python 2.7 'module' object has no attribute 'urlopen' 请问怎么解决 代码如下

#coding:utf8
import urllib2
import cookielib

url="http://www.baidu.com"

print '第一种方法'
response1=urllib2.urlopen(url)
print response1.getcode()
print len(response1.read())

print '第二种方法'
request=urllib2.Request(url)
request.add_header("user-agent", "Mozilla/5.0")
response2=request.urlopen(request)
print response2.getcode()
print len(response2.read())

print '第三种方法'
cj=cookielib.CookieJar()
opener=request.build_opener(request.HTTPCookieProcessor(cj))
request.install_opener(opener)
response3=request.urlopen(url)
print response3.getcode()
print cj
print len(response3.read())