bind class template in seperate file using pybind11

1_structure_of_project

pybind_cpp_cmake
   -- /include/sample_class_template.h
   -- /lib/pybind11
   -- /src/binding.cpp
          /binding_module_class_template.cpp
          /sample_class_template.cpp
   CMakeLists.txt

binding.cpp

#include <pybind11/pybind11.h>
#include <pybind11/complex.h>
#include <pybind11/stl.h>
#include <pybind11/functional.h>
#include <pybind11/numpy.h>

// ignore the unnecessary header file declared till this line

#include "sample_class_template.h"
#include "sample_class_template.cpp"

namespace py = pybind11;

template <typename T = int>
void class_template_do_add_testing(py::module &m, const std::string& typestr1);


PYBIND11_MODULE(somecode, m) 
{
  class_template_do_add_testing<int>(m, "int");
}

binding_module_class_template.cpp

#include "sample_class_template.h"
#include "sample_class_template.cpp"

#include <pybind11/pybind11.h>
#include <pybind11/complex.h>
#include <pybind11/stl.h>

namespace py = pybind11;

template <typename T = int>
void class_template_do_add_testing(py::module &m, const std::string& typestr1)
{
py::class_< DO_ADD<int>>(m, "DO_ADD")
         .def(py::init<int>())
         .def("show_val", &DO_ADD<int>::show_val);
};

CMakeLists.txt

cmake_minimum_required(VERSION 3.10)
project(somecode)

set(MAIN_TARGET_NAME ${PROJECT_NAME})

set(LIB_GEN_PATH ${PROJECT_SOURCE_DIR}/scripts CACHE STRING "Where generated library will be placed")

# include all header file. required to make cpp lib and fotr pybind module
include_directories(${PROJECT_SOURCE_DIR}/include) 

# for pybind11 module
add_subdirectory(lib/pybind11)

# a unique name is set for the pybind module
set(PYBIND_TARGET_NAME somecode)

# linking all file which will be binded by pybind. All required cpp file will come here
pybind11_add_module(${PYBIND_TARGET_NAME} ${PROJECT_SOURCE_DIR}/src/sample_class_template.cpp
                                          ${PROJECT_SOURCE_DIR}/src/binding_module_class_template.cpp
                                          ${PROJECT_SOURCE_DIR}/src/binding.cpp)

# module path(*_cpython_*.so file) for pybind
set_target_properties(${PYBIND_TARGET_NAME}
    PROPERTIES
    LIBRARY_OUTPUT_DIRECTORY ${LIB_GEN_PATH}
)

sample_class_template.cpp

#include "sample_class_template.h"
#include <iostream>

/**
 * A sample class template function definition
 */

template <typename T>
void DO_ADD<T>:: show_val(){
    cout<<"from show_val function x: "<<x<<endl;
}

sample_class_template.h

#ifndef _SAMPLE_CLASS_TEMPLATE_
#define _SAMPLE_CLASS_TEMPLATE_

#include <iostream>
using namespace std;

/**
 * A sample class template
 */

template <typename T>
class DO_ADD{
    private:
        T x;
    public:
        DO_ADD(T val):x(val)
                            {cout<<"DO_ADD constructor is called and x: "<<x<<endl;}
        
        void show_val();

        ~ DO_ADD() {};
};

#endif