5.爬虫 requests库讲解 高级用法

0.文件上传

import requests

files = {'file': open('favicon.ico', 'rb')}
response = requests.post("http://httpbin.org/post", files=files)
print(response.text)

1.获取cookies

import requests

response = requests.get("https://www.baidu.com")
print(response.cookies)
for key, value in response.cookies.items():
    print(key + '=' + value)

2.会话维持

import requests

requests.get('http://httpbin.org/cookies/set/number/123456789')
response = requests.get('http://httpbin.org/cookies')
print(response.text)

*可以通过http://httpbin.org/cookies/set/number/123456789对这个网址设置个cookies

输出结果如下：

{
  "cookies": {}
}

为空？！因为两次get请求，实际上相当于你用两个浏览器打开了不同的网页。用Session()方法试试？

import requests

s = requests.Session()
s.get('http://httpbin.org/cookies/set/number/123456789')
response = s.get('http://httpbin.org/cookies')
print(response.text)

输出结果如下：

{
  "cookies": {
    "number": "123456789"
  }
}

* 用Session()我们实现了维持会话登陆模拟登陆(即用于模拟在一个浏览器中打开同一站点的不同页面)

3.证书验证

import requests

response = requests.get('https://www.12306.cn')
print(response.status_code)
# 提示出现SSLError表示证书验证错误
#######################

#去除警告
import requests
from requests.packages import urllib3
urllib3.disable_warnings()
response = requests.get('https://www.12306.cn', verify=False)
print(response.status_code)

#######################

#指定一个本地证书用作客户端证书
import requests

response = requests.get('https://www.12306.cn', cert=('/path/server.crt', '/path/key'))
print(respo
nse.status_code)

4.代理设置

#无密码的
import requests

proxies = {
  "http": "http://127.0.0.1:9743",
  "https": "https://127.0.0.1:9743",
}

response = requests.get("https://www.taobao.com", proxies=proxies)
print(response.status_code)

##############################

#有密码的
import requests

proxies = {
    "http": "http://user:password@127.0.0.1:9743/",
}
response = requests.get("https://www.taobao.com", proxies=proxies)
print(response.status_code)

##############################

#代理不支持http，支持sockes
#pip3 install 'requests[socks]'
import requests

proxies = {
    'http': 'socks5://127.0.0.1:9742',
    'https': 'socks5://127.0.0.1:9742'
}
response = requests.get("https://www.taobao.com", proxies=proxies)
print(response.status_code)

5.超时设置

import requests
from requests.exceptions import ReadTimeout
try:
    response = requests.get("http://httpbin.org/get", timeout = 0.5)
    print(response.status_code)
except ReadTimeout:
    print('Timeout')

*timeout = （5，30） 5是连接超时时间 30是读取超时时间

*timeout = 35 35是连接和读取两者之和

*timeout = None 或者我不设置 代表永久等待

6.认证设置

import requests
from requests.auth import HTTPBasicAuth

r = requests.get('http://120.27.34.24:9001', auth=HTTPBasicAuth('user', ''))
#还可以像下面这样写 简单些(默认使用HTTPBasicAuth这个类来认证 当然这个网址访问不了的)
#r = requests.get('http://120.27.34.24:9001', auth=('user', '123'))
print(r.status_code)

7.异常处理

import requests
from requests import ReadTimeout, ConnectionError, RequestException
try:
    response = requests.get("http://httpbin.org/get", timeout = 0.5)
    print(response.status_code)
except ReadTimeout:
    print('Timeout')
except ConnectionError:
    print('Connection error')
except RequestException:
    print('Error')

*可以去requests库的官方文档，找到API，再看里面的异常！！

8.Prepared Request

*在urllib里，可以将请求表示为数据结构，其余各个参数都可以通过一个Request对象来表示.

*在requests里，用Prepared Request同样可以做到！

from requests import Request,Session
url = "..."
data = {'...':'...'}
headers = {'User-Agent':'...'}
s = Session()
req = Request('POST',url,data = data,headers = headers)
prepped = s.prepare_request(req)
r = s.send(prepped)
print(r.text)

*在这里，我们引入Request，然后用url、data、headers参数构造了一个Requests对象，这时候调用Session的prepare_request()方法将其转换为一个Prepared Request对象，然后再调用send方法发送即可。

*有了这个Requests对象，就可以将请求当作独立的对象来看待，这样在进行队列调度时会非常方便。