Function PyArray_Compress

numpy/core/src/multiarray/item_selection.c:2312–2351

NUMPY_API * Compress */

 * Compress
 */
NPY_NO_EXPORT PyObject *
PyArray_Compress(PyArrayObject *self, PyObject *condition, int axis,
                 PyArrayObject *out)
{
    PyArrayObject *cond;
    PyObject *res, *ret;

    if (PyArray_Check(condition)) {
        cond = (PyArrayObject *)condition;
        Py_INCREF(cond);
    }
    else {
        PyArray_Descr *dtype = PyArray_DescrFromType(NPY_BOOL);
        if (dtype == NULL) {
            return NULL;
        }
        cond = (PyArrayObject *)PyArray_FromAny(condition, dtype,
                                    0, 0, 0, NULL);
        if (cond == NULL) {
            return NULL;
        }
    }

    if (PyArray_NDIM(cond) != 1) {
        Py_DECREF(cond);
        PyErr_SetString(PyExc_ValueError,
                        "condition must be a 1-d array");
        return NULL;
    }

    res = PyArray_Nonzero(cond);
    Py_DECREF(cond);
    if (res == NULL) {
        return res;
    }
    ret = PyArray_TakeFrom(self, PyTuple_GET_ITEM(res, 0), axis,
                           out, NPY_RAISE);
    Py_DECREF(res);
    return ret;
}

/*
 * count number of nonzero bytes in 48 byte block