[MMTK] Temporary implementation of integrator in python

[Rune Larsen]

Hi all 

Im trying to implement a new integrator using the MMTK
packages. It is just for testing, so I am writing it
in python. I'm a beginner both in respect to python
and with the MMTK package. I've hoped to find a
template integrator written intirely in python but
I've only come across C implementations. Now I'am a
bit confused with respect to Universe function calls. 

Now for the questions :

Does Universe.configration() return a real copi of the
atom positions ? 

Does Universe.energy() evaluate the energy before
returning ? 

(risk of sounding stupid) Do I have to negate the
energy gradient of 
Universe.energyAndGradient() 
to get the force or is it implied ? And are they both
evaluated before they are returned ?  

My integration is made within a for-loop, and I write
a trajectory file using snapshot ... is there a better
way ? TrajectoryOutput takes "step numbers" as
arguments but I dont know where to define the "step"

It is a lot of questions :-). I would be grateful for
answers or references to the documentation.

Regards Rune