Understanding & making infinite bullets to shoot in Pygame - python-3.x

Question

I'm learning python and also pygame, and I want to know why the bullets doesn't display, I tough that maybe the screen.update_screen() can be interfering but no, that's not the case, I need help to undertand how Bullets work in python because clearly my method is not working, I've seen many methods in other posts, and they use a limited ammount of bullets to shoot (don't know why, in my case I want infinite bullets) so what should I add to see the Bullets, I know that I need to add a remover for seing a "movement" in the display, but I don't know how, any help is appreciated.
# -*- coding: utf-8 -*-
import pygame
class Screen(pygame.sprite.Sprite):
def __init__(self):
pygame.sprite.Sprite.__init__(self)
pygame.display.set_caption("Space Game")
self.screen_width = 800
self.screen_heigh = 600
self.picture = pygame.image.load("screen.png")
self.screen = pygame.display.set_mode((self.screen_width, self.screen_heigh))
def update_screen(self):
self.screen.blit(self.picture, (0, 0))
def update_obj(self, object):
self.screen.blit(object.picture, object.rect)
def update_shoot(self, object):
for y in range(object.rect.centery, 600, 10):
self.screen.blit(object.picture, (object.rect.centerx, object.rect.centery + y))
class Ship(pygame.sprite.Sprite):
def __init__(self):
pygame.sprite.Sprite.__init__(self)
self.picture = pygame.image.load("ship.png")
self.rect = self.picture.get_rect()
self.rect.centerx = 400
self.rect.centery = 500
class Bullet(pygame.sprite.Sprite):
def __init__(self, object):
pygame.sprite.Sprite.__init__(self)
self.picture = pygame.image.load("shoot.png")
self.rect = self.picture.get_rect()
self.rect.centerx = object.rect.centerx
self.rect.centery = (object.rect.centery + 25)
def main():
pygame.init()
done = False
clock = pygame.time.Clock()
screen = Screen()
ship = Ship()
bullet = Bullet(ship)
while not done:
keys = pygame.key.get_pressed()
if keys[pygame.K_LEFT]:
ship.rect.centerx -= 5
if keys[pygame.K_RIGHT]:
ship.rect.centerx += 5
if keys[pygame.K_UP]:
ship.rect.centery -= 5
if keys[pygame.K_DOWN]:
ship.rect.centery += 5
for event in pygame.event.get():
if event.type == pygame.QUIT:
done = True
elif event.type == pygame.KEYDOWN:
if event.key == pygame.K_ESCAPE:
done = True
if event.key == pygame.K_SPACE:
print ("shoot")
#for some weird reason the bullet doesn't display
screen.update_shoot(bullet)
screen.update_screen()
screen.update_obj(ship)
pygame.display.update()
clock.tick(10)
pygame.quit()
if __name__ == "__main__":
main()

Answer 1

To shoot bullets you usually create instances of a Bullet class and add them to a list, pygame.sprite.Group or another container. Then you iterate over this container and call the update method of the bullet in which its position is changed. To blit the images of the sprites/objects you iterate again over the container and just blit the images onto the screen. With sprite groups you can just call sprite_group.update() and sprite_group.draw(screen) instead of iterating yourself. BTW, pygame sprites have to have a self.image attribute not a self.picture in order to work with sprite groups (take a look at Program Arcade Games for more information).
I started to modify a few things in your example to show you how to use sprite groups, but then ended up changing your whole Screen class into a Game class (which I recommend to use in the future).
import sys
import pygame
class Game:
def __init__(self):
self.done = False
self.screen_width = 800
self.screen_height = 600
self.image = pygame.Surface((800, 600))
self.image.fill((30, 40, 50))
self.screen = pygame.display.set_mode(
(self.screen_width, self.screen_height))
# all_sprites is used to update and draw all sprites together.
self.all_sprites = pygame.sprite.Group()
# You'll probably need a separate bullet_group
# later for collision detection with enemies.
self.bullet_group = pygame.sprite.Group()
self.ship = Ship()
self.all_sprites.add(self.ship)
bullet = Bullet(self.ship)
self.bullet_group.add(bullet)
self.all_sprites.add(bullet)
def handle_events(self):
keys = pygame.key.get_pressed()
if keys[pygame.K_LEFT]:
self.ship.rect.centerx -= 5
if keys[pygame.K_RIGHT]:
self.ship.rect.centerx += 5
if keys[pygame.K_UP]:
self.ship.rect.centery -= 5
if keys[pygame.K_DOWN]:
self.ship.rect.centery += 5
for event in pygame.event.get():
if event.type == pygame.QUIT:
self.done = True
elif event.type == pygame.KEYDOWN:
if event.key == pygame.K_ESCAPE:
self.done = True
if event.key == pygame.K_SPACE:
bullet = Bullet(self.ship)
self.bullet_group.add(bullet)
self.all_sprites.add(bullet)
def update(self):
# Calls `update` methods of all contained sprites.
self.all_sprites.update()
def draw(self):
self.screen.blit(self.image, (0, 0))
self.all_sprites.draw(self.screen) # Draw the contained sprites.
pygame.display.update()
class Ship(pygame.sprite.Sprite):
def __init__(self):
pygame.sprite.Sprite.__init__(self)
self.image = pygame.Surface((20, 30))
self.image.fill((50, 170, 230))
# A nicer way to set the start pos with `get_rect`.
self.rect = self.image.get_rect(center=(400, 500))
class Bullet(pygame.sprite.Sprite):
def __init__(self, ship):
pygame.sprite.Sprite.__init__(self)
self.image = pygame.Surface((7, 7))
self.image.fill((230, 140, 30))
self.rect = self.image.get_rect()
self.rect.centerx = ship.rect.centerx
self.rect.centery = ship.rect.centery - 25
def update(self):
self.rect.y -= 5 # Move up 5 pixels per frame.
def main():
pygame.init()
pygame.display.set_caption('Space Game')
clock = pygame.time.Clock()
game = Game()
while not game.done:
game.handle_events()
game.update()
game.draw()
clock.tick(30)
if __name__ == '__main__':
main()
pygame.quit()
sys.exit()