Timer in Pygame displaying same values

Question

I'm trying to make a reaction time tester in Pygame, but the timer for each attempt is displaying 0. When the screen is red, pressing the down key is supposed to record the time taken. I'm not sure exactly where I'm supposed to place the timer, as I'm struggling to understand how the event loop actually works.

import pygame, sys
import random
from random import randint
import time
from time import sleep
from pygame.locals import *
FPS = 30
fpsClock = pygame.time.Clock()
DISPLAYSURF = pygame.display.set_mode((400, 300), 0, 32)
pygame.display.set_caption('Test')

WHITE = (255, 255, 255)
RED = (255, 0, 0)
y = False
x = 0

while True:


    if y is False:
        y = True
        DISPLAYSURF.fill(WHITE)

        start = time.time()
        sleep(randint(1,3))

    else:
        y = False
        DISPLAYSURF.fill(RED)
        time.sleep(2)



    for event in pygame.event.get():

        if x < 5:
            if event.type == QUIT:
                pygame.quit()
                sys.exit()
            if event.type == pygame.KEYDOWN:
                if y is True:
                    end = time.time()
                    print(end - start)
                    x += 1



        else:
            pygame.quit()
            sys.exit()



    pygame.display.update()
    fpsClock.tick(FPS)

Answer 1

I'm not sure if it works exactly as you expect but it checks time reaction on red color in miliseconds, and it works without time.sleep()

import pygame
import random

# --- constants ---

FPS = 30

WHITE = (255, 255, 255)
RED   = (255,   0,   0)

# --- main ---

pygame.init()
screen = pygame.display.set_mode((400, 300))
pygame.display.set_caption('Test')

repeats = 5

testing = False
color = WHITE

current_time = pygame.time.get_ticks()

# random time to start test 
start_test = current_time + random.randint(1, 3)*1000 # 1000ms = 1s

# - mainloop -

fps_clock = pygame.time.Clock()

while True:

    # - events -

    for event in pygame.event.get():

        if event.type == pygame.QUIT:
            pygame.quit()
            exit()
        elif event.type == pygame.KEYDOWN:
            if testing:
                end = pygame.time.get_ticks()
                print(end - start, 'ms')
                repeats -= 1

    # - other

    if repeats == 0:
        pygame.quit()
        exit()

    current_time = pygame.time.get_ticks()

    # is it time to start displaying red color
    if not testing and current_time >= start_test:
        testing = True
        color = RED
        start = pygame.time.get_ticks()
        # display white color
        stop_test = current_time + 2*1000 # 1000ms = 1s

    # is it time to stop displaying red color
    if testing and current_time >= stop_test:
        testing = False
        color = WHITE
        # random time to start next test 
        start_test = current_time + random.randint(1, 3)*1000 # 1000ms = 1s

    # - draws -

    screen.fill(color)
    pygame.display.flip()

    fps_clock.tick(FPS)