参考代码：

# 方法1
ip = input("请输入IP:")
if len(ip.split(".")) !=4:
    print("NO")
    exit()
elif " " in ip.split("."):
    print("NO")
    exit()
else:
    new_list = [int(i) for i in ip.split(".")]
    for i in new_list:
        if not 0 <= i < 255:
            print("NO")
            break
    else:
        print("YES")

# 方法2
import IPy 
def is_ip(address): 
  try: 
    IPy.IP(address) 
    return "YES"
  except Exception as e: 
    return "NO"
address = input("请输入IP:")
is_ip(address)

input_ip=[int(x)  for x in input("请输入IP:").split(".")]
if len(input_ip) != 4:
    print("NO")
    exit()
for i in range(len(input_ip)):
    if i==0 :
        if not 0< input_ip[i]<=255:
            print("NO")
            exit()
    else:
        if not 0<= input_ip[i] <=255:
            print("NO")
            exit()
print("YES")

package main

import (
    "fmt"
    "net"
)

func main() {
    /*
    问题描述： 输入一个 ip 地址，若合法，返回 YES；不合法，返回 NO
    问题示例： 输入: 101.138.125.3 输出: YES
     */

    ip := "192.172.1"

    if address := net.ParseIP(ip); address == nil {
        fmt.Println("NO")
    } else {
        fmt.Println("YES")
    }

}