My sprite continues to keep moving even after releasing the key in pygame

Question

My sprite continues to keep moving even after releasing the key. How can I stop the sprite from moving when I release an arrow key?

This is my Paddle sprite class. Here I gave the paddle a speed and the speed should be added to the sprite when the key is pressed.

#Paddle sprite
class Paddle(pygame.sprite.Sprite):
    def __init__(self):
        pygame.sprite.Sprite.__init__(self)
        self.image = pygame.Surface((90,20))
        self.image.fill(white)
        self.rect = self.image.get_rect()
        self.rect.centerx = (width//2)
        self.rect.bottom = height-15
        self.speedx = 0
     def update(self):
        keys = pygame.key.get_pressed()
        if keys[pygame.K_LEFT]:
            self.speedx = -5
        if keys[pygame.K_RIGHT]:
            self.speedx = 5
        self.rect.x+=self.speedx

I added all the sprites to a sprite group

#All elements of the game
all_sprites = pygame.sprite.Group()
paddle = Paddle()
all_sprites.add(paddle)

This is the mainloop. I think there's some kind of looping the addition of speed to the sprite but I can't find it.

#Game mainloop
run=True
while run:
    #FPS of gameplay
    clock.tick(fps)

    #Event mainloop
    for event in pygame.event.get():
        if event.type==pygame.QUIT:
           run=False

    #Updating all objects in the game
    all_sprites.update()

    #On screen
    wn.fill(black)
    all_sprites.draw(wn)

    pygame.display.flip()

pygame.quit()
run=True
while run:

    #Event mainloop
    for event in pygame.event.get():
        if event.type==pygame.QUIT:
           run=False

    #Updating all objects in the game
    all_sprites.update()

    #On screen
    wn.fill(black)
    all_sprites.draw(wn)

    pygame.display.flip()

    pygame.quit()

Answer 1

You've to reset the speed (self.speedx), if neither LEFT nor RIGHT is pressed:

class Paddle(pygame.sprite.Sprite):

    # [...]

    def update(self):
        keys = pygame.key.get_pressed()
        if keys[pygame.K_LEFT]:
            self.speedx = -5
        if keys[pygame.K_RIGHT]:
            self.speedx = 5

        if not keys[pygame.K_LEFT] and not keys[pygame.K_RIGHT]:
            self.speedx = 0

        self.rect.x+=self.speedx  

Because on each update call, the position still gets updated, and since the speed doesn't get reset, it keeps moving in the direction that it had set before.

---

Alternatively the speed can be set 0, at the begin of update:

class Paddle(pygame.sprite.Sprite):

    # [...]

    def update(self):

        self.speedx = 0

        keys = pygame.key.get_pressed()
        if keys[pygame.K_LEFT]:
            self.speedx = -5
        if keys[pygame.K_RIGHT]:
            self.speedx = 5

        self.rect.x+=self.speedx