Skip to content

gh-91484: Allow memoryview cast for F-contiguous #137803

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
wants to merge 3 commits into
base: main
Choose a base branch
from
+32 −3
Open

gh-91484: Allow memoryview cast for F-contiguous #137803

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
3 commits
Select commit Hold shift + click to select a range
597ae6a
allow memoryview cast for F-contiguous
jamie2779 Aug 15, 2025
3cc8a7e
📜🤖 Added by blurb_it.
blurb-it[bot] Aug 15, 2025
20df3ab
fix lint issue
jamie2779 Aug 15, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
26 changes: 26 additions & 0 deletions Lib/test/test_buffer.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -2846,6 +2846,32 @@ class BEPoint(ctypes.BigEndianStructure):
self.assertEqual(m2.strides, (1,))
self.assertEqual(m2.suboffsets, ())

def test_memoryview_cast_f_contiguous_ND_1D(self):
nd = ndarray(list(range(12)),shape=[3, 4], format='B', flags=ND_FORTRAN)
m = memoryview(nd)
self.assertTrue(m.f_contiguous)
self.assertTrue(m.contiguous)

m1 = m.cast('B')
self.assertEqual(m1.ndim, 1)
self.assertEqual(m1.shape, (m.nbytes,))
self.assertEqual(m1.strides, (1,))
self.assertTrue(m1.c_contiguous)
self.assertTrue(m1.contiguous)
self.assertEqual(m1.tobytes(), memoryview(nd).tobytes(order='F'))

for fmt in ('B', 'b', 'c', 'H', 'I'):
size = struct.calcsize(fmt)
if m.nbytes % size == 0:
m2 = m.cast(fmt)
self.assertEqual(m2.ndim, 1)
self.assertEqual(m2.shape, (m.nbytes // size,))
self.assertTrue(m2.contiguous)

m3 = m[::-1]
with self.assertRaises(TypeError):
m3.cast('B')

def test_memoryview_tolist(self):

# Most tolist() tests are in self.verify() etc.
Expand Down
1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Core_and_Builtins/2025-08-15-06-28-45.gh-issue-91484.huCgHt.rst
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
memoryview.cast() now allows casting from N-D to 1-D for F-contiguous.
8 changes: 5 additions & 3 deletions Objects/memoryobject.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1456,9 +1456,11 @@ memoryview_cast_impl(PyMemoryViewObject *self, PyObject *format,
CHECK_RESTRICTED(self);

if (!MV_C_CONTIGUOUS(self->flags)) {
PyErr_SetString(PyExc_TypeError,
"memoryview: casts are restricted to C-contiguous views");
return NULL;
if(shape || self->view.ndim == 1 || !MV_F_CONTIGUOUS(self->flags)) {
PyErr_SetString(PyExc_TypeError,
"memoryview: casts are restricted to C-contiguous views");
return NULL;
}
}
if ((shape || self->view.ndim != 1) && zero_in_shape(self)) {
PyErr_SetString(PyExc_TypeError,
Expand Down
Loading