from ASE import Atom,ListOfAtoms
from Dacapo import Dacapo
from ASE.Trajectories import NetCDFTrajectory
import os

inputfile='trajinputfile'
traj= NetCDFTrajectory(inputfile)
atoms=traj.GetListOfAtoms()
unitcell=[]
atoms.SetUnitCell(unitcell,fix=True)
calc=Dacapo(your settings)
atoms.SetCalculator(calc)
atoms.GetPotentialEnergy()