Python异常处理从try-except到自定义异常的全过程

try:
    result = 10 / 0
except ZeroDivisionError:
    print("不能除以零！")

try:
    number = int(input("请输入一个数字："))
    result = 100 / number
except ValueError:
    print("输入无效！请输入数字。")
except ZeroDivisionError:
    print("不能除以零！")

try:
    file = open("不存在的文件.txt", "r")
except FileNotFoundError as e:
    print(f"错误信息：{e}")
    print(f"错误类型：{type(e).__name__}")

try:
    file = open("data.txt", "r")
    content = file.read()
except FileNotFoundError:
    print("文件未找到")
else:
    print(f"文件内容：{content}")
finally:
    print("清理工作完成")
    if 'file' in locals():
        file.close()

try:
    # 可能出错的代码
    risky_operation()
except Exception as e:
    print(f"发生错误：{e}")
    # 记录日志或进行其他处理

def check_age(age):
    if age < 0:
        raise ValueError("年龄不能为负数")
    if age > 150:
        raise ValueError("年龄不现实")
    return age

try:
    check_age(-5)
except ValueError as e:
    print(f"验证失败：{e}")

class ValidationError(Exception):
    """数据验证错误"""
    pass
class InsufficientFundsError(Exception):
    """余额不足错误"""
    def __init__(self, balance, amount):
        self.balance = balance
        self.amount = amount
        super().__init__(f"余额 {balance} 不足，需要 {amount}")
# 使用自定义异常
class BankAccount:
    def __init__(self, balance=0):
        self.balance = balance
    def withdraw(self, amount):
        if amount > self.balance:
            raise InsufficientFundsError(self.balance, amount)
        self.balance -= amount
        return self.balance
# 测试
account = BankAccount(100)
try:
    account.withdraw(200)
except InsufficientFundsError as e:
    print(f"取款失败：{e}")
    print(f"当前余额：{e.balance}")
    print(f"请求金额：{e.amount}")

def parse_config(data):
    try:
        return json.loads(data)
    except json.JSONDecodeError as e:
        raise ConfigError("配置文件格式错误") from e
# 这样可以看到完整的异常链

# 不需要手动关闭文件，with会自动处理
with open("data.txt", "r") as file:
    content = file.read()
    # 即使这里发生异常，文件也会被正确关闭