如何在 module.reload() 后保持 py::objects 存活

Question

重新加载模块后 my_module 它的所有对象都被删除，但我想从 C++ 中删除这些对象。如何防止Python删除对象？

#include <iostream>
#include <pybind11/embed.h>
class Obj{ ~Obj(){std::cout << "deleted" << std::endl;} };

PYBIND11_EMBEDDED_MODULE(module_obj, m) {
  py::class_<Obj>(m,"Obj");
}

/*
#my_module.py
import module_obj
o = module_obj.Obj()
*/

py::scoped_interpreter intpr;
auto my_module = py::module::import("my_module")
auto* o = my_module.attr("o").cast<Obj*>()
my_module.reload() // now o is deleted, how to prevent it?

Answer 1

您需要将 o 对象的引用计数保持在零以上。最简单的方法是在 C++ 端创建 py::object（或者，等效地在 python 端创建一个对象）

#include <iostream>
#include <pybind11/embed.h>

namespace py=pybind11;

class Obj {
public:
  ~Obj() {
    std::cout << "deleted" << std::endl;
  }
};

PYBIND11_EMBEDDED_MODULE(my_module, m) {
  py::class_<Obj>(m, "Cat")
      .def(py::init());
}

int main() {
  py::scoped_interpreter intpr;
  std::cout << "Loading... " << std::endl;
  auto my_module = py::module::import("my_module");
  std::cout << "Load complete. " << std::endl;

  py::object o = my_module.attr("Cat")(); // create new cat, automatically increases/decreases ref count 
  std::cout << "Reloading... " << std::endl;
  my_module.reload(); // now o is deleted, how to prevent it?
  std::cout << "Reload complete. " << std::endl;
}

输出：

Loading... 
Load complete. 
Reloading... 
Reload complete. 
deleted

如何在 module.reload() 后保持 py::objects 存活

How to keep py::objects alive after module.reload()

c++

pybind11

输出：