Serhiy Storchaka added the comment: Thank you Martin. In general the patch LGTM, but I'm not expert in English writing. There are other functions and slots with twofold purpose: PyObject_SetItem, PySequence_SetItem, PySequence_SetSlice, PyMapping_SetItemString, PySequenceMethods.sq_ass_item, PyMappingMethods.mp_ass_subscript. May be address them in this issue? I'm not sure about documenting the deletion for PyObject_SetAttr and like. All these functions have Del-counterpart. Deleting by Set-function with NULL may be a side effect and be deprecated in future. May be worth to discuss this on Python-Dev. For PySys_SetObject the deletion if value is NULL already is documented, but there is no PySys_DelObject. ---------- _______________________________________ Python tracker <report@bugs.python.org> <http://bugs.python.org/issue25701> _______________________________________