是否可以通过 Cython 通过引用从 Python 到 C++ 传递值？

Question

Is it possible to create a C++ object that contains a pointer to a Python variable? My concern is that the Python variable is a PyObject and thus there is no way that C++ could read it properly.

To make an example, here is the tutorial from the official Cython website slightly altered for my question. The results from main.py are wrong

Main.py (where the Rectangle object is used)

import rect
x0, y0, x1, y1 = 1, 2, 3, 4
rect_obj = rect.PyRectangle(x0, y0, x1, y1)
print(rect_obj.get_area())

x0 = 10                       # change value PyRectangle points to
print(rect_obj.get_area())

Result

-403575482
-407128282

Rectangle.cpp

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

namespace shapes {

    // Overloaded constructor
    Rectangle::Rectangle (int x0, int y0, int x1, int y1) {
        this->x0 = &x0;
        this->y0 = y0;
        this->x1 = x1;
        this->y1 = y1;
    }

    // Return the area of the rectangle
    int Rectangle::getArea () {
        return (this->x1 - *(this->x0)) * (this->y1 - this->y0);
    }
}

For the sake of clarity, I did not post the other files as I do not think they are necessary for understanding my question.

Answer 1

On performing some experiments I found a solution, where you have to explicitly call the cinit method that you have defined in the .pyx file.

The new python file would look something like this

import rect
x0, y0, x1, y1 = 1, 2, 3, 4 \
rect_obj = rect.PyRectangle() \
rect_obj._cinit_(x0, y0, x1, y1) \
print(rect_obj.get_size()) \
print(rect_obj.get_area())

and your .pyx looks as this

from Rectangle cimport Rectangle

cdef class PyRectangle:
    cdef Rectangle c_rect

def _cinit_(self, int x0, int y0, int x1, int y1):
    self.c_rect = Rectangle(x0, y0, x1, y1)

def get_area(self):
    return self.c_rect.getArea()

def get_size(self):
    cdef int width, height
    self.c_rect.getSize(&width, &height)
    return width, height

def move (self, dx, dy):
    self.c_rect.move(dx, dy)