In Python lässt sich Prozessieren von Trees und Selektion sehr einfach erledigen:
import ROOT # open file on wbe server myf = ROOT.TFile.Open("http://www.etp.physik.uni-muenchen.de/kurs/comp10/uebungen/Z0-Versuch/data/ntz0mhmc.root") # retrieve tree mychain = ROOT.gROOT.FindObject( "h5000" ) # N events nentries = mychain.GetEntriesFast() print (nentries , " Events in Tree " ) hnct = ROOT.TH1F("hnct","Ncharged",50,0,50) # loop over tree i=0 for x in mychain: # event features attached to x in each iteration i += 1 if i<=20: # print some info for 1st 20 entries print x.Event, x.Ncharged, x.E_ecal hnct.Fill( x.Ncharged ) # fill Ncharged histo # hnct.Draw() # draw hist when done