Brett C. wrote:
Walter Dörwald wrote:
[...]
but we could add a new feature to that: Add a new exception subclass named Info that can be used to wrap exceptions without influencing the type of the exception raised. This could be used by code higher up in the call chain to add information to the exception without changing the type that gets caught in the except statement. For example filter() could be changed to add information about the iteration index where the exception happened:
class spam: def __getitem__(self, index): if index==42: raise TypeError return None
x = filter(None, spam())
this might give:
Traceback (most recent call last): File "spam.py", line 8, in ? x = filter(None, foo()) File "spam.py", line 4, in __getitem__ raise TypeError("ouch") TypeError: ouch Info: in filter() at index 42
So have a function that takes the current exception, stores it as an attribute of a new one,
This could be done automatically, i.e. whenever you call PyErr_SetString() etc. the currently active exception will be normalized and put into a fourth global variable (exc_cause). In Python code whenever a exception handler raises a new exception the exception that is currently handled could be set as the cause for this exception automatically by the raise statement.
and have exception-handling code no of the possible existence of the attribute and print out the info if it exists?
I'd say, the attribute should always be there, but should be initialized to None in the Exception constructor (they same should probably be done for the traceback attribute). Bye, Walter Dörwald