Very Broken Preliminary Move Code

#!/usr/local/bin/python2.7

def Move(self, board, xDir, yDir):
    #X = 1 -> Right
    #X = -1 -> Left
    #Y = 1 -> Down
    #Y = -1 -> Up
    for Xb in range(len(board)-1)[::yDir]:
        for Yb in range(Xb):
            try:
                if board[Xb][Yb].value == board[Xb][Yb+yDir] \
                    and board[Xb][Yb].justcombined == False \
                    and board[Xb][Yb+yDir].justcombined == False:

                        board[Xb][Yb+yDir].value = 0

                        for t in range(3)[::yDir]:
                            try:
                                board[Xb][t] = board[Xb][t+yDir]
                            except IndexError:
                                board[Xb][t].value = 0

                else:
                    pass
            except IndexError:
                pass
    for Yb in range(len(board)-1)[::xDir]:
        for Xb in range(Yb):
            try:
                if board[Xb][Yb].value == board[Xb+xDir][Yb] \
                    and board[Xb][Yb].justcombined == False \
                    and board[Xb+xDir][Yb].justcombined == False:

                        board[Xb+xDir][Yb].value = 0

                        for t in range(3)[::xDir]:
                            try:
                                board[t][Yb] = board[t+xDir][Yb]
                            except IndexError:
                                board[t][Yb].value = 0

                else:
                    pass
            except IndexError:
                pass