New submission from Davide Rizzo <sorcio@gmail.com>: The documentation (at least the obvious places, see Doc/reference/datamodel.rst) says classes and class instances have the '__dict__' attribute, but nothing is said about what happens when assigning to it (like obj.__dict__ = something). As far as I understand that's undefined behavior and other implementations may not work the same as CPython (and CPython itself behaves differently between versions). I'd submit a documentation patch if I knew how to specify this matter. Maybe just say the behavior is not defined? ---------- assignee: docs@python components: Documentation, Interpreter Core messages: 165538 nosy: davide.rizzo, docs@python priority: normal severity: normal status: open title: Behavior of assigning to __dict__ is not documented versions: Python 2.7, Python 3.3, Python 3.4 _______________________________________ Python tracker <report@bugs.python.org> <http://bugs.python.org/issue15360> _______________________________________