Python学习笔记--Python 爬虫入门 -17-2 urllib_error+proxy

- urllib.error
    - URLError产生的原因：
        - 没网
        - 服务器链接失败
        - 知不道制定服务器
        - 是OSError的子类
        - 案例V07

from  urllib import  request,error
"""
URLError 的使用
"""
if __name__ == '__main__':

    url = 'http://www.aimmon.com'
    try:
        req = request.Request(url)
        rsp = request.urlopen(req,timeout=5)
        rsp = rsp.read()
        html = rsp.decode()
        print(html)
    except error.URLError as u:
        print("URLERROR..{}".format(u))
        print("URLError..{}".format(u.reason))
    except Exception as e:
        print(e)




>>>URLERROR..
>>>URLError..timed out

    - HTTPError, 是URLError的一个子类
        - 案例v08
    

from  urllib import  request,error
"""
URLError 的使用
"""
if __name__ == '__main__':

    url = 'https://blog.csdn.net/error/404.html'
    try:
        req = request.Request(url)
        rsp = request.urlopen(req)
        rsp = rsp.read()
        html = rsp.decode()
        print(html)
    except error.HTTPError as h:
        print("HTTPERROR..{}".format(h))
        print("HTTPError...{}".format(h.reason))
    except error.URLError as u:
        print("URLERROR..{}".format(u))
        print("URLError..{}".format(u.reason))
    except Exception as e:
        print(e)


>>> HTTPERROR..HTTP Error 404: Not Found
>>> HTTPError...Not Found

    - 两者区别：
        - HTTPError是对应的HTTP请求的返回码错误, 如果返回错误码是400以上的，则引发HTTPError
        - URLError对应的一般是网络出现问题，包括url问题
        - 关系区别： OSError > URLError > HTTPError
- UserAgent 
    - UserAgent： 用户代理，简称UA， 属于heads的一部分，服务器通过UA来判断访问者身份
    - 常见的UA值，使用的时候可以直接复制粘贴，也可以用浏览器访问的时候抓包
              

   1.Android

      Mozilla/5.0 (Linux; Android 4.1.1; Nexus 7 Build/JRO03D) AppleWebKit/535.19 (KHTML, like Gecko) Chrome/18.0.1025.166 Safari/535.19
      Mozilla/5.0 (Linux; U; Android 4.0.4; en-gb; GT-I9300 Build/IMM76D) AppleWebKit/534.30 (KHTML, like Gecko) Version/4.0 Mobile Safari/534.30
      Mozilla/5.0 (Linux; U; Android 2.2; en-gb; GT-P1000 Build/FROYO) AppleWebKit/533.1 (KHTML, like Gecko) Version/4.0 Mobile Safari/533.1

   2.Firefox

      Mozilla/5.0 (Windows NT 6.2; WOW64; rv:21.0) Gecko/20100101 Firefox/21.0
      Mozilla/5.0 (Android; Mobile; rv:14.0) Gecko/14.0 Firefox/14.0

   3.Google Chrome

      Mozilla/5.0 (Windows NT 6.2; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/27.0.1453.94 Safari/537.36
      Mozilla/5.0 (Linux; Android 4.0.4; Galaxy Nexus Build/IMM76B) AppleWebKit/535.19 (KHTML, like Gecko) Chrome/18.0.1025.133 Mobile Safari/535.19

   4.iOS

      Mozilla/5.0 (iPad; CPU OS 5_0 like Mac OS X) AppleWebKit/534.46 (KHTML, like Gecko) Version/5.1 Mobile/9A334 Safari/7534.48.3
      Mozilla/5.0 (iPod; U; CPU like Mac OS X; en) AppleWebKit/420.1 (KHTML, like Gecko) Version/3.0 Mobile/3A101a Safari/419.3

    - 设置UA可以通过两种方式：
        - heads
        - add_header
        - 案例v09 
        

from  urllib import  request,error
"""
访问一个网站,更改自己的UserAgent进行伪装
"""
if __name__ == '__main__':

    try:
        url = "http://www.baidu.com"
        """
        1.使用head 
        """
        # headers = {}
        # headers['UserAgent'] ='Mozilla/5.0 (Linux; Android 4.1.1; Nexus 7 Build/JRO03D) AppleWebKit/535.19 (KHTML, like Gecko) Chrome/18.0.1025.166 Safari/535.19'
        # req = request.Request(url, headers=headers)
        """
        2.使用add_header 方法
        """
        req = request.Request(url)
        req.add_header("UserAgent",'Mozilla/5.0 (Windows NT 6.2; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/27.0.1453.94 Safari/537.36')
        rsp = request.urlopen(req)
        html = rsp.read().decode()
        print(len(html))
        print(html)
    except error.HTTPError as h:
        print("HTTPERROR..{}".format(h.reason))
    except error.URLError as u:
        print("URLERROR...{}".format(u.reason))
    except Exception as e:
        print("Exception..{}".format(e))

- ProxyHandler处理（代理服务器）
    - 使用代理IP，是爬虫的常用手段
    - 获取代理服务器的地址：
        - www.xicidaili.com
        - www.goubanjia.com
    - 代理用来隐藏真实访问中，代理也不允许频繁访问某一个固定网站，所以，代理一定要很多很多
    - 基本使用步骤：
        1. 设置代理地址
        2. 创建ProxyHandler
        3. 创建Opener
        4. 安装Opener
    - 案例v10(请更换ip地址)

"""
使用代理访问百度
"""
from  urllib import  request,error

from  urllib import  request,error
"""
访问一个网站,更改自己的UserAgent进行伪装
"""
if __name__ == '__main__':

    try:
        url = "http://www.ithome.com"
        # 1.设置代理ip地址
        proxy ={'http':'39.135.24.12:80'}
        # 2.创建ProxyHandler
        proxy_handler = request.ProxyHandler(proxy)
        # 3.创建opener
        opener = request.build_opener(proxy_handler)
        # 4.安装opener
        request.install_opener(opener)
        # req = request.Request(url)
        # req.add_header("UserAgent",'Mozilla/5.0 (Windows NT 6.2; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/27.0.1453.94 Safari/537.36')
        rsp = request.urlopen(url)
        html = rsp.read().decode()
        print(len(html))
        print(html)
    except error.HTTPError as h:
        print("HTTPERROR..{}".format(h.reason))
    except error.URLError as u:
        print("URLERROR...{}".format(u.reason))
    except Exception as e:
        print("Exception..{}".format(e))