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from PhysicsTools.PythonAnalysis.cmstools import *
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from ROOT import *
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# prepare the FWLite autoloading mechanism
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gSystem.Load("libFWCoreFWLite.so")
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AutoLibraryLoader.enable()
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# load the file with the generator output
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theFile = TFile("generatorOutput.root")
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events = theFile.Get("Events")
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# Needed for SetAddress to work right
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events.GetEntry()
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# set the buffers for the branches you want to access
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# 1) create a buffer
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# 2) open the root branch
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# 3) connect buffer and branch
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# example: generator particles
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source = edm.HepMCProduct()
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sourceBranch = events.GetBranch(events.GetAlias("source"))
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sourceBranch.SetAddress(source)
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# now loop over the events
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for index in all(events):
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# update all branches - the buffers are filled automatically
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# Hint: put all you branches in a list and loop over it
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sourceBranch.GetEntry(index)
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events.GetEntry(index,0)
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# do something with the data
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genEvent = source.GetEvent();
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print genEvent.event_number()
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