On Wed, Jan 1, 2020 at 6:40 AM Andrew Svetlov <andrew.svet...@gmail.com> wrote:
> __del__ is very useful not for interpreter shutdown but as a regular > destructor in object's lifecycle. > The reason we should warn people against ever implementing __del__ is that people rarely actually understand object lifecycle. Its presence guarantees delayed garbage collection and that its code will code execute in a context way outside of normal control flow that all other methods are invoked from. -gps > > Action on the shutdown is another beast. > Personally, I prefer to do all finalization works by explicit calls > instead. > > On Wed, Jan 1, 2020 at 2:39 AM Yonatan Zunger <zun...@humu.com> wrote: > > > > Hey everyone, > > > > I just encountered yet another reason to beware of __del__: when it's > called during interpreter shutdown, for reasons which are kind of obvious > in retrospect, if it calls notify() on a threading.Condition, the waiting > thread may or may not ever actually receive it, and so if it does that and > then tries to join() the thread the interpreter may hang in a hard-to-debug > way. > > > > This isn't something that can reasonably be fixed, and (like in most > cases involving __del__) there's a very simple fix of using > weakref.finalize instead. My question for the dev list: How would people > feel about changing the documentation for the method to more bluntly warn > people against using it, and refer them to weakref.finalize and/or > atexit.register as an alternative? The text already has an undertone of > "lasciate ogni speranza, voi ch'entrate" but it may be helpful to be more > explicit to avoid people getting caught in unexpected pitfalls. > > > > Yonatan > > _______________________________________________ > > Python-Dev mailing list -- python-dev@python.org > > To unsubscribe send an email to python-dev-le...@python.org > > https://mail.python.org/mailman3/lists/python-dev.python.org/ > > Message archived at > https://mail.python.org/archives/list/python-dev@python.org/message/AAZQBWD6PHC4PVNCCPX4A2745SS7B3LS/ > > Code of Conduct: http://python.org/psf/codeofconduct/ > > > > -- > Thanks, > Andrew Svetlov > _______________________________________________ > Python-Dev mailing list -- python-dev@python.org > To unsubscribe send an email to python-dev-le...@python.org > https://mail.python.org/mailman3/lists/python-dev.python.org/ > Message archived at > https://mail.python.org/archives/list/python-dev@python.org/message/57CDW4NIYEQ3JEVX2JVCJDA5TXTC5MBR/ > Code of Conduct: http://python.org/psf/codeofconduct/ >
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