Python node read value of input parameter

[dvonch]

I don't fully understand the purpose of the output terminal on the python node input parameter which I have pointed out in the image above. You'll note that the online documentation doesn't show these outputs as being wired, so why do they exist?

When discussing the input parameter, the online documentation says "You can resize the Python Node to add more terminals. You pass a value to the Python function by wiring to the left terminal of a terminal pair. You read the value of a parameter after the function call by wiring from the right terminal of a terminal pair."

I'm interested in the part about reading the value of a parameter after the function call. My questions for the experts are:

1. Can the parameter change during the function call or will it always be identical to the value passed into the input parameter?

2. If it is always identical, why bother with the output terminal? Perhaps it could be used to control data flow, but the session out and/or error output is better for that purpose. 

thanks