Raise TypeError when a group is indexed with None

Fixes #3092
MDAnalysis · Feb 3, 2022 · c7f701b · c7f701b
1 parent 2ecd5ed
commit c7f701b
Showing 1 changed file with 3 additions and 1 deletion.
diff --git a/package/MDAnalysis/core/groups.py b/package/MDAnalysis/core/groups.py
@@ -569,7 +569,9 @@ def __getitem__(self, item):
         # because our _ix attribute is a numpy array
         # it can be sliced by all of these already,
         # so just return ourselves sliced by the item
-        if isinstance(item, numbers.Integral):
+        if item is None:
+            raise TypeError('None cannot be used to index a group.')
+        elif isinstance(item, numbers.Integral):
             return self.level.singular(self.ix[item], self.universe)
         else:
             if isinstance(item, list) and item:  # check for empty list