Guido:
There's a lot of C code out there that catches e.g. AttributeError and replaces it with a more specific error (e.g. BifurcationError("can't bifurcate the sploorg") replacing AttributeError("__bifurcate__"). I think this would cause end user confusion.
But that is a different case. As I understand it, chaining would only occur if a second exception was raised *before* the current exception was caught -- e.g. if there's a bug in a piece of code in a finally block that's being executed while unwinding to find an exception handler. In the case you're talking about, the AttributeError has been caught by the time the BifurcationError is raised, so there would be no chaining, and thus the traceback output would be the same regardless of whether chained tracebacks were printed or not. As for whether chained tracebacks should be printed when they occur, I'll have to think about that. If they are, probably the one for the most recently raised exception should be printed last, since one tends to look at the bottom of the traceback first to find the cause of the immediate problem (I do, at least). Greg Ewing, Computer Science Dept, +--------------------------------------+ University of Canterbury, | A citizen of NewZealandCorp, a | Christchurch, New Zealand | wholly-owned subsidiary of USA Inc. | greg@cosc.canterbury.ac.nz +--------------------------------------+