项目频率计数在python [英] item frequency count in python

问题描述

我是一个python新手，所以也许我的问题是非常noob。
假设我有一个单词列表，我想找到每个单词出现在该列表中的次数。
显而易见的方式是：

I'm a python newbie, so maybe my question is very noob. Assume I have a list of words, and I want to find the number of times each word appears in that list. Obvious way to do this is:

words = "apple banana apple strawberry banana lemon"
uniques = set(words.split())
freqs = [(item, words.split.count(item)) for item in uniques]
print(freqs)

但我发现这个代码不是很好，因为这种方式通过单词列表运行两次，一次建立集合，出现次数。
当然，我可以写一个函数来运行列表和做计数，但那不会是那么pythonic。那么，是否有更高效的和蟒蛇的方式？

But I find this code not very good, because this way program runs through words list twice, once to build the set, and second time counting the number of appearances. Of course, I could write a function to run through list and do the counting, but that wouldn't be so pythonic. So, is there a more efficient and pythonic way?

推荐答案

defaultdict 来救援！

from collections import defaultdict

words = "apple banana apple strawberry banana lemon"

d = defaultdict(int)
for word in words.split():
    d[word] += 1

这在O（n）中运行。

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