stop script w/o exiting interpreter

[Alan Isaac]

Please note that this post has subject
"stop script w/o exiting interpreter".

The object is to work at the *interactive* interpreter,
without leaving it.

Here is an example goal:
start a Python shell,
execfile a script,
exit the script at line 25,
and return to the Python shell.

E.g., some languages include a ``stop`` statement that you can put on line
25.
Ideally, I would like the equivalent of this.

Solutions suggested in this thread included:
- raise SystemExit
     but this will exit the interpreter
- sys.exit()
     but this will exit the interpreter
- use pdb's set_trace()
     but I think that answers a different question.
     (However it does work to raise BdbQuit, but I'd like something less
messy.)
- wrap all code in functions and test the functions
     but this does not apply to my current use case
- use PyScripter
     but this is overkill for my very simple goal

Note that I can just put the undefined name ``stop`` on any line
I want, and the script will stop execucting at that line and will
return to the interactive interpreter, as I wish.  It is just that it
returns with an error message, and I'd like to avoid that.

Thanks,
Alan Isaac