I keep a cache of transactions to flush (to persistent storage) on the event of a watermark or object finalization. Since __del__ is no longer guaranteed to be called on every object, is the appropriate approach to hook a similar function (or __del__ itself) into atexit.register (during initialization)?
If I'm not mistaken, this will cause the object to which the method is bound to hang around until program termination. This isn't likely to be a problem, but maybe there's a more elegant solution?
Note: I know using __del__ is non-ideal because it can cause uncatchable exceptions, but I can't think of another way to do this short of cascading finalize() calls all the way through my program. TIA!
If you don't need your object to be alive at the time you perform the flush, you could use weak references
This is similar to your proposed solution, but rather than using a real reference, store a list of weak references, with a callback function to perform the flush. This way, the references aren't going to keep those objects alive, and you won't run into any circular garbage problems with __del__ methods.
You can run through the list of weak references on termination to manually flush any still alive if this needs to be guaranteed done at a certain point.