On Saturday, January 31, 2015 at 5:06:54 PM UTC-8, Volker Braun wrote: > > On Saturday, January 31, 2015 at 3:59:05 PM UTC-5, Jeroen Demeyer wrote: >> >> In any case: after removing __del__ from Expect and Interface, all >> doctests pass, so it's not that bad. >> > > Also __del__ is never going to be reliably called in the face of cyclic > references, >
That is not true: In Python2, cycles with objects with __del__ methods in them are not automatically deleted, so the methods are reliably *not* called, because the objects aren't destructed. In Python3, it is guaranteed that a __del__ method on an object is called at least once. If you do evil stuff such as making the object reachable again in the __del__, then python will prevent the cycle from being destructed, but now you're on your own concerning the state in which your objects are (and it could happen that the __del__ gets called again). so I'm all for taking it out. Cleanup should be done elsewhere (or do it in > Cython __deallocate__ > That will require careful design. By the time a __dealloc__ is executed, the object is already torn down considerably, so just calling a method ".quit()" on the object is not a good idea. I think Jeroen's suggestion of somehow subclassing so that the object returned by Expect.spawn can do proper tear-down (that probably means registering with it the strings that should be sent to the interface to precipitate a tear-down) is a good idea. These objects will be fairly limited, so guaranteeing they are not in cycles won't be too bad. Then having a __del__ method to do the clean-up there should be acceptable. Another workaround would be to put all the cleanup in a call-back of a weakref, and store the weakref in a global dictionary somewhere. The callback should of course not hold any strong references, but it will be able to get a pointer to the original object via the weakref that is available to the callback. Upon exit from the system there is of course no guarantee that the weakref callback will get executed, because it might get deleted before the interface. -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-devel+unsubscr...@googlegroups.com. To post to this group, send email to sage-devel@googlegroups.com. Visit this group at http://groups.google.com/group/sage-devel. For more options, visit https://groups.google.com/d/optout.
