How to get inner exception traceback

[Peter Otten]

Thomas Guettler wrote:

> How can you get the traceback of the inner exception?

You have to record it yourself or it will be lost.
 
> try:
>      try:
>          import does_not_exit
>      except ImportError:
>          raise Exception("something wrong")
> except:
>      ...
> 
> 
> Background: In Django some exceptions are caught and a new
> exception gets raised. Unfortunately the real error is hard
> to find. Sometimes I help myself and change (in this example)
> ImportError to e.g. IOError and then I can see the real root
> of the problem. But maybe there is a way to get the inner
> exception and its traceback. This could be displayed in the
> debug view.

You can get the current exception and traceback with

sys.exc_info() 

and later print or format it using the traceback module.

>>> try:
...     1/0
... except Exception:
...     x = sys.exc_info()
...     raise ValueError
...
Traceback (most recent call last):
  File "<stdin>", line 5, in <module>
ValueError
>>> traceback.print_exception(*x)
Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
ZeroDivisionError: integer division or modulo by zero

Peter