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

As we told you before, you really shouldn't rely on __del__ being called when the interpreter exits. There are two options for doing this properly:

The first is atexit

import os
import atexit

class Logger(object):   
    def on_exit(self):
        print "os: %s." % os

logger = Logger()
atexit.register(logger.on_exit)

This makes sure that your logger gets finalized at exit.

---

*Reading a little more into your problem, since you plan on having a single instance bound to a module which defines the instances's class, the context manager solution below won't work for this since there's no way to stay in the context for the entire execution of your program. You'll need to use atexit.register. However, from the standpoint of program design, I would much prefer to use a context manager to manage my resources than atexit.register if restructuring the code would allow it.

The second (better*) way to do it is make your class a context manager which executes the cleanup code when you exit the context. Then your code would look like:

import os
class Logger(object):
    def __enter__(self):
        return self
    def __exit__(self, exc_type, exc_value, traceback):
        print "os:",str(os)

with Logger() as logger:
    #do something ...