What is the best way to re-raise any exception with a message
supplemented with additional information (e.g. line number in a
template)? Let's say for simplicity I just want to add "sorry" to every
exception message. My naive solution was this:
try:
...
except Exception, e:
raise e.__class__, str(e) + ", sorry!"
This works pretty well for most exceptions, e.g.
>>> try:
... 1/0
... except Exception, e:
... raise e.__class__, str(e) + ", sorry!"
...
Traceback (most recent call last):
File "<stdin>", line 4, in <module>
ZeroDivisionError: integer division or modulo by zero, sorry!
But it fails for some exceptions that cannot be instantiated with a
single string argument, like UnicodeDecodeError which gets "converted"
to a TypeError:
>>> try:
... unicode('\xe4')
... except Exception, e:
... raise e.__class__, str(e) + ", sorry!"
...
Traceback (most recent call last):
File "<stdin>", line 4, in <module>
TypeError: function takes exactly 5 arguments (1 given)
Another approach is using a wrapper Extension class:
class SorryEx(Exception):
def __init__(self, e):
self._e = e
def __getattr__(self, name):
return getattr(self._e, name)
def __str__(self):
return str(self._e) + ", sorry!"
try:
unicode('\xe4')
except Exception, e:
raise SorryEx(e)
But then I get the name of the wrapper class in the message:
__main__.SorryEx: 'ascii' codec can't decode byte 0xe4 in position 0:
ordinal not in range(128), sorry!
Yet another approach would be to replace the __str__ method of e, but
this does not work for new style Exceptions (Python 2.5).
Any suggestions?
-- Chris
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