Attaching a live interpreter to a script?

[Kannon]

I'm sure this has come up before, but my google-fu is just not strong
enough to find it out of 10,000~ posts, and apologies if this is
obvious.

What I'd like to do is attach an interpreter to a program running from
a script (I.E, not something I typed into the live interpreter). It'd
be an awesome way to debug programs, as well as tweak parameters and
such at runtime. Ideally, I'd like it to be something in pure python
so I could throw it into Jython and IronPython as well. (Though, I can
actually code Java and C#, so implementing it is something I could do
myself, if needed.) I was thinking maybe something I could throw into
a tkinter window or similar, but I wasn't able to find anything on how
to pass stuff directly to the interpreter.

Any ideas, or if this is even possible would be nice. Thanks in
advance.