Looks like the memory _is_ freed.  As Guido said, "It may be available
for reallocation within Python, just not given back to the operating
system".  I suggest closing this as invalid.

paul@gonzo:~$ python
Python 2.3.5 (#2, Oct 16 2006, 19:19:48)
[GCC 3.3.5 (Debian 1:3.3.5-13)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import gc
>>> len ([object for object in gc.get_objects () if isinstance (object,
list)])
25
>>> aList = []
>>> for i in xrange(5E5):
...     aList += [[]]
...     for j in xrange(10):
...         aList[-1].append([]
...
...
KeyboardInterrupt
>>>         aList[-1].append([]
KeyboardInterrupt
>>>
paul@gonzo:~/emacs$ python
Python 2.3.5 (#2, Oct 16 2006, 19:19:48)
[GCC 3.3.5 (Debian 1:3.3.5-13)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import gc
>>> len ([object for object in gc.get_objects () if isinstance (object,
list)])
25
>>> aList = []
>>> for i in xrange(5E5):
...     aList += [[]]
...     for j in xrange(10):
...         aList[-1].append([])
...
__main__:1: DeprecationWarning: integer argument expected, got float
>>> del aList
>>> len ([object for object in gc.get_objects () if isinstance (object,
list)])
25