THStack and pyROOT

EDIT: SOLVED The problem was that the histogram I was trying to retrieve did not exist. TFile::Get() does actually get the right class and no cast is needed. Sorry!


I feel this is very very basic, but I cannot find the solution. In this small piece of code:

        mystack=THStack("ratios_combined","combination of ratios for different isocuts")
        print "the name is ",mystack.GetName()
        for isamp in ListOfSamples:
                print "file to get =", filetoget
                print "the class is ",hist.Class_Name()

I get the output:

the class is  TObject
TypeError: void THStack::Add(TH1* h, Option_t* option = "") =>
    could not convert argument 1

It seems that THStack needs a TH1-inherited object. How can I make this happen? How can I make pyroot aware that “hist” is a TH1D ?