python自然语言处理——学习笔记：Chapter3纠错

2017-12-06更新：很多代码执行结果与书中不一致，是因为python的版本不一致。如果发现有问题，可以参考英文版：

http://www.nltk.org/book/

第三章，P87有一段处理html的代码：

>>>raw = nltk.clean_html(html)
>>>tokens = nltk.word_tokenize(raw)
>>>tokens

可是我们执行会有如下错误：

>>> raw = nltk.clean_html(html)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Library/Python/2.7/site-packages/nltk/util.py", line 356, in clean_html
    raise NotImplementedError ("To remove HTML markup, use BeautifulSoup's get_text() function")
NotImplementedError: To remove HTML markup, use BeautifulSoup's get_text() function

根据官方网站：介绍http://www.nltk.org/_modules/nltk/util.html
def clean_html(html):
raise NotImplementedError ("To remove HTML markup, use BeautifulSoup's get_text() function")
[docs]def clean_url(url):
raise NotImplementedError ("To remove HTML markup, use BeautifulSoup's get_text() function")
网站：http://stackoverflow.com/questions/10524387/beautifulsoup-get-text-does-not-strip-all-tags-and-javascript介绍：
以后的版本，似乎不支持clean_html()和clean_url()这两个函数
Support for clean_html and clean_url will be dropped for future versions of nltk. Please use BeautifulSoup for now...it's very unfortunate.
有关处理HTML 的内容，可以使用http://www.crummy.com/software/BeautifulSoup/上的Beautiful Soup 软件包。

安装：sudo pip install beautifulsoup4

之后替换书上的代码：

from __future__ import division
import nltk, re, pprint
from urllib import urlopen
from bs4 import BeautifulSoup

def read_html():
    url = "http://news.bbc.co.uk/2/hi/health/2284783.stm"
    html = urlopen(url).read()
    soup = BeautifulSoup(html)
    text = soup.get_text()
    print text
    tokens = nltk.word_tokenize(text)
    print tokens

def main():
    read_html()

if __name__ == '__main__':
    main()

上述脚本文件可以独立运行，运行结果与书上一致