Ronald Oussoren <ronaldousso...@mac.com> added the comment:
Python's is behaving as expected here (but see below): the slots definition tells the interpreter which attribute names can be set on an instance and "__slots__" is not one of those attributes in your code. "a.__slots__ += ..." will try to set the "a.__slots__" attribute (see Eryk's message for documentation on this) and that results in the exception you are seeing. What surprised me is that A.__slots__ is mutable at all, the value of that attribute during class construction affects the layout of instances and that layout won't change when you change A.__slots__ later on. That is: class A: __slots__ = ['a'] a = A() a.a = ... # OK a.b = ... # raises AttributeError A.__slots__ = ['b'] a.a = ... # still OK a.b = ... # still raises AttributeError I don't know if this should be considered a bug or that this is intended behaviour. ---------- components: +Interpreter Core -Library (Lib) nosy: +ronaldoussoren versions: +Python 3.11, Python 3.9 -Python 3.8 _______________________________________ Python tracker <rep...@bugs.python.org> <https://bugs.python.org/issue46550> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
