RDataFrame::Histo1D from PyROOT

[Attila_Krasznahorkay]

Hi @eguiraud,

I thought I’d ask it here rather than in a private e-mail.

I’m playing with RDataFrame since a few days. After some struggle I was able to make it work in C++, so now I’m looking at doing some simple things in Python. And I’m having a lot of problems with the Histo1D function. Whenever I try to use it in a very simple manner, I get:

Traceback (most recent call last):
  File "test.py", line 18, in <module>
    hist = df.Histo1D( "ElectronsPt" )
TypeError: can not resolve method template call for 'Histo1D'

Looking at Doxygen I see that this function is heavily overloaded.

https://root.cern.ch/doc/v614/classROOT_1_1RDF_1_1RInterface.html#a247ca3aeb7ce5b95015b7fae72983055

Still, I would’ve hoped that it would be possible to call it in such a simple way… (In this example “ElectronsPt” is an std::vector<float> variable.)

Is there something I forgot about? Or is it really a case of PyROOT not being able to find which overload to use here?

Cheers,
Attila

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ROOT Version: 6.14/04
Platform: x86_64-mac1013-clang100-opt
Compiler: Apple Clang 10.0

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[Attila_Krasznahorkay]

Aaaargh… Never mind.

The problem was that I tried to call this function on a “state” of the object that did not have “ElectronsPt” defined yet. Weird that it would fail in this way though…

Still, once I call the function correctly after the Define(...) call, it now runs.

Cheers,
Attila

[eguiraud]

Ah weekend had this report already, in this case in which it is trying to figure out the right template overload to call PyROOT ends up hiding the exception that the c++ is throwing and gives a vague message instead.

Maybe @etejedor can comment further.

Let us know if you missed something that would have made your first steps with RDF smoother.

Cheers,
Enrico