Python爬虫学习==>第八章：Requests库详解

学习目的：

　　request库比urllib库使用更加简洁，且更方便。

正式步骤

Step1：什么是requests

　　requests是用Python语言编写，基于urllib，采用Apache2 Licensed开源协议的HTTP库。它比urllib更加方便，可以节约大量工作时间，还完全满足HTTP测试需求，是一个简单易用的HTTP库。

Step2：实例引入

# -*-  coding:utf-8 -*-

import requests

response = requests.get('http://www.baidu.com')
print(type(response))
print(response.content)
print(response.status_code)
print(response.text)
print(type(response.text))
print(response.cookies)

重要：

response.content()：这是从网络上直接抓取的数据，没有经过任何的解码，是一个bytes类型，
response.text()：这是str类型数据，是requests库将response.content进行解码的字符串，解码需要指定一个编码方式，requests会根据自己的猜测来判断编码方式，有时候会判断错误，所以最稳妥的办法是response.content.decode("utf-8")，指定一个编码方式手动解码

Step3：各种请求方式

# -*-  coding:utf-8 -*-
import requests

requests.post('http://httpbin.org/post')
requests.put('http://httpbin.org/put')
requests.delete('http://httpbin.org/delete')
requests.head('http://httpbin.org/get')
requests.options('http://httpbin.org/get')

get请求
① 基本用法

# -*-  coding:utf-8 -*-

import requests

response = requests.get('http://httpbin.org/get')
print(response.text)

运行结果：

{
  "args": {}, 
  "headers": {
    "Accept": "*/*", 
    "Accept-Encoding": "gzip, deflate", 
    "Connection": "close", 
    "Host": "httpbin.org", 
    "User-Agent": "python-requests/2.18.4"
  }, 
  "origin": "222.94.50.178", 
  "url": "http://httpbin.org/get"
}

②带参数的get请求

import requests


data = {
    'name':'python','age':17
}

response = requests.get('http://httpbin.org/get',params=data)
print(response.text)

运行结果：

{
  "args": {
    "age": "17", 
    "name": "python"
  }, 
  "headers": {
    "Accept": "*/*", 
    "Accept-Encoding": "gzip, deflate", 
    "Connection": "close", 
    "Host": "httpbin.org", 
    "User-Agent": "python-requests/2.18.4"
  }, 
  "origin": "222.94.50.178", 
  "url": "http://httpbin.org/get?name=python&age=17"
}

get和post请求的区别：

GET是从服务器上获取数据，POST是向服务器传送数据
GET请求参数显示，都显示在浏览器网址上，HTTP服务器根据该请求所包含URL中的参数来产生响应内容，即“Get”请求的参数是URL的一部分。例如： http://www.baidu.com/s?wd=Chinese
POST请求参数在请求体当中，消息长度没有限制而且以隐式的方式进行发送，通常用来向HTTP服务器提交量比较大的数据（比如请求中包含许多参数或者文件上传操作等），请求的参数包含在“Content-Type”消息头里，指明该消息体的媒体类型和编码，
注意：避免使用Get方式提交表单，因为有可能会导致安全问题。比如说在登陆表单中用Get方式，用户输入的用户名和密码将在地址栏中暴露无遗。

③解析Json

import requests
import json

response = requests.get('http://httpbin.org/get')
print(response.json())
print(type(response.json()))

④获取二进制数据

# -*-  coding:utf-8 -*-
'''
保存百度图标
'''
import requests

response = requests.get('https://www.baidu.com/img/bd_logo1.png')
with open('baidu.png','wb') as f:
    f.write(response.content)
    f.close()

⑤添加headers
如果直接爬取知乎的网站，是会报错的，如：

import requests

response = requests.get('https://www.zhihu.com/explore')
print(response.text)

运行结果：

<html><body><h1>500 Server Error</h1>
An internal server error occured.
</body></html>

解决办法：

import requests
headers = {
    'user-agent':'Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/65.0.3325.181 Safari/537.36'
}
response = requests.get('https://www.zhihu.com/explore',headers = headers)
print(response.text)

就是添加一个headers,就可以正常抓取,而headers中的数据，我是通过chrome浏览器自带的开发者工具去找了然后copy过来的

基本POST请求

import requests

data = {
    'name':'python','age' : 18
}
headers = {
    'user-agent':'Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/65.0.3325.181 Safari/537.36'
}

response = requests.post('http://httpbin.org/post',data=data,headers=headers)
print(response.json())

实例：爬取拉勾网python职位，并把数据保存为字典

# -*-  coding:utf-8 -*-

import requests

headers = {
    'User-Agent' :'Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) '
                         'Chrome/69.0.3497.100 Safari/537.36',
    'Referer':"https://www.lagou.com/jobs/list_python?labelWords=&fromSearch=true&suginput="
}

data = {
    'first':"True",
    'pn':"1",
    'kd' :"python"
}
url = 'https://www.lagou.com/jobs/positionAjax.json?needAddtionalResult=false'

response = requests.get(url,headers=headers,params=data)
print(response.json())

响应

import requests
'''
response属性
'''
response = requests.get('http://www.baidu.com')
print(response.status_code,type(response.status_code))
print(response.history,type(response.history))
print(response.cookies,type(response.cookies))
print(response.url,type(response.url))
print(response.headers,type(response.headers))

运行结果：

200 <class 'int'>
[] <class 'list'>
<RequestsCookieJar[<Cookie BDORZ=27315 for .baidu.com/>]> <class 'requests.cookies.RequestsCookieJar'>
http://www.baidu.com/ <class 'str'>
{'Server': 'bfe/1.0.8.18', 'Date': 'Thu, 05 Apr 2018 06:27:33 GMT', 'Content-Type': 'text/html', 'Last-Modified': 'Mon, 23 Jan 2017 13:28:24 GMT', 'Transfer-Encoding': 'chunked', 'Connection': 'Keep-Alive', 'Cache-Control': 'private, no-cache, no-store, proxy-revalidate, no-transform', 'Pragma': 'no-cache', 'Set-Cookie': 'BDORZ=27315; max-age=86400; domain=.baidu.com; path=/', 'Content-Encoding': 'gzip'} <class 'requests.structures.CaseInsensitiveDict'>

状态码判断
状态码参考表 http://www.cnblogs.com/wuzhiming/p/8722422.html

# -*-  coding:utf-8 -*-

import requests

response = requests.get('http://www.cnblogs.com/hello.html')
exit() if not response.status_code == requests.codes.not_found else print('404 not found')

response1 = requests.get('http://www.baidu.com')
exit() if not response1.status_code == requests.codes.ok else print('Request Successly')

高级操作
①文件上传

import requests

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

运行结果不演示

②获取cookie

import requests

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

③会话维持

import requests

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

④证书验证

import requests

#verify=False表示不进行证书验证
response = requests.get('https://www.12306.cn',verify=False)
print(response.status_code)

手动指定证书

response1 = requests.get('https://www.12306.cn',cert=('/path/server.crt','/path/key'))

⑤代理设置

import requests
#用法示例，代理可以自己百度免费的代理
proxies = {
    'http':'http://127.0.0.1:端口号',
    'https':'https://ip:端口号',
    'http':'http://username:password@ip:端口号'
}

response = requests.get('http://www.baidu.com',proxies=proxies)
print(response.status_code)

⑥超时设置

import requests

response = requests.get('http://httpbin.org/get',timeout = 1)
print(response.status_code)

⑦认证设置

import requests
from requests.auth import HTTPBasicAuth

response = requests.get('http://127.0.0.1:8888',auth=('user','password'))
response1 = requests.get('http://127.0.0.1:8888',auth=HTTPBasicAuth('user','passwrd'))
print(response.status_code)

PS：127.0.0.1:8888只是举例

⑧异常处理

import requests
from requests.exceptions import ReadTimeout,HTTPError,RequestException

try:
    response = requests.get('http://httpbin.org/get',timeout = 0.01)
    print(response.status_code)
except ReadTimeout:
    print("TIME OUT")
except HTTPError:
    print('HTTP ERROR')
except RequestException:
    print("ERROR")

学习总结：

　　通过爬虫的学习可以进一步的掌握python的基础应用，我的目的就是这个，后面继续学习

Python爬虫学习==>第八章：Requests库详解

学习目的：

正式步骤

Step1：什么是requests

Step2：实例 引入

Step3：各种请求方式

学习总结：

Step2：实例引入