Python多异常捕获 - 多个except与元组捕获

try:
    # 可能引发多种异常的代码
    语句块
except ValueError:
    # 处理ValueError
    处理代码1
except TypeError:
    # 处理TypeError
    处理代码2
except KeyError:
    # 处理KeyError
    处理代码3

try:
    # 可能引发异常的代码
    语句块
except (ValueError, TypeError, KeyError) as e:
    # 统一处理这三种异常
    print(f"发生错误：{type(e).__name__} - {e}")

# 正确示例：子类在前，父类在后
try:
    # 某些操作
    pass
except FileNotFoundError:  # 子类
    print("文件未找到")
except OSError:           # 父类
    print("操作系统错误")
except Exception:         # 所有异常的基类（放在最后）
    print("其他异常")

# 错误示例：父类在前，子类永远无法被匹配
try:
    # 某些操作
    pass
except Exception:         # 这个会捕获所有异常
    print("任何异常")
except FileNotFoundError:  # 永远不会被执行！
    print("文件未找到")
# 这会导致 SyntaxWarning 或逻辑错误

def process_user_input():
    """处理用户输入的完整示例"""
    data = {"users": [{"name": "小明", "age": "25"}]}

    try:
        index = int(input("请输入用户索引："))
        user = data["users"][index]
        age = int(user["age"])
        print(f"用户：{user['name']}，年龄：{age}")
    except ValueError as e:
        print(f"输入值错误：请输入有效的整数。详情：{e}")
    except IndexError as e:
        print(f"索引超出范围：有效范围是 0-{len(data['users'])-1}。详情：{e}")
    except KeyError as e:
        print(f"键不存在：{e}")
    except TypeError as e:
        print(f"类型错误：{e}")

# 测试各种场景
# 输入 "abc" -> ValueError
# 输入 "10" -> IndexError
# 正常输入 "0" -> 输出用户信息

import os

def safe_read_file(filename):
    """安全读取文件，统一处理IO相关异常"""
    try:
        with open(filename, 'r', encoding='utf-8') as f:
            return f.read()
    except (FileNotFoundError, PermissionError, IsADirectoryError) as e:
        print(f"文件读取失败：{type(e).__name__} - {e}")
        return None
    except UnicodeDecodeError:
        print(f"编码错误：文件不是UTF-8编码")
        return None

# 测试
safe_read_file("nonexistent.txt")     # FileNotFoundError
safe_read_file("/root/secret.txt")    # PermissionError
safe_read_file("/tmp")                # IsADirectoryError

def calculate_and_save(a, b, filename):
    """计算结果并保存到文件"""
    try:
        result = a / b
        with open(filename, 'w') as f:
            f.write(str(result))
        print(f"计算结果已保存：{result}")
    except ZeroDivisionError:
        print("错误：除数不能为零")
    except TypeError:
        print("错误：参数必须是数字")
    except (FileNotFoundError, PermissionError) as e:
        print(f"文件操作失败：{type(e).__name__} - {e}")
    except OSError as e:
        print(f"系统错误：{e}")
    finally:
        print("操作完成")

# 测试
calculate_and_save(10, 2, "result.txt")    # 成功
calculate_and_save(10, 0, "result.txt")    # ZeroDivisionError
calculate_and_save("a", 2, "result.txt")   # TypeError
calculate_and_save(10, 2, "/root/out.txt") # PermissionError