I'm creating a C++ extension for python. It creates a module parent that contains a sub-module child. The child has one method hello(). It works fine if I call it as
import parent
parent.child.hello()
> 'Hi, World!'
If I try to import my function it fails
import parent
from parent.child import hello
> Traceback (most recent call last):
> File "<stdin>", line 1, in <module>
> ModuleNotFoundError: No module named 'parent.child'; 'parent' is not a package
parent.child
> <module 'child'>
here is my code setup.py
from setuptools import Extension, setup
# Define the extension module
extension_mod = Extension('parent',
sources=['custom.cc'])
# Define the setup parameters
setup(name='parent',
version='1.0',
description='A C++ extension module for Python.',
ext_modules=[extension_mod],
)
and my custom.cc
#include <Python.h>
#include <string>
std::string hello() {
return "Hi, World!";
}
static PyObject* hello_world(PyObject* self, PyObject* args) {
return PyUnicode_FromString(hello().c_str());
}
static PyMethodDef ParentMethods[] = {
{nullptr, nullptr, 0, nullptr}
};
static PyMethodDef ChildMethods[] = {
{"hello", hello_world, METH_NOARGS, ""},
{nullptr, nullptr, 0, nullptr}
};
static PyModuleDef ChildModule = {
PyModuleDef_HEAD_INIT,
"child",
"A submodule of the parent module.",
-1,
ChildMethods,
nullptr,
nullptr,
nullptr,
nullptr
};
static PyModuleDef ParentModule = {
PyModuleDef_HEAD_INIT,
"parent",
"A C++ extension module for Python.",
-1,
ParentMethods,
nullptr,
nullptr,
nullptr,
nullptr
};
PyMODINIT_FUNC PyInit_parent(void) {
PyObject* parent_module = PyModule_Create(&ParentModule);
if (!parent_module) {
return nullptr;
}
PyObject* child_module = PyModule_Create(&ChildModule);
if (!child_module) {
Py_DECREF(parent_module);
return nullptr;
}
PyModule_AddObject(parent_module, "child", child_module);
return parent_module;
}
I install and build with python setup.py build install.
So, how do I make sure that my parent is a package?
My code is a toy example but I actually want both modules defined on C++ level. I don't want to split them into several modules - since they are sharing some C++ code.
I'm hoping for something similar to approach of this answer Python extension with multiple modules