On 29 July 2017 at 04:56, Mike Miller <python-ideas@mgmiller.net> wrote:
Nice. Ok, so there are different dimensions of mutability.
Still, haven't found any "backdoors" to object(), the one I claimed was immutable.
It's possible to write builtin types that are truly immutable, and there are several examples of that (direct instances of object, tuple instances, instances of the builtin numeric types), but it isn't particularly straightforward to make Python defined classes truly immutable. While this gets close for stateless instances (akin to instantiating object() directly): >>> class MostlyImmutable: ... __slots__ = () ... @property ... def __class__(self): ... return type(self) ... It's far more difficult to actually store any meaningful state without making it open to mutation in some way (since it needs to settable from __new__, and Python doesn't provide any inherent mechanism from distinguishing those cases from post-creation modifications). Cheers, Nick. -- Nick Coghlan | ncoghlan@gmail.com | Brisbane, Australia