python中l(wèi)xml模塊的使用詳解

更新時(shí)間：2023年08月21日 15:24:50 作者：埃菲爾沒(méi)有塔尖

lxml是python的一個(gè)解析庫(kù)，支持HTML和XML的解析，支持XPath解析方式，而且解析效率非常高,這篇文章主要來(lái)和大家講解一下lxml模塊的使用，感興趣的可以了解一下

lxml是python的一個(gè)解析庫(kù)，支持HTML和XML的解析，支持XPath解析方式，而且解析效率非常高

1.lxml的安裝

pip install lxml

2.導(dǎo)入lxml 的 etree 庫(kù)

 from lxml import etree

3.利用etree.HTML，將字符串轉(zhuǎn)化為Element對(duì)象,Element對(duì)象具有xpath的方法,返回結(jié)果的列表，能夠接受bytes類(lèi)型的數(shù)據(jù)和str類(lèi)型的數(shù)據(jù)。

from lxml import etree
html = etree.HTML(response.text) 
ret_list = html.xpath("xpath字符串")

也可以這樣使用：

from lxml import etree
htmlDiv = etree.HTML(response.content.decode())
hrefs = htmlDiv.xpath("http://h4//a/@href")

4.把轉(zhuǎn)化后的element對(duì)象轉(zhuǎn)化為字符串，返回bytes類(lèi)型，etree.tostring(element)

假設(shè)我們現(xiàn)有如下的html字符換，嘗試對(duì)他進(jìn)行操作:

<div> <ul> 
<li class="item-1"><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，此處缺少一個(gè) </li> 閉合標(biāo)簽 
</ul> </div>

代碼示例：

from lxml import etree
text = ''' <div> <ul> 
        <li class="item-1"><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(text)
print(type(html)) 
handeled_html_str = etree.tostring(html).decode()
print(handeled_html_str)

輸出結(jié)果：

<class 'lxml.etree._Element'>
<html><body><div> <ul>
<li class="item-1"><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>

可以發(fā)現(xiàn)，lxml確實(shí)能夠把確實(shí)的標(biāo)簽補(bǔ)充完成，但是請(qǐng)注意lxml是人寫(xiě)的，很多時(shí)候由于網(wǎng)頁(yè)不夠規(guī)范，或者是lxml的bug。

即使參考url地址對(duì)應(yīng)的響應(yīng)去提取數(shù)據(jù)，任然獲取不到，這個(gè)時(shí)候我們需要使用etree.tostring的方法，觀察etree到底把html轉(zhuǎn)化成了什么樣子，即根據(jù)轉(zhuǎn)化后的html字符串去進(jìn)行數(shù)據(jù)的提取。

5.lxml的深入練習(xí)

from lxml import etree
text = ''' <div> <ul> 
        <li class="item-1"><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(text)
#獲取href的列表和title的列表
href_list = html.xpath("http://li[@class='item-1']/a/@href")
title_list = html.xpath("http://li[@class='item-1']/a/text()")
#組裝成字典
for href in href_list:
    item = {}
    item["href"] = href
    item["title"] = title_list[href_list.index(href)]
    print(item)

輸出為：

{'href': 'link1.html', 'title': 'first item'}
{'href': 'link2.html', 'title': 'second item'}
{'href': 'link4.html', 'title': 'fourth item'}

6.lxml模塊的進(jìn)階使用

返回的是element對(duì)象，可以繼續(xù)使用xpath方法，對(duì)此我們可以在后面的數(shù)據(jù)提取過(guò)程中：先根據(jù)某個(gè)標(biāo)簽進(jìn)行分組，分組之后再示例如下：

from lxml import etree
text = ''' <div> <ul> 
        <li class="item-1"><a>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(text)
li_list = html.xpath("http://li[@class='item-1']")
print(li_list)

結(jié)果為：

[<Element li at 0x11106cb48>, <Element li at 0x11106cb88>, <Element li at 0x11106cbc8>]數(shù)據(jù)的提取

可以發(fā)現(xiàn)結(jié)果是一個(gè)element對(duì)象，這個(gè)對(duì)象能夠繼續(xù)使用xpath方法

先根據(jù)li標(biāo)簽進(jìn)行分組，之后再進(jìn)行數(shù)據(jù)的提取

from lxml import etree
text = ''' <div> <ul> 
        <li class="item-1"><a>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> '''
#根據(jù)li標(biāo)簽進(jìn)行分組
html = etree.HTML(text)
li_list = html.xpath("http://li[@class='item-1']")
#在每一組中繼續(xù)進(jìn)行數(shù)據(jù)的提取
for li in li_list:
    item = {}
    item["href"] = li.xpath("./a/@href")[0] if len(li.xpath("./a/@href"))>0 else None
    item["title"] = li.xpath("./a/text()")[0] if len(li.xpath("./a/text()"))>0 else None
    print(item)

結(jié)果是：

{'href': None, 'title': 'first item'}
{'href': 'link2.html', 'title': 'second item'}
{'href': 'link4.html', 'title': 'fourth item'}

7.案列：貼吧極速版

代碼如下：

import requests
from lxml import etree
class TieBaSpider:
    def __init__(self, tieba_name):
        #1. start_url
        self.start_url= "http://tieba.baidu.com/mo/q---C9E0BC1BC80AA0A7CE472600CDE9E9E3%3AFG%3D1-sz%40320_240%2C-1-3-0--2--wapp_1525330549279_782/m?kw={}&lp=6024".format(tieba_name)
        self.headers = {"User-Agent": "Mozilla/5.0 (Linux; Android 8.0; Pixel 2 Build/OPD3.170816.012) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/66.0.3359.139 Mobile Safari/537.36"}
        self.part_url = "http://tieba.baidu.com/mo/q---C9E0BC1BC80AA0A7CE472600CDE9E9E3%3AFG%3D1-sz%40320_240%2C-1-3-0--2--wapp_1525330549279_782"
    def parse_url(self,url): #發(fā)送請(qǐng)求，獲取響應(yīng)
        # print(url)
        response = requests.get(url,headers=self.headers)
        return response.content
    def get_content_list(self,html_str): #3. 提取數(shù)據(jù)
        html = etree.HTML(html_str)
        div_list = html.xpath("http://body/div/div[contains(@class,'i')]")
        content_list = []
        for div in div_list:
            item = {}
            item["href"] = self.part_url+div.xpath("./a/@href")[0]
            item["title"] = div.xpath("./a/text()")[0]
            item["img_list"] = self.get_img_list(item["href"], [])
            content_list.append(item)
        #提取下一頁(yè)的url地址
        next_url = html.xpath("http://a[text()='下一頁(yè)']/@href")
        next_url = self.part_url + next_url[0] if len(next_url)>0 else None
        return content_list, next_url
    def get_img_list(self,detail_url, img_list):
        #1. 發(fā)送請(qǐng)求，獲取響應(yīng)
        detail_html_str = self.parse_url(detail_url)
        #2. 提取數(shù)據(jù)
        detail_html = etree.HTML(detail_html_str)
        img_list += detail_html.xpath("http://img[@class='BDE_Image']/@src")
        #詳情頁(yè)下一頁(yè)的url地址
        next_url = detail_html.xpath("http://a[text()='下一頁(yè)']/@href")
        next_url = self.part_url + next_url[0] if len(next_url)>0 else None
        if next_url is not None: #當(dāng)存在詳情頁(yè)的下一頁(yè)，請(qǐng)求
            return self.get_img_list(next_url, img_list)
        #else不用寫(xiě)
        img_list = [requests.utils.unquote(i).split("src=")[-1] for i in img_list]
        return img_list
    def save_content_list(self,content_list):#保存數(shù)據(jù)
        for content in content_list:
            print(content)
    def run(self): #實(shí)現(xiàn)主要邏輯
        next_url = self.start_url
        while next_url is not None:
            #1. start_url
            #2. 發(fā)送請(qǐng)求，獲取響應(yīng)
            html_str = self.parse_url(next_url)
            #3. 提取數(shù)據(jù)
            content_list, next_url = self.get_content_list(html_str)
            #4. 保存
            self.save_content_list(content_list)
            #5. 獲取next_url，循環(huán)2-5
if __name__ == '__main__':
    tieba = TieBaSpider("每日中國(guó)")
    tieba.run()

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