python -i (interactive environment)

[Joe]

When you run "python -i scriptname.py" after the script completes you left 
at the interactive command prompt.

Is there a way to have this occur from a running program?

In other words can I just run scriptname.py (NOT python -i scriptname.py) 
and inside of scriptname.py I decide that I want to fall back to the 
interactive prompt?

I've searched and so far the only thing I've come up with is to use pdb, but 
that is not exactly the same as the interactive prompt.

Is there any way to do it that I have missed?

Thanks.