python - I made a border in this pong game, but the paddles can cross it. How do I stop that?

Question

I made a border in this pong game, and the paddles on the screen can cross it. I have done this before in another piece of code, but everything's different now. I have a main idea of how to do it, you probably need an if statement, but I don't have everything.

You can delete "pygame.load.image()" because you need the image with the code in a folder, so you can delete it. It will be better because you can try it out on your python

#import modules
import pygame 
pygame.init()
#setting the variables for the window
WIDTH = 750
HEIGHT = 500
#making the window
win = pygame.display.set_mode((WIDTH, HEIGHT))
pygame.display.set_caption("Pong Game")
#setting the most important variables
dest = (0, 0)
dest2 = (200, 200)
dest3 = (200, 50)
white = (255, 255, 255)
black = (0, 0, 0) 
green = (0, 255, 0)
red = (255, 0, 0)
yellow = (255, 255, 222)
#load the images
image = pygame.image.load("birdupbg.png")
image2 = pygame.image.load("birdup.png")
#making the paddle class
class Paddle(pygame.sprite.Sprite):
    def __init__(self):
        pygame.sprite.Sprite.__init__(self)
        self.image = pygame.Surface([10, 75])
        self.image.fill(yellow)
        self.rect = self.image.get_rect()
        self.points = 0
#making the ball class
class Ball(pygame.sprite.Sprite):
    def __init__(self):
        pygame.sprite.Sprite.__init__(self)
        self.image = pygame.Surface([10, 10])
        self.image.fill(red)
        self.rect = self.image.get_rect()
        self.speed = 15 
        self.dx = 1
        self.dy = 1
        self.dx2 = 1
        self.dy2 = 1
#making the paddles
paddle1 = Paddle()
paddle1.rect.x = 25
paddle1.rect.y = 100

paddle2 = Paddle()
paddle2.rect.x = 715
paddle2.rect.y = 225


paddle3 = Paddle()
paddle3.rect.x = 715
paddle3.rect.y = 100

paddle4 = Paddle()
paddle4.rect.x = 25
paddle4.rect.y = 225
#paddle speed
paddle_speed = 50

pong = Ball()
pong.rect.x = 375
pong.rect.y = 250

ball = Ball()

all_sprites = pygame.sprite.Group()
all_sprites.add(paddle1, paddle2, paddle3, paddle4, pong)

#drawing the score and the word "pong" 
def redraw():
    win.fill(black)
    win.blit(image, dest)
    pygame.draw.line(win, (255, 255, 255), [0, 200], [900, 200], 10)
    font = pygame.font.SysFont("impact", 40)
    text = font.render("PONG", False, white)
    textRect = text.get_rect()
    textRect.center = (750//2, 25)
    win.blit(text, textRect)


    p1_score = font.render(str(paddle1.points), False, white)
    p1Rect = p1_score.get_rect()
    p1Rect.center = (50, 50)
    win.blit(p1_score, p1Rect)

    p2_score = font.render(str(paddle2.points), False, white)
    p2Rect = p2_score.get_rect()
    p1Rect.center = (700, 50)
    win.blit(p2_score, p1Rect)
    
    all_sprites.draw(win)
    pygame.display.update()
#what happens when the window runs
run = True

while run:
    pygame.time.delay(100)

    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            run = False
    #if a certain key is pressed, move something
    key = pygame.key.get_pressed()
    if key[pygame.K_w]:
        paddle1.rect.y += -paddle_speed
    if key[pygame.K_s]:
        paddle1.rect.y +=  paddle_speed
    if key[pygame.K_UP]:
        paddle2.rect.y += -paddle_speed
    if key[pygame.K_DOWN]:
        paddle2.rect.y +=  paddle_speed
    if key[pygame.K_i]:
        paddle3.rect.y += -paddle_speed
    if key[pygame.K_j]:
        paddle3.rect.y += paddle_speed
    if key[pygame.K_1]:
        paddle4.rect.y += -paddle_speed
    if key[pygame.K_2]:
        paddle4.rect.y += paddle_speed
    pong.rect.x += pong.speed * pong.dx
    pong.rect.y += pong.speed * pong.dy
    #scoring system
    if pong.rect.y > 480:
        pong.dy = -1
    if pong.rect.x > 735:
        pong.rect.x, pong.rect.y = 375, 250
        pong.dx = -1
        paddle1.points += 1
        if pong.rect.y < -1:
            pong.dy = 1

    if pong.rect.x < 10:
        pong.rect.x, pong.rect.y = 375, 250
        pong.dx = 1
        paddle2.points += 1

    #if the ball and paddle collide, bounce off it
    if paddle1.rect.colliderect(pong.rect):
        pong.dx = 1
    if paddle2.rect.colliderect(pong.rect):
        pong.dx = -1
    if paddle1.rect.colliderect(pong.rect):
        pong.dx = 1
    if paddle3.rect.colliderect(pong.rect):
        pong.dx = -1
    if paddle4.rect.colliderect(pong.rect):
        pong.dx = 1
    #Call the redraw function
    redraw()  
    #update the window and quit it
    pygame.display.flip()
pygame.quit()

Answer 1

PyGame has a feature that does exactly what you want it to do. Use pygame.Rect objects and pygame.Rect.clamp() respectively pygame.Rect.clamp_ip():

Returns a new rectangle that is moved to be completely inside the argument Rect.

With this function, an object can be kept completely in the window. Get the window rectangle with get_rect and clamp the object in the window:

while run:
    # [...]

    key = pygame.key.get_pressed()
    if key[pygame.K_w]:
        paddle1.rect.y += -paddle_speed
    
    # [...]
    
    winRect = win.get_rect()
    paddle1.rect.clamp_ip(winRect)
    paddle2.rect.clamp_ip(winRect)
    paddle3.rect.clamp_ip(winRect)
    paddle4.rect.clamp_ip(winRect)

    # [...]