如何使用 boost/python 从 C++ 的 .py 文件中导入 class？

Question

EDIT: Looks like I've messed up the solution from the second post, but it's still giving me an error after I corrected it.

Edit: I tried importing using a full path but it gave me a relative import error. I made another post about it here

the directories looks like this:

project
   |__ utilities
   |      |__ foo.py
   |
   |__ boost_extensions
   |      |__ myclass.cpp
   |      |__ myclass.so
   |
   |__ someotherstuff
   |      |__ bar.py      
   |
   |__ __main__.py

From bar.py I can just import something from foo.py like this:

from ..utilities.foo import Foo

However, from myclass.cpp I'm not sure how to import it. I've tried

boost::python::object mod = boost::python::import("..utilities.foo");

and

boost::python::object mod = boost::python::import("../utilities/foo.py");

both gave me an error module not found error:

ModuleNotFoundError: No module named '.'

I've also seen this post and tried the accepted answer but it did not work (same error as before):

boost::python::object mod;
void set_global(){
    try{
        setenv("PYTHONPATH", ".", 1);
        Py_Initialize();
        mod = boost::python::import("..utilities.foo");
    }
}

I have also tried using sys and os however it still gave me an error (from an answer to this post ):

    try{
        setenv("PYTHONPATH", ".", 1);
        Py_Initialize();
        boost::python::object sys = import("sys");
        boost::python::object os = import("os");
        // sys.path.append(os.path.join(os.path.dirname(__file__), '..', 'Common'))
        // os.path.dirname(__file__)
        boost::python::object arg1 = os.attr("path").attr("dirname")("__file__");
        // os.path.join(arg1, '..', 'Common')
        boost::python::object arg2 = os.attr("path").attr("join")(arg1, "..", "Common");
        // sys.path.append(arg2)
        sys.attr("path").attr("append")(arg2);
        mod = boost::python::import("..utilities.foo");
    } catch(int e){
        cout << "import failed" << endl;
    }

error message:

ModuleNotFoundError: No module named '.'

How am I supposed to import the module?

Thanks

Answer 1

I figured out a workaround: since Python modules are also PyObjects, I can load the module in Python and pass it to C++ as a variable. Here's the code:

The C++ file:

boost::python::object mod;
void set_global(boost::python::object foo_module){
    mod = foo_module;
    // this is for testing
    boost::python::object test = mod.attr("Foo")(new A(1,1,1), NULL, 12);
    A* a = extract<A*>(test.attr("_A")) ;
    cout << a->_x << endl << a->_y << endl << a->_z << endl;
}

In python (from this answer ):

from .utilities import foo as foo_module
set_globals(foo_module)

output:

1
1
1