List of histograms in pyROOT


I am trying to get a list with a set of histograms but when I try to append each one I get an error I don’t understand, it seems like the histograms cannot be added to a list? Is there a way I can do it?

This is my code:

histos = [] histo = TH2D("2dhist","Title",nmix,0,1,nmix,0,1) for iW in range(nmix): Wbr = iW*Step for iH in range(nmix): Hbr = iH*Step Zbr = 1-(Wbr+Hbr) nEvents = reweight(Histogram,mass,[Zbr,Wbr,Hbr]) histo.SetBinContent(iW+1,iH+1,nEvents) histos.append[histo]

And this is the output with the error

Using file: output/VLQAnalysis_BBS_350_AF_ee.root Using histotram: cut7_decay_flag <class 'ROOT.TH1D'> Traceback (most recent call last): File "", line 93, in <module> histos.append[histo] TypeError: 'builtin_function_or_method' object is unsubscriptable

Using extend instead of append gives me the same result, which is not surprising.
The reweight function just retuns a number based on the content on different bins of the histogram. The code works as expected if I do it for each histogram separately but I need to crate an array of them.

Thanks a lot in advance,

You’re going to kick yourself for a silly mistake:

This is a method call, note the round brackets:


This tries to access the element with index or key “histo” from the collection stored in histos.append:



Oh you are right! Thanks a lot, that was really silly… I haven’t seen that and I have been staring at it for while now… Time to go to sleep I think.

Thanks again,