使用字符串函数的If语句

def validate_email(email):
    if len(email) < 5:
        return "Email is too short"
    
    if "@" not in email:
        return "Email must contain '@'"
    
    parts = email.split("@")
    if len(parts) != 2:
        return "Email must contain exactly one '@'"
    
    username, domain = parts
    if "." not in domain:
        return "Domain must contain '.'"
    
    return "Valid email"

# 测试
print(validate_email("user@example.com"))  # 输出: Valid email
print(validate_email("user@example"))      # 输出: Domain must contain '.'
print(validate_email("userexample.com"))   # 输出: Email must contain '@'

length = len("hello")
if isinstance(length, int):
    print("Length is an integer:", length)

def is_valid_email(email):
    return "@" in email and "." in email.split("@")[1]

if is_valid_email("user@example.com"):
    print("Valid email")
else:
    print("Invalid email")