[Zope] Unique ID generation

I'm writing a simple ZClass (and a second ZClass which contains the first) and I would like the constructor for this class to be able to auto-generate unique IDs for the instances rather than making the owner choose one. What I've tried isn't working, but I don't really know what I'm doing here...I figure this must be a fairly common problem, so what is the best way to handle it? The ID needs only be unique within its container object (i.e., doesn't have to be globally unique). I have full control over the container class, so solutions involving setting properties on that class are OK. TIA, -- Tim Moore