rotating spiral in matrix by python

X,Y = map(int,raw_input().split(' '))

lis = [[-1 for i in xrange(Y)] for j in xrange(X)]

x,y = 0,0

dx,dy = 0,1

count = 0

while lis[x][y] == -1:

    lis[x][y] = count

    count+=1

    x,y = x+dx,y+dy

    if x in [-1,X] or y in [-1,Y] or lis[x][y] != -1:

        x,y = x-dx,y-dy

        dx,dy = dy,-dx

        x,y = x+dx,y+dy

for L in lis:

    for val in L:

        print '%3d'%val,

    print

>> 6 6

 0   1   2   3   4   5

 19  20  21  22  23   6

 18  31  32  33  24   7

 17  30  35  34  25   8

 16  29  28  27  26   9

 15  14  13  12  11  10

have fun.