一文深入探讨Python中的异常捕获机制

try:
    # 可能引发异常的代码
    result = 10 / 0
except ZeroDivisionError:
    # 异常处理代码
    print("不能除以零！")

try:
    num = int("abc")  # 这会引发ValueError
    result = 10 / num
except (ValueError, ZeroDivisionError) as e:
    print(f"发生错误: {e}")

try:
    # 代码块
except Exception as e:
    print(f"发生未知错误: {e}")

try:
    # 尝试执行的代码
    file = open("example.txt", "r")
    content = file.read()
except FileNotFoundError:
    print("文件未找到")
except IOError:
    print("读取文件时出错")
else:
    # 如果没有异常发生，执行这里
    print("文件读取成功")
finally:
    # 无论是否发生异常都会执行
    file.close() if 'file' in locals() else None

def validate_age(age):
    if age < 0:
        raise ValueError("年龄不能为负数")
    return age

try:
    validate_age(-5)
except ValueError as e:
    print(e)

class MyCustomError(Exception):
    """自定义异常类"""
    pass

try:
    raise MyCustomError("这是一个自定义错误")
except MyCustomError as e:
    print(e)

def read_file(file_path):
    try:
        with open(file_path, 'r') as file:
            return file.read()
    except FileNotFoundError:
        print(f"错误：文件 {file_path} 未找到")
        return None
    except PermissionError:
        print(f"错误：没有权限读取文件 {file_path}")
        return None
    except Exception as e:
        print(f"读取文件时发生未知错误: {e}")
        return None

import requests

def fetch_url(url):
    try:
        response = requests.get(url, timeout=5)
        response.raise_for_status()  # 如果响应状态码不是200，抛出HTTPError
        return response.text
    except requests.exceptions.RequestException as e:
        print(f"请求URL {url} 时出错: {e}")
        return None

def validate_user_input(username, age):
    errors = []
    try:
        if not username:
            raise ValueError("用户名不能为空")
        if not isinstance(username, str):
            raise TypeError("用户名必须是字符串")
        if age < 0 or age > 120:
            raise ValueError("年龄必须在0-120之间")
    except ValueError as ve:
        errors.append(str(ve))
    except TypeError as te:
        errors.append(str(te))
    
    if errors:
        print("验证错误:")
        for error in errors:
            print(f"- {error}")
        return False
    return True