统计序列中元素的频度

某随机序列(例：[12, 5, 6, 4, 6, 5, 5, 7])中，找到出现次数最高的3个元素，它们出现的次数是多少

1.将序列转换为字典{元素:频度}，根据字典中的值排序

1)创建列表

from random import randint
data = [randint(0, 20) for _ in range(30)]
d = dict.fromkeys(data,0)
for i in data:
    d[i] += 1
d1 = sorted([(v, k) for k, v in d.items()], reverse = True)[:3]
print(d1)

2)堆

from random import randint
import heapq
data = [randint(0, 20) for _ in range(30)]
d = dict.fromkeys(data,0)
for i in data:
    d[i] += 1
d2 = heapq.nlargest(3, ((v, k) for k, v in d.items()))
print(d2)

2.标准库collections中的Counter对象

推荐

from random import randint
from collections import Counter
data = [randint(0, 20) for _ in range(30)]
c = Counter(data)
print(c.most_common(3))

某篇英文文章的单词，进行词频统计，找到出现次数最高的10个单词，他们出现次数是多少

import re
from collections import Counter
article = "I'm pretty passionate about all kinds of technologies"
wordlist = re.split("\W+", article)
c1 = Counter(wordlist)
print(c1.most_common(3))