域名格式校验

import re

def validate_domain(domain):
    pattern = r'^[a-zA-Z0-9-]+(\.[a-zA-Z0-9-]+)*\.[a-zA-Z]{2,}$'
    if re.match(pattern, domain):
        return True
    else:
        return False

# 测试
print(validate_domain("example.com"))  # True
print(validate_domain("example..com")) # False

import dns.resolver

def validate_domain_dns(domain):
    try:
        answers = dns.resolver.resolve(domain, 'A')
        return True
    except dns.resolver.NXDOMAIN:
        return False
    except dns.resolver.NoAnswer:
        return False
    except dns.resolver.Timeout:
        return False

# 测试
print(validate_domain_dns("example.com"))  # True
print(validate_domain_dns("nonexistentdomain.com"))  # False