Converting C++ to pyroot: How to get a file object from a file in pyroot?

Question

I am doing neutrino research that requires me to do data analysis by overlaying histograms. We are using ROOT. I am currently trying to convert the following code from C++ to pyroot:

#include "TFile.h"
#include "TH1F.h"
#include "TCanvas.h"
#include "TString.h"
void myscript()
{
  //get a histogram named vtx_0 from the file 5A_data
  TFile* file = TFile::Open("5A_data");
  TH1F* hist = file->Get("vtx_0");
  TCanvas* canvas = new TCanvas("c1", "Dynamic Filling Example", 200, 10, 700,500);
  hist->Draw();
}

This is the code I have so far, re-written in python:

from ROOT import TFile, TH1F, TCanvas, TString
def myscript():
  #get vtx_0 from 5A_data
  TFile file1 = open("5A_data")
  TH1F hist =

I have had limited exposure to Python. The Python code above was created mostly from looking at various online examples, and so I am not even sure if what I have written up to this point is correct.
What I am most in need of, and what I have been unable to find online, is how to covert the following line in C++ to its equivalent in Python.
```
TH1F* hist = file->Get("vtx_0");
```

How does one do this?

In addition, if you see anything amiss with the Python code I have written so far, please tell me what I did wrong and how I might fix it. Thank you.

score 1 · Answer 1 · answered Jul 20 '18 at 18:34

types are not needed for variable declaration, and something like this might get you started:

from ROOT import TFile, TH1F, TCanvas, TString
def myscript():
    tf = TFile("5A_data")
    print(dir(tf))
    #tree = tf.Get("vtx_0")
    fo = tf.GetObject("vtx_0")
    print(dir(fo))
    for x in fo:
        print(x)
    import pdb;pdb.set_trace()

referenced:

Converting C++ to pyroot: How to get a file object from a file in pyroot?

1 Answers1