Guido van Rossum wrote: [SNIP - bunch of points from Guido] > Do we really need both __context__ and __cause__? Methinks that you > only ever need one: either you explicitly chain a new exception to a > cause, and then the context is probably the same or irrelevant, or you > don't explicitly chain, and then cause is absent. Since the traceback > printing code is to prefer __cause__ over __context__, why can't we > unify these? About the only reason I can think of is that with > __cause__ you know it was intentional and with __context__ you know it > wasn't; but when is it important knowing the difference? >
I am with Guido. I don't think the need to know if an exception was chained explicitly or implicitly will be important enough to warrant a separate attribute. And if people care that much that can tack on a random attribute like explicit_chain or something to the exception on their own. [SNIP] > In Java, I often find the way chained tracebacks are printed > confusing, because the "deepest" stack frame (where the exception > originally occurred) is no longer at the top of the printout. I > expect the same confusion to happen for Python, since it prints > everything in the exact opposite order as Java does, so again the > original exception is somewhere in the middle. I don't think I want > to fix this by printing the outermost exception first and the chained > exception later (which would keep the stack frames in their proper > order but emphasizes the low-level exception rather than the one that > matches the except clause that would have caught it at the outermost > level), but I might want to add an extra line at the very end (and > perhaps at each chaining point) warning the user that the exception > has a chained counterpart that was printed earlier. > Just a simple "[chained exception]" note or something? Sounds good. [SNIP] > You should probably reference the proposal (pending a PEP; I think > Brett is working on it?) My plan is to write the "Exceptions in Python 3000" PEP shortly after I start my internship. Going to put that at a higher priority than the AST branch to make sure I get to it some time before I leave the country. =) -Brett _______________________________________________ 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
