In PoserPython, is there any universal 'stop this script here, progress no further' command?

For instance:

   actor = scene.CurrentActor()
   # If no light is currently selected in the scene, then display this message and stop the script.
   if not actor.IsLight():
      poser.DialogSimple.MessageBox("To run this script, please first select a light.")
      >>> STOP HERE! <<
   else:
      if actor.IsLight():
   # OK, we have a light selected, so continue running the script.
          lights = scene.Lights()
          for light in lights:

What needs to go on the line >>> STOP HERE! << to cause the script to exit gracefully? I see "Return" used in other scripts, but that fails to prevent the script from continuing to run.

there is no "stop" that I am aware of but there are ways to make it do what you are asking

for instance

import poser
scene = poser.Scene()
def test_for_light( ):
    return True if scene.CurrentActor().IsLight() else False

if test_for_light():
    put the body of your script here
else:
    poser.DialogSimple.MessageBox("To run this script, please first select a light.")

or

import poser
scene = poser.Scene():
if scene.CurrentActor().IsLight():
    do something
else:
    send message 

but you do not need to test if the current actor is a light if you are going to cycle through the lights anyway

you could do something like

import poser
scene = poser.Scene()
for light in scene.Lights():
    light.SetLightOn( not light.LightOn() )

doing it this way, python would only affect lights, not other types of actors.

Thanks you so much, Structure, that's solved it. After a bit of rebuilding I now have a working script to turn off all lights except the currently selected one, do some useful things, then turn them all back on again.

I found, though, that at first I had 'invalid syntax' error on your 'Else:' — this was fixed by indenting all the way down the script. Below is a visual example of what I mean:

if test_for_light():
    put the body of your script here
    <- indent
    <- indent
    <- indent
    <- indent
    <- indent
    <- indent
    <- indent
    <- indent
    <- indent
else:
    poser.DialogSimple.MessageBox("To run this script, please first select a light.")

In other words, the script has to have "a clear run" down the indents to get at the "else:" command. If not then it throws an 'invalid syntax' error. This should be useful to know for other beginners reading this in years to come.

Glad you got it working

There is a Python function to abort a script: sys.exit()

But in Poser-Python this stops not only the script. It stops Poser :)

Nonetheless, there is a another, "pythonic" way to interrupt a running script (even if it's nicer done with program logic).

class StopScript(Exception):
    pass


def abc(parm):
    if parm > 10:
        raise StopScript()
    else:
        print parm

try:
    abc(20)
except StopScript:
    print "Script aborted"

sys.exit()

Yes, I tried that. I'd never seen Poser exit so fast! Quicker than a Ctrl + Del and a forced stop, in Windows.

Thanks for the addition option, adp001.