> On 6 Feb 2020, at 13:01, Frank Millman <fr...@chagford.com> wrote: > > Hi all > > I have noticed a change in behaviour in Python 3.8 compared with previous > versions of Python going back to at least 2.7. I am pretty sure that it is > not a problem, and is caused by my relying on a certain sequence of events at > shutdown, which of course is not guaranteed. However, any change in behaviour > is worth reporting, just in case it was unintended, so I thought I would > mention it here. > > I have a module (A) containing common objects shared by other modules. I have > a module (B) which imports one of these common objects - a set(). > > Module B defines a Class, and creates a global instance of this class when > the module is created. This instance is never explicitly deleted, so I assume > it gets implicitly deleted at shutdown. It has a __del__() method (only for > temporary debugging purposes, so will be removed for production) and the > __del__ method uses the set() object imported from Module A. > > This has worked for years, but now when the __del__ method is called, the > common object, which was a set(), has become None. > > My assumption is that Module A gets cleaned up before Module B, and when > Module B tries to access the common set() object it no longer exists. > > I have a workaround, so I am just reporting this for the record.
I recall reading that shutdown had changed in 3.8, but cannot find the email/webpage that I read. These days I assume that __del__ will almost never be useful and use exploit calls to tell an object I am finished with it and it can do its resource clean up. Barry > > Frank Millman > > -- > https://mail.python.org/mailman/listinfo/python-list > -- https://mail.python.org/mailman/listinfo/python-list
