Repeatedly get and save TH2D in TFile

ROOT
#1

Dear ROOTers,

How can I repeatedly get all the TH2D objects (with known names) from a file, alter them and then append them again in the same file?

I tried many things, but nothing worked out sofar.

for i in indices:
if file.FindObjectAnyFile(“my_object”) == None:
hist = ROOT.TH2F(“my_object”,…)
hist = file.get(“my_object”)
…
hist.Fill(…)
…
hist.Append(“my_object”)

Why does this not work?

#2

Hi,

is the file opened in “UPDATE”? Otherwise, better to post in the ROOT Support forum, as this question isn’t PyROOT specific (and outside my limited knowledge).

Cheers,
Wim

#3

Hi,

Do you mean to over-ride the old content and add it along side the old content (it is to over-ride, is writting a new file an option?)?

hist.Append("my_object") Why does this not work?How does it fail? … humm actually what do you mean by it (do you really mean to try to append a string to the histogram?) … the closest I can think of that you might mean is :file.Append(hist) which is already implied (any histogram read from a TFile is already Appended/attached to the TFile).

Philippe.