第三方库：Requests模块

Requests模块是一个用于网络访问的模块，类似的模块有urllib，urllib2，httplib，httplib2等
在爬虫中常使用的模块：
获取网页内容的----- urllib, requests
分析网页常用的模块------ re, bs4(beautifulsoup4)

一 安装Requests

pip install requests

示例:

import requests
url = 'http://www.taobao.com'
response = requests.get(url)

print(response)
print(response.text)
print(type(response.text))

可以看到 get类就可以直接访问了，再通过该类中的方法，就可以查看具体的内容了。并且还可以看到其内容的类型是字符串
还可以查看其访问状态和cookie信息等

print(response.status_code)
print(response.cookies)

二 具体的Requests操作

1.常见的请求方式

上传与删除：

import requests

response = requests.post('http://httpbin.org/post', data={'name' : 'fentiao', 'age':10})
print(response.text)

response = requests.delete('http://httpbin.org/delete', data={'name' : 'fentiao'})
print(response.text)

2.带参数的get请求

比如说要访问一个网址（url1 = 'https://movie.douban.com/subject/4864908/comments?start=20&limit=20&sort=new_score&status=P），但是它太长了
这时就可以将其解析，后面的参数可以作为参数传进去

import  requests
data = {
    'start': 20,
    'limit': 40,
    'sort': 'new_score',
    'status': 'P',
}
url = 'https://movie.douban.com/subject/4864908/comment'
response = requests.get(url, params=data)
print(response.url)

3.解析json格式

和json模块相结合，将所需的内容转换成所需要的格式

import requests
ip = input("请输入查询的IP：")
url = "http://ip.taobao.com/service/getIpInfo.php?ip=%s" %(ip)
response = requests.get(url)
content  = response.json()
print(content)
print(type(content))

4.获取二进制数据

1). 下载图片

import requests
url = 'https://gss0.bdstatic.com/-4o3dSag_xI4khGkpoWK1HF6hhy/baike/w%3D268%3Bg%3D0/sign=4f7bf38ac3fc1e17fdbf8b3772ab913e/d4628535e5dde7119c3d076aabefce1b9c1661ba.jpg'
response = requests.get(url)

with open('github.png', 'wb') as f:
    # response.text ： 返回字符串的页面信息
    # response.content ： 返回bytes的页面信息
    f.write(response.content)

2)下载视频

import requests
url = "http://gslb.miaopai.com/stream/sJvqGN6gdTP-sWKjALzuItr7mWMiva-zduKwuw__.mp4"
response = requests.get(url)
with open('/tmp/learn.mp4', 'wb') as f:
    f.write(response.content)

5. 添加headers信息

可以直接添加header信息，更加简洁的进行浏览器的伪装

import requests
url = 'http://www.cbrc.gov.cn/chinese/jrjg/index.html'
user_agent = 'Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Firefox/45.0'
headers = {
    'User-Agent': user_agent
}
response = requests.get(url, headers=headers)
print(response.text)
print(response.status_code)

6.响应信息的操作

1).对象常用的属性：

import requests
url = 'http://www.cbrc.gov.cn/chinese/jrjg/index.html'
user_agent = 'Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Firefox/45.0'
headers = {
    'User-Agent': user_agent
}
response = requests.get(url, headers=headers)
print(response.text)
print(response.content)
print(response.status_code)
print(response.headers)
print(response.url)

2).状态码的判断
利用三元运算符来进行判断

import requests
url = 'http://www.cbrc.gov.cn/chinese/jrjg/index.html'
user_agent = 'Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Firefox/45.0'
headers = {
    'User-Agent': user_agent
}
response = requests.get(url, headers=headers)
exit() if response.status_code != 200 else print("请求成功")

7.上传文件

import  requests
# 上传的数据信息(字典存储)
data = {'file':open('github.png', 'rb')}
response = requests.post('http://httpbin.org/post', files=data)
print(response.text)

8.获取cookie信息

1).获得的cookie信息是以字典的形式存在的

import  requests

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

2).读取已经存在的cookie信息访问网址内容

import  requests

# 设置一个cookie: name='westos'
response1 = requests.get('http://httpbin.org/cookies/set/name/westos')
response2 = requests.get('http://httpbin.org/cookies')
print(response1.text)
print(response2.text)

但是发现在第二次访问的时候，cookie信息并没有存在。
这是因为在第一次访问时，会话跟踪，但是在第二次访问时，会话已经断开，进行的是第二次的会话跟踪
这里就需要在两次访问之间将会话维持住，不让其断开

requests 中的 session 提供了这样的作用

import  requests

# 设置一个cookie: name='westos'
s = requests.session()
response1 = s.get('http://httpbin.org/cookies/set/name/westos')
response2 = s.get('http://httpbin.org/cookies')
print(response1.text)
print(response2.text)

9.忽略证书验证

有些网站是需要进行证书验证的，比如我们熟知的12306

#忽略证书验证
import  requests
url = 'https://www.12306.cn'
response = requests.get(url, verify=False)
print(response.status_code)
print(response.text)

10.代理设置

设置超时时间：为 0.1s ，是访问不成功的

import requests
proxy = {
    'https': '171.221.239.11:808',
    'http': '218.14.115.211:3128'
}
try:
    response = requests.get('http://httpbin.org/get', proxies=proxy,  timeout=0.1)
except:
    print('time out')
else:
    print(response.text)