I found Basak's helpful reply below on Stackoverflow. (How to repeat last command in python interpreter shell?) Can someone please specify which button to click on AFTER selecting "history-next" and "history-previous" to change the keys in Python Idle? I didn't want to inadvertently do the wrong thing and then get stuck. Just the OK button for each button? And then type in the key I want? Thanks.
Basak: "In IDLE, go to Options -> Configure IDLE -> Keys and there select history-next and then history-previous to change the keys. Then click on Get New Keys for Selection and you are ready to choose whatever key combination you want."