__del__ not working with cyclic reference?

[Jane Austine]

I have some code using singleton pattern. The singleton instance
is shared as a class variable. The problem is that the singleton
instance is not cleared automatically.

Following is a simplified version that shows the problem:

--------
#foobar.py
class FooBar:
    def __del__(self):
        print "FooBar removed"

FooBar.foobar=FooBar()
--------

c:\python23>python foobar.py

c:\python23>

It doesn't print anything.

Why is this so? Due to the cyclic reference? Isn't python's gc
supposed to treat it? What singleton idiom is recommended 
otherwise?

Thanks

Jane