On 26 March 2015 at 22:30, Victor Stinner <victor.stin...@gmail.com> wrote: > Hi, > > Here is the first draft of my PEP to chain automatically exceptions at > C level in Python 3.5. Plain text version of the PEP below. HTML > version of the PEP: > > https://www.python.org/dev/peps/pep-0490/ > > It has already an implementation, the pyerr_chain.patch file attached to > http://bugs.python.org/issue23763 > > The patch is very short.
I like the idea, but I think it would raise the priority of the proposed change to the display of chained exceptions in http://bugs.python.org/issue12535 That proposal suggests adding the line "<truncated: another exception occurred>" to the start of earlier tracebacks in the chain so you get an up front hint that a chained exception will be shown after the initial traceback. > Backward compatibility > ====================== > > A side effect of chaining exceptions is that exceptions store > traceback objects which store frame objects which store local > variables. Local variables are kept alive by exceptions. A common > issue is a reference cycle between local variables and exceptions: an > exception is stored in a local variable and the frame indirectly > stored in the exception. The cycle only impacts applications storing > exceptions. > > The reference cycle can now be fixed with the new > ``traceback.TracebackException`` object introduced in Python 3.5. It > stores informations required to format a full textual traceback without > storing local variables. Also potentially worth noting here is "traceback.clear_frames()", introduced in 3.4 to explicitly clear local variables from a traceback: https://docs.python.org/3/library/traceback.html#traceback.clear_frames PEP 442 also makes it more likely that cycles will be cleared properly, even if some of the objects involved have __del__ methods: https://www.python.org/dev/peps/pep-0442/ However, I'll grant that neither of those can be backported the way that traceback.TracebackException can be. Cheers, Nick. -- Nick Coghlan | ncogh...@gmail.com | Brisbane, Australia _______________________________________________ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
