BUG: df.iloc[:, :1] with EA column

Author: jbrockmendel

pandas/core/internals/blocks.py

@@ -1809,6 +1809,11 @@ def _slice(self, slicer):
             if not com.is_null_slice(slicer[0]):
                 raise AssertionError("invalid slicing for a 1-ndim categorical")
             slicer = slicer[1]
+        elif not isinstance(slicer, tuple) and self.ndim == 2:
+            # reached via getitem_block via _slice_take_blocks_ax0
+            # TODO(EA2D): wont be necessary with 2D EAs
+            # treat this like (slicer, slice(None)
+            slicer = slice(None)
 
         return self.values[slicer]
 

pandas/tests/extension/base/getitem.py

@@ -40,6 +40,10 @@ def test_iloc_frame(self, data):
         result = df.iloc[:4, 0]
         self.assert_series_equal(result, expected)
 
+        # GH#32957 null slice along index, slice along rows
+        result = df.iloc[:, :1]
+        self.assert_frame_equal(result, df[["A"]])
+
     def test_loc_series(self, data):
         ser = pd.Series(data)
         result = ser.loc[:3]