将PyArrayObject数据类型转换为C数组

Question

我想在C扩展中使用我的Numpy数组。 在这种情况下，许多示例使用PyArrayObject的结构，

array->data , array->strides[0] , array->strides[1] , ...

如果我想以更熟悉（或更整洁）的方式到达我的数组，以及像

array[i][j]

我该怎么办呢？ 我应该使用类型转换（bool *）array-> data并使用我创建的C数组吗？ （我的元素是bools）

我现在的功能声明是（当然没有完成）

static PyObject *
xor_masking(PyObject *self, PyObject *args)
{

PyObject *input;
PyObject *mask;
PyObject *adjacency;
PyObject *state;
PyArrayObject *arr_mask;
PyArrayObject *arr_adjacency;
PyArrayObject *arr_state;
PyArrayObject *arr_next_state;

double sum;
int counter_node, n_nodes;

/*  PyArg_ParseTuple
 *  checks if from args, the pointers of type "O" can be extracted, and extracts them
 */

if (!PyArg_ParseTuple(args, "OOO:xor_masking_C", &mask, &adjacency, &state))
    return NULL;

/*
 *  The pointer returned by PyArray_ContiguousFromObject is typecasted to
 *  a PyArrayObject Pointer and array is pointed to the same address.
 */

arr_mask = (PyArrayObject *)
PyArray_ContiguousFromObject(mask, PyArray_BOOL, 2, 2);
arr_adjacency = (PyArrayObject *)
PyArray_ContiguousFromObject(adjacency, PyArray_BOOL, 2, 2);
arr_state = (PyArrayObject *)
PyArray_ContiguousFromObject(state, PyArray_BOOL, 2, 2);

if (array == NULL)
    return NULL;

int n_mask_0 = mask->dimensions[0];
int n_mask_1 = mask->dimensions[1];
int n_adjacency_0 = adjacency->dimensions[0];
int n_adjacency_1 = adjacency->dimensions[1];
int n_state_0 = state->dimensions[0];
int n_nodes = n_state_0;
/*
 * if the dimensions don't match, return NULL
 */

bool c_mask[n_nodes][n_nodes];

if (n_mask_0 != n_mask_1 || n_adjacency_0 != n_adjacency_1 ||
n_adjacency_0 != n_mask_0 || n_adjacency_0 != n_adjacency_1) {
    return NULL;
}

/*
 *    The 2D arrays are introduced as follows
 *    array[i][j] = (array->data + i*array->strides[0] + j*array->strides[1])
 */

for (counter_node = 0; i < n_mask; i++){
    *row_start = (array->data + i*array->strides[0]);
}


//Py_DECREF();

//return PyFloat_FromDouble();
}

谢谢！

Answer 1

我不确定这是否能回答你的问题但是，为了在C中获取你的NumPy数据，你可以尝试创建一个迭代器来循环你的数组。它没有给你索引你在之后（[i] [j]）但它涵盖整个阵列

static PyObject *func1(PyObject *self, PyObject *args) {
    PyArrayObject *X;
    int ndX;
    npy_intp *shapeX;
    NpyIter *iter;
    NpyIter_IterNextFunc *iternext;
    PyArray_Descr *dtype;
    double **dataptr;

    PyArg_ParseTuple(args, "O!", &PyArray_Type, &X);
    ndX = PyArray_NDIM(X);
    shapeX = PyArray_SHAPE(X);
    dtype = PyArray_DescrFromType(NPY_DOUBLE);
    iter = NpyIter_New(X, NPY_ITER_READONLY, NPY_KEEPORDER, NPY_NO_CASTING, dtype);
    iternext = NpyIter_GetIterNext(iter, NULL);
    dataptr = (double **) NpyIter_GetDataPtrArray(iter);
    do {
        cout << **dataptr << endl; //Do something with the data in your array
    } while (iternext(iter));   
    NpyIter_Deallocate(iter);
    return Py_BuildValue(...);
}

Answer 2

我想你会想看看这个： http ： //docs.scipy.org/doc/numpy/reference/c-api.array.html

特别是，

void* PyArray_GETPTR3(PyObject* obj, <npy_intp> i, <npy_intp> j, <npy_intp> k)

和朋友。 如果API没有提供，David Heffernan会感到惊讶的是这些功能。

Answer 3

这是所有答案中最脏的，我猜，但是2年前，我最终实现了这样的功能：

只需在此处添加它以记录它。 如果您正在阅读本文，则应查看其他更好的解决方案。

https://gist.github.com/mehmetalianil/6643299

Answer 4

这应该对你有帮助。

http://mail.scipy.org/pipermail/numpy-discussion/2003-November/014837.html