from G4Calo import GeometryDescriptor, G4System

cw = GeometryDescriptor()#the width of the calorimeter is 50 cm times 50 cm (also steerable, but I'd leave it)
cw.addLayer(10,"G4_Si",True) #10 cm of Silicon, active
cw.addLayer(1,"G4_Pb",False) #1 cm of Lead, passive
cw.addLayer(10,"G4_Si",True, 3) #10 cm of Silicon, active, 3x3 segmentation

G4System = G4System
G4System.init(cw)
G4System.run_batch(100, "gamma", 1, 5) #100 events, photons, 1000 MeV to 5000 MeV

#G4s.run_visualize("gamma", 1, 5) 
G4System.printMaterial("G4_Pb")