How to access elements of std.vector<double> object type in PyROOT

[Austin_Shipley]

I am fairly new to using ROOT, so please bear with me.

Currently, I am trying to comb through the data from a ROOT file and access the particular entries of a tree. The issue I am having is that I don’t know how to interface with std.vector data types in PyROOT.

Here is my code:

f = TFile.Open("/Users/user/work/GEMC_Sim/GEMC_Simulation/clas12Tags/config/Trials.root")

#f.ls()

tree = f.Get('flux')

tree.Print()

for idx,event in enumerate(tree):
    
    print(idx,event.pid)
            

{}
{ 11 }
{}
{ 11,11 }
…

In this output, there are either these empty braces or they are filled with individual particle index values or they are grouped together with multiple entries. What I want is to create a separate index that increases by one every time that one 11 is identified in each brace. For instance, {11,11,11} would increase the index by one. Similarly, {11} would also increase the index by one.

If this was a normal python data type I would know how to work with this, but I am a bit confused as to how to work with the std.vector data type. Any insight or suggestions is greatly appreciated.

ROOT Version: ROOT 6.24/06

---

[couet]

Welcome to the ROOT forum.
I guess @etejedor can help you.

[etejedor]

Hello,

You can work with an std::vector from Python in the same way you would do it from C++ – all its methods are available. You can also iterate over it in a pythonic way (for elem in vector: …) or access individual positions. Iterating should be enough to check that all elements are 11.