Support Ellipsis in NDCube.__getitem__

changelog/818.feature.rst

@@ -0,0 +1 @@
+Added Ellipsis functionality to ndcube.mixins.ndslicing

ndcube/mixins/ndslicing.py

@@ -28,6 +28,19 @@ def __getitem__(self, item):
             meta = self.meta
             self.meta = None
 
+        if isinstance(item, tuple) and Ellipsis in item:
+            if item.count(Ellipsis) > 1:
+                raise IndexError("An index can only have a single ellipsis ('...')")
+
+            expanded_item = []
+            for i in item:
+                if i is Ellipsis:
+                    expanded_item.extend([slice(None)] * (len(self.shape) - len(item) + 1))
+                else:
+                    expanded_item.append(i)
+
+            item = tuple(expanded_item)
+
         # Slice cube.
         item = tuple(sanitize_slices(item, len(self.shape)))
         sliced_cube = super().__getitem__(item)

ndcube/mixins/tests/test_ndslicing.py

@@ -0,0 +1,20 @@
+import numpy as np
+import pytest
+
+from astropy.wcs import WCS
+
+from ndcube import NDCube
+
+
+@pytest.fixture
+def sample_ndcube():
+    data = np.random.rand(4, 4, 4)
+    wcs = WCS(naxis=3)
+    return NDCube(data, wcs)
+
+def test_ellipsis_usage(sample_ndcube):
+    sliced_cube = sample_ndcube[..., 1]
+    assert sliced_cube.data.shape == (4, 4)
+
+    with pytest.raises(IndexError, match="An index can only have a single ellipsis"):
+        sample_ndcube[..., ..., 1]