Chapter 10 - Tic Tac Toe

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# Tic Tac Toe import random def drawBoard(board): # This function prints out the board that it was passed. # "board" is a list of 10 strings representing the board (ignore index 0) print(' | |') print(' ' + board[7] + ' | ' + board[8] + ' | ' + board[9]) print(' | |') print('-----------') print(' | |') print(' ' + board[4] + ' | ' + board[5] + ' | ' + board[6]) print(' | |') print('-----------') print(' | |') print(' ' + board[1] + ' | ' + board[2] + ' | ' + board[3]) print(' | |') def inputPlayerLetter(): # Let's the player type which letter they want to be. # Returns a list with the player's letter as the first item, and the computer's letter as the second. letter = '' while not (letter == 'X' or letter == 'O'): print('Do you want to be X or O?') letter = input().upper() # the first element in the tuple is the player's letter, the second is the computer's letter. if letter == 'X': return ['X', 'O'] else: return ['O', 'X'] def whoGoesFirst(): # Randomly choose the player who goes first. if random.randint(0, 1) == 0: return 'computer' else: return 'player' def playAgain(): # This function returns True if the player wants to play again, otherwise it returns False. print('Do you want to play again? (yes or no)') return input().lower().startswith('y') def makeMove(board, letter, move): board[move] = letter def isWinner(bo, le): # Given a board and a player's letter, this function returns True if that player has won. # We use bo instead of board and le instead of letter so we don't have to type as much. return ((bo[7] == le and bo[8] == le and bo[9] == le) or # across the top (bo[4] == le and bo[5] == le and bo[6] == le) or # across the middle (bo[1] == le and bo[2] == le and bo[3] == le) or # across the bottom (bo[7] == le and bo[4] == le and bo[1] == le) or # down the left side (bo[8] == le and bo[5] == le and bo[2] == le) or # down the middle (bo[9] == le and bo[6] == le and bo[3] == le) or # down the right side (bo[7] == le and bo[5] == le and bo[3] == le) or # diagonal (bo[9] == le and bo[5] == le and bo[1] == le)) # diagonal def getBoardCopy(board): # Make a duplicate of the board list and return it the duplicate. dupeBoard = [] for i in board: dupeBoard.append(i) return dupeBoard def isSpaceFree(board, move): # Return true if the passed move is free on the passed board. return board[move] == ' ' def getPlayerMove(board): # Let the player type in his move. move = ' ' while move not in '1 2 3 4 5 6 7 8 9'.split() or not isSpaceFree(board, int(move)): print('What is your next move? (1-9)') move = input() return int(move) def chooseRandomMoveFromList(board, movesList): # Returns a valid move from the passed list on the passed board. # Returns None if there is no valid move. possibleMoves = [] for i in movesList: if isSpaceFree(board, i): possibleMoves.append(i) if len(possibleMoves) != 0: return random.choice(possibleMoves) else: return None def getComputerMove(board, computerLetter): # Given a board and the computer's letter, determine where to move and return that move. if computerLetter == 'X': playerLetter = 'O' else: playerLetter = 'X' # Here is our algorithm for our Tic Tac Toe AI: # First, check if we can win in the next move for i in range(1, 10): copy = getBoardCopy(board) if isSpaceFree(copy, i): makeMove(copy, computerLetter, i) if isWinner(copy, computerLetter): return i # Check if the player could win on his next move, and block them. for i in range(1, 10): copy = getBoardCopy(board) if isSpaceFree(copy, i): makeMove(copy, playerLetter, i) if isWinner(copy, playerLetter): return i # Try to take one of the corners, if they are free. move = chooseRandomMoveFromList(board, [1, 3, 7, 9]) if move != None: return move # Try to take the center, if it is free. if isSpaceFree(board, 5): return 5 # Move on one of the sides. return chooseRandomMoveFromList(board, [2, 4, 6, 8]) def isBoardFull(board): # Return True if every space on the board has been taken. Otherwise return False. for i in range(1, 10): if isSpaceFree(board, i): return False return True print('Welcome to Tic Tac Toe!') while True: # Reset the board theBoard = [' '] * 10 playerLetter, computerLetter = inputPlayerLetter() turn = whoGoesFirst() print('The ' + turn + ' will go first.') gameIsPlaying = True while gameIsPlaying: if turn == 'player': # Player's turn. drawBoard(theBoard) move = getPlayerMove(theBoard) makeMove(theBoard, playerLetter, move) if isWinner(theBoard, playerLetter): drawBoard(theBoard) print('Hooray! You have won the game!') gameIsPlaying = False else: if isBoardFull(theBoard): drawBoard(theBoard) print('The game is a tie!') break else: turn = 'computer' else: # Computer's turn. move = getComputerMove(theBoard, computerLetter) makeMove(theBoard, computerLetter, move) if isWinner(theBoard, computerLetter): drawBoard(theBoard) print('The computer has beaten you! You lose.') gameIsPlaying = False else: if isBoardFull(theBoard): drawBoard(theBoard) print('The game is a tie!') break else: turn = 'player' if not playAgain(): break

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Copyright © 2008, 2009, 2010 by Albert Sweigart
"Invent Your Own Computer Games with Python" 2nd Edition is free to copy and distribute under the Creative Commons Attribution-Noncommercial-Share Alike 3.0 United States License.