Python how to ensure that __del__() method of an object is called before the module dies?

Question

Earlier today I asked this question about the __del__() method of an object which uses an imported module. The problem was that __del__() wants to

Answer 1

Attach a reference to the function with a keyword parameter:

import os

class Logger(object):    
    def __del__(self, os=os):
        print "os: %s." %os

or bind it to a class attribute:

import os

class Logger(object):
    def __init__(self):
        self.os = os

    def __del__(self):
        print "os: %s." % self.os

By creating a local (enough) reference, Python will not look up os as a global, but with a local reference, which are stored with the instance or with the function itself, respectively.

Globals are looked up at runtime (which is why the __del__ function in your other question fails if os has already been cleaned up), while a function local is cleared up together with the function object, or in case of a instance attribute, with the instance.