python - TypeError : list indices must be integers, 不是 str(实际上是 bool 转换)

Question

import nltk
import random
from nltk.corpus import movie_reviews

documents=[(list(movie_reviews.words(fileid)),category)
           for category in movie_reviews.categories()
           for fileid in movie_reviews.fileids(category)]

random.shuffle(documents)
#print(documents[1])

all_words=[]

for w in movie_reviews.words():
    all_words.append(w.lower())

all_words=nltk.FreqDist(all_words)

word_features = list(all_words.keys())[:3000]

def find_features(document):
    words = set(document)
    features=[]
    for w in word_features:
        features[w]= (w in words)

    return features

print((find_features(movie_reviews.words('neg/cv000_29416.txt'))))

featuresets = [(find_features(rev), category) for (rev,category) in documents]

---

运行后，我收到错误

features[w]= (w in words)
TypeError: list indices must be integers, not str

请帮我解决一下...

Answer 1

唯一需要做的改变是 features 必须初始化为 dict ({}) 而不是 list ([]) 然后你可以填充它的内容。

TypeError 是因为 word_features 是一个 strings 列表，您试图使用列表对其进行索引，而列表不能包含字符串指数。

features={}
for w in word_features:
    features[w] = (w in words)

这里，word_features中的元素构成字典的keys，features保存 bool 值，True基于相同的元素是否出现在 words 中(由于调用 set())和 False 中，反之亦然情况。