#!/usr/bin/env python
# coding: utf-8

# # Access TTree in Python using PyROOT and fill a histogram
# <hr style="border-top-width: 4px; border-top-color: #34609b;">

# First import the ROOT Python module.

# In[1]:


import ROOT


# Optional: activate the JavaScript visualisation to produce interactive plots.

# In[2]:


get_ipython().run_line_magic('jsroot', 'on')


# Open a file which is located on the web. No type is to be specified for "f".

# In[3]:


f = ROOT.TFile.Open("https://root.cern.ch/files/summer_student_tutorial_tracks.root");


# Loop over the TTree called "events" in the file. It is accessed with the dot operator.
# Same holds for the access to the branches: no need to set them up - they are just accessed by name, again with the dot operator.

# In[4]:


h = ROOT.TH1F("TracksPt","Tracks;Pt [GeV/c];#",128,0,64)
for event in f.events:
    for track in event.tracks:
        h.Fill(track.Pt())
c = ROOT.TCanvas()
h.Draw()
c.Draw()