Lifetime Of Static Class Members/class References?

I was asked to show how to do a singleton like solution for the old chestnut of a special logger. At pains to point out the reasons for not doing this sort of thing, still, I tri

Solution 1:

Module globals are cleaned up on Python exit, and your class reference is already gone by the time the __del__ hook is run.

Don't count on globals still being there. Rather, use type(self) to get the class reference:

def __del__(self):
    print "destructing", self.name
    cls = type(self)
    if not cls._finalised.get(self.name):
        print "first destruction"
        self.logger.info('** My Epilogue **')
        cls._finalised[self.name] = True

This is documented in the big Warning section on the object.__del__ hook documentation:

Also, when __del__() is invoked in response to a module being deleted (e.g., when execution of the program is done), other globals referenced by the __del__() method may already have been deleted or in the process of being torn down (e.g. the import machinery shutting down). For this reason, __del__() methods should do the absolute minimum needed to maintain external invariants.

Take into account that module globals are maintained in a dictionary, and thus the order in which they are cleared is subject to the current implementation-and-Python-version-dependent order of the dictionary when being cleared.