Minimax algorithm for Tic Tac Toe Python

I kind of understand how the minimax algorithm works for Tic Tac Toe python but I have no idea how to actually code it in Python... this is what I have so far:

from copy import deepcopy

class TicTacToeBrain :

    def __init__(self, player = "x") :
        self._squares = {}
        self._copySquares = {}
        self._winningCombos = (
        [0, 1, 2], [3, 4, 5], [6, 7, 8],
        [0, 3, 6], [1, 4, 7], [2, 5, 8],
        [0, 4, 8], [2, 4, 6])

    def createBoard(self) :
        for i in range(9) :
            self._squares[i] = None
        print(self._squares)

    def showBoard(self) :
        print(self._squares[0], self._squares[1], self._squares[2])
        print(self._squares[3], self._squares[4], self._squares[5])
        print(self._squares[6], self._squares[7], self._squares[8])

    def getAvailableMoves(self) :
        self._availableMoves = []
        for i in range(9) :
            if self._squares[i] == None :
                self._availableMoves.append(i)
        return self._availableMoves

    def makeMove(self, position, player) :
        self._squares[position] = player
        self.showBoard()

    def complete(self) :
        if None not in self._squares.values() :
            return True
        if self.getWinner() != None :
            return True
        return False

    def getWinner(self) :
        for player in ("x", "o") :
            for combos in self._winningCombos :
                if self._squares[combos[0]] == player and self._squares[combos[1]] == player and self._squares[combos[2]] == player :
                    return player
        if None not in self._squares.values() :
            return "tie"
        return None

    def getEnemyPlayer(self, player) :
        if player == "x" :
            return "o"
        return "x"

    def minimax(self, node, player, depth = 0, first = True) :
        if first :
            best = 0
            self._copySquares = deepcopy(self._squares)

        if node.complete() :
            if node.getWinner() == "x" :
                self._squares = self._copySquares
                return -1 - depth
            elif node.getWinner() == "tie" :
                self._squares = self._copySquares
                return 0
            elif node.getWinner() == "o" :
                self._squares = self._copySquares
                return 1 + depth
            best = None
        for move in node.getAvailableMoves() :
            depth += 1
            node.makeMove(move, player)
            print()
            val = self.minimax(node, node.getEnemyPlayer(player), depth, first = False)
            print(val)
            if player == "o" :
                if val > best :
                    best = val
            else :
                if val < best :
                    best = val
            return best
            print()
            print()

    def printCopy(self) :
        print(self._copySquares)

However, it never prints out all the scenarios....someone please help !!! This is due for a project on Monday..