Python 2中是urllib+urllib2
Python 2 name Python 3 name：
urllib2.urlopen() urllib.request.urlopen()
urllib2.install_opener() urllib.request.install_opener()
urllib2.build_opener() urllib.request.build_opener()
urllib2.URLError urllib.error.URLError
urllib2.HTTPError urllib.error.HTTPError
urllib2.Request urllib.request.Request
urllib2.OpenerDirector urllib.request.OpenerDirector
urllib2.BaseHandler urllib.request.BaseHandler
urllib2.HTTPDefaultErrorHandler urllib.request.HTTPDefaultErrorHandler
urllib2.HTTPRedirectHandler urllib.request.HTTPRedirectHandler
urllib2.HTTPCookieProcessor urllib.request.HTTPCookieProcessor
urllib2.ProxyHandler urllib.request.ProxyHandler
urllib2.HTTPPasswordMgr urllib.request.HTTPPasswordMgr
urllib2.HTTPPasswordMgrWithDefaultRealm urllib.request.HTTPPasswordMgrWithDefaultRealm
urllib2.AbstractBasicAuthHandler urllib.request.AbstractBasicAuthHandler
urllib2.HTTPBasicAuthHandler urllib.request.HTTPBasicAuthHandler
urllib2.ProxyBasicAuthHandler urllib.request.ProxyBasicAuthHandler
urllib2.AbstractDigestAuthHandler urllib.request.AbstractDigestAuthHandler
urllib2.HTTPDigestAuthHandler urllib.request.HTTPDigestAuthHandler
urllib2.ProxyDigestAuthHandler urllib.request.ProxyDigestAuthHandler
urllib2.HTTPHandler urllib.request.HTTPHandler
urllib2.HTTPSHandler urllib.request.HTTPSHandler
urllib2.FileHandler urllib.request.FileHandler
urllib2.FTPHandler urllib.request.FTPHandler
urllib2.CacheFTPHandler urllib.request.CacheFTPHandler
urllib2.UnknownHandler urllib.request.UnknownHandler
