bullet.py

import pygame
from pygame.sprite import Sprite

class Bullet(Sprite):
    """A class to manage bullets fired from the ship"""

    def __init__(self,ai_settings,screen,ship):
        """create a bullet object at ship's current position."""
        super().__init__()
        self.screen=screen

        #create a bullet rect at (0,0) and then set correct position.
        self.rect=pygame.Rect(0,0,ai_settings.bullet_width,ai_settings.bullet_height)
        self.rect.centerx=ship.rect.centerx
        self.rect.top=ship.rect.top

        #store the bullet's position as a decimal value.
        self.y=float(self.rect.y)

        self.color=ai_settings.bullet_color
        self.speed_factor=ai_settings.bullet_speed_factor

    def update(self):
        """move the bullet up the screen."""
        #update the decimal position of the bullet.
        self.y-=self.speed_factor
        #update the rect positon.
        self.rect.y=self.y

    def draw_bullet(self):
        """draw the bullet to the screen."""
        pygame.draw.rect(self.screen,self.color,self.rect)