游戏简介：在九宫格内进行，如果一方抢先于另一方向（横、竖、斜）连成3子，则获得胜利。游戏中输入方格位置代号的形式如下：
设计前的思路：
游戏中，board棋盘存储玩家、计算机的落子信息，未落子处未EMPTY。由于人机对战，需要实现计算机智能性，下面是为这个计算机机器人设计的简单策略：
如果有一步棋可以让计算机机器人在本轮获胜，那就选那一步走。
否则，如果有一步棋可以让玩家在本轮获胜，那就选那一步走。
否则，计算机机器人应该选择最佳位置来走。
最佳位置就是中间，其次是四个角
定义第一个元组best_weizhi存储最佳方格位置：
按优劣顺序排序的下棋位置
best_weizhi= (4, 0, 2, 6, 8, 1, 3, 5, 7)
井字棋盘输赢判断规则只有8种方式。每种获胜方式都被写成一个元组，利用嵌套元组表达：
win = ((0, 1, 2), (3, 4, 5), (6, 7, 8), (0, 3, 6),(1, 4, 7), (2, 5, 8), (0, 4, 8), (2, 4, 6))
代码：
#全局常量best_weizhi= (4, 0, 2, 6, 8, 1, 3, 5, 7)win = ((0, 1, 2), (3, 4, 5), (6, 7, 8), (0, 3, 6),(1, 4, 7), (2, 5, 8), (0, 4, 8), (2, 4, 6)) X = "X"O = "O"EMPTY = " "#定义函数产生一个新的棋盘def new_board():board = []for square in range(9):board.append(EMPTY)return board#询问该谁下棋def ask_yes_no(question):response = None#如果输入不是"y", "n"，继续重新输入while response not in ("y", "n"):response = input(question).lower()return response#询问谁先走，先走方为X，后走方为O#函数返回电脑方、玩家的角色代号def pieces():go_first = ask_yes_no("玩家你是否先走 (y/n): ")if go_first == "y":print("\n玩家你先走.")human = Xcomputer = Oelse:print("\n电脑先走.")computer = Xhuman = Oreturn computer, human#显示棋盘def display_board(board):board2=board[:]#创建副本，修改不影响原来列表boardfor i in range(len(board)):if board[i]==EMPTY:board2[i]=iprint("\t", board2[0], "|", board2[1], "|", board2[2])print("\t", "---------")print("\t", board2[3], "|", board2[4], "|", board2[5])print("\t", "---------")print("\t", board2[6], "|", board2[7], "|", board2[8], "\n")#输入你想下的位置数字def ask_number(question, low, high):response = Nonewhile response not in range(low, high):response = int(input(question))return response#产生可以合法走棋位置序列（也就是还未下过子位置）def legal_moves(board):moves = []for i in range(9):if board[i] == EMPTY:moves.append(i)return moves#判断输赢def winner(board):for row in win:if board[row[0]] == board[row[1]] == board[row[2]] != EMPTY:winner = board[row[0]]return winner #返回赢方#棋盘没有空位置if EMPTY not in board:return "True"#"平局和棋，游戏结束"return False#人走棋def human_move(board, human):legal = legal_moves(board)move = Nonewhile move not in legal:move = ask_number("你走那个位置? (0 - 9):", 0, 9)if move not in legal:print("\n此位置已经落过子了")return move#电脑走棋def computer_move(board, computer, human):# make a copy to work with since function will be changing listboard = board[:]#创建副本，修改不影响原来列表board#按优劣顺序排序的下棋位置best_weizhi# 如果电脑能赢，就走那个位置for move in legal_moves(board):board[move] = computerif winner(board) == computer:print("电脑下棋位置是" ,move)return move# 取消走棋方案board[move] = EMPTY# 如果玩家能赢，就堵住那个位置for move in legal_moves(board):board[move] = humanif winner(board) == human:print("电脑下棋位置是" ,move)return move#取消走棋方案board[move] = EMPTY#不是上面情况则，也就是这一轮时都赢不了则#从最佳下棋位置表中挑出第一个合法位置for move in best_weizhi:if move in legal_moves(board):print("电脑下棋位置是" ,move)return move#转换角色def next_turn(turn):if turn == X:return Oelse:return X#主方法：def main():computer, human = pieces()turn = Xboard = new_board()display_board(board)while not winner(board):if turn == human:move = human_move(board, human)board[move] = humanelse:move = computer_move(board, computer, human)board[move] = computerdisplay_board(board)turn = next_turn(turn)the_winner = winner(board)#游戏结束输出输赢信息if the_winner == computer:print("电脑赢!\n") elif the_winner == human: print("玩家赢!\n")elif the_winner == "True":#"平局" print("平局,和棋，游戏结束\n")# start the programmain()input("按任意键退出游戏.")
在最后附上结果图：
至此一个简单的井字棋就完成了。
