global destructor not called?

[Neal Becker]

To implement logging, I'm using a class:
class logger (object):
    def __init__ (self, name):
        self.name = name
        self.f = open (self.name, 'w')
    def write (self, stuff):
        self.f.write (stuff)
    def close (self):
        self.f.close()
    def flush (self):
        self.f.flush()
    def reopen (self):
        self.f.flush()
        self.f.close()
        os.rename (self.name, self.name + '.old')
        self.f = open (self.name, 'w')
    def __del__ (self):
        try:
            os.remove (self.name + '.old')
        except:
            pass

And setting:
sys.stderr = logger(...)

It seems my cleanup (__del__) is never called, even though I believe my
program exits normally.  What's wrong?