Simple rainfall animation in Pygame

Question

I made the following code. It's a simple animation of 'raindrops' falling and splattering once they reach the ground. The images I use can be found here: https://i.sstatic.net/oKOVA.jpg

import pygame, sys
from pygame import locals 
import random
import itertools
def listenToQuit():
 for event in pygame.event.get():
 if event.type == locals.QUIT:
 pygame.quit()
 sys.exit()
def makeNewDrop(display, drops):
 # there isa 15% chance we'll make a new drop, each frame
 x = display.get_width() * random.random() # a random xpostion
 return RainDrop(x, display, drops) 
class RainDrop(pygame.sprite.Sprite):
 img = pygame.image.load('assests/rain_drop.png')
 def __init__(self, x, display, group):
 # call the super constructor, and pass in the 
 # group you've created and it is automatically added to the group every 
 # time you create an instance of this class
 pygame.sprite.Sprite.__init__(self, group) 
 self.y = 0
 self.x = x
 self.fall_step = 5
 self.display = display
 self.die = False
 self. animation = iter([
 pygame.image.load('assests/splatter_1.png'),
 pygame.image.load('assests/splatter_2.png'),
 pygame.image.load('assests/splatter_3.png'),
 pygame.image.load('assests/splatter_4.png')
 ])
 def update(self):
 self.checkIfShouldDie()
 self.fall()
 if self.die:
 try:
 self.img = next(self.animation)
 except StopIteration:
 self.kill()
 self.display.blit(self.img, (self.x,self.y))
 def fall(self):
 self.y = self.y + self.fall_step
 def checkIfShouldDie(self):
 if self.img.get_rect().bottom + self.y >= self.display.get_height():
 self.die = True
 self.y = self.display.get_height() - self.img.get_rect().bottom - 5
if __name__ == '__main__':
 pygame.init()
 drops = pygame.sprite.Group()
 cooldown = 0
 fps = 30
 clock = pygame.time.Clock()
 main_display = pygame.display.set_mode((400,400),0,32)
 pygame.display.set_caption("rain!") 
 while True:
 main_display.fill((255,255,255))
 if random.random() >= 0.85 and cooldown == 0:
 # a 15% change we'll make a new drop, each frame
 # assuming we didn't make a drop in the last few frames
 drop = makeNewDrop(main_display, drops) # automatically added to the drops group
 cooldown = cooldown + 5
 drops.update()
 # reduce cooldown
 cooldown = 0 if cooldown <= 0 else cooldown - 1
 listenToQuit()
 pygame.display.update()
 clock.tick(30)

How can this code be improved? Specifically the part where I iterator over animations and catch the StopIteration error seems very hacky to me.

Answer 1

PEP8

The official Python style guide will suggest that:

• there be two newlines between functions at the global scope, and only one newline between functions in the class scope (i.e. check_if_should_die)
• functions be named in lower_snake_case, i.e. listen_to_quit

Hard exit

Currently, you have a forever-loop that only exits on sys.exit. Instead, simply return a boolean from listenToQuit (which can be called should_quit), and if the return value is true, break out of the loop.

Abbreviated imports

pygame.sprite.Sprite can just be Sprite if you from pygame.sprite import Sprite.

Typo

assests -> assets

Generator

 self. animation = iter([
 pygame.image.load('assests/splatter_1.png'),
 pygame.image.load('assests/splatter_2.png'),
 pygame.image.load('assests/splatter_3.png'),
 pygame.image.load('assests/splatter_4.png')
 ])

can be

self.animation = iter(
 pygame.image.load(f'assets/splatter_{i}.png')
 for i in range(1, 5)
)

Generally I don't think your iter/StopIteration approach is that bad. That said, you can rework it by changing your outer while True into a for drop in drops, where drops is an iterable through four instances of a drop object tied to a specific asset.

• Mitchell van Zuylen: Quick question just to be sure I understand: The last suggestion of for drop in drops would work for an animation functionality, but this would not work if I would want this animation to only be the backdrop, and later add more functionality such as listening to keyboard input etc? Thanks for the detailed answer! It's very useful