import ROOT,aa """ exmaple to show how to write an 'offline' file using OutputEventFile class. """ f = ROOT.OutputEventFile("myfile.root") header = ROOT.Head() header.set_line("sometag","custom_file") f.write_header(header) for i in range( 10 ) : evt = ROOT.Evt() evt.id = i evt.mc_trks.resize(1) evt.mc_trks[0].dir.set( 0,0,1 ) evt.mc_trks[0].E = 1000 f.write(evt) del f # this closes the file f = ROOT.EventFile( "myfile.root" ) for evt in f : print(evt)