gistfile1.py

class SquareSpiral:
    _basic_map = {(0, 0): False,
                  (0, 1): True,
                  (1, 0): True,
                  (1, 1): True}

    def __init__(self, w, h):
        assert (w - 2) % 4 == 0
        assert (h - 2) % 4 == 0
        assert w == h
        self.w = w
        self.h = h
        if w > 2 and h > 2:
            self.inner = SquareSpiral(w - 4, h - 4)
        else:
            self.inner = None

    def black_at(self, x, y):
        if self.w == 2 and self.h == 2:
            return self._basic_map[(x, y)]
        else:
            # Detect the borders
            if y == self.h - 1:
                return True
            if x == self.w - 1:
                return True
            if y == 0:
                return x > 0
            if x == 0:
                return False
            if y == self.h - 2:
                return False
            if x == self.w - 2:
                return False
            if y == 1:
                return x == 1
            if x == 1:
                return True
            return self.inner.black_at(x - 2, y - 2)

ss = SquareSpiral(34, 34)

for y in xrange(34):
    for x in xrange(34):
        print '#' if ss.black_at(x, 33 - y) else ' ',
    print ''