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[PY3]——找出一个序列中出现次数最多的元素/collections.Counter 类的用法

问题

怎样找出一个序列中出现次数最多的元素呢?

解决方案

collections.Counter 类就是专门为这类问题而设计的, 它甚至有一个有用的 most_common() 方法直接给了你答案

collections.Counter 类

1. most_common(n)统计top_n

from collections import Counterwords = [    look, into, my, eyes, look, into, my, eyes,    the, eyes, the, eyes, the, eyes, not, around, the,    eyes, "don‘t", look, around, the, eyes, look, into,    my, eyes, "you‘re", under]#创建Counter对象word_counts=Counter(words)#most_common(n)函数可直接统计top-ntop_three=word_counts.most_common(3)print(type(top_three))<class list>print(top_three)[(eyes, 8), (the, 5), (look, 4)]

 

2. 统计任意元素出现的次数

Counter 对象可以接受任意的由可哈希(hashable)元素构成的序列对象

在底层实现上,一个 Counter 对象就是一个字典,将元素映射到它出现的次数上

print(word_counts[look])4print(word_counts["you‘re"])1

 

3. 两个Counter对象之间可以互相使用数学运算符,从而叠加/叠减统计

word1 = [    look, into, my, eyes, look, into, my, eyes,    the, eyes, the, eyes, the, eyes, not, around, the,    eyes, "don‘t", look, around, the, eyes, look, into,    my, eyes, "you‘re", under]word2 = [why,are,you,not,looking,in,my,eyes]a=Counter(word1)b=Counter(word2)print(a)Counter({eyes: 8, the: 5, look: 4, into: 3, my: 3, around: 2, not: 1, under: 1, "you‘re": 1, "don‘t": 1})print(b)Counter({eyes: 1, not: 1, are: 1, you: 1, in: 1, why: 1, my: 1, looking: 1})print(a+b)Counter({eyes: 9, the: 5, my: 4, look: 4, into: 3, around: 2, not: 2, under: 1, looking: 1, you: 1, why: 1, in: 1, are: 1, "you‘re": 1, "don‘t": 1})print(a-b)Counter({eyes: 7, the: 5, look: 4, into: 3, around: 2, my: 2, under: 1, "you‘re": 1, "don‘t": 1})

 

[PY3]——找出一个序列中出现次数最多的元素/collections.Counter 类的用法