我在运行代码时遇到了这个错误：AttributeError: ‘NoneType’ object has no attribute ‘items’。以下是我的代码：

import nltk
import random
from nltk.corpus import movie_reviews
from nltk.classify import NaiveBayesClassifier
from nltk.probability import FreqDist
documents = [ (list(movie_reviews.words(fileid)), category)
            for category in movie_reviews.categories()
                for fileid in movie_reviews.fileids(category)]
random.shuffle(documents)
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]
print (word_features)
def find_features(documents):
    words = set(documents)
    features = {}
    for w in word_features:
        features[w] = (w in words)
featuresets = [(find_features(rev), category) for (rev, category) in documents]
training_set = featuresets[:1500]
testing_set = featuresets[1500:]
classifier = nltk.NaiveBayesClassifier.train(training_set)
print ("Naive Bayes Classifier Algo Accuracy: ",nltk.classify.accuracy(classifier, testing_set))*100)
classifier.show_most_informative_features(15)

我一直在按照一个视频教程进行学习，教程中的代码与这里的一样。在教程中运行正常，但在我的环境中却显示以下错误：

AttributeError: 'NoneType' object has no attribute 'items'

错误发生在以下这行代码：

classifier = nltk.NaiveBayesClassifier.train(training_set)

这是什么原因？有什么解决方案吗？

回答：

您没有从函数中返回列表。在您的 find_feature 函数中使用以下代码：

def find_features(documents):
    words = set(documents)
    features = {}
    for w in word_features:
        features[w] = (w in words)
    return features #添加这一行