Python pygame problem--pygame.error: video system not initialized

pygame.error: video system not initialized, anyone knows how to fix it?

import sys
import pygame


class AlienInvasion:


    def __int__(self):
        pygame.init()
        self.screen = pygame.display.set_mode((1200, 800))
        pygame.display.set_caption("Alien Invasion")

    def run_game(self):
        while True:
            for event in pygame.event.get():
                if event.type == pygame.QUIT:
                    sys.exit()
            pygame.display.flip()


if __name__ == '__main__':
    ai = AlienInvasion()
    ai.run_game()`import sys
import pygame


class AlienInvasion:


    def __int__(self):
        pygame.init()
        self.screen = pygame.display.set_mode((1200, 800))
        pygame.display.set_caption("Alien Invasion")

    def run_game(self):
        while True:
            for event in pygame.event.get():
                if event.type == pygame.QUIT:
                    sys.exit()
            pygame.display.flip()


if __name__ == '__main__':
    ai = AlienInvasion()
    ai.run_game()

Traceback (most recent call last): File "C:\Users\leozh\OneDrive\Desktop\pythonProject\alien_invasion.py", line 28, in ai.run_game() File "C:\Users\leozh\OneDrive\Desktop\pythonProject\alien_invasion.py", line 18, in run_game for event in pygame.event.get(): pygame.error: video system not initialized