urllib
urllib提供了一系列操作url的功能。
Get
urllib的request模块可以非常方便的抓取URL内容，也就是发送一个GET请求到指定界面。然后返回HTTP的响应:
例如，对豆瓣的一个URL:https://api.douban.com/v2/book/2129650 进行抓取，并返回响应:
from urllib import request
with request.urlopen('https://api.douban.com/v2/book/2129650') as f:
data =f.read()
print('Status:',f.status,f.reason)
for k,v in f.getheader():
print('%s :%s' % (k,v))
print('Data:',data.decode('utf-8'))
可以看到HTTP响应的头和JSON的数据
Status: 200 OK
Server: nginx
Date: Tue, 26 May 2015 10:02:27 GMT
Content-Type: application/json; charset=utf-8Content-Length: 2049Connection: closeExpires: Sun, 1 Jan 2006 01:00:00 GMTPragma: no-cache
Cache-Control: must-revalidate, no-cache, private
X-DAE-Node: pidl1
Data: {"rating":{"max":10,"numRaters":16,"average":"7.4","min":0},"subtitle":"","author":["廖雪峰编著"],"pubdate":"2007-6","tags":[{"count":20,"name":"spring","title":"spring"}...}如果我们想要模拟浏览器发送GET请求，就需要使用Request对象。通过往Requesｔ对象里面添加HTTP头，我们就可以把请求伪装成浏览器。例如，模拟Iphone6去请求豆瓣首页:
from urllib import request
req =request.Request('http://www.douban.com/')
req.add_header('User-Agent','Mozilla/6.0(iPhone: CPU iPhone OS 8_0 like Mac OS X) AppleWebKit/536.26 (KHTML, like Gecko) Version/8.0 Mobile/10A5376e Safari/8536.25')
with request.urlopen(req) as f:
data =f.read()
print('Status:',f.status,f.reason)
for k,v in f.getheaders():
print('%s :%s' % (k,v))
print('Data:',data.decode('utf-8'))
Post
如果我们要以一个POST发送一个请求，只需要把参数data以bytes形式传入;
我们模拟一个微博登陆，先读取登陆的邮箱和口令，然后按照weibo.cn的登录页格式以username=xxx &password =xx的编码传入:
from urllib import request, parse
print('Login to weibo.cn...')
email = input('Email: ')
passwd = input('Password: ')
login_data = parse.urlencode([
('username', email),
('password', passwd),
('entry', 'mweibo'),
('client_id', ''),
('savestate', '1'),
('ec', ''),
('pagerefer', 'https://passport.weibo.cn/signin/welcome?entry=mweibo&r=http%3A%2F%2Fm.weibo.cn%2F')
])
req = request.Request('https://passport.weibo.cn/sso/login')
req.add_header('Origin', 'https://passport.weibo.cn')
req.add_header('User-Agent', 'Mozilla/6.0 (iPhone; CPU iPhone OS 8_0 like Mac OS X) AppleWebKit/536.26 (KHTML, like Gecko) Version/8.0 Mobile/10A5376e Safari/8536.25')
req.add_header('Referer', 'https://passport.weibo.cn/signin/login?entry=mweibo&res=wel&wm=3349&r=http%3A%2F%2Fm.weibo.cn%2F')with request.urlopen(req, data=login_data.encode('utf-8')) as f:
print('Status:', f.status, f.reason) for k, v in f.getheaders():
print('%s: %s' % (k, v))
print('Data:', f.read().decode('utf-8'))如果我们登陆成功.我们获得的响应如下:
Status: 200 OK
Server: nginx/1.2.0
...Set-Cookie: SSOLoginState=1432620126; path=/; domain=weibo.cn
...
Data: {"retcode":20000000,"msg":"","data":{...,"uid":"1658384301"}}如果登陆失败：
...
Data: {"retcode":50011015,"msg":"\u7528\u6237\u540d\u6216\u5bc6\u7801\u9519\u8bef","data":{"username":"example@python.org","errline":536}}Handler
如果还需要更复杂的控制，比如通过一个Proxy去访问网站，我们需要使用ProxyHandler来处理，示例代码如下:
proxy_handler = urllib.request.ProxyHandler({'http': 'http://www.example.com:3128/'})
proxy_auth_handler = urllib.request.ProxyBasicAuthHandler()
proxy_auth_handler.add_password('realm', 'host', 'username', 'password')
opener = urllib.request.build_opener(proxy_handler, proxy_auth_handler)with opener.open('http://www.example.com/login.html') as f:
pass小结：
urllib提供的功能就是利用程序去解决执行各种HTTP请求。如果要模拟浏览器完成各种特定功能，就需要把请求伪装成浏览器。伪装的方式是先监控浏览器发出的请求，再根据浏览器的请求头来伪装，User-Agent头就是用来标识浏览器的。
