Weakrefs to classes that derive from str

[Ron Garret]

In article <bvednVgyNqMbptffRVn-ig at comcast.com>,
 Steven Bethard <steven.bethard at gmail.com> wrote:

> Ron Garret wrote:
> > Why doesn't this work?
> > 
> >>>>from weakref import ref
> >>>>class C(str): pass
> > ... 
> >>>>ref(C())
> > Traceback (most recent call last):
> >   File "<stdin>", line 1, in ?
> > TypeError: cannot create weak reference to 'C' object
> 
> Note that you don't need the class redirection:
> 
> py> ref('')
> Traceback (most recent call last):
>    File "<interactive input>", line 1, in ?
> TypeError: cannot create weak reference to 'str' object
> 
> But I don't know why strings aren't valid arguments to ref...

None of the native types (int, float, list, tuple, etc.) can have weak 
references, but wrapping them in a class is supposed to get around that.  
And it does -- for all classes except str.

rg