Reading Values using PyROOT

[Ananda_Padhmanabhan]

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ROOT Version: Not Provided
Platform: Not Provided
Compiler: Not Provided

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I am trying to read out values from a ROOT file using PyROOT and is stuck with this issue. Any help is appreciated.

I based my code on this link. I think I am following everything as is given in that example. However, instead of it reading out momentum values as it is supposed to, I am getting a constant output of zeros. My tree structure is given as in the figure as shown by TBrowser.

import ROOT
rootFile = "file.root"

f = ROOT.TFile(rootFile,'read')
tree = f.Get('FCS_ParametrizationInput')
leaves = tree.GetListOfLeaves()

# define dynamically a python class containing root Leaves objects
class PyListOfLeaves(dict) :
    pass

# create an istance
pyl = PyListOfLeaves()

for i in range(0,leaves.GetEntries() ) :
    leaf = leaves.At(i)
    name = leaf.GetName()
    # add dynamically attribute to my class 
    pyl.__setattr__(name,leaf)

    if name == 'TruthPz':
        break


nev = tree.GetEntries()
for iev in range(0,nev) :
    tree.GetEntry(iev)
    # get values from the tree using Python class pyl which contains leaves
    # objects 
    px = pyl.TruthPx.GetValue()
    py = pyl.TruthPy.GetValue()
    pz = pyl.TruthPz.GetValue()

    print(px)
    if iev == 10:
        break

[sbinet]

PyAIDA is super ancient and completely deprecated (since… 2005, give or take).

something like this ought to work:

import ROOT
fname = "file.root"

f = ROOT.TFile.Open(fname)
tree = f.Get("FCS_ParametrizationInput")

n = 0
for evt in tree:
    px = evt.TruthPx
    py = evt.TruthPy
    pz = evt.TruthPz

    print("px={} py={} pz={}".format(px,py,pz))
    n += 1
    if n > 10:
        break
    pass

hth,
-s