Function arraydescr_field_subset_view

numpy/core/src/multiarray/descriptor.c:3553–3646

}

NPY_NO_EXPORT PyArray_Descr *
arraydescr_field_subset_view(PyArray_Descr *self, PyObject *ind)
{
    int seqlen, i;
    PyObject *fields = NULL;
    PyObject *names = NULL;
    PyArray_Descr *view_dtype;

    seqlen = PySequence_Size(ind);
    if (seqlen == -1) {
        return NULL;
    }

    fields = PyDict_New();
    if (fields == NULL) {
        goto fail;
    }
    names = PyTuple_New(seqlen);
    if (names == NULL) {
        goto fail;
    }

    for (i = 0; i < seqlen; i++) {
        PyObject *name;
        PyObject *tup;

        name = PySequence_GetItem(ind, i);
        if (name == NULL) {
            goto fail;
        }

        /* Let the names tuple steal a reference now, so we don't need to
         * decref name if an error occurs further on.
         */
        PyTuple_SET_ITEM(names, i, name);

        tup = PyDict_GetItemWithError(self->fields, name);
        if (tup == NULL) {
            if (!PyErr_Occurred()) {
                PyErr_SetObject(PyExc_KeyError, name);
            }
            goto fail;
        }

        /* disallow use of titles as index */
        if (PyTuple_Size(tup) == 3) {
            PyObject *title = PyTuple_GET_ITEM(tup, 2);
            int titlecmp = PyObject_RichCompareBool(title, name, Py_EQ);
            if (titlecmp < 0) {
                goto fail;
            }
            if (titlecmp == 1) {
                /* if title == name, we were given a title, not a field name */
                PyErr_SetString(PyExc_KeyError,
                            "cannot use field titles in multi-field index");
                goto fail;
            }
            if (PyDict_SetItem(fields, title, tup) < 0) {