如何用Python编写多线程程序

我的意思是,我想创建一个注意Ctrl+S和Q的函数。

但我的程序没有注意到。

我的代码是:

import threading, pygame, sys
from pygame.locals import *
from time import sleep

pygame.init()
screen = pygame.display.set_mode((1160, 640), 0, 0)
screen.fill((255, 255, 255))
pygame.display.flip()

def background():
    while True:
        for event in pygame.event.get():
            if event.type == pygame.KEYDOWN:
                if pygame.key.get_mods() & pygame.KMOD_CTRL and event.key == pygame.K_s:
                    print('GOOD')

def foreground():
    while True:
        for event in pygame.event.get():
            if event.type == pygame.KEYDOWN:
                if event.key == pygame.K_q:
                    print('HELLO_WORLD')
            if event.type == QUIT:
                pygame.quit()
                sys.exit()

b = threading.Thread(name='background', target=background)

b.start()
foreground()