On 2/28/07, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote: > > On Wed, 28 Feb 2007 18:10:21 -0800, Guido van Rossum <[EMAIL PROTECTED]> > wrote: > >I am beginning to think that there are serious problems with attaching > >the traceback to the exception; I really don't like the answer that > >pre-creating an exception is unpythonic in Py3k. > > In Twisted, to deal with asynchronous exceptions, we needed an object to > specifically represent a "raised exception", i.e. an Exception instance with > its attached traceback and methods to manipulate it. > > You can find its API here: > > http://twistedmatrix.com/documents/current/api/twisted.python.failure.Failure.html > > Perhaps the use-cases for attaching the traceback object to the exception > would be better satisfied by simply having sys.exc_info() return an object > with methods like Failure? Reading the "motivation" section of PEP 344, it > describes "passing these three things in parallel" as "tedious and > error-prone". Having one object one could call methods on instead of a > 3-tuple which needed to be selectively passed on would simplify things. > > For example, chaining could be accomplished by doing something like this: > > sys.current_exc_thingy().chain() > > I can't think of a good name for the new object type, since "traceback", > "error", "exception" and "stack" all already mean things in Python.
I'm guessing you didn't see James Knight's proposal. If we can agree on more Java-esque exception semantics, the exception object could serve this purpose just fine. I'm thinking that in that case an explicit with_traceback(tb) should perhaps clone the exception; the clone could be fairly simple by constructing a new uninitialized instance (the way unpickling does) and filling its dict with a copy of the original's dict, overwriting the traceback. (Also, if Brett's exception reform is accepted, we should call this attribute just traceback, not __traceback__.) -- --Guido van Rossum (home page: http://www.python.org/~guido/) _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
