hist000_TH1_first.py

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## \file
## \ingroup tutorial_hist
## Hello World example for TH1
##
## Shows how to create, fill and write a histogram to a ROOT file.
##
## \macro_code
## \macro_output
##
## \date November 2024
## \author Giacomo Parolini (CERN)
 
import ROOT
 
# Open the file to write the histogram to
with ROOT.TFile.Open("outfile.root", "RECREATE") as outFile:
   # Create the histogram object
   # There are several constructors you can use (see TH1). In this example we use the
   # simplest one, accepting a number of bins and a range.
   histogram = ROOT.TH1D("histogram", "My first ROOT histogram", nbinsx = 30, xlow = 0.0, xup = 10.0)
 
   # Fill the histogram. In this simple example we use a fake set of data.
   # The 'D' in TH1D stands for 'double', so we fill the histogram with doubles.
   # In general you should prefer TH1D over TH1F unless you have a very specific reason
   # to do otherwise.
   values = [1, 2, 3, 3, 3, 4, 3, 2, 1, 0]
   for val in values:
      histogram.Fill(val)
 
   # Write the histogram to `outFile`.
   outFile.WriteObject(histogram, histogram.GetName())
 
   # When `with` block exits, `outFile` will close itself and write its contents to disk.