I am using the first step example in pybind11's documentation
#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");
}
everything works fine, i can use it in python shell:
import example
example.add(2, 3) #returns 5
Now i made a simple change to use float instead of int for input for add(), everything compiles. and i want to reload the module example so i can test the new float based add(). However, i can not figure out a way to reload the example module. importlib.reload does not work, %autorelaod 2 in IPython does not work either.
both approached tested to work with pure python based modules, but not the c++ and pybind11 based modules.
Did I miss anything here? or it ought to be like this?
UPDATE: seems it is a known issue related to How to Reload a Python3 C extension module?
Python's import mechanism will never dlclose() a shared library. Once loaded, the library will stay until the process terminates.
pybind11 module and ctypes module seems to share the same traits here regarding how the module is loaded/imported. Also quote from https://github.com/pybind/pybind11/issues/2511:
The way C extensions are loaded by Python does not allow them to be reloaded (in contract to Python modules, where the Python code can just be reloaded and doesn't refer to a dynamically loaded library)
I now just wonder if there is a method to wrap this up in a more convenient way for reloading the module. E.g., spawn a subprocess for a new python shell that copies all C extensions related variable/module, and substitute the original one.