Python内置函数之raise函数详解与实战案例

raise [Exception [, args [, traceback]]]

def divide(a, b):
    if b == 0:
        raise ValueError("除数不能为零")
    return a / b
try:
    result = divide(10, 0)
except ValueError as e:
    print(f"错误: {e}")  # 输出: 错误: 除数不能为零

def greet(name):
    if not isinstance(name, str):
        raise TypeError("name 必须是字符串")
    print(f"Hello, {name}")
greet(123)  # 抛出 TypeError

class InvalidEmailError(Exception):
    """邮箱格式错误"""
    def __init__(self, email, message="邮箱格式不正确"):
        self.email = email
        self.message = message
        super().__init__(self.message)
    def __str__(self):
        return f"{self.email} -> {self.message}"

def validate_email(email):
    if "@" not in email:
        raise InvalidEmailError(email)
    return email
try:
    validate_email("test.com")
except InvalidEmailError as e:
    print(f"验证失败: {e}")  # 输出: 验证失败: test.com -> 邮箱格式不正确

def parse_int(s):
    try:
        return int(s)
    except ValueError as e:
        # 保留原始错误并抛出新异常
        raise TypeError("无法将输入转换为整数") from e
try:
    parse_int("abc")
except TypeError as e:
    print(f"外层错误: {e}")
    print(f"原始错误: {e.__cause__}")

def register_user(age):
    if age < 18:
        raise ValueError("必须年满18岁才能注册")
    # 注册逻辑...

def fetch_data(url):
    response = requests.get(url)
    if response.status_code != 200:
        raise ConnectionError(f"请求失败: {response.status_code}")
    return response.json()

class BankAccount:
    def __init__(self, balance):
        self.balance = balance
    def withdraw(self, amount):
        if amount > self.balance:
            raise RuntimeError("余额不足")
        self.balance -= amount

# 不推荐：返回错误码
def divide(a, b):
    if b == 0:
        return None, "除数不能为零"
    return a / b, None
# 推荐：抛出异常
def divide(a, b):
    if b == 0:
        raise ValueError("除数不能为零")
    return a / b

raise ValueError  # 正确：raise ValueError()

try:
    1 / 0
except ZeroDivisionError:
    raise ValueError("自定义错误")  # 丢失原始错误信息
# 应使用：raise ValueError("自定义错误") from e