Using PyROOT code in a ROOT macro

ROOT
1

Hello, I have a short python script that I would like to call from a regular ROOT macro. Here is the original script:

[code]import Get_Info
import time, numpy, sys

runnum = int(sys.argv[1])
info = Get_Info.Get_Info(runnum)
st,sd = info[‘Start time’],info[‘Start date’]
et,ed = info[‘end time’],info[‘end date’]

sdt = time.mktime(time.strptime(st+sd,"%H:%M:%S%m/%d/%Y"))
edt = time.mktime(time.strptime(et+ed,"%H:%M:%S%m/%d/%Y"))
delta = (edt-sdt)

nevents = int(info[‘No. Events’])
evt_times = numpy.arange(sdt,edt,delta/nevents)
[/code]

Now, I would like to call this script inside a ROOT macro such that I can get the array evt_times for a given integer as a command-line argument. I looked at the TPython documentation but couldn’t get anything to work. I tried creating a class with a member function that returns a TVectorD:

class Evt_Times(): def __init__(self): print 'Creating Evt_Times object...' def evt_times(self,runnum): info = Get_Info.Get_Info(runnum) ... nevents = int(info['No. Events']) evt_times = numpy.arange(sdt,edt,delta/nevents) return ROOT.TVectorD(len(evt_times),evt_times)

But then in the ROOT interpreter none of the commands that I tried seemed to work:

root [0] TPython::LoadMacro("dateinterpolate.py")
root [1] et = Evt_Times()
Creating Evt_Times object...
(class Evt_Times::Evt_Times)4355969680
root [2] et.evt_times(387)
Error: Can't call Evt_Times::evt_times(387) in current scope (tmpfile):1:
Possible candidates are...
(in Evt_Times)
public: TPyReturnEvt_Timesevt_times Evt_Times::evt_times();
*** Interpreter error recovered ***
root [4] et->evt_times(387)
Error: Can't call Evt_Times::evt_times(387) in current scope (tmpfile):1:
Possible candidates are...
(in Evt_Times)
public: TPyReturnEvt_Timesevt_times Evt_Times::evt_times();
*** Interpreter error recovered ***
root [5] et::evt_times(387)
Error: Function evt_times(387) is not defined in current scope  (tmpfile):1:
*** Interpreter error recovered ***
root [6] Evt_Times::evt_times(387)
Error: cannot call member function without object (tmpfile):1:
  (compiled)   0 TPyReturnEvt_Timesevt_times Evt_Times::evt_times();
Calling : Evt_Times::evt_times(int);
Match rank: file     line  signature
*** Interpreter error recovered ***
root [7] TVectorD tvd = (TVectorD*)et.evt_times(387)
Error: Can't call Evt_Times::evt_times(387) in current scope (tmpfile):1:
Possible candidates are...
(in Evt_Times)
public: TPyReturnEvt_Timesevt_times Evt_Times::evt_times();
*** Interpreter error recovered ***

Any ideas on where to go would be appreciated. I would like to have access to the array evt_times inside ROOT, ideally as a TVector or as a more basic type.

Thank you,
Jean-François

1 Like
2

Hi,

instead of: et = Evt_Times() use: Evt_Times et;And no, I don’t know why it makes a difference. Perhaps b/c the latter statement is valid C++, whereas the former isn’t, and the code then takes some different path through CINT.

Cheers,
Wim

3

I’m still not able to get the TVector in ROOT. Do I want to do

Evt_Times et;
TVectorD tvd = (TVectorD*) et.evt_times(387)

or something? I also tried (void*), not casting, putting et.evt_times(387) in a constructor…

4

Hi,

it’s two steps: one cast to (void*) to convince CINT to call the converter, then another (TVectorD*) cast to convince it of the class (for some reason, the assignment itself isn’t enough; note also that the assignment is to a TVectorD*, not TVectorD: you’d have to dereference for that to work). Note that I also think that the python script should either keep the TVectorD alive, or relinquish ownership if the object is returned like this.

Evt_Times et; TVectorD* tvd = (TVectorD*)(void*) et.evt_times(387)or:

Evt_Times et; TVectorD tvd = *(TVectorD*)(void*) et.evt_times(387)
For the copy (second statement), the lifetime of the TPyReturn should be sufficient to do the copy before the vector is deleted from the python side.

Cheers,
Wim

5

Thanks, now it works in my macro.

I am able to include this in a ROOT macro that I run without compilation, but if I ask for +compilation, ACLiC complains:

[quote]root [0]
Processing my_analysis.C+("…/rootfiles/Outputs/Run0464")…
Info in TUnixSystem::ACLiC: creating shared library /Users/jfcaron/Projects/TRIUMFBeamTest/standard_analysis/./my_analysis_C.so
In file included from /Users/jfcaron/Projects/TRIUMFBeamTest/standard_analysis/my_analysis_C_ACLiC_dict.cxx:17:
In file included from /Users/jfcaron/Projects/TRIUMFBeamTest/standard_analysis/my_analysis_C_ACLiC_dict.h:34:
/Users/jfcaron/Projects/TRIUMFBeamTest/standard_analysis/./my_analysis.C:540:3: error: use of undeclared identifier 'Evt_Times’
Evt_Times et;
^
/Users/jfcaron/Projects/TRIUMFBeamTest/standard_analysis/./my_analysis.C:541:39: error: use of undeclared identifier 'et’
TVectorD * tvd = (TVectorD*)(void*) et.evt_times(runnum);
^
2 errors generated.
clang: error: no such file or directory: '/Users/jfcaron/Projects/TRIUMFBeamTest/standard_analysis/my_analysis_C_ACLiC_dict.o’
Error in : Compilation failed!
Error: Function my_analysis("…/rootfiles/Outputs/Run0464") is not defined in current scope :0:
*** Interpreter error recovered ***
[/quote]
Is it possible to allow this to work with the macro compiled? I understand that the python part will not be compiled, but I thought it should be possible to have the compiled C++ code talk to the python side…at least I was able to compile and run a shorter example macro with TPython::Exec().

6

Hi,

not used this way: the LoadMacro() code makes use of the class generator feature of CINT to dynamically create the corresponding C++ classes in CINT. Naturally, the C++ compiler wants to see, for static compilation, a file containing the C++ class definition of Evt_Times, and there’s no such thing.

You could use the Python C-API to manipulate the Python objects, but they’d have to stay on the Python side then.

Note that TPython::Exec() is different: it takes a const char* and returns a Bool_t, so no unknown C++ classes there.

Cheers,
Wim

1 Like
7

What if I refactored the code to not use a class, but instead to just define a python function that takes an integer argument and returns a TVector. I could execute the code with a compiled macro with TPython::Exec, but would I be able to copy the vector into ROOT?

What if the python code was just a script that sent the contents of the vector to stdout, could my ROOT macro pick it up somehow?

Thanks for any ideas.

8

If the function returning a TVectorD lives in a module, something like this would do for both interpreted macro and complied function:[code]#include “TPython.h”
#include “TVectorD.h”

void mymacro() {
TPython::Exec(“import MyModule”);
TVectorD* tvd2 = (TVectorD*)(void*)TPython::Eval(“MyModule.myfunc()”);
}[/code]With again taking care that the lifetime of the TVectorD is properly handled.

Cheers,
Wim

1 Like