Why is this a mem leak?

[Mel Wilson]

In article <410044cb$1 at clarion.carno.net.au>, Steve <steve at hotmail.com> wrote:
>I saw an article online
>(http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/65333) where it
>explains how one can find out if there's a memory leak in ones program.
>How is there a memory leak in this:
>
>     # make a leak
>     l = []
                        1 reference to the new list, in the namespace
                        under 'l'.   Reference count == 1

>     l.append(l)
                        1 more reference to the list, in its own
                        [0] element. Reference count == 2
>     del l
                        The reference in the namespace is removed.
                        Reference count = 1

>??? Shouldn't deleting an object explicitly give the GC a better chance
>to find the object? Won't deleting it cause it's reference to go down
>(another question: which GC is python 2.3 using? Refcount or
>Generational?). Isn't 'del' similar to 'free'ing in C??

   Not really.  `del` removes a reference, which usually
culminates in freeing the storage, after all the required
dels are done.

For no memory leak:

    l = []          # ref count = 1, i.e. l
    l.append (l)    # ref count = 2, i.e. l and :itself:[0]
    m = l           # ref count = 3, i.e. l, :itself:[0] and m
    del l           # ref count = 2, i.e. :itself:[0] and m
    del m[0]        # ref count = 1, i.e. m
    del m           # ref count = 0, and the objects space can be collected

(Here :itself:  is made-up language, no way a valid Python
identifier, but how else to discuss a reference that isn't
part of any namespace?)

        Regards.        Mel.