[Paraview] What is the difference between pvbatch and pvpython ?

[houssen]

Hello,

What is the difference between pvbatch and pvpython ? (general purpose 
question)

My understanding is that one can always use python scripts (from 
paraview, pvbatch, pvpython), paraview has the GUI, pvbatch is "paraview 
in batch mode" (that is paraview without the gui). But what is the 
purpose of pvpython ? When is it needed to use pvbatch or pvpython 
instead of the other one ? Or what can do pvbatch that pvpython can not 
do ?

Franck