Class and instance related questions.

[Asaf Las]

On Friday, January 24, 2014 10:45:30 PM UTC+2, Chris Angelico wrote:
> On Sat, Jan 25, 2014 at 7:32 AM, Asaf Las <r.... at gmail.com> wrote:
> > On Friday, January 24, 2014 6:37:29 PM UTC+2, Chris Angelico wrote:
> >> On Sat, Jan 25, 2014 at 3:31 AM, Asaf Las <r... at gmail.com> wrote:
> >> > Hi
> >> > Is there way to get list of instances of particular
> >> > class through class itself? via metaclass or any other method?
> >> Not automatically, but you can make a class that keeps track of its
> >> instances with a weak reference system.

> > By "not automatically" do you mean there is no way to get references 
> > to instances of class via python's provided methods or attributes for class
> > object at time the class object is created?
> 
> Correct.
> 
> > And usage of weak reference was suggested only to allow class instances
> > garbage collected if for example class static container attribute will be
> > used as class instance reference storage?
> Weak references mean that the objects will be disposed of as normal,
> but that you'll know that they've gone.
> 
> >> > Another question - if class is object is it possible
> >> > to delete it? If it is possible then how instances
> >> > of that class will behave?
> 
> >> It's possible to unbind the name, but every instance retains a
> >> reference to its class, so the class itself won't disappear until
> >> there are no instances left of it.
> >> ChrisA
> 
> > That is interesting. Is it also reference count mechanism or something else?
> 
> Yes. [1]
> 
> ChrisA
> 
> [1] Within the bounds of the question asked, I think a simple "Yes" is
> more useful here than a long and detailed explanation of the many
> Pythons and how not all of them refcount at all. Consider this
> footnote my apology to the experts who would otherwise feel that I'm
> majorly misleading the OP. Sorry.

Chris, i like answers which open doors to my curiosity :-)
yet i should spend my credits very carefully :-)

Thanks

Asaf