MultiGrid: Set to using list for cell content

buddih09 · Jan 16, 2020 · 745c04a · 745c04a
1 parent 7ae78e1
commit 745c04a
Showing 1 changed file with 3 additions and 2 deletions.
diff --git a/mesa/space.py b/mesa/space.py
@@ -424,12 +424,13 @@ class MultiGrid(Grid):
     @staticmethod
     def default_val():
         """ Default value for new cell elements. """
-        return set()
+        return []
 
     def _place_agent(self, pos, agent):
         """ Place the agent at the correct location. """
         x, y = pos
-        self.grid[x][y].add(agent)
+        if agent not in self.grid[x][y]:
+            self.grid[x][y].append(agent)
         self.empties.discard(pos)
 
     def _remove_agent(self, pos, agent):