06.02.20 14:58, Frank Millman пише:
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.
Do you import a common object *from* a module or import a module and
access a common object as its attribute?
If the latter, the change may be related to
https://bugs.python.org/issue33331 . Modules are now cleaned up in the
reversed order of importing.
In any case, the order of cleaning up modules is not specified/
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