I'm trying to understand the internals of the CPython garbage collector, specifically when the destructor is called. So far, the behavior is intuitive, but the following case trips me up:

1. Disable the GC.
2. Create an object, then remove a reference to it.
3. The object is destroyed and the __del__ method is called.

I thought this would only happen if the garbage collector was enabled. Can someone explain why this happens? Is there a way to defer calling the destructor?

import gc
import unittest

_destroyed = False

class MyClass(object):

    def __del__(self):
        global _destroyed
        _destroyed = True

class GarbageCollectionTest(unittest.TestCase):

    def testExplicitGarbageCollection(self):
        gc.disable()
        ref = MyClass()
        ref = None
        # The next test fails. 
        # The object is automatically destroyed even with the collector turned off.
        self.assertFalse(_destroyed) 
        gc.collect()
        self.assertTrue(_destroyed)

if __name__=='__main__':
    unittest.main()

Disclaimer: this code is not meant for production -- I've already noted that this is very implementation-specific and does not work on Jython.