一、打开一个网页获取所有的内容
from urllib import urlopen
doc = urlopen(http://www.baidu.com).read()
print doc
二、获取http头
from urllib import urlopen
doc = urlopen(http://www.baidu.com)
print doc.info()
print doc.info().getheader('content-type')
 三、使用代理
    1. 查看环境变量
print n.join([%s=%s % (k, v) for k, v in os.environ.items()])
print os.getenv(http_proxy)
    2. 设置环境变量
import   os 
os.putenv(http_proxy,   http://proxyaddr:)
     3. 使用代理
# use http://www.someproxy.com:3128 for http proxying
proxies = {'http': 'http://www.someproxy.com:3128'}
filehandle = urllib.urlopen(some_url, proxies=proxies)
# don't use any proxies
filehandle = urllib.urlopen(some_url, proxies={})
# use proxies from environment - both versions are equivalent
filehandle = urllib.urlopen(some_url, proxies=none)
filehandle = urllib.urlopen(some_url)