Issue #23632: Memoryviews now allow tuple indexing (including for multi-dimensional memoryviews).

Doc/library/stdtypes.rst

@@ -3282,10 +3282,8 @@ copying.
    the view. The :class:`~memoryview.itemsize` attribute will give you the
    number of bytes in a single element.
 
-   A :class:`memoryview` supports slicing to expose its data. If
+   A :class:`memoryview` supports slicing and indexing to expose its data.
-   :class:`~memoryview.format` is one of the native format specifiers
+   One-dimensional slicing will result in a subview::
-   from the :mod:`struct` module, indexing will return a single element
-   with the correct type. Full slicing will result in a subview::
 
     >>> v = memoryview(b'abcefg')
     >>> v[1]
@@ -3297,25 +3295,29 @@ copying.
     >>> bytes(v[1:4])
     b'bce'
 
-   Other native formats::
+   If :class:`~memoryview.format` is one of the native format specifiers
+   from the :mod:`struct` module, indexing with an integer or a tuple of
+   integers is also supported and returns a single *element* with
+   the correct type.  One-dimensional memoryviews can be indexed
+   with an integer or a one-integer tuple.  Multi-dimensional memoryviews
+   can be indexed with tuples of exactly *ndim* integers where *ndim* is
+   the number of dimensions.  Zero-dimensional memoryviews can be indexed
+   with the empty tuple.
+
+   Here is an example with a non-byte format::
 
       >>> import array
       >>> a = array.array('l', [-11111111, 22222222, -33333333, 44444444])
-      >>> a[0]
+      >>> m = memoryview(a)
+      >>> m[0]
       -11111111
-      >>> a[-1]
+      >>> m[-1]
       44444444
-      >>> a[2:3].tolist()
+      >>> m[::2].tolist()
-      [-33333333]
-      >>> a[::2].tolist()
       [-11111111, -33333333]
-      >>> a[::-1].tolist()
-      [44444444, -33333333, 22222222, -11111111]
 
-   .. versionadded:: 3.3
+   If the underlying object is writable, the memoryview supports
-
+   one-dimensional slice assignment. Resizing is not allowed::
-   If the underlying object is writable, the memoryview supports slice
-   assignment. Resizing is not allowed::
 
       >>> data = bytearray(b'abcefg')
       >>> v = memoryview(data)
@@ -3348,12 +3350,16 @@ copying.
       True
 
    .. versionchanged:: 3.3
+      One-dimensional memoryviews can now be sliced.
       One-dimensional memoryviews with formats 'B', 'b' or 'c' are now hashable.
 
    .. versionchanged:: 3.4
       memoryview is now registered automatically with
       :class:`collections.abc.Sequence`
 
+   .. versionchanged:: 3.5
+      memoryviews can now be indexed with tuple of integers.
+
    :class:`memoryview` has several methods:
 
    .. method:: __eq__(exporter)

Lib/test/test_buffer.py

@@ -11,6 +11,7 @@
 # memoryview tests is now in this module.
 #
 
+import contextlib
 import unittest
 from test import support
 from itertools import permutations, product
@@ -2825,6 +2826,13 @@ class TestBufferProtocol(unittest.TestCase):
         m = memoryview(ex)
         self.assertRaises(TypeError, eval, "9.0 in m", locals())
 
+    @contextlib.contextmanager
+    def assert_out_of_bounds_error(self, dim):
+        with self.assertRaises(IndexError) as cm:
+            yield
+        self.assertEqual(str(cm.exception),
+                         "index out of bounds on dimension %d" % (dim,))
+
     def test_memoryview_index(self):
 
         # ndim = 0
@@ -2851,12 +2859,31 @@ class TestBufferProtocol(unittest.TestCase):
         self.assertRaises(IndexError, m.__getitem__, -8)
         self.assertRaises(IndexError, m.__getitem__, 8)
 
-        # Not implemented: multidimensional sub-views
+        # multi-dimensional
         ex = ndarray(list(range(12)), shape=[3,4], flags=ND_WRITABLE)
         m = memoryview(ex)
 
-        self.assertRaises(NotImplementedError, m.__getitem__, 0)
+        self.assertEqual(m[0, 0], 0)
-        self.assertRaises(NotImplementedError, m.__setitem__, 0, 9)
+        self.assertEqual(m[2, 0], 8)
+        self.assertEqual(m[2, 3], 11)
+        self.assertEqual(m[-1, -1], 11)
+        self.assertEqual(m[-3, -4], 0)
+
+        # out of bounds
+        for index in (3, -4):
+            with self.assert_out_of_bounds_error(dim=1):
+                m[index, 0]
+        for index in (4, -5):
+            with self.assert_out_of_bounds_error(dim=2):
+                m[0, index]
+        self.assertRaises(IndexError, m.__getitem__, (2**64, 0))
+        self.assertRaises(IndexError, m.__getitem__, (0, 2**64))
+
+        self.assertRaises(TypeError, m.__getitem__, (0, 0, 0))
+        self.assertRaises(TypeError, m.__getitem__, (0.0, 0.0))
+
+        # Not implemented: multidimensional sub-views
+        self.assertRaises(NotImplementedError, m.__getitem__, ())
         self.assertRaises(NotImplementedError, m.__getitem__, 0)
 
     def test_memoryview_assign(self):
@@ -2945,10 +2972,27 @@ class TestBufferProtocol(unittest.TestCase):
         m = memoryview(ex)
         self.assertRaises(NotImplementedError, m.__setitem__, 0, 1)
 
-        # Not implemented: multidimensional sub-views
+        # multi-dimensional
         ex = ndarray(list(range(12)), shape=[3,4], flags=ND_WRITABLE)
         m = memoryview(ex)
+        m[0,1] = 42
+        self.assertEqual(ex[0][1], 42)
+        m[-1,-1] = 43
+        self.assertEqual(ex[2][3], 43)
+        # errors
+        for index in (3, -4):
+            with self.assert_out_of_bounds_error(dim=1):
+                m[index, 0] = 0
+        for index in (4, -5):
+            with self.assert_out_of_bounds_error(dim=2):
+                m[0, index] = 0
+        self.assertRaises(IndexError, m.__setitem__, (2**64, 0), 0)
+        self.assertRaises(IndexError, m.__setitem__, (0, 2**64), 0)
 
+        self.assertRaises(TypeError, m.__setitem__, (0, 0, 0), 0)
+        self.assertRaises(TypeError, m.__setitem__, (0.0, 0.0), 0)
+
+        # Not implemented: multidimensional sub-views
         self.assertRaises(NotImplementedError, m.__setitem__, 0, [2, 3])
 
     def test_memoryview_slice(self):
@@ -2961,8 +3005,8 @@ class TestBufferProtocol(unittest.TestCase):
         self.assertRaises(ValueError, m.__setitem__, slice(0,2,0),
                           bytearray([1,2]))
 
-        # invalid slice key
+        # 0-dim slicing (identity function)
-        self.assertRaises(TypeError, m.__getitem__, ())
+        self.assertRaises(NotImplementedError, m.__getitem__, ())
 
         # multidimensional slices
         ex = ndarray(list(range(12)), shape=[12], flags=ND_WRITABLE)

Misc/NEWS

@@ -10,6 +10,9 @@ Release date: 2015-03-28
 Core and Builtins
 -----------------
 
+- Issue #23632: Memoryviews now allow tuple indexing (including for
+  multi-dimensional memoryviews).
+
 - Issue #23192: Fixed generator lambdas.  Patch by Bruno Cauet.
 
 - Issue #23629: Fix the default __sizeof__ implementation for variable-sized

Objects/memoryobject.c

@@ -192,10 +192,10 @@ PyTypeObject _PyManagedBuffer_Type = {
 #define VIEW_ADDR(mv) (&((PyMemoryViewObject *)mv)->view)
 
 /* Check for the presence of suboffsets in the first dimension. */
-#define HAVE_PTR(suboffsets) (suboffsets && suboffsets[0] >= 0)
+#define HAVE_PTR(suboffsets, dim) (suboffsets && suboffsets[dim] >= 0)
 /* Adjust ptr if suboffsets are present. */
-#define ADJUST_PTR(ptr, suboffsets) \
+#define ADJUST_PTR(ptr, suboffsets, dim) \
-    (HAVE_PTR(suboffsets) ? *((char**)ptr) + suboffsets[0] : ptr)
+    (HAVE_PTR(suboffsets, dim) ? *((char**)ptr) + suboffsets[dim] : ptr)
 
 /* Memoryview buffer properties */
 #define MV_C_CONTIGUOUS(flags) (flags&(_Py_MEMORYVIEW_SCALAR|_Py_MEMORYVIEW_C))
@@ -332,11 +332,11 @@ copy_base(const Py_ssize_t *shape, Py_ssize_t itemsize,
         char *p;
         Py_ssize_t i;
         for (i=0, p=mem; i < shape[0]; p+=itemsize, sptr+=sstrides[0], i++) {
-            char *xsptr = ADJUST_PTR(sptr, ssuboffsets);
+            char *xsptr = ADJUST_PTR(sptr, ssuboffsets, 0);
             memcpy(p, xsptr, itemsize);
         }
         for (i=0, p=mem; i < shape[0]; p+=itemsize, dptr+=dstrides[0], i++) {
-            char *xdptr = ADJUST_PTR(dptr, dsuboffsets);
+            char *xdptr = ADJUST_PTR(dptr, dsuboffsets, 0);
             memcpy(xdptr, p, itemsize);
         }
     }
@@ -364,8 +364,8 @@ copy_rec(const Py_ssize_t *shape, Py_ssize_t ndim, Py_ssize_t itemsize,
     }
 
     for (i = 0; i < shape[0]; dptr+=dstrides[0], sptr+=sstrides[0], i++) {
-        char *xdptr = ADJUST_PTR(dptr, dsuboffsets);
+        char *xdptr = ADJUST_PTR(dptr, dsuboffsets, 0);
-        char *xsptr = ADJUST_PTR(sptr, ssuboffsets);
+        char *xsptr = ADJUST_PTR(sptr, ssuboffsets, 0);
 
         copy_rec(shape+1, ndim-1, itemsize,
                  xdptr, dstrides+1, dsuboffsets ? dsuboffsets+1 : NULL,
@@ -2057,7 +2057,7 @@ tolist_base(const char *ptr, const Py_ssize_t *shape,
         return NULL;
 
     for (i = 0; i < shape[0]; ptr+=strides[0], i++) {
-        const char *xptr = ADJUST_PTR(ptr, suboffsets);
+        const char *xptr = ADJUST_PTR(ptr, suboffsets, 0);
         item = unpack_single(xptr, fmt);
         if (item == NULL) {
             Py_DECREF(lst);
@@ -2091,7 +2091,7 @@ tolist_rec(const char *ptr, Py_ssize_t ndim, const Py_ssize_t *shape,
         return NULL;
 
     for (i = 0; i < shape[0]; ptr+=strides[0], i++) {
-        const char *xptr = ADJUST_PTR(ptr, suboffsets);
+        const char *xptr = ADJUST_PTR(ptr, suboffsets, 0);
         item = tolist_rec(xptr, ndim-1, shape+1,
                           strides+1, suboffsets ? suboffsets+1 : NULL,
                           fmt);
@@ -2171,33 +2171,66 @@ memory_repr(PyMemoryViewObject *self)
 /*                          Indexing and slicing                          */
 /**************************************************************************/
 
-/* Get the pointer to the item at index. */
 static char *
-ptr_from_index(Py_buffer *view, Py_ssize_t index)
+lookup_dimension(Py_buffer *view, char *ptr, int dim, Py_ssize_t index)
 {
-    char *ptr;
+    Py_ssize_t nitems; /* items in the given dimension */
-    Py_ssize_t nitems; /* items in the first dimension */
 
     assert(view->shape);
     assert(view->strides);
 
-    nitems = view->shape[0];
+    nitems = view->shape[dim];
     if (index < 0) {
         index += nitems;
     }
     if (index < 0 || index >= nitems) {
-        PyErr_SetString(PyExc_IndexError, "index out of bounds");
+        PyErr_Format(PyExc_IndexError,
+                     "index out of bounds on dimension %d", dim + 1);
         return NULL;
     }
 
-    ptr = (char *)view->buf;
+    ptr += view->strides[dim] * index;
-    ptr += view->strides[0] * index;
 
-    ptr = ADJUST_PTR(ptr, view->suboffsets);
+    ptr = ADJUST_PTR(ptr, view->suboffsets, dim);
 
     return ptr;
 }
 
+/* Get the pointer to the item at index. */
+static char *
+ptr_from_index(Py_buffer *view, Py_ssize_t index)
+{
+    char *ptr = (char *)view->buf;
+    return lookup_dimension(view, ptr, 0, index);
+}
+
+/* Get the pointer to the item at tuple. */
+static char *
+ptr_from_tuple(Py_buffer *view, PyObject *tup)
+{
+    char *ptr = (char *)view->buf;
+    Py_ssize_t dim, nindices = PyTuple_GET_SIZE(tup);
+
+    if (nindices > view->ndim) {
+        PyErr_Format(PyExc_TypeError,
+                     "cannot index %zd-dimension view with %zd-element tuple",
+                     view->ndim, nindices);
+        return NULL;
+    }
+
+    for (dim = 0; dim < nindices; dim++) {
+        Py_ssize_t index;
+        index = PyNumber_AsSsize_t(PyTuple_GET_ITEM(tup, dim),
+                                   PyExc_IndexError);
+        if (index == -1 && PyErr_Occurred())
+            return NULL;
+        ptr = lookup_dimension(view, ptr, dim, index);
+        if (ptr == NULL)
+            return NULL;
+    }
+    return ptr;
+}
+
 /* Return the item at index. In a one-dimensional view, this is an object
    with the type specified by view->format. Otherwise, the item is a sub-view.
    The function is used in memory_subscript() and memory_as_sequence. */
@@ -2229,6 +2262,32 @@ memory_item(PyMemoryViewObject *self, Py_ssize_t index)
     return NULL;
 }
 
+/* Return the item at position *key* (a tuple of indices). */
+static PyObject *
+memory_item_multi(PyMemoryViewObject *self, PyObject *tup)
+{
+    Py_buffer *view = &(self->view);
+    const char *fmt;
+    Py_ssize_t nindices = PyTuple_GET_SIZE(tup);
+    char *ptr;
+
+    CHECK_RELEASED(self);
+
+    fmt = adjust_fmt(view);
+    if (fmt == NULL)
+        return NULL;
+
+    if (nindices < view->ndim) {
+        PyErr_SetString(PyExc_NotImplementedError,
+                        "sub-views are not implemented");
+        return NULL;
+    }
+    ptr = ptr_from_tuple(view, tup);
+    if (ptr == NULL)
+        return NULL;
+    return unpack_single(ptr, fmt);
+}
+
 Py_LOCAL_INLINE(int)
 init_slice(Py_buffer *base, PyObject *key, int dim)
 {
@@ -2277,6 +2336,22 @@ is_multislice(PyObject *key)
     return 1;
 }
 
+static Py_ssize_t
+is_multiindex(PyObject *key)
+{
+    Py_ssize_t size, i;
+
+    if (!PyTuple_Check(key))
+        return 0;
+    size = PyTuple_GET_SIZE(key);
+    for (i = 0; i < size; i++) {
+        PyObject *x = PyTuple_GET_ITEM(key, i);
+        if (!PyIndex_Check(x))
+            return 0;
+    }
+    return 1;
+}
+
 /* mv[obj] returns an object holding the data for one element if obj
    fully indexes the memoryview or another memoryview object if it
    does not.
@@ -2332,6 +2407,9 @@ memory_subscript(PyMemoryViewObject *self, PyObject *key)
 
         return (PyObject *)sliced;
     }
+    else if (is_multiindex(key)) {
+        return memory_item_multi(self, key);
+    }
     else if (is_multislice(key)) {
         PyErr_SetString(PyExc_NotImplementedError,
             "multi-dimensional slicing is not implemented");
@@ -2376,14 +2454,15 @@ memory_ass_sub(PyMemoryViewObject *self, PyObject *key, PyObject *value)
             return -1;
         }
     }
-    if (view->ndim != 1) {
-        PyErr_SetString(PyExc_NotImplementedError,
-            "memoryview assignments are currently restricted to ndim = 1");
-        return -1;
-    }
 
     if (PyIndex_Check(key)) {
-        Py_ssize_t index = PyNumber_AsSsize_t(key, PyExc_IndexError);
+        Py_ssize_t index;
+        if (1 < view->ndim) {
+            PyErr_SetString(PyExc_NotImplementedError,
+                            "sub-views are not implemented");
+            return -1;
+        }
+        index = PyNumber_AsSsize_t(key, PyExc_IndexError);
         if (index == -1 && PyErr_Occurred())
             return -1;
         ptr = ptr_from_index(view, index);
@@ -2418,7 +2497,19 @@ memory_ass_sub(PyMemoryViewObject *self, PyObject *key, PyObject *value)
         PyBuffer_Release(&src);
         return ret;
     }
-    else if (PySlice_Check(key) || is_multislice(key)) {
+    if (is_multiindex(key)) {
+        char *ptr;
+        if (PyTuple_GET_SIZE(key) < view->ndim) {
+            PyErr_SetString(PyExc_NotImplementedError,
+                            "sub-views are not implemented");
+            return -1;
+        }
+        ptr = ptr_from_tuple(view, key);
+        if (ptr == NULL)
+            return -1;
+        return pack_single(ptr, value, fmt);
+    }
+    if (PySlice_Check(key) || is_multislice(key)) {
         /* Call memory_subscript() to produce a sliced lvalue, then copy
            rvalue into lvalue. This is already implemented in _testbuffer.c. */
         PyErr_SetString(PyExc_NotImplementedError,
@@ -2591,8 +2682,8 @@ cmp_base(const char *p, const char *q, const Py_ssize_t *shape,
     int equal;
 
     for (i = 0; i < shape[0]; p+=pstrides[0], q+=qstrides[0], i++) {
-        const char *xp = ADJUST_PTR(p, psuboffsets);
+        const char *xp = ADJUST_PTR(p, psuboffsets, 0);
-        const char *xq = ADJUST_PTR(q, qsuboffsets);
+        const char *xq = ADJUST_PTR(q, qsuboffsets, 0);
         equal = unpack_cmp(xp, xq, fmt, unpack_p, unpack_q);
         if (equal <= 0)
             return equal;
@@ -2626,8 +2717,8 @@ cmp_rec(const char *p, const char *q,
     }
 
     for (i = 0; i < shape[0]; p+=pstrides[0], q+=qstrides[0], i++) {
-        const char *xp = ADJUST_PTR(p, psuboffsets);
+        const char *xp = ADJUST_PTR(p, psuboffsets, 0);
-        const char *xq = ADJUST_PTR(q, qsuboffsets);
+        const char *xq = ADJUST_PTR(q, qsuboffsets, 0);
         equal = cmp_rec(xp, xq, ndim-1, shape+1,
                         pstrides+1, psuboffsets ? psuboffsets+1 : NULL,
                         qstrides+1, qsuboffsets ? qsuboffsets+1 : NULL,