How do I access the command history from IDLE?

python python-idle

I think you are looking for the history-previous action, which isbound to Alt+P by default.
You can remap it in "Options -> Configure IDLE -> Keys"
You can also access this command from the top menu in IDLE: "Shell -> Previous History"

Incidentally, why don't you try a better (less ugly, for starters) shell like bpython or ipython?

python python-idle

just use Alt+P to go up. Similarly, Alt+N could be used to go down.

python python-idle

If you're on mac, it's ctrl+p.

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