Python

#!/usr/bin/env pythonimport numpy as npfrom ase import moleculefrom gpaw import GPAWatoms = molecule('H2O')atoms.center(vacuum=4.0)atoms.set_pbc(False)calc = GPAW(h=0.3, width=0.1, nbands=-5)atoms.set_calculator(calc)atoms.get_forces()import vtkfrom ase.visualize.vtk.atoms import vtkAtomsusewx = Falsetry:    import wx    usewx = Trueexcept ImportError:    passif usewx:    from vtk.wx.wxVTKRenderWindow import wxVTKRenderWindow    app = wx.PySimpleApp()    frame = wx.Frame(None, -1, 'wxVTKRenderWindow', size=(800,600))    widget = wxVTKRenderWindow(frame, -1)    win = widget.GetRenderWindow()    ren = vtk.vtkRenderer()    win.AddRenderer(ren)else:    ren = vtk.vtkRenderer()    win = vtk.vtkRenderWindow()    win.AddRenderer(ren)    win.SetSize(800,600)    iren = vtk.vtkRenderWindowInteractor()    iren.SetRenderWindow(win)    style = vtk.vtkInteractorStyleTrackballCamera()    iren.SetInteractorStyle(style)va = vtkAtoms(atoms)va.add_cell()va.add_axes()va.add_forces()va.add_actors_to_renderer(ren)if usewx:    frame.Show()    app.MainLoop()else:    iren.Initialize()    win.OffScreenRenderingOff()    win.Render()    iren.Start()