New submission from Eric Cousineau <eric.cousineau@tri.global>: Due to how `PyObject_CallFinalizer` is written in python3, `__del__` will only *ever* be called once.
In my use case, I am experimenting with a feature in `pybind11` to prevent slicing with Python class instances that inherit from pybind11-C++ base classes, which involves detecting when an instance loses all reference in Python (`Py_REFCNT(...) == 0`) but still has reference in C++ (`shared_ptr::count() > 0`), and reviving the Python portion when this situation happens. In python2, I could do this without a hitch, as a resurrected object could have its `__del__` method called multiple times (through `tp_dealloc` I believe?). But in python3, the object is marked with `_PyGC_SET_FINALIZED(...)`, thus preventing `__del__` from being called again. It'd be nice to either (a) somehow allow `__del__` to be called naturally without too much fuss or, at the least, (b) have this reflected in the documentation: https://docs.python.org/3/reference/datamodel.html#object.__del__ See attached `revive_test`. Example execution: ``` $ python2 ./revive_test.py Revive Destroy [ Done ] $ python3 ./revive_test.py Revive [ Done ] ``` ---------- assignee: docs@python components: Documentation files: revive_test.py messages: 308660 nosy: Eric Cousineau, docs@python priority: normal severity: normal status: open title: Difference in ressurrection behavior with __del__ in py2 vs. py3 type: behavior versions: Python 3.4, Python 3.5, Python 3.6 Added file: https://bugs.python.org/file47339/revive_test.py _______________________________________ Python tracker <rep...@bugs.python.org> <https://bugs.python.org/issue32377> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
