1、简介html
XPath 是一门在 XML 文档中查找信息的语言。XPath 可用来在 XML 文档中对元素和属性进行遍历。XPath 是 W3C XSLT 标准的主要元素，而且 XQuery 和 XPointer 都构建于 XPath 表达之上。python
参照python爬虫
2、安装scrapy
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pip3 install lxml
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3、使用ide
一、导入post
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from
lxml
import
etree
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二、基本使用ui
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from
lxml
import
etree
wb_data
=
"""
<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>
</ul>
</div>
"""
html
=
etree.HTML(wb_data)
print
(html)
result
=
etree.tostring(html)
print
(result.decode(
"utf-8"
))
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从下面的结果来看，咱们打印机html其实就是一个python对象，etree.tostring(html)则是不全里html的基本写法，补全了缺胳膊少腿的标签。url
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<Element html at
0x39e58f0
>
<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>
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三、获取某个标签的内容(基本使用)，注意，获取a标签的全部内容，a后面就不用再加正斜杠，不然报错。spa
写法一code
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html
=
etree.HTML(wb_data)
html_data
=
html.xpath(
'/html/body/div/ul/li/a'
)
print
(html)
for
i
in
html_data:
print
(i.text)
<Element html at
0x12fe4b8
>
first item
second item
third item
fourth item
fifth item
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写法二（直接在须要查找内容的标签后面加一个/text()就行）
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html
=
etree.HTML(wb_data)
html_data
=
html.xpath(
'/html/body/div/ul/li/a/text()'
)
print
(html)
for
i
in
html_data:
print
(i)
<Element html at
0x138e4b8
>
first item
second item
third item
fourth item
fifth item
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四、打开读取html文件
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#使用parse打开html的文件
html
=
etree.parse(
'test.html'
)
html_data
=
html.xpath(
'//*'
)<br>
#打印是一个列表，须要遍历
print
(html_data)
for
i
in
html_data:
print
(i.text)
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html
=
etree.parse(
'test.html'
)
html_data
=
etree.tostring(html,pretty_print
=
True
)
res
=
html_data.decode(
'utf-8'
)
print
(res)
打印：
<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>
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五、打印指定路径下a标签的属性（能够经过遍历拿到某个属性的值，查找标签的内容）
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html
=
etree.HTML(wb_data)
html_data
=
html.xpath(
'/html/body/div/ul/li/a/@href'
)
for
i
in
html_data:
print
(i)
打印：
link1.html
link2.html
link3.html
link4.html
link5.html
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六、咱们知道咱们使用xpath拿到得都是一个个的ElementTree对象，因此若是须要查找内容的话，还须要遍历拿到数据的列表。
查到绝对路径下a标签属性等于link2.html的内容。
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html
=
etree.HTML(wb_data)
html_data
=
html.xpath(
'/html/body/div/ul/li/a[@href="link2.html"]/text()'
)
print
(html_data)
for
i
in
html_data:
print
(i)
打印：
[
'second item'
]
second item
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七、上面咱们找到所有都是绝对路径（每个都是从根开始查找），下面咱们查找相对路径，例如，查找全部li标签下的a标签内容。
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html
=
etree.HTML(wb_data)
html_data
=
html.xpath(
'//li/a/text()'
)
print
(html_data)
for
i
in
html_data:
print
(i)
打印：
[
'first item'
,
'second item'
,
'third item'
,
'fourth item'
,
'fifth item'
]
first item
second item
third item
fourth item
fifth item
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八、上面咱们使用绝对路径，查找了全部a标签的属性等于href属性值，利用的是/---绝对路径，下面咱们使用相对路径，查找一下l相对路径下li标签下的a标签下的href属性的值，注意，a标签后面须要双//。
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html
=
etree.HTML(wb_data)
html_data
=
html.xpath(
'//li/a//@href'
)
print
(html_data)
for
i
in
html_data:
print
(i)
打印：
[
'link1.html'
,
'link2.html'
,
'link3.html'
,
'link4.html'
,
'link5.html'
]
link1.html
link2.html
link3.html
link4.html
link5.html
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九、相对路径下跟绝对路径下查特定属性的方法相似，也能够说相同。
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html
=
etree.HTML(wb_data)
html_data
=
html.xpath(
'//li/a[@href="link2.html"]'
)
print
(html_data)
for
i
in
html_data:
print
(i.text)
打印：
[<Element a at
0x216e468
>]
second item
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十、查找最后一个li标签里的a标签的href属性
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html
=
etree.HTML(wb_data)
html_data
=
html.xpath(
'//li[last()]/a/text()'
)
print
(html_data)
for
i
in
html_data:
print
(i)
打印：
[
'fifth item'
]
fifth item
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十一、查找倒数第二个li标签里的a标签的href属性
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html
=
etree.HTML(wb_data)
html_data
=
html.xpath(
'//li[last()-1]/a/text()'
)
print
(html_data)
for
i
in
html_data:
print
(i)
打印：
[
'fourth item'
]
fourth item
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十二、若是在提取某个页面的某个标签的xpath路径的话，能够以下图：
//*[@id="kw"]
解释：使用相对路径查找全部的标签，属性id等于kw的标签。
#!/usr/bin/env python
# -*- coding:utf-8 -*-
from scrapy.selector import Selector, HtmlXPathSelector
from scrapy.http import HtmlResponse
html = """<!DOCTYPE html>
<html>
<head lang="en">
<meta charset="UTF-8">
<title></title>
</head>
<body>
<ul>
<li class="item-"><a id='i1' href="link.html">first item</a></li>
<li class="item-0"><a id='i2' href="llink.html">first item</a></li>
<li class="item-1"><a href="llink2.html">second item<span>vv</span></a></li>
</ul>
<div><a href="llink2.html">second item</a></div>
</body>
</html>
"""
response = HtmlResponse(url='http://example.com', body=html,encoding='utf-8')
# hxs = HtmlXPathSelector(response)
# print(hxs)
# hxs = Selector(response=response).xpath('//a')
# print(hxs)
# hxs = Selector(response=response).xpath('//a[2]')
# print(hxs)
# hxs = Selector(response=response).xpath('//a[@id]')
# print(hxs)
# hxs = Selector(response=response).xpath('//a[@id="i1"]')
# print(hxs)
# hxs = Selector(response=response).xpath('//a[@href="link.html"][@id="i1"]')
# print(hxs)
# hxs = Selector(response=response).xpath('//a[contains(@href, "link")]')
# print(hxs)
# hxs = Selector(response=response).xpath('//a[starts-with(@href, "link")]')
# print(hxs)
# hxs = Selector(response=response).xpath('//a[re:test(@id, "i\d+")]')
# print(hxs)
# hxs = Selector(response=response).xpath('//a[re:test(@id, "i\d+")]/text()').extract()
# print(hxs)
# hxs = Selector(response=response).xpath('//a[re:test(@id, "i\d+")]/@href').extract()
# print(hxs)
# hxs = Selector(response=response).xpath('/html/body/ul/li/a/@href').extract()
# print(hxs)
# hxs = Selector(response=response).xpath('//body/ul/li/a/@href').extract_first()
# print(hxs)
# ul_list = Selector(response=response).xpath('//body/ul/li')
# for item in ul_list:
# v = item.xpath('./a/span')
# # 或
# # v = item.xpath('a/span')
# # 或
# # v = item.xpath('*/a/span')
# print(v)