This is because when we run a loop until it's termination the Kernel is in busy state and so IN [*]
is shown up. Since Kernel is busy and if we just leave that cell to execute completely and switch to another cell to run, the corresponding cell will get busy and so again for that cell IN[*]
is shown.
In that case you just need to restart your jupyter notebook and all is fine then.
But be sure that your loop will terminate this time or else again this error will turn up.