One more thing: many of the multiple output algorithms have specific Get methods for their other outputs. For example, the clip filter has the method GetClippedOutput() which would have a corresponding property called 'clipped_output` so the following is always possible:
output = (source >> clip).execute()
c_output = clip.clipped_output
But I am starting to like this idea a lot:
output, c_output = (source >> clip).execute()