PyGame, waiting for computer to decide its move - python-3.x

Question

Okay
So I am building a tic-tac-toe on pygame in which A player can play against player, computer vs player or computer vs computer.
I have already developed the code for a MiniMaxAgent() which takes its input as a 2D matrix and returns the (row, col) where it would play a move. The thing is that this code can take several seconds to execute on an nxn board. Because of this the pyGame Code hangs.
Sample event loop:
while running:
mouseClicked = False
DISPLAYSURF.fill(BGCOLOR)
renderBoard()
#event handlers
for event in pygame.event.get():
if event.type == QUIT:
pygame.quit()
sys.exit()
if event.type == MOUSEMOTION:
mouseX, mouseY = event.pos
elif event.type == MOUSEBUTTONUP:
mouseX, mouseY = event.pos
mouseClicked = True
row, col = players[currentPlayer].turn(currentPlayer*board.state)
board.state[row][col] = currentPlayer
currentPlayer = currentPlayer * -1
pygame.display.update()
As you can see, when I call the function players[currentPlayer].turn(), It should return me the optimal move in some seconds. But PyGame freezes.
How should I implement this?

Answer 1

A simple solution is to run the blocking function in question in a Thread. This will allow your game loop to keep running.
Here's a simple example. Note how the loop keeps running while the turn function wastes some time.
import pygame
import pygame.freetype
import random
import time
import threading
pygame.init()
screen = pygame.display.set_mode((800, 300))
PLAYER_TURN, AI_TURN = 0, 1
font = pygame.freetype.Font(None, 30)
state = PLAYER_TURN
running = True
result = None
def turn(boardstate):
print('thinking about ' + boardstate + '....')
time.sleep(1)
print('thinking very hard....')
time.sleep(1)
global result
global state
result = random.randint(10, 100)
state = PLAYER_TURN
r = pygame.rect.Rect((0, 250, 100, 50))
while running:
for e in pygame.event.get():
if e.type == pygame.QUIT:
running = False
elif e.type == pygame.MOUSEBUTTONUP:
if state == PLAYER_TURN:
state = AI_TURN
threading.Thread(target=turn, args=['an argument']).start()
screen.fill(pygame.color.Color('grey'))
if state == PLAYER_TURN:
font.render_to(screen, (50, 50), 'It is your turn. Click anything')
if result:
font.render_to(screen, (50, 180), 'AI said: ' + str(result))
elif state == AI_TURN:
font.render_to(screen, (50, 50), 'Waiting for AI')
pygame.draw.rect(screen, pygame.color.Color('red'), r)
r.move_ip(1, 0)
if not screen.get_rect().contains(r):
r.x = 0
pygame.display.update()