邮箱域名怎么去

def extract_domain(email):
    # 分割电子邮件地址，获取域名部分
    domain = email.split('@')[-1]
    return domain

# 示例
email_address = "user@example.com"
domain = extract_domain(email_address)
print(domain)  # 输出: example.com

import re

def is_valid_email(email):
    # 简单的电子邮件格式验证正则表达式
    regex = r'^[a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+\.[a-zA-Z0-9-.]+$'
    return re.match(regex, email) is not None

def extract_domain_safe(email):
    if is_valid_email(email):
        return email.split('@')[-1]
    else:
        return "Invalid email format"

# 示例
email_address = "user@example.com"
domain = extract_domain_safe(email_address)
print(domain)  # 输出: example.com

invalid_email = "userexample.com"
domain = extract_domain_safe(invalid_email)
print(domain)  # 输出: Invalid email format