import socket

def is_valid_ip(ip):
    try:
        # 尝试将字符串解析为IP地址
        socket.inet_aton(ip)
        return True
    except socket.error:
        return False

# 测试
print(is_valid_ip("192.168.1.1"))  # True
print(is_valid_ip("256.256.256.256"))  # False
print(is_valid_ip("192.168.1"))  # False