直接上demo代码了
包括：直接拉取，使用Reuqest(post/get),使用代理，cookie,跳转处理

#!/usr/bin/python
# -*- coding:utf-8 -*-
# urllib2_test.py
# author: wklken
# 2012-03-17 wklken@yeah.net


import urllib,urllib2,cookielib,socket

url = "http://www.testurl....." #change yourself
#最简单方式
def use_urllib2():
 try:
 f = urllib2.urlopen(url, timeout=5).read()
 except urllib2.URLError, e:
 print e.reason
 print len(f)

#使用Request
def get_request():
 #可以设置超时
 socket.setdefaulttimeout(5)
 #可以加入参数 [无参数，使用get，以下这种方式，使用post]
 params = {"wd":"a","b":"2"}
 #可以加入请求头信息，以便识别
 i_headers = {"User-Agent": "Mozilla/5.0 (Windows; U; Windows NT 5.1; zh-CN; rv:1.9.1) Gecko/20090624 Firefox/3.5",
 "Accept": "text/plain"}
 #use post,have some params post to server,if not support ,will throw exception
 #req = urllib2.Request(url, data=urllib.urlencode(params), headers=i_headers)
 req = urllib2.Request(url, headers=i_headers)

 #创建request后，还可以进行其他添加,若是key重复，后者生效
 #request.add_header('Accept','application/json')
 #可以指定提交方式
 #request.get_method = lambda: 'PUT'
 try:
 page = urllib2.urlopen(req)
 print len(page.read())
 #like get
 #url_params = urllib.urlencode({"a":"1", "b":"2"})
 #final_url = url + "?" + url_params
 #print final_url
 #data = urllib2.urlopen(final_url).read()
 #print "Method:get ", len(data)
 except urllib2.HTTPError, e:
 print "Error Code:", e.code
 except urllib2.URLError, e:
 print "Error Reason:", e.reason

def use_proxy():
 enable_proxy = False
 proxy_handler = urllib2.ProxyHandler({"http":"http://proxyurlXXXX.com:8080"})
 null_proxy_handler = urllib2.ProxyHandler({})
 if enable_proxy:
 opener = urllib2.build_opener(proxy_handler, urllib2.HTTPHandler)
 else:
 opener = urllib2.build_opener(null_proxy_handler, urllib2.HTTPHandler)
 #此句设置urllib2的全局opener
 urllib2.install_opener(opener)
 content = urllib2.urlopen(url).read()
 print "proxy len:",len(content)

class NoExceptionCookieProcesser(urllib2.HTTPCookieProcessor):
 def http_error_403(self, req, fp, code, msg, hdrs):
 return fp
 def http_error_400(self, req, fp, code, msg, hdrs):
 return fp
 def http_error_500(self, req, fp, code, msg, hdrs):
 return fp

def hand_cookie():
 cookie = cookielib.CookieJar()
 #cookie_handler = urllib2.HTTPCookieProcessor(cookie)
 #after add error exception handler
 cookie_handler = NoExceptionCookieProcesser(cookie)
 opener = urllib2.build_opener(cookie_handler, urllib2.HTTPHandler)
 url_login = "https://www.yourwebsite/?login"
 params = {"username":"user","password":"111111"}
 opener.open(url_login, urllib.urlencode(params))
 for item in cookie:
 print item.name,item.value
 #urllib2.install_opener(opener)
 #content = urllib2.urlopen(url).read()
 #print len(content)
#得到重定向 N 次以后最后页面URL
def get_request_direct():
 import httplib
 httplib.HTTPConnection.debuglevel = 1
 request = urllib2.Request("http://www.google.com")
 request.add_header("Accept", "text/html,*/*")
 request.add_header("Connection", "Keep-Alive")
 opener = urllib2.build_opener()
 f = opener.open(request)
 print f.url
 print f.headers.dict
 print len(f.read())

if __name__ == "__main__":
 use_urllib2()
 get_request()
 get_request_direct()
 use_proxy()
 hand_cookie()