Load C libraries from Python code

[AFanthomme]

Hi !

The question has probably already been asked, but I really couldn’t find any satisfactory answer so here I go.

I have some C file, category.c, which defines a certain number of functions (among which CategorySimple(int)) that I would like to access from python. What I found suggested to use :

import ROOT
ROOT.gROOT.LoadMacro(“Category.cc+”)

This step works, but I do not understand how I can access categorySimple after that as it does not become an attribute of ROOT / gROOT nor a function in my program’s namespace.

What is the exact effect of LoadMacro?
Thank you in advance !

Thank you in advance for your help

[bellenot]

This should work:

>>> import ROOT
>>> ROOT.gROOT.LoadMacro("Category.cc+")
>>> ROOT.CategorySimple()

At least it works for me:

>>> import ROOT
>>> ROOT.gROOT.LoadMacro("testgui.cxx+")
0
>>> ROOT.MyMainFrame(0, 600, 400)
<ROOT.MyMainFrame object ("fMainFrame2") at 0x06319930>
>>>

[AFanthomme]

That is quite surprising, when I do this I inevitably get an “attribute error” at the last step…
The functions in the c file are defined through :
extern “C” int categorySimple(int n){…}

Could this somehow interfere with what I am trying to do?
(the LoadMacro yields 0 though)

[bellenot]

No, using extern "C" works for me as well…
BTW, which version of ROOT are you using (and which platform/compiler)?

[AFanthomme]

I’m running root 6.06.1 built for linuxx8664gcc on a linux machine
Also I use python 2.7.10

[bellenot]

So please remove the extern "C" statement and try again…

[AFanthomme]

Ok I tried a minimal exemple with just a Hello world function in a file, and clearly LoadMacro works.
Somehow however it does not seem to like the functions from Category.C

[AFanthomme]

After more tests, it turns out that the problem clearly comes from the extern “C” in the definition.