Loading compiled libraries into PyROOT

ROOT
1

Hello,

I’m trying to use some compiled code in PyROOT. I compile it as standalone code, producing two .so files, and they work with other compiled C ROOT code, but I can’t yet figure out how to make it work in Python. Could someone point out what I’m doing wrong?

my simpleminded script:

from ROOT import gSystem
gSystem.Load(’/CalibrationDataInterfaceROOT_cxx’)
gSystem.Load(’/libBTagCalib’)

all fine to here

from ROOT import CalibrationDataInterfaceROOT

gives ImportError: cannot import name CalibrationDataInterfaceROOT

do I need to put “#pragma link” sorts of things into the C code?

Thanks!

2

Hi,

how did you compile the C++ code? Did you generate dictionaries for it? You say that you use it from C. For C, python has the ctypes module if need be.

Cheers,
Wim

3

Hi,

The code have two headers and two source files. From them, the standalone make command that the developers provide creates:
BTagCalib_Dict.h
BTagCalib_Dict.C
obj
libBTagCalib.so
obj/CalibrationDataInterfaceBase.o
obj/CalibrationDataInterfaceROOT.o
obj/BTagCalib_Dict.o
obj/dep/CalibrationDataInterfaceROOT.d
obj/dep/CalibrationDataInterfaceBase.d

The BTagCalib_Dict.h file has things like
extern G__linked_taginfo G__BTagCalib_DictLN_AnalysiscLcLCalibrationDataInterfaceROOT;
which I guess is the CalibrationDataInterfaceROOT that I’m trying to import.

I just gSystem.Load the libBTagCalib.so file. Do I need to add in the others as well?

4

Hi,

I would assume that the .so build from the _Dict.C file is linked against the original library, and that that is the library to load.

Cheers,
Wim

5

The code’s developer has explained to me how it’s to be done! What they do in their Python script is

import ROOT
ROOT.gSystem.Load(‘libBTagCalib’)
bjet_SF = ROOT.Analysis.CalibrationDataInterfaceROOT(‘SV0’, ‘EnvTestFile.env’)

Maybe that’s the syntax because CalibrationDataInterfaceROOT in in the Analysis namespace? I’m not sure. Anyway, it works for me now!