本篇文章主要介绍了python爬虫之xpath的基本使用详解，现在分享给大家，也给大家做个参考。一起过来看看吧

一、简介

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，并且 XQuery 和 XPointer 都构建于 XPath 表达之上。

二、安装

pip3 install lxml

三、使用

1、导入

from lxml import etree

2、基本使用

from lxml import etree

wb_data = """

• first item
• second item
• third item
• fourth item
• fifth item

"""

html = etree.HTML(wb_data)

print(html)

result = etree.tostring(html)

print(result.decode("utf-8"))

从下面的结果来看，我们打印机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。

• first item
• second item
• third item
• fourth item
• fifth item

3、获取某个标签的内容(基本使用)，注意，获取a标签的所有内容，a后面就不用再加正斜杠，否则报错。

写法一

html = etree.HTML(wb_data)

html_data = html.xpath('/html/body/p/ul/li/a')

print(html)

for i in html_data:

print(i.text)

first item

second item

third item

fourth item

fifth item

写法二(直接在需要查找内容的标签后面加一个/text()就行)

html = etree.HTML(wb_data)

html_data = html.xpath('/html/body/p/ul/li/a/text()')

print(html)

for i in html_data:

print(i)

first item

second item

third item

fourth item

fifth item

4、打开读取html文件

#使用parse打开html的文件

html = etree.parse('test.html')

html_data = html.xpath('//*')
#打印是一个列表，需要遍历

print(html_data)

for i in html_data:

print(i.text)

html = etree.parse('test.html')

html_data = etree.tostring(html,pretty_print=True)

res = html_data.decode('utf-8')

print(res)

打印：

• first item
• second item
• third item
• fourth item
• fifth item

5、打印指定路径下a标签的属性(可以通过遍历拿到某个属性的值，查找标签的内容)

html = etree.HTML(wb_data)

html_data = html.xpath('/html/body/p/ul/li/a/@href')

for i in html_data:

print(i)

打印：link1.html

link2.html

link3.html

link4.html

link5.html

6、我们知道我们使用xpath拿到得都是一个个的ElementTree对象，所以如果需要查找内容的话，还需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。

html = etree.HTML(wb_data)

html_data = html.xpath('/html/body/p/ul/li/a[@href="link2.html" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" ]/text()')

print(html_data)

for i in html_data:

print(i)

打印：['second item']

second item

7、上面我们找到全部都是绝对路径(每一个都是从根开始查找)，下面我们查找相对路径，例如，查找所有li标签下的a标签内容。

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

8、上面我们使用绝对路径，查找了所有a标签的属性等于href属性值，利用的是/---绝对路径，下面我们使用相对路径，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标签后面需要双//。

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

9、相对路径下跟绝对路径下查特定属性的方法类似，也可以说相同。

html = etree.HTML(wb_data)

html_data = html.xpath('//li/a[@href="link2.html" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" ]')

print(html_data)

for i in html_data:

print(i.text)

打印：[]

second item

10、查找最后一个li标签里的a标签的href属性

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

11、查找倒数第二个li标签里的a标签的href属性

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

12、如果在提取某个页面的某个标签的xpath路径的话，可以如下图：

//*[@id="kw"]

解释：使用相对路径查找所有的标签，属性id等于kw的标签。

常用

#!/usr/bin/env python

# -*- coding:utf-8 -*-

from scrapy.selector import Selector, HtmlXPathSelector

from scrapy.http import HtmlResponse

html = """

• first item
• first item
• second itemvv

second item

"""

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" rel="external nofollow" rel="external nofollow" ][@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)

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