[PyGame] newbie needs help with space invaders

[metulburr]

screen.blit is what is drawing the image. And with the way you coded it, it is only in a callback function that only runs at the time you are pressing the spacebar down. So it is only being drawn when you have the spacebar down.

I suggest to learn classes as well. Because it is far easier to maintain as well as understand code of a class Ship and a class Bullet than using globals.

My tutorials series does this concept.

import pygame as pg
   
pg.init()
  
class Laser:
    def __init__(self, loc):
        self.image = pg.Surface((5,40)).convert()
        self.image.fill((255,255,0))
        self.rect = self.image.get_rect(center=loc)
        self.speed = 5
          
    def update(self):
        self.rect.y -= self.speed
      
    def render(self, surf):
        surf.blit(self.image, self.rect)
   
class Player:
    def __init__(self, screen_rect):
        self.screen_rect = screen_rect
        #self.image = pg.image.load('spaceship.png').convert()
        self.image = pg.Surface([50,50])
        self.image.fill((0,0,255))
        self.image.set_colorkey((255,0,255))
        self.transformed_image = pg.transform.rotate(self.image, 180)
        start_buffer = 300
        self.rect = self.image.get_rect(
            center=(screen_rect.centerx, screen_rect.centery + start_buffer)
        )
        self.dx = 300
        self.lasers = []
          
    def get_event(self, event):
        if event.type == pg.KEYDOWN:
            if event.key == pg.K_SPACE:
                self.lasers.append(Laser(self.rect.center))
          
    def update(self, keys, dt):
        self.rect.clamp_ip(self.screen_rect)
        if keys[pg.K_LEFT]:
            self.rect.x -= self.dx * dt
        elif keys[pg.K_RIGHT]:
            self.rect.x += self.dx * dt
        for laser in self.lasers:
            laser.update()
           
    def draw(self, surf):
        for laser in self.lasers:
            laser.render(surf)
        surf.blit(self.transformed_image, self.rect)
   
screen = pg.display.set_mode((800,600))
screen_rect = screen.get_rect()
player = Player(screen_rect)
clock = pg.time.Clock()
done = False
while not done:
    keys = pg.key.get_pressed()
    for event in pg.event.get(): 
        if event.type == pg.QUIT:
            done = True
        player.get_event(event)
    screen.fill((0,0,0))
    delta_time = clock.tick(60)/1000.0
    player.update(keys, delta_time)
    player.draw(screen)
    pg.display.update()