Python中异常处理：十个你可能忽视的问题示例-蒲公英云

Python中异常处理：十个你可能忽视的问题示例

在Python编程中，异常处理是非常重要的一部分。它可以帮助我们优雅地处理程序中的错误情况，避免程序突然崩溃。以下是一些可能被忽视的异常处理问题示例：

未捕获的异常：

def divide(a, b):
    return a / b
try:
    result = divide(10, 0)
except ZeroDivisionError as e:
    print(f"Error: {e}, Handling it...")
    # 在这里，你可以选择忽略错误或者提供一个备选方案
    result = "Warning! Division by zero is not allowed."
print(result)

没有正确处理特定异常：

def read_file(file_path):
    try:
        with open(file_path, 'r') as f:
            content = f.read()
            return content
    except FileNotFoundError:
        print(f"{file_path}} not found.")
        # 在这里，你可以选择直接抛出异常或者提供备选方案
        return "File not found!"
    except Exception as e:
        print(f"Error: {e}, Handling it...")
        # 处理通用异常，例如所有非FileNotFoundError的异常
        return "Internal server error!"
content = read_file("non_existent_file.txt")
print(content)

过度捕获：

def divide(a, b):
    if not isinstance(b, (int, float))):
        raise ValueError("Second argument must be a number.")
    return a / b
try:
    result = divide(10, "hello"))
except Exception as e:
    print(f"Error: {e}, Handling it...")
    # 这里可能会导致过度捕获
    result = "Invalid input. Number required."
print(result)

使用finally块来清理资源：

def open_file(file_path):
    try:
        with open(file_path, 'r') as f:
            content = f.read()
            return content
    except FileNotFoundError:
        print(f"{file_path}} not found.")
        # 使用finally块确保文件被正确关闭
        finally:
            if "file_path" in locals():
                os.remove(file_path)  # 如果文件是本地的，删除它
        return "File not found!"
    except Exception as e:
        print(f"Error: {e}, Handling it...")
        return "Internal server error!"
content = open_file("non_existent_file.txt")
print(content)

使用with语句处理资源：

def read_and_write_file(file_path):
    try:
        with open(file_path, 'r') as f_read:
            content = f_read.read()
            with open(file_path, 'w') as f_write:
                f_write.write(content.upper())
                return "Content updated."
    except FileNotFoundError:
        print(f"{file_path}} not found.")
        return "File not found!"
    except Exception as e:
        print(f"Error: {e}, Handling it...")
        return "Internal server error!"
content = read_and_write_file("test_file.txt")
print(content)

避免在except块中再次抛出异常：

def divide(a, b):
    if not isinstance(b, (int, float))):
        raise ValueError("Second argument must be a number.")
    return a / b
try:
    result = divide(10, "hello"))
except ValueError as ve:
    print(f"Error: {ve}, Handling it...")
    # 这里避免了再次抛出异常
    result = "Invalid input. Number required."
except Exception as e:
    print(f"Error: {e}, Handling it...")
    return "Internal server error!"
print(result)

使用断言（assert）来检查预期的条件：

def divide(a, b):
    assert isinstance(b, (int, float))), "Second argument must be a number."
    return a / b
try:
    result = divide(10, "hello"))
except AssertionError as ae:
    print(f"Error: {ae}, Handling it...")
    # 在这里，你可以选择忽略错误或者提供一个备选方案
    result = "Invalid input. Number required."
except Exception as e:
    print(f"Error: {e}, Handling it...")
    return "Internal server error!"
print(result)

在异常处理中使用更具体的异常类型：

def divide(a, b):
    try:
        result = a / b
        if isinstance(result, float) and result.is_integer():
            result = int(result)
        return result
    except ZeroDivisionError as zde:
        print(f"Error: {zde}, Handling it...")
        # 在这里，你可以选择忽略错误或者提供一个备选方案
        return "Cannot divide by zero!"
    except Exception as e:
        print(f"Error: {e}, Handling it...")
        return "An unexpected error occurred!"
result = divide(10, 0))
print(result)

使用try-except-finally块来组织代码，无论是否发生异常：

 def read_and_write_file(file_path):
     try:
         with open(file_path, 'r') as f_read:
             content = f_read.read()
             if content:
                 with open(file_path, 'w') as f_write:
                     f_write.write(content.upper())
                     return "Content updated."
                 else:
                     return "File is empty or does not exist."
     except FileNotFoundError:
         print(f"{file_path}} not found.")
         return "File not found!"
     except Exception as e:
         print(f"Error: {e}, Handling it...")
         return "An unexpected error occurred!"
 content = read_and_write_file("test_file.txt")
 print(content)