how to storage old shape on screen in pygame

Question

while messing with draw fuction i came up with a question can i make a list of shape then draw all of them and add more shape to list in pygame? for example there are 3 shape i want to draw all 3 shape then i add th4 shape in the list while on display screen. My try is to use for in code like this

for shape in shapes:
   pygame.draw.rect(surface, color, shape)

i also try to use pygame.draw.rect(surface,color,shape for shape in shapes) but i got no luck

you wanna add a shape in the shapes list while the for loop is running? — marick, Jan 19 '23 at 08:51

score 1 · Answer 1 · answered Jan 19 '23 at 12:44

You shouldn't change a list while you're iterating though it. Trying to create fancy list comprehensions is unlikely to help you especially if you're learning. If you're still really keen, look up the build in function map() instead on how to apply a function to an iterable.

Here is an example that adds random rectangles to a list on mouse-clicks and then draws them all:

import random
import pygame

WIDTH = 640
HEIGHT = 480
FPS = 30

pygame.init()
window = pygame.display.set_mode((WIDTH, HEIGHT))
shapes = []
clock = pygame.time.Clock()
running = True
while running:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False
        elif event.type == pygame.MOUSEBUTTONUP:
            x = random.randint(0, WIDTH - 1)  # randint includes endpoints
            y = random.randint(0, HEIGHT - 1) 
            shape = pygame.Rect(x, y, random.randint(20, 100), random.randint(20, 100))
            shapes.append(shape)
    # draw surface - fill background
    window.fill(pygame.color.Color("grey"))
    ## draw shapes
    for shape in shapes:
        pygame.draw.rect(window, "firebrick", shape)
    # show surface
    pygame.display.update()
    # limit frames
    clock.tick(FPS)
pygame.quit()

If you run this code and click a few times, note that the scroll wheel can generate lots of clicks, you'll see something like this:

If you want to do things more complicated, for example, make each rectangle a different color you can create sprites to control your shapes and store information and sprite groups to easily control them. Here's an example.

how to storage old shape on screen in pygame

1 Answers1