http://cslai.coolsilon.com/2014/09/12/spiraling-number/

spiral.py

def spiral(max_x, max_y):
    matrix = []
    for i in range(0, max_y):
        matrix.append([0] * max_x)
    
    x, y, n, xdir, ydir = 0, 0, 0, 1, 0

    while 1:
        n = n + 1
        matrix[y][x] = n
        x, y = x + xdir, y + ydir

        if (x < 0 or x >= max_x or y < 0 or y >= max_y or matrix[y][x] > 0):
            x, y = x - xdir, y - ydir
            xdir, ydir = -ydir, xdir
            x, y = x + xdir, y + ydir

            if (matrix[y][x] > 0):
                break

    for i in matrix:
        for j in i:
            print '{0:2}'.format(j),
        print

spiral(5, 5)