如何清除 pygame 事件队列？

Question

I use pygame to design a psychophysical experiment. The general flow of the experiment is that two objects appear in each trial, then press the left and right direction keys to select one of them, the system will inform the result, and then make the next trial. Now I have found such a problem: when running on some computers, if I press the left and right keys multiple times in one trial, the event queue should be cleared before the next selection when running on the normal computer, and the results should be given after the selection on this trial, which is also true on my personal laptop(the next selection will not be affected by pressing multiple times); However, on some computers, when running the same program, it will execute the selection of the next few times in sequence according to the sequence of pressing keys (it will automatically select according to the sequence about key without making a selection). In addition, even if the program is encapsulated with pyinstaller on the normal computer, the problem will still occur when the encapsulated program used on the problematic computer. How can I solve it?

Here is the program segment. If you need to run the total program, I will provide it with you.

# wait for a click
def wait4click(duration=1500):
    left = (WIN_LENGTH / 4 - IMG_HEIGHT / 2, WIN_WIDTH / 2 - IMG_WIDTH / 2)
    right = (3 * WIN_LENGTH / 4 - IMG_HEIGHT / 2, WIN_WIDTH / 2 - IMG_WIDTH / 2)
    pygame.event.clear()
    t_start = pygame.time.get_ticks()
    while True:
        t_now = pygame.time.get_ticks()
        if t_now - t_start > duration:
            return 'BLANK'
        else:
            for event in pygame.event.get():
                if event.type == KEYDOWN:

                    if event.key == K_LEFT:
                        choice = 'left'
                        pygame.draw.polygon(win, red, [eval(choice),
                                                       (eval(choice)[0] + IMG_HEIGHT, eval(choice)[1]), (
                                                           eval(choice)[0] + IMG_HEIGHT,
                                                           eval(choice)[1] + IMG_WIDTH),
                                                       (eval(choice)[0], eval(choice)[1] + IMG_WIDTH)], 10)
                    elif event.key == K_RIGHT:
                        choice = 'right'
                        pygame.draw.polygon(win, red, [eval(choice),
                                                       (eval(choice)[0] + IMG_HEIGHT, eval(choice)[1]), (
                                                       eval(choice)[0] + IMG_HEIGHT,
                                                       eval(choice)[1] + IMG_WIDTH),
                                                   (eval(choice)[0], eval(choice)[1] + IMG_WIDTH)], 10)
                    elif event.key in [K_ESCAPE]:
                        resp = pygame.key.name(event.key)
                        pygame.event.clear()
                        return resp
                    else:
                        continue
                    pygame.event.clear()
                    return choice

train_list = ['p1', 'p1', 'p2', 'p2', 'p2', 'p2', 'p1', 'p1']
for i in range(len(train_list)):
    [correct_cue_loc, wrong_cue_loc] = draw_cue(train_list[i], introduction=True, symbol=True) # draw two objects
    subj_choose = wait4click(duration=1500)
    break_signal = train_judgement(subj_choose)  # judge and show the result on the screen
    if break_signal:
        break
    pygame.time.wait(1000)
    fadeout()    # equal to win.fill(grey),[output][/output] pygame.display.update()
    text_msg('+')
    pygame.time.wait(1000)
    win.fill(grey)

Answer 1

I've spend quite a bit of time on your question because it came up yesterday in a game I'm messing with/trying to fix. The answer seems to be

time.sleep()

I have absolutely no idea why or how your going to implement it in your code. The following code works consistently to get proper timings. Even if your press and hold the key from the first to the second timer, the second timing will trigger on the KEYUP as you lift your finger:

import pygame, sys, time

if __name__ == '__main__':
    pygame.init()
    screen_width = 600
    screen_height = 600
    screen = pygame.display.set_mode((screen_width, screen_height))
    clock = pygame.time.Clock()

    print('timer started')
    t_start = pygame.time.get_ticks()
    pygame.event.clear()
    event =  pygame.event.wait()
    if event.type == pygame.KEYDOWN:
        if event.key == pygame.K_SPACE:
            print('we got a space')
        if event.key == pygame.K_RIGHT:
            print('we got a Right')
        if event.key == pygame.K_LEFT:
            print('we got a Left')
    pygame.event.clear()
    t_now = pygame.time.get_ticks()
    print(f"timer ended {t_now - t_start} ticks")
    time.sleep(1)  # without this line it doesn't work right
                   # and I have no ^&$% idea why.

    print('timer started again')
    t_start = pygame.time.get_ticks()
    pygame.event.clear()
    event =  pygame.event.wait()
    if event.type == pygame.KEYDOWN:
        if event.key == pygame.K_SPACE:
            print('we got a space')
        if event.key == pygame.K_RIGHT:
            print('we got a Right')
        if event.key == pygame.K_LEFT:
            print('we got a Left')
    t_now = pygame.time.get_ticks()
    print(f"timer ended {t_now - t_start} ticks")

Good luck, but asynchronous interrupt processing will drive you bats**t crazy over time.