Basically agreeing with what's been said already: IPython is an application that has Python (and some other things) as a dependency. So is IDLE. Python itself should ideally not be bundled with any applications -- it's a historical accident that IDLE is in the stdlib. Of course there should be a basic command prompt, but I think that the existing one based on GNU readline is fine for that purpose.

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--Guido van Rossum (python.org/~guido)