I have a C++ function returning a std::vector and I want to use it in python, so I'm using the C numpy api:
static PyObject *
py_integrate(PyObject *self, PyObject *args){
...
std::vector<double> integral;
cpp_function(integral); // This changes integral
npy_intp size = {integral.size()};
PyObject *out = PyArray_SimpleNewFromData(1, &size, NPY_DOUBLE, &(integral[0]));
return out;
}
Here's how I call it from python:
import matplotlib.pyplot as plt
a = py_integrate(parameters)
print a
fig = plt.figure()
ax = fig.add_subplot(111)
ax.plot(a)
print a
What happens is: The first print is ok, the values are correct. But when I plot a they are not; in the second print I see very strange values like 1E-308 1E-308 ... or 0 0 0 ... as an uninitialized memory. I don't understand why the first print is ok.
Partial solution (not working):
static void DeleteVector(void *ptr)
{
std::cout << "Delete" << std::endl;
vector * v = static_cast<std::vector<double> * >(ptr);
delete v;
return;
}
static PyObject *
cppfunction(PyObject *self, PyObject *args)
{
std::vector<double> *vector = new std::vector<double>();
vector->push_back(1.);
PyObject *py_integral = PyCObject_FromVoidPtr(vector, DeleteVector);
npy_intp size = {vector->size()};
PyArrayObject *out;
((PyArrayObject*) out)->base = py_integral;
return (PyObject*)(out);
}
Copyright Notice：Content Author:「Ruggero Turra」，Reproduced under the CC 4.0 BY-SA copyright license with a link to the original source and this disclaimer.
Link to original article：https://stackoverflow.com/questions/2924827/numpy-array-c-api