rain.py

import pygame
from pygame.sprite import Sprite

class Rain(Sprite):
    def __init__(self, ai_game):
        super().__init__()
        self.screen = ai_game.screen
        self.settings = ai_game.settings

        # Load the alien image and set its rect attribute.
        self.image = pygame.image.load('images/drop.bmp')
        self.rect = self.image.get_rect()

        # Start each new alien near the top left of the screen.
        self.rect.x = self.rect.width
        self.rect.y = self.rect.height

        # Store the alien's exact horizontal position
        self.x = float(self.rect.x)
        self.y = float(self.rect.y)


    def check_bottom(self):
        screen_rect = self.screen.get_rect()
        if self.rect.bottom >= screen_rect.bottom:
            self.y = 0

    def update(self):
        self.y += self.settings.rain_fall_speed
        self.rect.y = self.y