NORTH, EAST, SOUTH, WEST = range(4)

class Compass:

compass = [NORTH, EAST, SOUTH, WEST]

def __init__(self, direction=NORTH):

self.direction = direction

def left(self):

self.direction = self.compass[self.direction - 1]

def right(self):

self.direction = self.compass[(self.direction + 1) % 4]

class Robot:

def __init__(self, direction=NORTH, x=0, y=0):

self.compass = Compass(direction)

self.x = x

self.y = y

def advance(self):

if self.direction == NORTH:

self.y += 1

elif self.direction == SOUTH:

self.y -= 1

elif self.direction == EAST:

self.x += 1

elif self.direction == WEST:

self.x -= 1

def turn_left(self):

self.compass.left()

def turn_right(self):

self.compass.right()

def move(self, commands):

instructions = {'A': self.advance,

'R': self.turn_right,

'L': self.turn_left}

for cmd in commands:

if cmd in instructions:

instructions[cmd]()

@property

def direction(self):

return self.compass.direction

@property

def coordinates(self):

return (self.x, self.y)