Python neighbors all pointing to same value

Question

I am making a minesweeper clone in Python and I am running into issues setting the "Neighbors"

This is the class:

class Box:
    hasBomb = False
    numBombNeighbors = 0
    clicked = False
    xcoord = 0
    ycoord = 0
    neighbors = [None, None, None, None, None, None, None, None]

    def __init__(self):
        self.hasBomb = False
        self.numBombNeighbors = 0
        self.clicked = False
        self.xcoord = 0
        self.ycoord = 0
        for i in xrange(8):
            self.neighbors[i] = None

Then I make the board

def getRandomBoard():
    # we will hide 50 random bombs
    result = []
    for i in xrange(BOARDWIDTH):
        result.append([])
        for j in xrange(BOARDHEIGHT):
            new_box = Box()
            new_box.xcoord = i
            new_box.ycoord = j
            result[i].append(new_box)


    # set all the neighbors
    result = setNeighbros(result)

    for i in range(BOARDWIDTH):
        for j in range(BOARDHEIGHT):
            print result[i][j].xcoord
            print result[0][0].neighbors[5].xcoord

And this is the function to set the Neighbors:

def setNeighbros(board):
    for i in range(len(board)):
        for j in range(len(board[i])-1):
            if j > 0:
                board[i][j].neighbors[0] = board[i][j-1]
            if j > 0 and i < len(board) -1:
                board[i][j].neighbors[1] = board[i+1][j-1]
            if i < len(board) - 1:
                board[i][j].neighbors[2] = board[i+1][j]
            if i < len(board) - 1 and j < len(board[i]) - 1:
                board[i][j].neighbors[3] = board[i+1][j+1]
            if j < len(board[i]) - 1:
                board[i][j].neighbors[4] = board[i][j+1]
            if j < len(board[i]) - 1 and i > 0:
                board[i][j].neighbors[5] = board[i-1][j+1]
            if i >  0:
                board[i][j].neighbors[6] = board[i-1][j]
            if i > 0 and j > 0:
                board[i][j].neighbors[7] = board[i-1][j-1]
    return board

In the Board making function, I print the xcoord and the xcoord of neighbor 5 to check the problem, and the problem is coming from setting the neighbors. During the creation of the neighbors they are all pointing to the correct neighbor, but after it finishes they are all pointing to the same neighbor, but I know the array of boxes is all holding different boxes since they have different xcoord. If someone could tell me why the neighbors are all pointing at the same box, I would appreciate it.

score 1 · Answer 1 · answered Apr 27 '14 at 01:42

The problem is that the class-level variables are shared among all instances of the class.

If you are coming from a language like Java, you can imagine the variables declared inside the class are all static variables.

Modify your class to remove all the class-level variables, and do all initialization of instance-level variables inside __init__.

class Box:

    def __init__(self):
        self.hasBomb = False
        self.numBombNeighbors = 0
        self.clicked = False
        self.xcoord = 0
        self.ycoord = 0
        self.neighbors = [None for i in xrange(8)]

Python neighbors all pointing to same value

1 Answers1