[Python]HTML/XML解析器Beautiful Soup
【简介】Beautiful Soup是一个可以从HTML或XML文件中提取数据的Python库。即HTML/XMLX的解析器。
它可以很好的处理不规范标记并生成剖析树(parse tree)。 它提供简单又常用的导航（navigating），搜索以及修改剖析树的操作。它可以大大节省你的编程时间。
【安装】
下载地址：点击打开链接
Linux平台安装：
如果你用的是新版的Debain或ubuntu,那么可以通过系统的软件包管理来安装:
$apt-getinstallPython-bs4
Beautiful Soup 4 通过PyPi发布,所以如果你无法使用系统包管理安装,那么也可以通过easy_install或pip来安装.包的名字是beautifulsoup4,这个包兼容Python2和Python3.
$easy_installbeautifulsoup4
$pipinstallbeautifulsoup4
(在PyPi中还有一个名字是BeautifulSoup的包,但那可能不是你想要的,那是Beautiful
Soup3的发布版本,因为很多项目还在使用BS3, 所以BeautifulSoup包依然有效。
但是如果你在编写新项目,那么你应该安装的beautifulsoup4)
如果你没有安装easy_install或pip,那你也可以下载BS4的源码,然后通过setup.py来安装。
$Pythonsetup.pyinstall
如果上述安装方法都行不通,Beautiful Soup的发布协议允许你将BS4的代码打包在你的项目中,这样无须安装即可使用.
作者在Python2.7和Python3.2的版本下开发Beautiful Soup, 理论上Beautiful Soup应该在所有当前的Python版本中正常工作
windows平台：
下载完成之后需要解压缩，假设放到D:/IT/Python27下。
运行cmd，切换到D:/IT/Python27/beautifulsoup4-4.3.2/目录下（根据自己解压缩后的目录和下载的版本号修改）。
运行命令：python setup.py build和python setup.py install
即可安装完毕<前提是你的python路径加入到环境变量中了>
【案例】
下面的一段HTML代码将作为例子被多次用到.这是爱丽丝梦游仙境的的一段内容(以后内容中简称为爱丽丝的文档):
html_doc = """
<html><head><title>The Dormouse's story</title></head>
<body>
<p class="title"><b>The Dormouse's story</b></p>
<p class="story">Once upon a time there were three little sisters; and their names were
<a href="http://example.com/elsie" class="sister" id="link1">Elsie</a>,
<a href="http://example.com/lacie" class="sister" id="link2">Lacie</a> and
<a href="http://example.com/tillie" class="sister" id="link3">Tillie</a>;
and they lived at the bottom of a well.</p>
<p class="story">...</p>
"""
使用BeautifulSoup解析这段代码,能够得到一个BeautifulSoup的对象,并能按照标准的缩进格式的结构输出:
from bs4 import BeautifulSoup
soup = BeautifulSoup(html_doc)
print(soup.prettify())
# <html>
#<head>
# <title>
# The Dormouse's story
# </title>
#</head>
#<body>
# <p class="title">
# <b>
# The Dormouse's story
# </b>
# </p>
# <p class="story">
# Once upon a time there were three little sisters; and their names were
# <a class="sister" href="http://example.com/elsie" id="link1">
# Elsie
# </a>
# ,
# <a class="sister" href="http://example.com/lacie" id="link2">
# Lacie
# </a>
# and
# <a class="sister" href="http://example.com/tillie" id="link2">
# Tillie
# </a>
# ; and they lived at the bottom of a well.
# </p>
# <p class="story">
# ...
# </p>
#</body>
# </html>
几个简单的浏览结构化数据的方法:
soup.title
# <title>The Dormouse's story</title>
soup.title.name
# u'title'
soup.title.string
# u'The Dormouse's story'
soup.title.parent.name
# u'head'
soup.p
# <p class="title"><b>The Dormouse's story</b></p>
soup.p['class']
# u'title'
soup.a
# <a class="sister" href="http://example.com/elsie" id="link1">Elsie</a>
soup.find_all('a')
# [<a class="sister" href="http://example.com/elsie" id="link1">Elsie</a>,
#<a class="sister" href="http://example.com/lacie" id="link2">Lacie</a>,
#<a class="sister" href="http://example.com/tillie" id="link3">Tillie</a>]
soup.find(id="link3")
# <a class="sister" href="http://example.com/tillie" id="link3">Tillie</a>
从文档中找到所有<a>标签的链接:
for link in soup.find_all('a'):
print(link.get('href'))
# http://example.com/elsie
# http://example.com/lacie
# http://example.com/tillie
从文档中获取所有文字内容:
print(soup.get_text())
# The Dormouse's story
#
# The Dormouse's story
#
# Once upon a time there were three little sisters; and their names were
# Elsie,
# Lacie and
# Tillie;
# and they lived at the bottom of a well.
#
# ...
【如何使用】
链接地址：点击打开链接
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