> The solution was to recognize when we where finished with it to set self.over_there to None. To my knowledge python does not handle all cyclic gc anyway. Here is
some information from the gc documentation:
A list of objects which the collector found to be unreachable but
could not be freed (uncollectable objects). By default, this list
contains only objects with __del__() methods.3.1Objects that have
__del__() methods and are part of a reference cycle cause the entire
reference cycle to be uncollectable, including objects not necessarily
in the cycle but reachable only from it. Python doesn't collect such
cycles automatically because, in general, it isn't possible for Python
to guess a safe order in which to run the __del__() methods. If you
know a safe order, you can force the issue by examining the garbage
list, and explicitly breaking cycles due to your objects within the
list. Note that these objects are kept alive even so by virtue of
being in the garbage list, so they should be removed from garbage too.
For example, after breaking cycles, do del gc.garbage[:] to empty the
list. It's generally better to avoid the issue by not creating cycles
containing objects with __del__() methods, and garbage can be examined
in that case to verify that no such cycles are being created.
So, do BoostFieldClass and Foo both implement __del__? Is there some
way you can eliminate one of them?
I can reproduce something similar with the code below, and I'm not
self.cb = cb
self.over_there = Bar()
print "Boost callback"
if __name__ == "__main__":
f = Foo()