How to use SetBranchAddress in pyroot?

[orby]

Hello everybody,

i’m quite new to python and pyROOT. I have used ROOT with CINT a little, but decided that for future learing i want to use pyroot, which seems to me a lot more comfortable in some ways.
I found my problem to fit in this thread, so i thought it best to post here.

My problem is the following:
I have root files like the one attached, and want to add them to a Chain and access the leafs in a loop.
With CINT i needed to define doubles x1 and x2 and use

TChain *c1 = new TChain("t1");
c1->Add("data.root");
c1->SetBranchAddress("x1",&x1);
c1->SetBranchAddress("x2",&x2);
for (int i=0; i<(c1->GetEntries());++i){
	c1->GetEntry(i);
	atgraph->SetPoint(i,x1,x2);
}

I want to use c1.GetEntry() with pyroot likewise, but can’t get it to work.
This thread hasn’t helped me too much.
In this one however:

How to read TTree with two branches using the same struct?

Hi, you’d have to create s1 and s2 structs to hold the values and use SetBranchAddress(), like you would in C++. The shortcut using member access does not work as it would require a two-step lookup (T.s2.bin), and the internal code is only expecting one step. As an alternate, you could change the labels in the .C code by calling them bin2, etc. They’re just labels and do not need to match the member names in the struct. Cheers, Wim

is a solution quite related to what i need, it’s a bit complicated though …
if someone could help, i’d be delighted . regards,
Martin

edit: attachment added
data.root (15.5 KB)