of tuple from scores dict  nl = []  while len(lot)> 0:      nl.append(max(lot, key=lambda x: x[1]))      lot.remove(nl[-1])  return nl[0:n]   top_n_scores(4, pN)  

输出结果:

[('dave', 10), ('jacinta', 10), ('james', 8), ('john', 6)]