How to approach this?

[jepler epler]

You may be aware of the idiom:

class C: pass

_instance = None
def SingletonMaker():
	global _instance
	if _instance is None:
		_instance = C()
	return _instance

thus, instead of instantiating C directly, you call SingletonMaker.

However, this doesn't do the other thing you want, which is to collect
_instance when it has no more users.

Something like the following ought to work:

class UsesSingleton:
	def __init__(self):
		self.instance = SingletonMaker()

	def __del__(self):
		if sys.getrefcount(self.instance) == 3:
			# _instance, self.instance, and the arg to
			# sys.getrefcount
			_instance = None
			# When the function ends, the refcount will
			# drop to 0, so self.instance will be collected
			# and the next call to SingletonMaker will
			# make a new one
		# else, there are other references to the instance...

Of course, if someone else stores a reference to the singleton object,
this won't work..

Jeff