Python 类型错误：列表索引必须是整数，而不是 str（实际上是布尔转换）
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TypeError: list indices must be integers, not str (boolean convertion actually)
提问by RokiDGupta
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]
After run, I am getting the error
运行后，我收到错误
features[w]= (w in words)
TypeError: list indices must be integers, not str
Please help me to solve it...
请帮我解决它...
回答by Nickil Maveli
Only change that needs to be made is that featuresmust be initialized to a dict({}) rather than a list([]) and then you could populate it's contents.
唯一需要进行的更改是features必须将其初始化为 a dict( {}) 而不是 a list( []) 然后您可以填充它的内容。
The TypeErrorwas because word_featuresis a list of stringswhich you were trying to index using a list and lists can't have string indices.
这TypeError是因为word_features是您尝试使用列表索引的字符串列表，并且列表不能具有字符串索引。
features={}
for w in word_features:
features[w] = (w in words)
Here, the elements present in word_featuresconstitute the keysof dictionary, featuresholding boolean values, Truebased on whether the same element appears in words(which holds unique items due to calling of set()) and Falsefor the vice-versa situation.
这里，存在于的元素word_features构成了keysof 字典，features保存布尔值，True基于相同的元素是否出现在words（由于调用而保存唯一项set()），False反之亦然。
回答by Raja Sattiraju
You have tried to index a list featureswith a string and it is not possible with python. List indices can only be integers. What you need is a dictionary.
您试图features用字符串索引一个列表，但用 python 是不可能的。列表索引只能是整数。你需要的是一个dictionary.
Try using a defaultdictmeaning that even if a key is not found in the dictionary, instead of a KeyErrorbeing thrown, a new entry is created
尝试使用一种defaultdict含义，即使在字典中找不到键，也不会KeyError抛出一个新条目，而是创建一个新条目
from collections import defaultdict
features = defaultdict()
for w in word_features:
features[w] = [w in words]
