Small adjustment and a not was missing rules

marl_factory_grid/environment/entity/entity.py

@@ -70,7 +70,7 @@ class Entity(EnvObject, abc.ABC):
             try:
                 self.bind_to(bind_to)
             except AttributeError:
-                print(f'Objects of {self.__class__.__name__} can not be bound to other entities.')
+                print(f'Objects of class "{self.__class__.__name__}" can not be bound to other entities.')
                 exit()
 
     def summarize_state(self) -> dict:  # tile=str(self.tile.name)

marl_factory_grid/environment/groups/global_entities.py

@@ -41,7 +41,7 @@ class Entities(Objects):
 
     @property
     def empty_positions(self):
-        empty_positions= [key for key in self.floorlist if self.pos_dict[key]]
+        empty_positions = [key for key in self.floorlist if not self.pos_dict[key]]
         shuffle(empty_positions)
         return empty_positions
 

marl_factory_grid/modules/batteries/rules.py

@@ -14,6 +14,7 @@ class Btry(Rule):
         self.initial_charge = initial_charge
 
     def on_init(self, state, lvl_map):
+        assert len(state[c.AGENT]), "There are no agents, did you already spawn them?"
         state[b.BATTERIES].spawn(state[c.AGENT], self.initial_charge)
 
     def tick_pre_step(self, state) -> List[TickResult]: