Python.h not found while building sample application with cmake and pybind11

Question

I want to build simple app with pybind11, pybind is already installed in my Ubuntu system with cmake (and make install). I use this simple cmake file:

cmake_minimum_required(VERSION 3.0 FATAL_ERROR)
project(trt_cpp_loader )
find_package(pybind11 REQUIRED)
add_executable(trt_cpp_loader main.cpp)
set_property(TARGET trt_cpp_loader PROPERTY CXX_STANDARD 11)

This is main.cpp:

#include <iostream>
#include <pybind11/embed.h>
namespace py = pybind11;

using namespace std;
int main(){return 0;}

when I build it, I get:

In file included from /usr/local/include/pybind11/pytypes.h:12:0,
                 from /usr/local/include/pybind11/cast.h:13,
                 from /usr/local/include/pybind11/attr.h:13,
                 from /usr/local/include/pybind11/pybind11.h:44,
                 from /usr/local/include/pybind11/embed.h:12,
                 from /home/stiv/lpr/trt_cpp_loader/main.cpp:2:
/usr/local/include/pybind11/detail/common.h:112:10: fatal error: Python.h: No such file or directory
 #include <Python.h>
          ^~~~~~~~~~
compilation terminated.

how can I fix this problem? (python-dev and python3-dev are already installed, Python.h is available)

Answer 1

You'll want to use the pybind11_add_module command (see https://pybind11.readthedocs.io/en/stable/compiling.html#building-with-cmake ) for the default case of creating an extension module.

If the goal is indeed to embed Python in an executable, it is your reponsibility to explicitly add python headers & libraries to the compiler/linker commands in CMake. (see https://pybind11.readthedocs.io/en/stable/compiling.html#embedding-the-python-interpreter on how to do that)

Answer 2

Following the Wenzel Jakob 's answer I want to put an example of CMakeLists.txt for compiling the example provided in this tutorial :

// example.cpp

#include <pybind11/pybind11.h>

int add(int i, int j) {
    return i + j;
}

PYBIND11_MODULE(example, m) {
    m.doc() = "pybind11 example plugin"; // optional module docstring

    m.def("add", &add, "A function which adds two numbers");
}

and

# example.py

import example

print(example.add(1, 2))

and

# CMakeLists.txt

cmake_minimum_required(VERSION 2.8.12)
project(example)

find_package(pybind11 REQUIRED)
pybind11_add_module(example example.cpp)

now in the root run

cmake .
make

now run the python code by

python3 example.py

PS I have also written some instructions here for compiling/installing the pybind11 .

Answer 3

Maybe just install the Python headers? For example, on Ubuntu you can install the sudo apt-get install python-dev (or python3-dev or pythonX.Y-dev ) package. That could resolve this.