python - dict的N个最大值与重复

Question

例如我们有这个字典：

scores={'L Messi':18, 'R Falcao':16, 'R Van Persie':14, 'F Torres':0, 'C Ronaldo':16}

所以，我需要实现一个函数，它将打印前 N 个最佳分数（最大值）。对于这个例子，如果n=3它应该打印这个：

L Messi 18
C Ronaldo 16
R Falcao 16
R Van Persie 14

有什么建议怎么做吗？

Answer 1

使用方法collections.Counter和.most_common()方法：

>>> from collections import Counter
>>> scores={'L Messi':18, 'R Falcao':16, 'R Van Persie':14, 'F Torres':0, 'C Ronaldo':16}
>>> scores = Counter(scores)
>>> for name, score in scores.most_common(4):
...     print '{}: {}'.format(name, score)
... 
L Messi: 18
R Falcao: 16
C Ronaldo: 16
R Van Persie: 14

如果你必须自己实现.most_common()代码，至少要引用.most_common()源代码，它使用heapq.

要获得最常见的值，您可以在此基础上构建：

def most_common_values(counter, count):
    values = set()
    most_common = iter(counter.most_common())
    while len(values) < count:
        key, value = next(most_common)
        values.add(value)
        yield key, value

对于您的示例：

>>> for name, score in most_common_values(scores, 3):
...     print '{}: {}'.format(name, score)
... 
L Messi: 18
R Falcao: 16
C Ronaldo: 16
R Van Persie: 14

Answer 2

scores = {'L Messi':18, 'R Falcao':16, 'R Van Persie':14, 'F Torres':0, 'C Ronaldo':16}
top_scores = sorted(set(scores.values()), reverse=True)[:3]
filtered = sorted([[e, scores[e]] for e in scores if scores[e] in top_scores], key=lambda k: k[1], reverse=True)
for n, s in filtered:
    print("%s: %s" % (n, s))