"Inner exception" (with traceback) in Python?

Question

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: Process…

Accepted Answer

Python 2

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.

"Inner exception" (with traceback) in Python?

Solution

Problem