读取html字符串
主要是将html_str构造成体
import lxml
import lxml.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>
"""
html = lxml.etree.HTML(text) # 处理文本
print(type(html))
print(html)
"""
<type 'lxml.etree._Element'>
<Element html at 0x134072c8>
"""
print(lxml.etree.tostring(html))
数据展示如下：
<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> # 注意，此处缺少一个 </li> 闭合标签
</ul>
</div>
</body></html>
从文件中读取html字符串
import lxml
"""
lxml.etree.HTML() 处理文本字符串
lxml.etree.parse() 处理的是文件内容
"""
import lxml.etree
html = lxml.etree.parse("1.html") # 处理文件
print(html)
print(type(html))
print(lxml.etree.tostring(html))
"""
报错：
lxml.etree.XMLSyntaxError: Opening and ending tag mismatch: meta line 4 and head, line 6, column 8
这个主要是标签不匹配的原因，将html中的meta标签去掉即可
"""
"""
知识点：lxml.etree.parse(html_file_path,解析器)，使用tostring()得到的数据是bytes类型的，decode解码查看
from lxml import etree
html = etree.parse('./test.html', etree.HTMLParser())
result = etree.tostring(html)
print(result.decode('utf-8'))
"""
各种标签元素的提取 (重点)
import lxml
import lxml.etree
html = lxml.etree.parse("1.html")
print(type(html))
res = html.xpath("//li") # 是一个列表，包含所有元素
print(res)
"""
[<Element li at 0x1359f248>, <Element li at 0x1359f208>, <Element li at 0x1359cc08>, <Element li at 0x1359c208>, <Element li at 0x1359ac88>]
"""
print(type(res[0]))
"""
<type 'lxml.etree._Element'>
"""
print(html.xpath("//li/@class")) # 取出li的所有结点的class名称
"""
将所有的lixia的class属性全部提取了出来
·若其中有的属性不存在，则跳过不显示
['item-0', 'item-1', 'item-inactive', 'item-1', 'item-0']
"""
print(html.xpath("//li/a/@href"))
"""
['link1.html', 'link2.html', 'link3.html', 'link4.html', 'link5.html']
"""
print(html.xpath("//li/a")) # li下面有5个节点，每个节点对应一个元素
print(html.xpath("//li/a/@href="link3.html""))
"""
True
判断匹配出来的元素中是否有与"link3.html"相匹配的元素，若有则返回Ture
"""
print(html.xpath("//li//@class"))
"""
会将li下面的所有的class属性全部抓取出来
['item-0', 'hhh', 'item-1', 'item-inactive', 'item-1', 'item-0']
"""
print(html.xpath("//li"))
print(html.xpath("//li[1]"))
print(html.xpath("//li[last()]"))
print(html.xpath("//li[last()-1]"))
"""
第一个/最后一个
[<Element li at 0x1368a2c8>, <Element li at 0x1368a288>, <Element li at 0x13687c88>, <Element li at 0x13687288>, <Element li at 0x13685d08>]
[<Element li at 0x1368a2c8>]
[<Element li at 0x13685d08>]
[<Element li at 0x137ad288>]
"""
print(html.xpath("//li[last()-1]/a/@href"))
"""
['link4.html']
"""
print(html.xpath("//*[@href="link4.html"]")) # 选取href="link4.html" 的元素
"""
[<Element a at 0x12f3d948>]
"""
print(html.xpath("//*[@href="link4.html"]/text()")) # text() 取出标签之间的文本数据
"""
['fourth item']
"""
