Python 之lxml解析模块

lxml 是一个HTML/XML的解析器，主要的功能是如何解析和提取 HTML/XML 数据。

一、lxml示例

1、初步

# 使用 lxml 的 etree 库
from lxml import etree 

text = ‘‘‘
<div>
    <ul>
         <li class="item-0"><a href="link1.html">first item</a></li>
         <li class="item-1"><a href="link2.html">second item</a></li>
         <li class="item-inactive"><a href="link3.html">third item</a></li>
         <li class="item-1"><a href="link4.html">fourth item</a></li>
         <li class="item-0"><a href="link5.html">fifth item</a> # 注意，此处缺少一个 </li> 闭合标签
     </ul>
 </div>
‘‘‘

#利用etree.HTML，将字符串解析为HTML文档
html = etree.HTML(text) 

# 按字符串序列化HTML文档
result = etree.tostring(html) 

print(result)

结果

<html><body>
<div>
    <ul>
         <li class="item-0"><a href="link1.html">first item</a></li>
         <li class="item-1"><a href="link2.html">second item</a></li>
         <li class="item-inactive"><a href="link3.html">third item</a></li>
         <li class="item-1"><a href="link4.html">fourth item</a></li>
         <li class="item-0"><a href="link5.html">fifth item</a></li>
</ul>
 </div>
</body></html>

2、从文件里读取内容

from lxml import etree

# 读取外部文件 hello.html
html = etree.parse(‘./hello.html‘)
result = etree.tostring(html, pretty_print=True)

print(result)

3、html内容

<html><body>
<div>
    <ul>
         <li class="item-0"><a href="link1.html">first item</a></li>
         <li class="item-1"><a href="link2.html">second item</a></li>
         <li class="item-inactive"><a href="link3.html">third item</a></li>
         <li class="item-1"><a href="link4.html">fourth item</a></li>
         <li class="item-0"><a href="link5.html">fifth item</a></li>
</ul>
 </div>
</body></html>

@1、获取所有的 <li> 标签

from lxml import etree

html = etree.parse(‘hello.html‘)
print type(html)  # 显示etree.parse() 返回类型

result = html.xpath(‘//li‘)

print result  # 打印<li>标签的元素集合
print len(result)
print type(result)
print type(result[0])


结果是
<type ‘lxml.etree._ElementTree‘>
[<Element li at 0x1014e0e18>, <Element li at 0x1014e0ef0>, <Element li at 0x1014e0f38>, <Element li at 0x1014e0f80>, <Element li at 0x1014e0fc8>]
5
<type ‘list‘>
<type ‘lxml.etree._Element‘>

@2、继续获取<li> 标签的所有 class属性

from lxml import etree

html = etree.parse(‘hello.html‘)
result = html.xpath(‘//li/@class‘)

print result

结果是
[‘item-0‘, ‘item-1‘, ‘item-inactive‘, ‘item-1‘, ‘item-0‘]

@3、继续获取<li>标签下href为 link1.html 的 <a> 标签

from lxml import etree

html = etree.parse(‘hello.html‘)
result = html.xpath(‘//li/a[@href="link1.html"]‘)

print result

运行结果

[<Element a at 0x10ffaae18>]

@4、获取<li> 标签下的所有 <span> 标签

from lxml import etree

html = etree.parse(‘hello.html‘)

#result = html.xpath(‘//li/span‘)
#注意这么写是不对的：
#因为 / 是用来获取子元素的，而 <span> 并不是 <li> 的子元素，所以，要用双斜杠

result = html.xpath(‘//li//span‘)

print result

运行结果

[<Element span at 0x10d698e18>]

@5、获取 <li> 标签下的<a>标签里的所有 class

from lxml import etree

html = etree.parse(‘hello.html‘)
result = html.xpath(‘//li/a//@class‘)

print result

运行结果

[‘blod‘]

@6、获取最后一个 <li> 的 <a> 的 href

from lxml import etree

html = etree.parse(‘hello.html‘)

result = html.xpath(‘//li[last()]/a/@href‘)
# 谓语 [last()] 可以找到最后一个元素

print result

运行结果

[‘link5.html‘]

@7、获取倒数第二个元素的内容

from lxml import etree

html = etree.parse(‘hello.html‘)
result = html.xpath(‘//li[last()-1]/a‘)

# text 方法可以获取元素内容
print result[0].text

运行结果

fourth item

@8、获取 class 值为 bold 的标签名

from lxml import etree

html = etree.parse(‘hello.html‘)

result = html.xpath(‘//*[@class="bold"]‘)

# tag方法可以获取标签名
print result[0].tag

运行结果

span

Python 之lxml解析模块

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