Legend not drawn from function in PyRoot

ROOT
1

Hi,

I am having trouble drawing legend, legend does not get drawn if I put the Draw statement in a function, though it does draw if the Draw statement is outside.

A simple example is

from ROfrom ROOT import *
file=TFile("SingleTopNtuple/SingleTop.ntuple.TDR_012.root")
tree=file.Get("UserData")

histo=TH1F("histo","", 100, -5,5)
tree.Draw("elec_eta>>histo", "")
legend=TLegend(0.6,0.6,0.8,0.8)
legend.AddEntry(histo, histo.GetName(), "l")
legend.Draw()

This does what I expect it to do. Draw histogram and legend. Now the following

from ROfrom ROOT import *
file=TFile("SingleTopNtuple/SingleTop.ntuple.TDR_012.root")
tree=file.Get("UserData")

def fun():
  histo=TH1F("histo","", 100, -5,5)
  tree.Draw("elec_eta>>histo", "")
  legend=TLegend(0.6,0.6,0.8,0.8)
  legend.AddEntry(histo, histo.GetName(), "l")
  legend.Draw()

fun()

does not draw the legend, only the histogram.
A workaround is

from ROfrom ROOT import *
file=TFile("SingleTopNtuple/SingleTop.ntuple.TDR_012.root")
tree=file.Get("UserData")

def fun():
  histo=TH1F("histo","", 100, -5,5)
  tree.Draw("elec_eta>>histo", "")
  legend=TLegend(0.6,0.6,0.8,0.8)
  legend.AddEntry(histo, histo.GetName(), "l")
  return legend

leg=fun()
leg.Draw()

this works the same as the first example.

Why does the second not work?

Thank you for your help.

Cheers
Akira

2

Please post PyROOT related problems to the PyRoot Forum

Rene

3

Hi,

I’m sorry, I didn’t know there existed one. I have copied this one and the other one (Draw options ignored after TH1::Sumw2 (PyRoot) ) to PyRoot Forum. Please feel free to delete them. Sorry for the trouble.

Cheers
Akira