fixed grabbing behaviour in agent (#1148)

* fixed grabbing behaviour in agent

* fixed the grabbing issues and itegrated into wumpus environment

* cleaned the code a bit

* fixing the code space formatting

* fixing format

Author: Omar

agents.py

@@ -27,11 +27,6 @@
 """
 
 # TODO
-# Implement grabbing correctly.
-# When an object is grabbed, does it still have a location?
-# What if it is released?
-# What if the grabbed or the grabber is deleted?
-# What if the grabber moves?
 # Speed control in GUI does not have any effect -- fix it.
 
 from utils import distance_squared, turn_heading
@@ -510,14 +505,17 @@ def execute_action(self, agent, action):
             agent.direction += Direction.L
         elif action == 'Forward':
             agent.bump = self.move_to(agent, agent.direction.move_forward(agent.location))
-        #         elif action == 'Grab':
-        #             things = [thing for thing in self.list_things_at(agent.location)
-        #                     if agent.can_grab(thing)]
-        #             if things:
-        #                 agent.holding.append(things[0])
+        elif action == 'Grab':
+            things = [thing for thing in self.list_things_at(agent.location) if agent.can_grab(thing)]
+            if things:    
+                agent.holding.append(things[0])
+                print("Grabbing ", things[0].__class__.__name__)
+                self.delete_thing(things[0])
         elif action == 'Release':
             if agent.holding:
-                agent.holding.pop()
+                dropped = agent.holding.pop()
+                print("Dropping ", dropped.__class__.__name__)
+                self.add_thing(dropped, location=agent.location)
 
     def default_location(self, thing):
         location = self.random_location_inbounds()
@@ -569,10 +567,7 @@ def random_location_inbounds(self, exclude=None):
     def delete_thing(self, thing):
         """Deletes thing, and everything it is holding (if thing is an agent)"""
         if isinstance(thing, Agent):
-            for obj in thing.holding:
-                super().delete_thing(obj)
-                for obs in self.observers:
-                    obs.thing_deleted(obj)
+            del thing.holding
 
         super().delete_thing(thing)
         for obs in self.observers:
@@ -964,24 +959,10 @@ def execute_action(self, agent, action):
 
         if isinstance(agent, Explorer) and self.in_danger(agent):
             return
-
+            
         agent.bump = False
-        if action == 'TurnRight':
-            agent.direction += Direction.R
-            agent.performance -= 1
-        elif action == 'TurnLeft':
-            agent.direction += Direction.L
-            agent.performance -= 1
-        elif action == 'Forward':
-            agent.bump = self.move_to(agent, agent.direction.move_forward(agent.location))
-            agent.performance -= 1
-        elif action == 'Grab':
-            things = [thing for thing in self.list_things_at(agent.location)
-                      if agent.can_grab(thing)]
-            if len(things):
-                print("Grabbing", things[0].__class__.__name__)
-                if len(things):
-                    agent.holding.append(things[0])
+        if action in ['TurnRight', 'TurnLeft', 'Forward', 'Grab']:
+            super().execute_action(agent, action)
             agent.performance -= 1
         elif action == 'Climb':
             if agent.location == (1, 1):  # Agent can only climb out of (1,1)