我在pygame的学习阶段，python代码显示属性错误，这里是代码

import pygame
from pygame.locals import (
    K_DOWN,
    K_UP,
    K_LEFT,
    K_RIGHT,
    K_ESCAPE,
    KEYDOWN,
    QUIT)
pygame.init()#initailaze the window
SCREEN_WIDTH = 600
SCREEN_HEIGHT = 600
screen_display = pygame.display.set_mode([SCREEN_WIDTH , SCREEN_HEIGHT])

# variable to keep loop running

running = True

# main loop begins here

while running:
    for event in pygame.event.get():
        if event.type == KEYDOWN:
            if event.key == K_ESCAPE:
                running = False
        elif event.type == QUIT:
             running = False
    screen_display = screen_display.fill((255,255,255))
    surface = pygame.Surface((50,50))
    surface.fill((0,0,0))
    rectangle = surface.get_rect()
    screen_display.blit(surface, (SCREEN_WIDTH/2, SCREEN_HEIGHT/2))
    pygame.display.flip()

pygame.quit()

输出结果如下所示

pygame 2.0.1 (SDL 2.0.14, Python 3.7.9)
Hello from the pygame community. https://www.pygame.org/contribute.html
Traceback (most recent call last):
  File "G:\project\game\start.py", line 27, in <module>
    screen_display.blit(surface, (SCREEN_WIDTH/2, SCREEN_HEIGHT/2))
AttributeError: 'pygame.Rect' object has no attribute 'blit'