Reading Leaves of a root branch using pyroot

[woywoy123]

Hello ROOT community,

I am fairly new to pyroot and this might be an easy question. I have a problem when trying to read events from a root file which has branches. The structure is as such:
Delphes>Jets>leaves
My attempt so far is this:

import ROOT
directory= str("MadGraph5/bin/pp/Events/run_01/tag_1_delphes_events.root")

Tree = ROOT.TFile(directory)
Delphes = ROOT.gROOT.FindObject("Delphes;1")

for i in Delphes:
	x = Delphes.Jet
	for z in x:
		read = x. GenJet.PT

when running this script I get an error "‘TClonesArray’ object has no attribute ‘GenJet’’. When I count the number of events using a simple i = i+1 counter I get the correct number of iterations. The most success I have had receiving adresses…

Thanks in advance

[eguiraud]

Hi,
shouldn’t it be z.GenJet rather than x.GenJet?

[woywoy123]

I just tried that out too and I get the same error sadly.

[eguiraud]

Hi,
can you provide a bit of data (even one event is enough) that I can try things on?

[woywoy123]

Hello Eguiraud,
Thanks again for helping me here is a screenshot of the root file I am trying to access.

[Danilo]

Hi,

shouldn’t this be

import ROOT
directory= str("MadGraph5/bin/pp/Events/run_01/tag_1_delphes_events.root")

File = ROOT.TFile(directory)
DelphesEvents = File.Delphes # This is your tree
for event in DelphesEvents:
	jets = event.Jet
	for jet in jets:
		print jet.PT

Cheers,
D

[woywoy123]

Hello Dpiparo,

Thank you for your contribution to this issue. I have tried using your code and actually this is one of the methods I used also and if you count the number of iterations the second for loop it does correspond to the number of events in that branch i.e. Jet. But I am getting the same error as before that ‘TObject’ object has no attribute ‘PT’’. Not sure why this is the case though.

[Danilo]

Hi,

are you sure the delphes libraries are available to ROOT?
What happens if you try the same loop in a C++ macro?

Cheers,
D

[woywoy123]

I havnt attempted it using C++ but I got it to work so here is the code:

import ROOT

#================ Extracting Data from Delphes root =====================#
directory= str("MadGraph5/bin/pp/Events/run_01/tag_1_delphes_events.root")
File = ROOT.TChain("Delphes;1")
File.Add(directory)
Number = File.GetEntries()

for i in range(Number):
	Entry = File.Get Entry(i)
	EntryFromBranch = File.Jet.GetEntries()
	for j in range(EntryFromBranch):
		PT = File.GetLeaf("Jet.PT").GetValue(j)