“内部例外” （跟踪）在Python中？ [英] "Inner exception" (with traceback) in Python?

问题描述

我的背景是C＃，而我刚刚开始用Python编程。当抛出异常时，我通常希望将其包装在另一个异常中，它添加更多信息，同时仍然显示完整的堆栈跟踪。在C＃中很简单，但是我该如何在Python中执行？

在C＃中，我会这样做：

  try 
 {
 ProcessFile（filePath）; 
} 
 catch（Exception ex）
 {
抛出新的ApplicationException（无法处理文件+ filePath，ex）; 
} 
  

在Python中我可以做类似的事情：

  try：
 ProcessFile（filePath）
除了异常作为e：
 raise异常（'无法处理文件'+ filePath ，e）
  

...但这会失去内部异常的追溯！

编辑：我想同时看到异常消息和两个堆栈跟踪，并将两者关联起来。也就是说，我想在输出中看到异常X发生在这里，然后异常Y在那里 - 与C＃中一样。这是否可能在Python 2.6中？看起来像我最近可以做的（基于Glenn Maynard的答案）是：

  try：
 ProcessFile filePath）
除了异常作为e：
 raise异常（'无法处理文件'+ filePath，e），无，sys.exc_info（）[2] 
  

这包括消息和回溯两者，但它不显示在追溯中的哪个异常。

解决方案

很简单通过追溯作为第三个参数来提高。

  import sys 
 class MyException（Exception）：pass 
 
 try：
 raise TypeError（test）
除了TypeError，e：
 raise MyException（），None，sys.exc_info（）[2] 
  

在捕获一个例外并重新提起另一个异常时，请务必执行此操作。

My background is in C# and I've just recently started programming in Python. When an exception is thrown I typically want to wrap it in another exception that adds more information, while still showing the full stack trace. It's quite easy in C#, but how do I do it in Python?

Eg. in C# I would do something like this:

try
{
  ProcessFile(filePath);
}
catch (Exception ex)
{
  throw new ApplicationException("Failed to process file " + filePath, ex);
}

In Python I can do something similar:

try:
  ProcessFile(filePath)
except Exception as e:
  raise Exception('Failed to process file ' + filePath, e)

...but this loses the traceback of the inner exception!

Edit: I'd like to see both exception messages and both stack traces and correlate the two. That is, I want to see in the output that exception X occurred here and then exception Y there - same as I would in C#. Is this possible in Python 2.6? Looks like the best I can do so far (based on Glenn Maynard's answer) is:

try:
  ProcessFile(filePath)
except Exception as e:
  raise Exception('Failed to process file' + filePath, e), None, sys.exc_info()[2]

This includes both the messages and both the tracebacks, but it doesn't show which exception occurred where in the traceback.

解决方案

It's simple; pass the traceback as the third argument to raise.

import sys
class MyException(Exception): pass

try:
    raise TypeError("test")
except TypeError, e:
    raise MyException(), None, sys.exc_info()[2]

Always do this when catching one exception and re-raising another.

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