python爬虫-数据解析（bs4）

基本知识概念

数据解析原理：

1. 标签定位
2. 提取标签、标签属性中存储的数据值

bs4数据解析原理：

• 1.实例化一个BeautifulSoup对象，并且将页面原码数据加载到该对象中
• 2.通过调用BeautifulSoup对象中相关的属性或方法进行标签定位和数据提取

环境安装：

pip install bs4

pip install lxml

如何实例化BeautifulSoup对象：

• from bs4 import BeautifulSoup
• 对象的实例化：

1.将本地的html文档中的数据加载到该对象中

fp = open('./test.html','r',encoding='utf-8')
soup = BeautifulSoup(fp,'lxml')

2.将互联网上获取的页面源码加载到该对象中

page_text = response.text
soup = BeautifulSoup(page_text,'lxml')

提供的用于数据解析的方法和属性：

- soup. tagName :返回的是文档中第一次 出现的tagName对应的标签

- soup. find() :
	- find( ' tagName ' ) :等同于soup. div
	- 属性定位:
		- soup. find( 'div' ,class_ , id/attr= ' song' ) 
	- soup. find_ all( 'tagName i ) :返回符合要求的所有标签(列表)
	
- select: 
	- select( '某种选择器(id, class, 标签...选择器) ' ),返回的是一个列表 。
	- 层级选择器: 
		- soup. select('.tang > ul > li > a'): >表示的是一个层级
		- oup. select(' .tang > ul a'): 空格表示的多个层级
		
- 获取标签之间的文本数据:
	- soup.a. text/string/get_ text( )
	- text/get_ text() :可以获取某一个标签中所有的文本内容
	- string:只可以获取该标签下面直系的文本内容
	
- 获取标签中属性值:
	- soup.a['href']

bs4实例 —— 爬取三国演义所有章节

需求：爬取三国演义所有章节

https://www.shicimingju.com/book/sanguoyanyi.html

from bs4 import BeautifulSoup
import requests
if __name__ == '__main__':
    headers = {
   
        'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/84.0.4147.105 Safari/537.36'
    }
    url = 'https://www.shicimingju.com/book/sanguoyanyi.html'
    page_text = requests.get(url=url,headers=headers).text
    soup = BeautifulSoup(page_text,'lxml')
    li_list = soup.select('.book-mulu > ul > li')
    fp = open('./三国演义小说.txt','w',encoding='utf-8')
    for li in li_list:
        title = li.a.string
        detail_url = 'https://www.shicimingju.com'+li.a['href']
        detail_page_text = requests.get(url=detail_url,headers=headers).text
        detail_soup = BeautifulSoup(detail_page_text, 'lxml')
        div_tag = detail_soup.find('div',class_='chapter_content')
        content = div_tag.text
        fp.write('\n' + title + ':' + content +'\n')
        print(title,'爬取成功')

发现出现乱码

response.text以文本格式查看的时候有乱码，可能是返回的内容被压缩了，这里修改一下
response.content.decode(“utf-8”) 按utf-8格式输出

from bs4 import BeautifulSoup
import requests
if __name__ == '__main__':
    headers = {
   
        'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/84.0.4147.105 Safari/537.36'
    }
    url = 'https://www.shicimingju.com/book/sanguoyanyi.html'
    page_text = requests.get(url=url,headers=headers).content.decode("utf-8")
    soup = BeautifulSoup(page_text,'lxml')
    li_list = soup.select('.book-mulu > ul > li')
    fp = open('./三国演义小说.txt','w',encoding='utf-8')
    for li in li_list:
        title = li.a.string
        detail_url = 'https://www.shicimingju.com'+li.a['href']
        detail_page_text = requests.get(url=detail_url,headers=headers).content.decode("utf-8")
        detail_soup = BeautifulSoup(detail_page_text, 'lxml')
        div_tag = detail_soup.find('div',class_='chapter_content')
        content = div_tag.text
        fp.write('\n' + title + ':' + content +'\n')
        print(title,'爬取成功')

效果图

练习2—爬取多情剑客无情剑小说所有章节

https://www.gulongwang.com/duo/

from bs4 import BeautifulSoup
import requests

if __name__ == '__main__':
    url = 'https://www.gulongwang.com/duo/'
    headers = {
   
        'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/84.0.4147.105 Safari/537.36'
    }
    page_text = requests.get(url=url,headers=headers).content.decode('GBK')
    soup = BeautifulSoup(page_text,'lxml')
    li_list = soup.select('.lb > ul > li')
    fp = open('./多情剑客无情剑.txt','w',encoding='utf-8')
    for li in li_list:
        title = li.a.string
        detail_url = 'https://www.gulongwang.com/'+li.a['href']
        detail_page_text = requests.get(url=detail_url,headers=headers).content.decode('GBK')
        detail_soup = BeautifulSoup(detail_page_text,'lxml')
        div_tag = detail_soup.find('div', class_='nr_con')
        content = div_tag.text
        fp.write('\n'+title+content+'\n')
        print(title,'爬取成功')

效果图