A more principled approach to avoiding the matplotlib problem - x[:, None] adds an empty dimension to a NumPy array x. This doesn't make sense for AnalogSignal, which can only be 2D, so we raise an IndexError.

The alternative would be to cast the object to a 3D Quantities array, but I think that would be unexpected behaviour.

Author: apdavison

neo/core/analogsignal.py

@@ -265,8 +265,11 @@ def __getitem__(self, i):
                     raise TypeError("%s not supported" % type(j))
                 if isinstance(k, (int, np.integer)):
                     obj = obj.reshape(-1, 1)
-                if k is not None:  # matplotlib _check_1d() calls__getitem__ with (:, None)
-                    obj.array_annotate(**deepcopy(self.array_annotations_at_index(k)))
+                elif k is None:
+                    # matplotlib _check_1d() calls__getitem__ with (:, None) and
+                    # reacts appropriately if an IndexError or ValueError is raised
+                    raise IndexError("Cannot add dimensions to an AnalogSignal")
+                obj.array_annotate(**deepcopy(self.array_annotations_at_index(k)))
         elif isinstance(i, slice):
             obj = super().__getitem__(i)
             if i.start:

neo/test/coretest/test_analogsignal.py

@@ -640,8 +640,7 @@ def test__getitem_should_return_single_quantity(self):
         self.assertRaises(IndexError, self.signal1.__getitem__, (99, 73))
 
     def test__getitem__with_tuple_slice_none(self):
-        item = self.signal1[:, None]
-        # we're just testing no error is raised
+        self.assertRaises(IndexError, self.signal1.__getitem__, (slice(None), None))
 
     def test__time_index(self):
         # scalar arguments