python - Try-Except-Else-Finally 返回 else 替代方案？

Question

我正在开发一个可以引发多个异常的函数。我想在它们的 except block 中处理这些异常，然后使用自定义消息和回溯返回结果。问题是 finally 得到保证，因此我无法在 else block 内返回任何内容。

如果引发一些 Exception，则此代码可以工作，但如果没有 Exception，则该代码不起作用。在这种情况下，我只想返回 {'success':True}。

所以从这段代码来看:

def foo():
    try:
        #some code
        return {'success':True}
    except FirstException:
        tb = traceback.format_exc()
        msg = 'There was FirstExc'
        return {'success':False,
                'tb':tb,
                'msg':msg}
    except SecondException:
        tb = traceback.format_exc()
        msg = 'There was SecondExc'
        return {'success':False,
                'tb':tb,
                'msg':msg}
    ...

我不想重复返回。我尝试过:

def foo():
    try:
        pass
    except FirstException:
        tb = traceback.format_exc()
        msg = 'There was FirstExc'
    except SecondException:
        tb = traceback.format_exc()
        msg = 'There was SecondExc'
    else:
        return {'success':True}
    finally:
        return {'success':False,
                'tb':tb,
                'msg':msg}

你知道怎么做吗？我知道我可以将 return {'success':True} 放入 try block 中，删除 finally 和 else block 并将 return {'success':False,'tb':tb,'msg':msg} 添加到每个 except block 中，但有很多 except block ，因此代码将重复多次。

还有其他选择吗？

Answer 1

不要使用finally block 。您希望仅在出现异常时返回 False，否则返回 True； finally 中的返回始终适用于这两种情况。

您可以从两个除了套件返回，也可以合并套件。

从两者返回会导致更多重复:

def foo():
    try:
        pass
    except FirstException:
        tb = traceback.format_exc()
        msg = 'There was FirstExc'
        return {'success':False,
                'tb':tb,
                'msg':msg}
    except SecondException:
        tb = traceback.format_exc()
        msg = 'There was SecondExc'
        return {'success':False,
                'tb':tb,
                'msg':msg}
    else:
        return {'success':True}

您可以将 except 套件合并为一个:

def foo():
    try:
        pass
    except (FirstException, SecondException) as e:
        tb = traceback.format_exc()
        exception_type = 'FirstExc' if isinstance(e, FirstException) else 'SecondExc'
        msg = 'There was {}'.format(exception_type)
        return {'success':False,
                'tb':tb,
                'msg':msg}
    else:
        return {'success':True}

另一种选择是首先构建返回值，然后根据需要添加信息:

def foo():
    result = {'success': True}
    try:
        pass
    except FirstException:
        tb = traceback.format_exc()
        msg = 'There was FirstExc'
        result = {'success': False, 'tb': tb, 'msg': msg}
    except SecondException:
        tb = traceback.format_exc()
        msg = 'There was SecondExc'
        result = {'success': False, 'tb': tb, 'msg': msg}
    finally:
        return result

这与 return-from-the- except-suite 选项实际上并没有什么不同。