Bob, here is a small example showing how easy it is to encounter the GC
problem:


from json import JSONDecoder
import weakref
import gc

class MyObject(object):
    def __init__(self):
        self.decoder = JSONDecoder(parse_constant=self.parse_constant)

    def parse_constant(self, *args, **kargs):
        """ XXX """

wr = weakref.ref(MyObject())
gc.collect()
print wr()