Adding axis limits in pyROOT

Question

I am trying to limit my x-axis in my pyROOT code. Right now the x-axis is way too long and makes the waveform that I am plotting look too thin. I need to limit the x-axis range to about (130,240) but everything I try comes back with an error so I need help. Any time I use a -> in the code it gives me a syntax error and I do not know why. Below is my code that I need the x-axis limit added to. Thank you..

import sys
sys.path.insert(1, "/home/diffuserdaq/DiffuserAnalysis/scripts")

import matplotlib
import matplotlib.pyplot as plt

import plot_waveformCOPY

from utilities.readscan import readscan

import ROOT


data = readscan("/home/diffuserdaq/DiffuserSetup/Oct13th_1.root","diffuser")

s0= data.scanpoints[0]

tgraph = ROOT.TGraph(len(s0.axis_time),s0.axis_time,s0.samples_PMT)

canvas = ROOT.TCanvas()
tgraph.Draw("ALP")
canvas.Print("plot.pdf")

gauss = ROOT.TF1("gaus","gaus",150,200)
gauss.SetParameter("Constant",-1.55)
gauss.SetParameter("Mean",185)
gauss.SetParameter("Sigma",5.0)

gauss.SetParLimits(0,-2.0,0.0)
gauss.SetParLimits(1,150.0,200.0)
gauss.SetParLimits(2,0.0,20.0)

fit_results = tgraph.Fit(gauss,"VBRS")
print("Fit Results",fit_results)

input(" press key to stop")

Answer 1

Before calling canvas.Print("plot.pdf") , you can try:

tgraph.GetXaxis().SetRangeUser(130, 240)

Regarding the usage of the -> operator, in Python it has not the same meaning as it has on C++, so you should never use it in the context of accessing a class member. Always use the dot operator instead.