Antoine Pitrou added the comment: weakrefs are traditionally cleared by the cyclic GC before calling any __del__ method. This used to be mandatory to eschew situations where a weakref callback could see cleared objects, but produces the side effect that __del__ methods can see dead weakrefs. This is also true pre-3.4, by the way, but perhaps the OP's __del__ wasn't called at all (if it was part of the cycle, the object would end up in gc.garbage instead)?
We could perhaps reverse the order, but then weakref callbacks may see __del__'ed objects. Hard to say which one is better, and keeping the traditional behaviour means less compatibility hassles. Some of this is discussed in Modules/gc_weakref.txt. In general, __del__ methods may see strange errors. For example, at interpreter shutdown, your __del__ method can be called while some modules have started unloading. Python 3.4 definitely tries to improve on all this, but there's no perfect solution, and some of the improvements might also backfire in some rare cases :-) ---------- nosy: +tim.peters versions: +Python 3.5 _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue23841> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
