Project Euler#28 Number spiral diagonals

#Starting with the number 1 and moving to the right in a clockwise direction a 5 by 5 spiral is formed as follows:

#21 22 23 24 25
#20  7  8  9 10
#19  6  1  2 11
#18  5  4  3 12
#17 16 15 14 13

#It can be verified that the sum of the numbers on the diagonals is 101.

#What is the sum of the numbers on the diagonals in a 1001 by 1001 spiral formed in the same way?

def moveR(row,col,times):
    for i in range(1,times+1):
        arr[row][col+1] = arr[row][col] + 1
        col += 1

def moveD(row,col,times):
    for i in range(1,times+1):
        arr[row+1][col] = arr[row][col] + 1
        row += 1

def moveL(row,col,times):
    for i in range(1,times+1):
        arr[row][col-1] = arr[row][col] + 1
        col -= 1

def moveU(row,col,times):
    for i in range(1,times+1):
        arr[row-1][col] = arr[row][col] + 1
        row -= 1


dim = 1001
arr = []

#Create an array of None elements
for i in range(dim):
    row = []
    for j in range(dim):
        row.append(None)
    arr.append(row)

row = dim/2
col = dim/2
startValue = 1
arr[row][col] = startValue #Starting Position

for j in range(1,dim+1):

    if row == 0 and col == 0:
        moveR(row,col,dim-1)
        col += j
    elif j%2 != 0:
        moveR(row,col,j)
        col += j
        moveD(row,col,j)
        row += j
    elif j%2 == 0:
        moveL(row,col,j)
        col -= j
        moveU(row,col,j)
        row -= j


count = 0
for i in range(dim):
    for j in range(dim):
        if i == j or i+j == dim-1:
            count += arr[i][j]

print count