Python 2.7使用nltk内置数据集对KNN进行情感分析

Question

由于我是编程新手，我想知道是否可以使用nltk内置电影评论数据集通过使用KNN来确定数据的极性来进行情绪分析？有没有办法这样做？

import nltk
from nltk.corpus import movie_reviews
from nltk.tokenize import word_tokenize

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


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

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

training_set = featuresets[500:1500]
testing_set = featuresets[:1500]

classifier = nltk.DecisionTreeClassifier.train(training_set)

print "Classifier accuracy percent:",(nltk.classify.accuracy(classifier, testing_set))*100 , "%"

string = raw_input("Enter the string: ")
print (classifier.classify(find_features(word_tokenize(string))))

我正在尝试将上面的代码从决策树转换为KNN