See How to center an image in the middle of the window in pygame?. If you want to center the image in the middle of the screen, you need to get the bounding rectangle of the image and set the center of the rectangle to the center of the screen:
screen.blit(image, screen.get_rect().center)
screen.blit(image, image.get_rect(center = screen.get_rect().center))
The same in single steps:
screen_rect = screen.get_rect()
screen_center = screen_rect.center
image_rect = image.get_rect()
image_rect.center = screen_center
screen.blit(image, image_rect)
Minimal example:
import pygame
pygame.init()
screen = pygame.display.set_mode((400, 400))
clock = pygame.time.Clock()
image = pygame.image.load("image.png")
run = True
while run:
clock.tick(100)
for event in pygame.event.get():
if event.type == pygame.QUIT:
run = False
screen.fill(0)
screen.blit(image, image.get_rect(center = screen.get_rect().center))
pygame.display.flip()
pygame.quit()
exit()