import numpy as np
import ROOT

np.random.seed(0)

# Create a one dimensional histogram and fill it with a gaussian distribution
h1d = ROOT.TH1D("h1d", "Test random numbers", nbinsx=200, xlow=0.0, xup=10.0)

# "gaus" is a predefined ROOT function. Here we are filling the histogram with
# 10000 values sampled from that distribution.
values = np.random.normal(0.0, 1.0, 10000)
h1d.Fill(values)

# Open a ROOT file and save the histogram
with ROOT.TFile.Open("fillrandom_py_uhi.root", "RECREATE") as myfile:
    myfile.WriteObject(h1d, h1d.GetName())