A-M baby

Task/Langtons-ant/Python/langtons-ant.py

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+width = 75
+height = 52
+nsteps = 12000
+
+class Dir: up, right, down, left = range(4)
+class Turn: left, right = False, True
+class Color: white, black = '.', '#'
+M = [[Color.white] * width for _ in xrange(height)]
+
+x = width // 2
+y = height // 2
+dir = Dir.up
+
+i = 0
+while i < nsteps and 0 <= x < width and 0 <= y < height:
+    turn = Turn.left if M[y][x] == Color.black else Turn.right
+    M[y][x] = Color.white if M[y][x] == Color.black else Color.black
+
+    dir = (4 + dir + (1 if turn else -1)) % 4
+    dir = [Dir.up, Dir.right, Dir.down, Dir.left][dir]
+    if   dir == Dir.up:    y -= 1
+    elif dir == Dir.right: x -= 1
+    elif dir == Dir.down:  y += 1
+    elif dir == Dir.left:  x += 1
+    else: assert False
+    i += 1
+
+print "\n".join("".join(row) for row in M)