Write a MazeAgent class to produce the states of the maze by exploring it. This
class should be defined in a file called maze_agent.py. MazeAgent is essentially a connector
class and the
class that you will use to access the Quagent bot indirectly. Your MazeAgent will implement all
the methods in the
stepCost just returning zero, because it's
too complicated to build mazes that have costs associated with paths.
The MazeAgent constructor should start like this:
def __init__(self, bot): # bot is a MazeBot object
The main challenge will be determining the bot's state and
successors of that state. The MazeBot class gives you
very simple interaction with the bot: you can see ahead of you, turn to the
left, run ahead into a wall, and check for gold, but you otherwise don't know anything about where you are or which way
you're facing. So your MazeAgent will have to keep track of those things itself,
as well as remembering the state it was in when it saw the gold – because finding
the gold is the goal of the game.
A simple solution is to store the agent's state and bearing as arbitrary integers, and
build a table of successors of each state as you explore the maze. You'll want
the bot to start in a corner (think about why). He doesn't necessarily do that,
so you should get that part working before you tackle the successor function.
To get started, take the "fun-first" approach I've described, and write
stub methods for
MazeWorld: have goalTest return False,
initialState return zero,
successorFn return a list containing the pair (None, None),
and takeAction doing nothing. Then you can
test your code by running
python mazetest.py 2
for a 2 X 2 maze. You will find yourself hovering in view of the bot, so you can
navigate around without
You'll lose sight of him when you run through a wall, so it takes
some skill and patience to track him. The currently supported maze sizes
are 2x2, 3x3, and 4x4.
Because the Quagents program sends so many messages to the terminal, you may
want to squelch them:
python mazetest.py 2 1> /dev/null
This says to send the standard-output stream (1>) to the "black hole"
file /dev/null. So how do you then put debugging printouts into your
test code? Just write a temporary debug function to send output to the standard-error
stream, in any class where you want to do this:
# this goes above any code that calls it
sys.stderr.write(s + '\n')
Of course, you should remove all debugging printout from your final code, or
I'll take off points!
What to Turn In
Send me an email with maze_agent.py, search.py, and
attached. Your search.py should contain comments explaining how your successor function
1 One would have to build a maze with multiple paths to the goal, and then associate
a cost with each path – perhaps total distance, or a "negative cost" obtained by picking up
good stuff like tofu along the way. If you want to earn some extra credit by
building your own mazes, ask me how!
2 Recall that the
between two points