Python之爬虫

HTTP请求

HTTP：HypertextTransferProtcol 超文本传输协议

1、请求行

POST/user/info?new_user=true HTTP/1.1

#资源了路径user/info 查询参数new_user=true 协议版本HTTP/1.1

2、请求头

Host:www.example.com
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; ×64)

#host指主机域名

User-Agent:curl/7.77.0

#告知服务器客户端的相关信息

Accept:*/*

#客户端想接受的响应数据是什么类型
3、请求体

{"username":"刘威","email":"liuwei@hotmail.com"}

HTTP响应

# 状态行
HTTP/1.1 200 OK
# 响应头
Date:Fri,27Jan 2023 02:10:50 GMT
Content-Type:text/html;charset=utf-8
# 响应体
<!DOCTYPE html><head><title>首页</title></head><body><h1>hello world!</h1></body>
</html>

在这里插入图片描述

获得页面响应

pip install requests

import requests
head = { "User-Agent": "Mozilla/5.0 (Windows NT 10.0; Win64; ×64)" }
response=requests.get("http://books.toscrape.com")
if response.ok:print(response.text)
else:print("error")

伪装用户访问

在这里插入图片描述

import requests
headers={"User-Agent": "Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/94.0.4606.71 Safari/537.36 Core/1.94.184.400 QQBrowser/11.3.5190.400"
}
response=requests.get("https://movie.douban.com/top250",headers=headers)
print(response.text)

打包数据

pip install bs4

from bs4 import BeautifulSoup
import requestscontent=requests.get("https://movie.douban.com/top250").text
# 传入BeautifulSoup的构造函数里
# 解析器
soup=BeautifulSoup(content,"html.parser")
# 能根据标签、属性等找出所有符合要求的元素
all_prices=soup.findAll("span",attrs={"class","title"})
for price in all_prices:print(price.string) #会把标签包围的文字返回给我们

爬取豆瓣top250

from bs4 import BeautifulSoup
import requests
# 伪装用户访问
headers={"User-Agent": "Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/94.0.4606.71 Safari/537.36 Core/1.94.184.400 QQBrowser/11.3.5190.400"
}
# 根据url格式进行自动翻页
for start_num in range(0,250,25):   response=requests.get(f"https://movie.douban.com/top250?start={start_num}",headers=headers) #我们就可以用f字符串去格式化html=response.text	#打包htmlsoup=BeautifulSoup(html,"html.parser")	#用html方式解析all_title=soup.findAll("span",attrs={"class":"title"})	#限制特定条件for title in all_title:	#遍历所需内容title_string=title.stringif "/" not in title_string:	#限制内容显示print(title_string)