用python创建桌面应用（二）

  上一篇文章我们已经创建好了数据层，接下来我们创建核心逻辑层。在这里我们需要知道游戏是如何运行的，游戏的流程是什么样的。想一下我们玩游戏的时候，一开始有个登录界面，在这里不实现这个功能。然后有一些选择菜单，比如开始游戏，游戏难度，退出等等。对于这个井字棋游戏，首先向用户展示一个选项菜单，并包含开始一个游戏或继续一个被保存游戏的选项。无论哪种情况，一旦游戏被设置，就会展示主面板并且提示用户选择一个格子。然后计算分析这个移动并以它的移动作为应答。之后，面板被再次展示出来知道一方获胜。下面是原书的模块交互序列图：

''' This is the main logic for a Tic-tac-toe game.It is not optimised for a quality game it simplygenerates random moves and checks the results ofa move for a winning line. Exposed functions are:newGame()saveGame()restoreGame()userMove()computerMove()'''import os, randomimport oxo_datadef newGame():#返回一个拥有9个空格的新列表    ' return new empty game'    return list(" " * 9)def saveGame(game):    ' save game to disk '    oxo_data.saveGame(game)    def restoreGame():#捕捉任何由于找不到数据文件所抛出的错误并验证保存游戏的长度    ''' restore previously saved game.    If game not restored successfully return new game'''    try:        game = oxo_data.restoreGame()        if len(game) == 9:            return game        else: return newGame()    except IOError:        return newGame()    def _generateMove(game):#寻找当前游戏中没有被使用的格子，然后随机选择一个格子来防止计算机的移动    ''' generate a random cell from thiose available.        If all cells are used return -1'''    options = [i for i in range(len(game)) if  game[i] == " "]    if options:       return random.choice(options)    else: return -1    def _isWinningMove(game):#判断输赢    wins = ((0,1,2), (3,4,5), (6,7,8),            (0,3,6), (1,4,7), (2,5,8),            (0,4,8), (2,4,6))    for a,b,c in wins:        chars = game[a] + game[b] + game[c]        if chars == 'XXX' or chars == 'OOO':            return True    return Falsedef userMove(game,cell):#用户移动    if game[cell] != ' ':        raise ValueError('Invalid cell')    else:        game[cell] = 'X'    if _isWinningMove(game):        return 'X'    else:        return ""def computerMove(game):#计算机移动    cell = _generateMove(game)    if cell == -1:        return 'D'    game[cell] = 'O'    if _isWinningMove(game):        return 'O'    else:        return ""def test():  #测试函数    result = ""    game = newGame()    while not result:        print(game)        try:           result = userMove(game, _generateMove(game))        except ValueError:            print("Oops, that shouldn't happen")        if not result:            result = computerMove(game)                    if not result: continue        elif result == 'D':            print("Its a draw")        else:            print("Winner is:", result)        print(game)if __name__ == "__main__":    test()

上面的文件名为：oxo_logic.py