Facebook numbers

facebook_numbers.py

def get_square(side_length):
    """
    Calculates square.
 
    Arguments:
        - side_length: int, length of square side.
 
    Returns:
        - List with values for square.
 
    """
 
    numbers = [[()] * side_length for _ in range(side_length)]
    directions = ((0, 1), (1, 0), (0, -1), (-1, 0))
    coord = (0, 0)
    dir_num = 0
    num = 1
 
    while num <= side_length ** 2:
        i, j = coord[0], coord[1]
        numbers[i][j] = num
 
        next_i, next_j = i + directions[dir_num][0], j + directions[dir_num][1]
        if next_i > len(numbers) - 1 or next_j > len(numbers[i]) - 1 or \
                numbers[next_i][next_j]:
            dir_num += 1
            dir_num -= (dir_num / 4) * 4
 
        coord = coord[0] + directions[dir_num][0], coord[1] + \
            directions[dir_num][1]
        num += 1
 
    return numbers