I’m trying to learn the minimax algorithm. my minimax algorithm just doesn’t work, The computer just plays “O” in the next available square. My entire source code is below (sorry for the wall of text). The bestScore variable stays at what it was initially set as (1000 or -1000 depending on if it was maximising or minimising) and it never returns one of the base cases. Not sure where to go from here

from json.encoder import INFINITY
from itertools import combinations

from pygame.examples import grid


class GameState():
    def __init__(self):
        self.grid = [["-","-","-"],
                     ["-","-","-"],
                     ["-","-","-"]]

        self.MagicSquare = [[4, 9, 2],
                            [3, 5, 7],
                            [8, 1, 6]]

        self.XtoMove = True
        self.gameOver = False
        self.Xsum = []
        self.Osum = []
        self.Xwins = False
        self.Owins = False
        self.draw = False

    def makeMove(self, row, col):
        totalX = 0
        totalO = 0


        if self.grid[row][col] == "-":

            if self.XtoMove == True:

                self.grid[row][col] = 'X'
                self.bestMove()
                #self.XtoMove = False
                self.Xsum.append(self.MagicSquare[row][col])

                for combo in combinations(self.Xsum, 3):
                    if sum(combo) == 15:
                        self.gameOver = True
                        self.Xwins = True

            if len(self.Xsum) + len(self.Osum) == 9:
                self.gameOver = True
                self.draw = True



    def checkDraw(self):
        if len(self.Xsum) + len(self.Osum) == 9:
            self.gameOver = True
            self.draw = True
            return True

    def checkWinner(self, player):

        if player == 'X':
            sums = self.Xsum
        else:
            sums = self.Osum

        for combo in combinations(sums, 3):
            if sum(combo) == 15:
                return True
        return False


    def minimax(self, grid, depth, isMaximising):
        if self.checkWinner("O"):
            return 1
        elif self.checkWinner("X"):
            return -1
        elif self.checkDraw():
            return 0

        if isMaximising:
            bestScore = -1000
            for r in range(3):
                for c in range(3):
                    if grid[r][c] == "-":
                        grid[r][c] = 'O'
                        score = self.minimax(grid, depth + 1, False)
                        grid[r][c] = "-"
                        bestScore = max(score, bestScore)

            return bestScore

        else:
            bestScore = 1000
            for r in range(3):
                for c in range(3):
                    if grid[r][c] == "-":
                        grid[r][c] = 'X'
                        score = self.minimax(grid, depth + 1, True)
                        grid[r][c] = "-"
                        bestScore = min(score, bestScore)
            return bestScore

    def bestMove(self):
        bestScore = -10000
        move = (-1, -1)
        for r in range(3):
            for c in range(3):
                if self.grid[r][c] == "-":
                    self.grid[r][c] = 'O'
                    score = self.minimax(self.grid, 0, False)
                    self.grid[r][c] = "-"
                    if score > bestScore:
                        bestScore = score
                        move = (r, c)

        if move != (-1,-1):
            self.grid[move[0]][move[1]] = 'O'
            self.Osum.append(self.MagicSquare[move[0]][move[1]])

            for combo in combinations(self.Osum, 3):
                if sum(combo) == 15:
                    self.gameOver = True
                    self.Owins = True

        if len(self.Xsum) + len(self.Osum) == 9 and not self.Owins:
            self.gameOver = True
            self.draw = True