Code Editor for app.py

import streamlit as st
import numpy as np

# Define constants
EMPTY = 0
PLAYER_X = 1
PLAYER_O = 2

# AI Player
class AI:
    def __init__(self, player):
        self.player = player

    def get_best_move(self, board):
        available_moves = [(i, j) for i in range(3) for j in range(3) if board[i, j] == EMPTY]
        best_move = None
        best_score = -np.inf

        for move in available_moves:
            board[move] = self.player
            score = self.minimax(board, False)
            board[move] = EMPTY
            if score > best_score:
                best_score = score
                best_move = move

        return best_move

    def minimax(self, board, is_maximizing):
        winner = self.check_winner(board)
        if winner == self.player:
            return 1
        elif winner == (PLAYER_O if self.player == PLAYER_X else PLAYER_X):
            return -1
        elif np.all(board != EMPTY):
            return 0

        if is_maximizing:
            best_score = -np.inf
            for i in range(3):
                for j in range(3):
                    if board[i, j] == EMPTY:
                        board[i, j] = self.player
                        score = self.minimax(board, False)
                        board[i, j] = EMPTY
                        best_score = max(best_score, score)
            return best_score
        else:
            best_score = np.inf
            for i in range(3):
                for j in range(3):
                    if board[i, j] == EMPTY:
                        board[i, j] = (PLAYER_O if self.player == PLAYER_X else PLAYER_X)
                        score = self.minimax(board, True)
                        board[i, j] = EMPTY
                        best_score = min(best_score, score)
            return best_score

    def check_winner(self, board):
        # Check rows, columns and diagonals
        for i in range(3):
            if np.all(board[i, :] == self.player):
                return self.player
            if np.all(board[:, i] == self.player):
                return self.player
        if board[1, 1] == self.player:
            if (board[0, 0] == board[2, 2] == self.player) or (board[0, 2] == board[2, 0] == self.player):
                return self.player
        return None

# Streamlit app
st.title('Tic Tac Toe with AI')

# Initialize state
if 'board' not in st.session_state:
    st.session_state.board = np.zeros((3, 3), dtype=int)
    st.session_state.turn = PLAYER_X
    st.session_state.ai = AI(PLAYER_O)
    st.session_state.winner = None

# Function to handle player move
def make_move(row, col):
    if st.session_state.board[row, col] == EMPTY and st.session_state.winner is None:
        st.session_state.board[row, col] = st.session_state.turn
        st.session_state.turn = PLAYER_O
        st.session_state.winner = st.session_state.ai.check_winner(st.session_state.board)

        if st.session_state.winner is None and np.any(st.session_state.board == EMPTY):
            ai_move = st.session_state.ai.get_best_move(st.session_state.board)
            st.session_state.board[ai_move] = PLAYER_O
            st.session_state.winner = st.session_state.ai.check_winner(st.session_state.board)
            st.session_state.turn = PLAYER_X

# Display the board
for i in range(3):
    cols = st.columns(3)
    for j in range(3):
        if cols[j].button('X' if st.session_state.board[i, j] == PLAYER_X else 'O' if st.session_state.board[i, j] == PLAYER_O else '', key=f'{i}-{j}'): 
            make_move(i, j)

# Check for winner
if st.session_state.winner:
    st.success('Player' + (' X' if st.session_state.winner == PLAYER_X else ' O') + ' wins!')
elif np.all(st.session_state.board != EMPTY):
    st.warning('It is a tie!')

# Reset game
if st.button('Reset Game'):
    st.session_state.board = np.zeros((3, 3), dtype=int)
    st.session_state.turn = PLAYER_X
    st.session_state.winner = None