python_怎样判断输入的字符串是否是ip地址

import re
import urllib
from urllib import request
ip_input = input('Please input a number')
li = [3, 4, 5, 6, 7]
print(li)
p = re.compile('^((25[0-5]|2[0-4]d|[01]?dd?).){3}(25[0-5]|2[0-4]d|[01]?dd?)$')  
if (p.match(ip_input) != None):
   print('This is an IP address')
else:
    print('It's not an Ip address)