QUST 朴素贝叶斯垃圾邮件分类

import os
import re
import string
import math

DATA_DIR = 'enron'
target_names = ['ham', 'spam']


def get_data(DATA_DIR):
    subfolders = ['enron%d' % i for i in range(1, 7)]
    data = []
    target = []
    for subfolder in subfolders:
        spam_files = os.listdir(os.path.join(DATA_DIR, subfolder, 'spam'))
        for spam_file in spam_files:
            with open(os.path.join(DATA_DIR, subfolder, 'spam', spam_file), encoding="latin-1") as f:
                data.append(f.read())
                target.append(1)
        ham_files = os.listdir(os.path.join(DATA_DIR, subfolder, 'ham'))
        for ham_file in ham_files:
            with open(os.path.join(DATA_DIR, subfolder, 'ham', ham_file), encoding="latin-1") as f:
                data.append(f.read())
                target.append(0)
    return data, target


X, y = get_data(DATA_DIR)


class SpamDetector_1(object):
    """Implementation of Naive Bayes for binary classification"""

    def clean(self, s):
        translator = str.maketrans("", "", string.punctuation)
        return s.translate(translator)

    def tokenize(self, text):
        text = self.clean(text).lower()
        return re.split("\W+", text)

    def get_word_counts(self, words):
        word_counts = {}
        for word in words:
            word_counts[word] = word_counts.get(word, 0.0) + 1.0
        return word_counts


class SpamDetector_2(SpamDetector_1):
    def fit(self, X, Y):
        self.num_messages = {}
        self.log_class_priors = {}
        self.word_counts = {}
        self.vocab = set()
        self.num_messages['spam'] = sum(1 for label in Y if label == 1)
        self.num_messages['ham'] = sum(1 for label in Y if label == 0)

        self.log_class_priors['spam'] = math.log(
            self.num_messages['spam'] / (self.num_messages['spam'] + self.num_messages['ham']))
        self.log_class_priors['ham'] = math.log(
            self.num_messages['ham'] / (self.num_messages['spam'] + self.num_messages['ham']))

        self.word_counts['spam'] = {}
        self.word_counts['ham'] = {}

        for x, y in zip(X, Y):
            c = 'spam' if y == 1 else 'ham'
            counts = self.get_word_counts(self.tokenize(x))
            for word, count in counts.items():
                if word not in self.vocab:
                    self.vocab.add(word) 
                if word not in self.word_counts[c]:
                    self.word_counts[c][word] = 0.0
                self.word_counts[c][word] += count


MNB = SpamDetector_2()
MNB.fit(X[100:], y[100:])


class SpamDetector(SpamDetector_2):
    def predict(self, X):
        result = []
        flag_1 = 0
        for x in X:
            counts = self.get_word_counts(self.tokenize(x)) 
            spam_score = 0
            ham_score = 0
            flag_2 = 0
            for word, _ in counts.items():
                if word not in self.vocab:
                    continue

                else:
                    if word in self.word_counts['spam'].keys() and word in self.word_counts['ham'].keys():
                        log_w_given_spam = math.log(
                            (self.word_counts['spam'][word] + 1) / (
                                    sum(self.word_counts['spam'].values()) + len(self.vocab)))
                        log_w_given_ham = math.log(
                            (self.word_counts['ham'][word] + 1) / (sum(self.word_counts['ham'].values()) + len(
                                self.vocab)))
                    if word in self.word_counts['spam'].keys() and word not in self.word_counts['ham'].keys():
                        log_w_given_spam = math.log(
                            (self.word_counts['spam'][word] + 1) / (
                                    sum(self.word_counts['spam'].values()) + len(self.vocab)))
                        log_w_given_ham = math.log(1 / (sum(self.word_counts['ham'].values()) + len(
                            self.vocab)))
                    if word not in self.word_counts['spam'].keys() and word in self.word_counts['ham'].keys():
                        log_w_given_spam = math.log(1 / (sum(self.word_counts['spam'].values()) + len(self.vocab)))
                        log_w_given_ham = math.log(
                            (self.word_counts['ham'][word] + 1) / (sum(self.word_counts['ham'].values()) + len(
                                self.vocab)))

                spam_score += log_w_given_spam
                ham_score += log_w_given_ham

                flag_2 += 1

                spam_score += self.log_class_priors['spam']
                ham_score += self.log_class_priors['ham']

            if spam_score > ham_score:
                result.append(1)
            else:
                result.append(0)

            flag_1 += 1

        return result


MNB = SpamDetector()
MNB.fit(X[100:], y[100:])
pred = MNB.predict(X[:100])
true = y[:100]

accuracy = 0
for i in range(100):
    if pred[i] == true[i]:
        accuracy += 1
print(accuracy)

 运行结果：

分类正确率为98%