On Fri, Jul 17, 2015 at 9:43 PM, Antoon Pardon <antoon.par...@rece.vub.ac.be> wrote: > On 07/17/2015 01:05 PM, Chris Angelico wrote: >> On Fri, Jul 17, 2015 at 8:48 PM, Antoon Pardon >> <antoon.par...@rece.vub.ac.be> wrote: >>> Just wondering, are traceback records of generators available? They are >>> if an exception is raised in the generator itself, but what if an exception >>> is raised in the loop that is driven by a generator. They don't appear in >>> the standard stack trace. >> Not sure what you mean here. Something like this? >> >> def gen(): >> yield stuff >> yield more stuff >> >> for stuff in gen(): >> bomb with exception >> >> The error didn't happen in the generator, so I wouldn't expect to see >> it in the traceback. > > Yes something like that. And I wouldn't expect it either but if it > is not present, is it because nobody thought about it or because it > is a bad idea or an idea difficult to implement? > >> There's still room for the cause of an error to >> not be in the traceback; imagine, for instance, a function that >> populates a concrete list, and then you iterate over the list. If that >> function sticks a None into the list and the subsequent processing is >> expecting all strings, that's going to bomb, but then you have to >> figure out where the None came from. If the traceback could include >> that, it'd be great, but some things aren't possible. > > Sure, but in this case, the generator is still active. The Runtime > would be able to jump to and somehow activates it's stack record > for the next value. So why would we expect it to be impossible to > include this trace back record in a stack trace?
Python could also give you stack traces for any other threads that are concurrently running, on the off-chance that one of them affected it. But the only influence the generator has on the loop is to yield a value or signal termination; if an exception is thrown in the loop itself, the local name 'stuff' should have all the information about that cause. Python isn't a mind-reader, no matter how much it may look like one, and it can't know that this function's return value should be shown as part of a completely different function's stack trace. ChrisA -- https://mail.python.org/mailman/listinfo/python-list
