python 爬虫 异常处理

import urllib.request
import urllib.error
try:
    data =urllib.request.urlopen("http://blog.csdn.net").read()
    print(data.decode())
except urllib.error.URLError  as err:
    if hasattr(err,"code"):
        print(err.code)
    if hasattr(err,"reason"):
        print(err.reason)