8000 ENH: PyArray_FromInterface checks descr if typestr is np.void by jaimefrio · Pull Request #5519 · numpy/numpy · GitHub
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ENH: PyArray_FromInterface checks descr if typestr is np.void #5519

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Merged
merged 1 commit into from
Mar 12, 2015
Merged

ENH: PyArray_FromInterface checks descr if typestr is np.void #5519

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66 changes: 61 additions & 5 deletions numpy/core/src/multiarray/ctors.c
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Expand Up @@ -2069,6 +2069,51 @@ PyArray_FromStructInterface(PyObject *input)
return NULL;
}

/*
* Checks if the object in descr is the default 'descr' member for the
* __array_interface__ dictionary with 'typestr' member typestr.
*/
NPY_NO_EXPORT int
_is_default_descr(PyObject *descr, PyObject *typestr) {
PyObject *tuple, *name, *typestr2;
#if defined(NPY_PY3K)
PyObject *tmp = NULL;
#endif
int ret = 0;

if (!PyList_Check(descr) || PyList_GET_SIZE(descr) != 1) {
return 0;
}
tuple = PyList_GET_ITEM(descr, 0);
if (!(PyTuple_Check(tuple) && PyTuple_GET_SIZE(tuple) == 2)) {
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I like the way this condition is expressed better than the one above ;)

return 0;
}
name = PyTuple_GET_ITEM(tuple, 0);
if (!(PyUString_Check(name) && PyUString_GET_SIZE(name) == 0)) {
return 0;
}
typestr2 = PyTuple_GET_ITEM(tuple, 1);
#if defined(NPY_PY3K)
/* Allow unicode type strings */
if (PyUnicode_Check(typestr2)) {
tmp = PyUnicode_AsASCIIString(typestr2);
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Looks like tmp can be NULL, assuming that the string cannot be converted to ascii. I'm not sure what the policy for this codec is.

if (tmp == NULL) {
return 0;
}
typestr2 = tmp;
}
#endif
if (PyBytes_Check(typestr2) &&
PyObject_RichCompareBool(typestr, typestr2, Py_EQ)) {
ret = 1;
}
#if defined(NPY_PY3K)
Py_XDECREF(tmp);
#endif

return ret;
}

#define PyIntOrLong_Check(obj) (PyInt_Check(obj) || PyLong_Check(obj))

/*NUMPY_API*/
Expand All @@ -2087,11 +2132,6 @@ PyArray_FromInterface(PyObject *origin)
npy_intp dims[NPY_MAXDIMS], strides[NPY_MAXDIMS];
int dataflags = NPY_ARRAY_BEHAVED;

/* Get the typestring -- ignore array_descr */
/* Get the shape */
/* Get the memory from __array_data__ and __array_offset__ */
/* Get the strides */

iface = PyArray_GetAttrString_SuppressException(origin,
"__array_interface__");
if (iface == NULL) {
Expand Down Expand Up @@ -2135,6 +2175,22 @@ PyArray_FromInterface(PyObject *origin)
goto fail;
}

/*
* If the dtype is NPY_VOID, see if there is extra information in
* the 'descr' attribute.
*/
if (dtype->type_num == NPY_VOID) {
PyObject *descr = PyDict_GetItemString(iface, "descr");
PyArray_Descr *new_dtype = NULL;

if (descr != NULL && !_is_default_descr(descr, attr) &&
PyArray_DescrConverter2(descr, &new_dtype) == NPY_SUCCEED &&
new_dtype != NULL) {
Py_DECREF(dtype);
dtype = new_dtype;
}
}

/* Get shape tuple from interface specification */
attr = PyDict_GetItemString(iface, "shape");
if (attr == NULL) {
Expand Down
6 changes: 4 additions & 2 deletions numpy/lib/stride_tricks.py
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Expand Up @@ -46,9 +46,11 @@ def as_strided(x, shape=None, strides=None, subok=False):
if strides is not None:
interface['strides'] = tuple(strides)
array = np.asarray(DummyArray(interface, base=x))
# Make sure dtype is correct in case of custom dtype
if array.dtype.kind == 'V':

if array.dtype.fields is None and x.dtype.fields is not None:
# This should only happen if x.dtype is [('', 'Vx')]
array.dtype = x.dtype

return _maybe_view_as_subclass(x, array)


Expand Down
23 changes: 23 additions & 0 deletions numpy/lib/tests/test_stride_tricks.py
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Expand Up @@ -290,6 +290,29 @@ def test_as_strided():
expected = np.array([[1, 2, 3, 4], [1, 2, 3, 4], [1, 2, 3, 4]])
assert_array_equal(a_view, expected)

# Regression test for gh-5081
dt = np.dtype([('num', 'i4'), ('obj', 'O')])
a = np.empty((4,), dtype=dt)
a['num'] = np.arange(1, 5)
a_view = as_strided(a, shape=(3, 4), strides=(0, a.itemsize))
expected_num = [[1, 2, 3, 4]] * 3
expected_obj = [[None]*4]*3
assert_equal(a_view.dtype, dt)
assert_array_equal(expected_num, a_view['num'])
assert_array_equal(expected_obj, a_view['obj'])

# Make sure that void types without fields are kept unchanged
a = np.empty((4,), dtype='V4')
a_view = as_strided(a, shape=(3, 4), strides=(0, a.itemsize))
assert_equal(a.dtype, a_view.dtype)

# Make sure that the only type that could fail is properly handled
dt = np.dtype({'names': [''], 'formats': ['V4']})
a = np.empty((4,), dtype=dt)
a_view = as_strided(a, shape=(3, 4), strides=(0, a.itemsize))
assert_equal(a.dtype, a_view.dtype)



class VerySimpleSubClass(np.ndarray):
def __new__(cls, *args, **kwargs):
Expand Down
0