Return an empty table if markers not found

mwcraig · Aug 24, 2023 · 4fc238d · 4fc238d
1 parent cd45745
commit 4fc238d
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Showing 3 changed files with 6 additions and 3 deletions.
diff --git a/astrowidgets/ginga.py b/astrowidgets/ginga.py
@@ -587,7 +587,8 @@ def get_markers(self, x_colname='x', y_colname='y',
                 tables.append(table)
 
             if len(tables) == 0:
-                return None
+                # No markers at all, return an empty table
+                return Table()
 
             stacked = vstack(tables, join_type='exact')
 

diff --git a/astrowidgets/interface_definition.py b/astrowidgets/interface_definition.py
@@ -231,7 +231,8 @@ def get_markers(self, x_colname: str = 'x', y_colname: str = 'y',
         Returns
         -------
         table : `astropy.table.Table`
-            The table containing the marker positions.
+            The table containing the marker positions. If no markers match the
+            ``marker_name`` parameter, an empty table is returned.
         """
         raise NotImplementedError
 

diff --git a/astrowidgets/tests/widget_api_test.py b/astrowidgets/tests/widget_api_test.py
@@ -282,7 +282,8 @@ def test_remove_marker_accepts_list(self):
         self.image.add_markers(tab, marker_name='test2')
 
         self.image.remove_markers(marker_name=['test1', 'test2'])
-        assert self.image.get_markers(marker_name='all') is None
+        marks = self.image.get_markers(marker_name='all')
+        assert isinstance(marks, Table) and len(marks) == 0
 
     def test_adding_markers_as_world(self, data, wcs):
         ndd = NDData(data=data, wcs=wcs)