Langton's ant

langton.py

#!/usr/bin/python
class Langton(object):

    def __init__(self):
        self.ant = ((0,0), 'E')
        self.black_squares = set()
        self.next = {'E':'S', 'S': 'W', 'W':'N', 'N':'E'}
        self.previous = {'E':'N', 'N': 'W', 'W':'S', 'S':'E'}
        self.max_y,self.max_x,self.min_y,self.min_x = 0,0,0,0
        self.transf = {'E':(1,0), 'S': (0,1), 'W':(-1,0) , 'N':(0,-1)}
    
    def move(self):
        if self.ant[0] in self.black_squares:
            direct = self.previous[self.ant[1]]
            self.black_squares.remove(self.ant[0])
        else:
            direct = self.next[self.ant[1]]
            self.black_squares.add(self.ant[0])
        new_pos = (self.ant[0][0] + self.transf[direct][0], self.ant[0][1] + self.transf[direct][1])
        self.max_x = max(self.max_x, new_pos[0])
        self.max_y = max(self.max_y, new_pos[1])
        self.min_x = min(self.min_x, new_pos[0])
        self.min_y = min(self.min_y, new_pos[1])
        self.ant = (new_pos, direct)
        
    def play(self,k):
        while k > 0:
            self.move()
            k -= 1
        for i in range(self.min_x,self.max_x+1):
            row = []
            for j in range(self.min_y,self.max_y+1):
                if (i,j) == self.ant[0]:
                    row.append(self.ant[1])
                elif (i,j) in self.black_squares:
                    row.append('#')
                else:
                    row.append(' ')
            print ','.join(row)
            
import sys
if __name__== "__main__":
    simulation = 100
    if len(sys.argv) > 1:
        simulation = int(sys.argv[1])
    l = Langton()
    l.play(simulation)