Question

提出子例外的好方法是什么（这是该术语）？场景：我想在发生http或ftp异常时引发自定义ConnectivityException。有没有办法提出ConnectivityException，以便异常被正确分类（即我应该能够判断是否因为http ot ftp而引发了ConnectivityException）？

Answer 1

标准技术是将ConnectivityException子类化为特定于每种错误条件的异常类：

class ConnectivityException(Exception): pass

class HTTPConnectivityException(ConnectivityException): pass

class FTPConnectivityException(ConnectivityException): pass

然后，您可以使用raise ConnectivityException或raise HTTPConnectivityException代替raise FTPConnectivityException，具体取决于您要指明的特定类型的错误。

可以使用多个异常块根据异常类型分派错误处理：

try:
    some_network_operation()
except HTTPConnectivityException as ex:
    # This will execute if the error is an HTTPConnectivityException.
except FTPConnectivityException as ex:
    # Likewise for FTPConnectivityException.
except ConnectivityException as ex:
    # The generic case; this block will execute if the ConnectivityException isn't 
    # an instance of one of the earlier specified subclasses.

请注意，异常处理块以词法顺序尝试;将使用指定异常对象所属的类的第一个块。在这种情况下，这意味着您需要将ConnectivityException块放在最后，否则它也会捕获HTTPConnectivityException和FTPConnectivityException。

Answer 2

您可以添加名为＆＃39; source＆＃39;的属性到ConnectivityException，并将其设置为＆＃39; http＆＃39;或者＆＃39; ftp＆＃39;根据具体情况，当捕获ConnectivityException时，检查source属性并决定做什么

这里我推荐另一种使用继承类

的方法

class ConnectivityException(Exception):
    pass # you can define some attributes and methods, here I just escape

class HTTPConnectivityException(ConnectivityException):
    pass

class FTPConnectivityException(ConnectivityException):
    pass

def func():
    if some_condition:
        raise HTTPConnectivityException()
    if some_other_condition:
        raise FTPConnectivityException()

def another_func():
    try:
        func()
    except HTTPConnectivityException as e:
        pass # you can do something here
    except FTPConnectivityException as e:
        pass

Python自定义异常和子异常

2 个答案: