问题
Python's threading documentation states:
All import attempts must be completed before the interpreter starts shutting itself down. This can be most easily achieved by only performing imports from non-daemon threads created through the threading module. Daemon threads and threads created directly with the thread module will require some other form of synchronization to ensure they do not attempt imports after system shutdown has commenced. Failure to abide by this restriction will lead to intermittent exceptions and crashes during interpreter shutdown (as the late imports attempt to access machinery which is no longer in a valid state).
I'm looking for example code that demonstrates this restriction.
来源：https://stackoverflow.com/questions/8456395/threaded-importing-while-interpreter-shuts-down