Minimax code for tic-tac-toe in python

Question

I've been trying to code a tic-tac-toe game but I'm facing a problem. For example if I put a cross on one of the corners, the bot should mark "O" in the centre but that doesn't happen. Instead, it marks it on adjacent to the cross. The bot is not choosing the right value on the matrix. Any help would be appreciated. PS: The first player is always human while the second player is the bot. Here's the code:

import re
current_board = [" ", " ", " ", " ", " ", " ", " ", " ", " "]
current_game = list(" | | \n_|_|_\n | | \n_|_|_\n | | \n | | \n")

def draw1():
    for i in range(9):
        if(i<3 and i>=0):
            current_game[2*i]=current_board[i]
        elif(i<6 and i>=3):
            current_game[2*(i-3)+12]=current_board[i]
        elif(i<9 and i>=6):
            current_game[2*(i-6)+24]=current_board[i]
    print "".join(current_game)

def win(board, depth):
    board="".join(board)
    regex1 = [r"XXX......", r"...XXX...", r"......XXX", r"X..X..X..", r".X..X..X.", r"..X..X..X", r"X...X...X", r"..X.X.X.."]
    for i in regex1:
        if bool(re.search(i, board)):
            return -10+depth
    regex2 = [r"OOO......", r"...OOO...", r"......OOO", r"O..O..O..", r".O..O..O.", r"..O..O..O", r"O...O...O", r"..O.O.O.."]
    for i in regex2:
        if bool(re.search(i, board)):
            return 10-depth

def draw(board):
    for i in board:
        if i==" ":
            return False
    return True

def assigning_values_to_a_move(board, isOplaying, depth):
    scorelist=[]
    if win(board, depth)==10-depth:
        return 10-depth
    elif win(board, depth)==-10+depth:
        return -10+depth
    elif draw(board):
        return 0
    else:
        if(isOplaying):
            for i in range(len(board)):
                if board[i]==" ":
                    board[i]="O"
                    scorelist.append(assigning_values_to_a_move(board, not isOplaying, depth+1))
                    board[i]=" "
            return max(scorelist)
        else:
            for i in range(len(board)):
                if board[i]==" ":
                    board[i]="X"
                    scorelist.append(assigning_values_to_a_move(board, isOplaying, depth+1))
                    board[i]=" "
            return min(scorelist)

def choosing_the_move(board, depth):
    current_value=-1000
    best_value=-1000
    best_index=-1
    for i in range(9):
        if board[i]==" ":
            board[i]="O"
            current_value=assigning_values_to_a_move(board, False, depth)
            if(current_value>best_value):
                best_value=current_value
                best_index=i
            board[i]=" "
    return best_index

for i in range(9):
    if i%2==0:
        y=int(raw_input())
        current_board[y]="X"
        draw1()
    else:
        current_board[choosing_the_move(current_board,i+1)]="O"
        draw1()

Have you done any debugging? Do you know how to step through the code? — Blorgbeard, Nov 16 '17 at 17:51
If you take a corner, for example if you type 0, the bot should choose the center otherwise it can be beaten. For example input the following: 0, 4, 6 and then 3 — Tobias, Nov 16 '17 at 18:03

score 0 · Answer 1 · answered Nov 16 '17 at 18:54

Tobias, It's a good start, but your algorithm is searching for the fewest moves for a win, correct? The fewest moves will occur when the player (X) makes poor choices.

For example, if the board looks like this.

O|X|X
O| |X 
 | |

I'd suggest you weight the positions based on the number of ways to win.

weights = [3,2,3,
           2,4,2,
           3,2,3]

Then calculate a move resulting in a win based on greatest weight.

Minimax code for tic-tac-toe in python

1 Answers1