Imagine you have this in mod.py:
import foo
class bar(object):
...
def __del__(self):
foo.cleanup(self.myhandle)
Seems fine right? In fact, there’s a nasty bug here. If I try to use this module in client.py like so:
import mod
mybar = bar()
Then you’re likely to get an exception when the program exits. This is
because Python, for some bizarre reason, Nones out the globals in
mod.py when taking down the interpreter. The actual __del__ method
can be called sometime after this, and it ends up trying
None.cleanup(), with the resultant AttributeError. It seems
extremely bizarre that it happens in this order, but it does (a real
example).