I am using Python IDLE for Python 3.8.5. I save my code normally, but when I run the module(F5) This box appear again and again
This is due to a bug that was fixed here, a few days after 3.8.5 was released. 3.9.0rc1 has the fix and it will be in 3.8.6, due sometime this month (September 2020).
The problem occurs with blank files (or at least no newline) created outside of IDLE and then edited with IDLE. The workaround for now is to create blank files with File => New on the IDLE menu, or add at least a newline ( or ) before editing with IDLE.