二级域名提取

def extract_second_level_domain(full_domain):
    parts = full_domain.split('.')
    if len(parts) < 3:
        return None  # 不是一个有效的域名
    return parts[0]

# 示例
full_domain = "mail.example.com"
second_level_domain = extract_second_level_domain(full_domain)
print(second_level_domain)  # 输出: mail

import idna

def extract_second_level_domain(full_domain):
    try:
        encoded_domain = idna.encode(full_domain)
        parts = encoded_domain.decode().split('.')
        if len(parts) < 3:
            return None  # 不是一个有效的域名
        return parts[0]
    except idna.IDNAError:
        return None

# 示例
full_domain = "mail.例子.测试"
second_level_domain = extract_second_level_domain(full_domain)
print(second_level_domain)  # 输出: mail