An agent, as defined in 2.1 is anything that can perceive its environment through sensors, and act upon that environment through actuators based on its agent program. This can be a dog, robot, or even you. As long as you can perceive the environment and act on it, you are an agent. This notebook will explain how to implement a simple agent, create an environment, and create a program that helps the agent act on the environment based on its percepts.
Before moving on, review the </b>Agent</b> and </b>Environment</b> classes in [agents.py](https://github.com/aimacode/aima-python/blob/master/agents.py).
Let's begin by importing all the functions from the agents.py module and creating our first agent - a blind dog.
In [1]:
from agents import *
class BlindDog(Agent):
def eat(self, thing):
print("Dog: Ate food at {}.".format(self.location))
def drink(self, thing):
print("Dog: Drank water at {}.".format( self.location))
dog = BlindDog()
What we have just done is create a dog who can only feel what's in his location (since he's blind), and can eat or drink. Let's see if he's alive...
In [2]:
print(dog.alive)
A park is an example of an environment because our dog can perceive and act upon it. The Environment class in agents.py is an abstract class, so we will have to create our own subclass from it before we can use it. The abstract class must contain the following methods:
In [3]:
class Food(Thing):
pass
class Water(Thing):
pass
class Park(Environment):
def percept(self, agent):
'''prints & return a list of things that are in our agent's location'''
things = self.list_things_at(agent.location)
print(things)
return things
def execute_action(self, agent, action):
'''changes the state of the environment based on what the agent does.'''
if action == "move down":
agent.movedown()
elif action == "eat":
items = self.list_things_at(agent.location, tclass=Food)
if len(items) != 0:
if agent.eat(items[0]): #Have the dog pick eat the first item
self.delete_thing(items[0]) #Delete it from the Park after.
elif action == "drink":
items = self.list_things_at(agent.location, tclass=Water)
if len(items) != 0:
if agent.drink(items[0]): #Have the dog drink the first item
self.delete_thing(items[0]) #Delete it from the Park after.
def is_done(self):
'''By default, we're done when we can't find a live agent,
but to prevent killing our cute dog, we will or it with when there is no more food or water'''
no_edibles = not any(isinstance(thing, Food) or isinstance(thing, Water) for thing in self.things)
dead_agents = not any(agent.is_alive() for agent in self.agents)
return dead_agents or no_edibles
In [4]:
from ipythonblocks import BlockGrid
from agents import *
color = {"Breeze": (225, 225, 225),
"Pit": (0,0,0),
"Gold": (253, 208, 23),
"Glitter": (253, 208, 23),
"Wumpus": (43, 27, 23),
"Stench": (128, 128, 128),
"Explorer": (0, 0, 255),
"Wall": (44, 53, 57)
}
def program(percepts):
'''Returns an action based on it's percepts'''
print(percepts)
return input()
w = WumpusEnvironment(program, 7, 7)
grid = BlockGrid(w.width, w.height, fill=(123, 234, 123))
def draw_grid(world):
global grid
grid[:] = (123, 234, 123)
for x in range(0, len(world)):
for y in range(0, len(world[x])):
if len(world[x][y]):
grid[y, x] = color[world[x][y][-1].__class__.__name__]
def step():
global grid, w
draw_grid(w.get_world())
grid.show()
w.step()
In [5]:
step()
In [ ]:
class BlindDog(Agent):
location = 1
def movedown(self):
self.location += 1
def eat(self, thing):
'''returns True upon success or False otherwise'''
if isinstance(thing, Food):
print("Dog: Ate food at {}.".format(self.location))
return True
return False
def drink(self, thing):
''' returns True upon success or False otherwise'''
if isinstance(thing, Water):
print("Dog: Drank water at {}.".format(self.location))
return True
return False
def program(percepts):
'''Returns an action based on it's percepts'''
for p in percepts:
if isinstance(p, Food):
return 'eat'
elif isinstance(p, Water):
return 'drink'
return 'move down'
In [ ]:
park = Park()
dog = BlindDog(program)
dogfood = Food()
water = Water()
park.add_thing(dog, 0)
park.add_thing(dogfood, 5)
park.add_thing(water, 7)
park.run(10)
That's how easy it is to implement an agent, its program, and environment. But that was a very simple case. What if our environment was 2-Dimentional instead of 1? And what if we had multiple agents?
To make our Park 2D, we will need to make it a subclass of XYEnvironment instead of Environment. Also, let's add a person to play fetch with the dog.
In [ ]:
class Park(XYEnvironment):
def percept(self, agent):
'''prints & return a list of things that are in our agent's location'''
things = self.list_things_at(agent.location)
print(things)
return things
def execute_action(self, agent, action):
'''changes the state of the environment based on what the agent does.'''
if action == "move down":
agent.movedown()
elif action == "eat":
items = self.list_things_at(agent.location, tclass=Food)
if len(items) != 0:
if agent.eat(items[0]): #Have the dog pick eat the first item
self.delete_thing(items[0]) #Delete it from the Park after.
elif action == "drink":
items = self.list_things_at(agent.location, tclass=Water)
if len(items) != 0:
if agent.drink(items[0]): #Have the dog drink the first item
self.delete_thing(items[0]) #Delete it from the Park after.
def is_done(self):
'''By default, we're done when we can't find a live agent,
but to prevent killing our cute dog, we will or it with when there is no more food or water'''
no_edibles = not any(isinstance(thing, Food) or isinstance(thing, Water) for thing in self.things)
dead_agents = not any(agent.is_alive() for agent in self.agents)
return dead_agents or no_edibles