The fact that "ls" shows a UID of 501 instead of your user name "Charlotte" strongly suggests you have an inconstantly defined user account.  Suggest you try cresting a new "Administrator" user via "System Preferences" -> "User & Groups" and try logging into that user and see if IDLE works there.  If that works, you may need some help trying to fix up your existing account.  You may be able to get some useful information with the decl command:

dscl . -read /Users/Charlotte

Good luck!