Thank you for your answer.

I cannot provide any error messages or stack traces
because it really *crashed*. python.exe suddenly stops
working and a windows pops up saying something
like "python.exe had a problem and needed to be closed"
I cannot say what the pop-up message exactly was because
I'm using Korean version windows and the message was
Korean. There were no python error messages or stack traces.

And the file temp.py I attached first was the file 
exactly reproducing the situation, at least in my
computer.
And I think it's perhaps a Korean windows problem or
related to some other programs in my computer.
I also tried to narrow down the cause but I couldn't find
any rules.
Maybe it is better to open a thread again when I get to
find some exact conditions on which the problem appears.

Thank you.