python网络爬虫学习笔记之二发起http请求及传参

野性酷女 2022-02-01 08:59 342阅读 0赞

# 获取响应内容 #

response对象有属性：  
text 请求返回的所有内容  
status\_code 状态码  
encoding 编码  
content 字节方式的响应内容，比如 以\\n表示回车符, 还有\\t \\r等  
r.json()  如果返回的是json串，则会使用Requests自带的json解码器进行json的解析

# 传递请求参数 #

import requests

dict = \{'key1' : 'value1', 'key2' : 'value2'\}  
link = 'http://httpbin.org/get'  
headers = \{'User-Agent' : 'Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/73.0.3683.103 Safari/537.36', 'Content-Type': 'text/html'\}  
r = requests.get(link, headers=headers, params=dict)  
print(r.content)  
print(r.status\_code)  
print(r.json())  
程序运行结果：  
b'\{\\n  "args": \{\\n    "key1": "value1", \\n    "key2": "value2"\\n  \}, \\n  "headers": \{\\n    "Accept": "\*/\*", \\n    "Accept-Encoding": "gzip, deflate", \\n    "Content-Type": "text/html", \\n    "Host": "httpbin.org", \\n    "User-Agent": "Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/73.0.3683.103 Safari/537.36"\\n  \}, \\n  "origin": "223.72.90.250, 223.72.90.250", \\n  "url": "https://httpbin.org/get?key1=value1&key2=value2"\\n\}\\n'  
200  
\{'args': \{'key1': 'value1', 'key2': 'value2'\}, 'headers': \{'Accept': '\*/\*', 'Accept-Encoding': 'gzip, deflate', 'Content-Type': 'text/html', 'Host': 'httpbin.org', 'User-Agent': 'Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/73.0.3683.103 Safari/537.36'\}, 'origin': '223.72.90.250, 223.72.90.250', 'url': 'https://httpbin.org/get?key1=value1&key2=value2'\}

可见通过params=dict已经正确传递了请求参数key1=value1&key2=value2 。另外，如果想将紧凑格式的json数据进行格式化，可以使用在线格式工具 http://www.bejson.com/

# 定制请求头 #

上面的例子中通过指定 headers参数传递了User-Agent，我们也可以传递更多的headers信息，如  
import requests

link = 'http://httpbin.org/get'  
headers = \{'Host' : 'www.santostang.com', 'User-Agent' : 'Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/73.0.3683.103 Safari/537.36', 'Content-Type': 'text/html'\}  
r = requests.get(link, headers=headers)  
print(r.status\_code)  
还可以传递更多的headers参数，从浏览器的请求中查看Request Headers 中的内容都可以加入。

# 发送post请求 #

import requests

dict = \{'key1' : 'value1', 'key2' : 'value2'\}  
headers = \{'Host' : 'www.santostang.com', 'User-Agent' : 'Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/73.0.3683.103 Safari/537.36', 'Content-Type': 'text/html'\}  
r = requests.post('http://httpbin.org/post', headers=headers, data=dict)  
print(r.text)  
运行结果：  
\{  
  "args": \{\},   
  "data": "key1=value1&key2=value2",   
  "files": \{\},   
  "form": \{\},   
  "headers": \{  
    "Accept": "\*/\*",   
    "Accept-Encoding": "gzip, deflate",   
    "Content-Length": "23",   
    "Content-Type": "text/html",   
    "Host": "www.santostang.com",   
    "User-Agent": "Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/73.0.3683.103 Safari/537.36"  
  \},   
  "json": null,   
  "origin": "223.72.90.250, 223.72.90.250",   
  "url": "https://www.santostang.com/post"  
\}  
post请求通过data参数指定请求的参数值

# 设置超时 #

import requests

r = requests.post('http://httpbin.org/post', timeout=0.001)  
print(r.text)  
运行结果：  
因为超时参数 timeout 设置的值0.001太小，执行后程序报错 socket.timeout: timed out

爬取豆瓣网的top250 电影

import requests
    from bs4 import BeautifulSoup
    
    def getMovies():
    	headers = {'Host' : 'movie.douban.com', 'User-Agent': 'Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/73.0.3683.103 Safari/537.36'}
    	movies = []
    	for i in range(0, 10):
    		r = requests.post('https://movie.douban.com/top250?start=' + str(i * 25), headers=headers)
    
    		soup = BeautifulSoup(r.text, 'lxml')
    		div_list = soup.find_all('div', class_='hd')
    		for div in div_list:
    			title = div.a.span.text
    			movies.append(title)
    
    	return movies
    		
    
    movies = getMovies()
    for i, movie in enumerate(movies):
    	print(str(i+1) + "==" + movie)

运行程序会显示豆瓣网的前250部电影。

BeautifulSoup的文档 可参考 [https://www.crummy.com/software/BeautifulSoup/bs4/doc.zh/][https_www.crummy.com_software_BeautifulSoup_bs4_doc.zh]

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[https_www.crummy.com_software_BeautifulSoup_bs4_doc.zh]: https://www.crummy.com/software/BeautifulSoup/bs4/doc.zh/
[2018111718160012.jpg]: https://img-blog.csdnimg.cn/2018111718160012.jpg
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