這篇文章主要介紹了python爬蟲之xpath的基本使用詳解，現在分享給大家，也給大家做個參考。一起來看看吧
一、簡介
#XPath 是一種在 XML 文件中尋找資訊的語言。 XPath 可用於在 XML 文件中對元素和屬性進行遍歷。 XPath 是 W3C XSLT 標準的主要元素，而 XQuery 和 XPointer 都建構在 XPath 表達之上。
二、安裝
pip3 install lxml
三、使用
1、導入
from lxml import etree
2、基本使用
from lxml import etree
wb_data = """
<p>
<ul>
<li class="item-0"><a href="link1.html" rel="external nofollow" rel="external nofollow" rel="external nofollow" >first item</a></li>
<li class="item-1"><a href="link2.html" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >second item</a></li>
<li class="item-inactive"><a href="link3.html" rel="external nofollow" rel="external nofollow" rel="external nofollow" >third item</a></li>
<li class="item-1"><a href="link4.html" rel="external nofollow" rel="external nofollow" rel="external nofollow" >fourth item</a></li>
<li class="item-0"><a href="link5.html" rel="external nofollow" rel="external nofollow" rel="external nofollow" >fifth item</a>
</ul>
</p>
"""
html = etree.HTML(wb_data)
print(html)
result = etree.tostring(html)
print(result.decode("utf-8"))從下面的結果來看，我們印表機html其實就是一個python對象，etree.tostring(html)則是不全裡html的基本寫法，補全了缺胳膊少腿的標籤。
<Element html at 0x39e58f0>
<html><body><p>
<ul>
<li class="item-0"><a href="link1.html" rel="external nofollow" rel="external nofollow" rel="external nofollow" >first item</a></li>
<li class="item-1"><a href="link2.html" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >second item</a></li>
<li class="item-inactive"><a href="link3.html" rel="external nofollow" rel="external nofollow" rel="external nofollow" >third item</a></li>
<li class="item-1"><a href="link4.html" rel="external nofollow" rel="external nofollow" rel="external nofollow" >fourth item</a></li>
<li class="item-0"><a href="link5.html" rel="external nofollow" rel="external nofollow" rel="external nofollow" >fifth item</a>
</li></ul>
</p>
</body></html>3、取得某個標籤的內容(基本使用)，注意，取得a標籤的所有內容，a後面就不用再加正斜杠，否則報錯。
寫法一
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) <Element html at 0x12fe4b8> first item second item third item fourth item fifth item
#寫法二（直接在需要尋找內容的標籤後面加上一個/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) <Element html at 0x138e4b8> first item second item third item fourth item fifth item
4、開啟讀取html檔案
#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，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：
<p>
<ul>
<li class="item-0"><a href="link1.html" rel="external nofollow" rel="external nofollow" rel="external nofollow" >first item</a></li>
<li class="item-1"><a href="link2.html" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >second item</a></li>
<li class="item-inactive"><a href="link3.html" rel="external nofollow" rel="external nofollow" rel="external nofollow" >third item</a></li>
<li class="item-1"><a href="link4.html" rel="external nofollow" rel="external nofollow" rel="external nofollow" >fourth item</a></li>
<li class="item-0"><a href="link5.html" rel="external nofollow" rel="external nofollow" rel="external nofollow" >fifth item</a></li>
</ul>
</p>5、列印指定路徑下a標籤的屬性（可以透過遍歷拿到某個屬性的值，找出標籤的內容）
html = etree.HTML(wb_data) html_data = html.xpath('/html/body/p/ul/li/a/@href') for i in html_data: print(i)
列印：
link1.html
link2.html
link3.html
link4.html
link5.html
6、我們知道我們使用xpath拿到得都是一個個的ElementTree對象，所以如果需要找內容的話，還需要遍歷拿到資料的列表。
查到絕對路徑下a標籤屬性等於link2.html的內容。
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)
列印：
#['second item']
second item
#7、上面我們找到全部都是絕對路徑（每一個都是從根開始查找），下面我們查找相對路徑，例如，查找所有li標籤下的a標籤內容。
html = etree.HTML(wb_data) html_data = html.xpath('//li/a/text()') print(html_data) for i in html_data: print(i)
印刷：
['first item', 'second item', 'third item', 'fourth item' , 'fifth item']
first item
second item
third item
fourth item
fifth item
8、上面我們使用絕對路徑，查找了所有a標籤的屬性等於href屬性值，利用的是/---絕對路徑，下面我們使用相對路徑，查找l相對路徑下li標籤下的a標籤下的href屬性的值，注意，a標籤後面需要雙//。
html = etree.HTML(wb_data) html_data = html.xpath('//li/a//@href') print(html_data) for i in html_data: print(i)
列印：
#['link1.html', 'link2.html', 'link3.html', ' link4.html', 'link5.html']
link1.html
link2.html
link3.html
link4.html
#link5.html
9、相對路徑下跟絕對路徑下查特定屬性的方法類似，也可以說相同。
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)
列印：
[
] #second item
10、找出最後一個li標籤裡的a標籤的href屬性
#html = etree.HTML(wb_data) html_data = html.xpath('//li[last()]/a/text()') print(html_data) for i in html_data: print(i)
列印：
['fifth item']
fifth item
11、找出倒數第二個li標籤裡的a標籤的href屬性
#html = etree.HTML(wb_data) html_data = html.xpath('//li[last()-1]/a/text()') print(html_data) for i in html_data: print(i)
列印：
['fourth item']
fourth item
12、如果在擷取某個頁面的某個標籤的xpath路徑的話，可以如下圖：
//*[@id="kw"]
解釋：使用相對路徑來尋找所有的標籤，屬性id等於kw的標籤。
常用
#!/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" rel="external nofollow" rel="external nofollow" >first item</a></li>
<li class="item-0"><a id='i2' href="llink.html" rel="external nofollow" >first item</a></li>
<li class="item-1"><a href="llink2.html" rel="external nofollow" rel="external nofollow" >second item<span>vv</span></a></li>
</ul>
<p><a href="llink2.html" rel="external nofollow" rel="external nofollow" >second item</a></p>
</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" 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)相關推薦：
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