Python学习笔记012_网络_异常

1,Python如何访问互联网?

url + lib =  urllib

>>> # 使用urllib包下的request模块
>>> 
>>> import urllib.request
>>> 
>>> # 使用函数 .urlopen(),第一个是 string形式的地址，或者Request对象

>>> response = urllib.request.urlopen("http://www.baidu.com/")
>>> print(response)
<http.client.HTTPResponse object at 0x02927610>
>>> # 读取返回的信息
>>> # 这里要返回的是二进制数据，需要解码的
>>> html = response.read()
>>> html = html.decode("utf-8")
>>> print(html)

 2, 下载一只猫?

　我们可以访问网站  http://placekitten.com/ ，我们只需要加上 宽度和高度参数就可以得到一张量身定制的猫的图片. 

如下形式 ： http://placekitten.com/g/200/300     http://placekitten.com/400/300    

# 编写一个 download_cat.py ，完成下载一张猫图 内容如下:

import urllib.request

response = urllib.request.urlopen("http://placekitten.com/g/200/300")
cat_img = response.read()

with open("cat_200_300.jpg","wb") as f:
    f.write(cat_img)

>>> 
>>> # 除了read()方法之外，还可以使用以下方法:
>>> # geturl()  info()  getcode()
>>> 
>>> response.geturl()
'http://placekitten.com/g/200/300'
>>> response.info()
<http.client.HTTPMessage object at 0x028A6E50>
>>> print(response.info())
Date: Tue, 02 Aug 2016 08:57:00 GMT
Content-Type: image/jpeg
Content-Length: 9162
Connection: close
Set-Cookie: __cfduid=d58fa9ee9079943b9db4ce64366aa85f61470128220; expires=Wed, 02-Aug-17 08:57:00 GMT; path=/; domain=.placekitten.com; HttpOnly
Accept-Ranges: bytes
X-Powered-By: PleskLin
Access-Control-Allow-Origin: *
Cache-Control: public
Expires: Thu, 31 Dec 2020 20:00:00 GMT
Server: cloudflare-nginx
CF-RAY: 2cc051e22cad22a0-LAX
>>> 
>>> response.getcode()
200
>>> 

 3,模拟有道翻译   POST请求

如果 urllib.request.urlopen(url,data) data参数被赋值时，就会使用POST请求，并且data参数是基于 application/x-www-form-urlencoded格式，可以使用urllib.parse.urlencode()处理data

import urllib.request
import urllib.parse
import json

url = 'http://fanyi.youdao.com/translate?smartresult=dict&smartresult=rule&smartresult=ugc&sessionFrom=null'

conent = input('请输入要翻译的内容:')

data = {'type':'AUTO','i':conent,'doctype':'json','xmlVersion':'1.8',
        'keyfrom':'fanyi.web','ue':'UTF-8','action':'FY_BY_CLICKBUTTON',
        'typoResult':'true'}

# encode 是把Unicode形式变成其它编码形式
data = urllib.parse.urlencode(data).encode('utf-8')
response = urllib.request.urlopen(url,data)

# decode 是把其它编码形式变成Unicode形式
html = response.read().decode("utf-8")


# html是一个json格式的字符串数据
target = json.loads(html)

print("翻译结果: %s" %(target['translateResult'][0][0]['tgt']))

Python编码问题的解决方案总结    http://bbs.fishc.com/thread-56452-1-1.html

 

  4,headers 设置

 

headers是一个字典形式的数据，有两种设置方式 第一种是在 urlopen(url,data，headers)的第三个参数中设置；第二种方式是生成Request对象，调用 add_header(key,value)添加 

服务器检查是程序访问还是浏览器访问一般是通过 

1. User-Agent:
   Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/31.0.1650.63 Safari/537.36

header ={}
header['User-Agent'] = 'Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/31.0.1650.63 Safari/537.36'

req = urllib.request.Request(url,data,header)
response = urllib.request.urlopen(req)

>>> req.headers
{'User-agent': 'Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/31.0.1650.63 Safari/537.36'}
>>> 

req = urllib.request.Request(url,data)
req.add_header('User-Agent','Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/31.0.1650.63 Safari/537.36')

time 模块的  sleep(5)  , 表示睡5秒钟

5,代理

　　步骤：

　　1,参数是一个字典{'类型':'代理IP:端口port'}

　　proxy_support = urllib.request.ProxyHandler({})

　　2,定制、创建一个opener

　　opener = urllib.request.build_opener(proxy_support )

　　3a. 安装opener

　　urllib.request.install_opener(opener)

　　3b.调用opener

　　opener.open(url)

 在网上搜索 代理IP，可以搜索到很多免费的代理IP  比如： http://www.xicidaili.com/

 

import urllib.request
import random

#该url地址是一个查询IP的地址
url = 'http://www.whatismyip.com.tw'

iplist = ['183.129.178.14:8080','123.57.190.51:7777','101.231.250.102:80']

proxy_support = urllib.request.ProxyHandler({'http':random.choice(iplist)})


opener = urllib.request.build_opener(proxy_support)
opener.addheaders=[('User-Agent','Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/31.0.1650.63 Safari/537.36')]

urllib.request.install_opener(opener)

response = urllib.request.urlopen(url)
html = response.read().decode("utf-8")
print(html)

小应用，下载煎蛋网的妹子图 http://jandan.net/ 

import urllib.request
import os
import random
'''
打开网址.
'''
def open_url(url):

   
    iplist = ['121.193.143.249:80','119.6.136.122:80','101.231.250.102:80']

    proxy_support = urllib.request.ProxyHandler({'http':random.choice(iplist)})


    opener = urllib.request.build_opener(proxy_support)
    opener.addheaders=[('User-Agent','Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/31.0.1650.63 Safari/537.36')]

    urllib.request.install_opener(opener)

    response = urllib.request.urlopen(url)
    html = response.read()

    #req = urllib.request.Request(url)
    #req.add_header('User-Agent','Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/45.0.2454.101 Safari/537.36')
    #response = urllib.request.urlopen(req)
    #html = response.read()

    return html

'''
获取当前要下载的图片编号
'''
def get_page(url):
    
    html = open_url(url).decode('utf-8')

    # 在html中查找 <span class="current-comment-page">[2081]</span>
    a = html.find('current-comment-page') + 23
    # 从a开始找 有中括号 ]
    b = html.find(']',a)
    
    return html[a:b]

def find_imgs(page_url):

    html = open_url(page_url).decode('utf-8')

    # 在html中查找 <img src="XXX.jpg">
    img_addrs = []

    find_start = html.find('ol class="commentlist"')
    find_end = html.find('/ol',find_start)
    
    a = html.find('img src=',find_start,find_end)

    while a != -1:
        #从a开始找，最多找255个字符
        b = html.find('.jpg',a,a+255)
        if b != -1:
           
            img_addrs.append(html[a+9:b+4])
        
        else:
            b =a + 9

        a = html.find('img src=', b,find_end)

    return img_addrs

def save_imgs(folder,img_addrs):
    print(folder)
    for each in img_addrs:
        # 图片地址 斜杠拆分，取最后一个
        img_name = each.split('/')[-1]
  
        with open(img_name,'wb') as f:
            img = open_url(each)
            f.write(img)



    
'''
下载妹子图，保存到folder文件夹，下载pages张图
'''
def download_mm(folder='ooxx' , pages = 10):
    #使用 os模块，创建文件夹和切换到该文件夹
    #os.mkdir(folder)
    os.chdir(folder)

    url = 'http://jandan.net/ooxx/'
    #获取要下载的当前图片编号
    page_num = int(get_page(url))

    # 组装下载链接
    for i in range(pages):
        page_num -= i
        page_url = url + 'page-' + str(page_num)+ '#comments'
        #从链接中获取图片地址
        image_addrs = find_imgs(page_url)
        # 下载保存图片
        save_imgs(folder,image_addrs)

    print('--download__over--')

if __name__ == '__main__':
    download_mm()

网络异常  URLError HTTPError ， HTTPError 是 URLError的子类