Problem in GetBinContent

Dear developers,

I have multiple root files Mc_1.root, Mc_2.root etc. In each root file I have a histogram name counter. I want to find the number of entries in each file, secondly I want to add all the entries to get total number of entries in all root files. Kindly help me to do this.


In a loop open the file containing this histogram, get it from file, get the number of entries, and cumulate the number of entries in some variable.

FWIW here is how I’d do it in Go and go-hep/rootio:

package main

import (


func main() {
	fnames := os.Args[1:]
	entries := 0.0
	for _, fname := range fnames {
		n, err := process(fname, "rigidity")
		if err != nil {
			log.Fatalf("error processing %q: %v", fname, err)
		fmt.Printf("file %q: %v\n", fname, n)
		entries += n
	fmt.Printf("\n==> total entries: %v\n", entries)

func process(fname, name string) (float64, error) {
	f, err := rootio.Open(fname)
	if err != nil {
		return 0, err
	defer f.Close()

	obj, ok := f.Get(name)
	if !ok {
		return 0, fmt.Errorf("file %q has no object called %q", f.Name(), name)

	h, ok := obj.(*rootio.H1F)
	if !ok {
		return 0, fmt.Errorf("object %q is not a TH1F", name)
	return h.Entries(), nil

and then:

$> go get
$> go run ./main.go /path/to/*.root
file "f1.root": 900000
file "f2.root": 900000
file "rigidity.root": 900000

==> total entries: 2.7e+06

(I just put 3 times the same file for that exercize)


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