how to explain this memory usage

[javalist]

Hello python-list,

        in the python 2.0 interpreter,I write some code to make the interpreter
        allocate more than 20M memory,and then I del all the object that I
        create,but python still using that 20M memory,I try import gc,and then
        use gc.collect,no good.python has 20M in memory still.
        also the interpreter has 20M in memory,but seems python knows they are
        pointing nothing and reuse these 20M when I try again allocating more
        object in python,it didn't increase memory until the first 20M is
        occupied by the new allocated object

Best regards,
 javalist                          mailto:javalist at 21cn.com