Home/ Questions/Q 7916209
In Process

The Archive Base Latest Questions

Editorial Team
  • 0
Asked: 2026-06-03T14:43:25+00:00

I have a big c++ program in a single .cpp file which defines a

  • 0

I have a big c++ program in a single .cpp file which defines a lot of classes(interdependent of each other) and finally runs a main function. Now I am interested only in using one of this classes in python, specifically one method of this class which accepts 5 floats as inputs and outputs one float. I am trying to find the simplest method to achieve this. After not having success with boost:python(mainly because of installation issues) I have come to Cython which in the current version supports C++. I could successfully run the Rectangle example given in the Cython tutorial but I can’t get how to proceed and adapt this to my case where I don’t need a so complicated .pyx file, and where I don’t have a .h file. Can somebody explain me in simple words what should I write in setup.py and in the .pyx file if my .cpp file has for example the structure:

...
class Nuclei {
public:
...
    double potential(float,float,float,float,float);
...
private:
...
};
...
Share

Leave an answer

You must login to add an answer.

Need An Account,

1 Answer

  1. Editorial Team

    If all you are looking to do is call a single function, Extending Python With C/C++ is probably the simplest approach. This page provides a good example.

    The relevant setup.py code in that example is

    from distutils.core import setup, Extension

module1 = Extension('demo',
                    define_macros = [('MAJOR_VERSION', '1'),
                                     ('MINOR_VERSION', '0')],
                    include_dirs = ['/usr/local/include'],
                    libraries = ['tcl83'],
                    library_dirs = ['/usr/local/lib'],
                    sources = ['demo.c'])

setup (name = 'PackageName',
       version = '1.0',
       description = 'This is a demo package',
       author = 'Martin v. Loewis',
       author_email = 'martin@v.loewis.de',
       url = 'http://docs.python.org/extending/building',
       long_description = '''
This is really just a demo package.
''',
       ext_modules = [module1])

    If the C++ code you want to call is in demo.c, it could be used with import demo in Python.

    Note that it is not nearly that simple- you’ll be creating a function that takes a PyObject * with arguments and returns a PyObject *, and a lot can be said about how those are constructed. Take a look at the pages linked to above- they are filled with examples.

    • 0