Why is param moveY not apearing? Pygame update method

Question

I'm trying to play around with pygame and I can draw an image as a sprite on the screen. I'm trying to move the sprite around with WASD by changing the x and y variables.

When I run the program, the sprite draws but doesn't move when I press the correct keys.

EDIT: I added an update method and the moveY param is saying it is not there, even though it clearly is, why is this?

Here's the code:

import pygame
pygame.init()

screen = pygame.display.set_mode((750, 750))

BLACK = (0, 0, 0)
WHITE = (255,255,255)
RED = (255,0,0)

class Sprite(pygame.sprite.Sprite):
    def __init__(self, pos):
        super(Sprite, self).__init__()
        self.image = demon
        self.pos = [x,y]
        self.rect = self.image.get_rect(center = pos)
    def update(self, moveX, moveY):
        pygame.sprite.Sprite.update(self)
        moveXY = [moveX,moveY]
        
        Sprite.pos[x] += moveXY[moveX]
        Sprite.pos[y] += moveXY[moveY] 
        
        

        
        
all_sprites_list = pygame.sprite.Group()

demon = pygame.image.load("C:/programming/doomman/cacodemon.png").convert_alpha()

x = 300
y = 300

my_sprite = Sprite((x, y))
all_sprites_list.add(my_sprite)
clock = pygame.time.Clock()
pygame.display.set_caption("Demon Dance")
carryOn = True
        
while carryOn == True:
    keys = pygame.key.get_pressed()
    
    for event in pygame.event.get():
            if event.type==pygame.QUIT:
                carryOn=False
            elif event.type == pygame.KEYDOWN:
                if keys[pygame.K_w]:
                    Sprite.update(0, 50)
                if keys[pygame.K_s]:
                    Sprite.update(0, -50)
                if keys[pygame.K_d]:
                    Sprite.update(50, 0)
                if keys[pygame.K_a]:
                    Sprite.update(-50, 0)
                    
    
    
    pygame.display.flip()
    clock.tick(60)
    all_sprites_list.draw(screen)

I'm not familiar with the pygame API, but integers in Python are passed by value (sort of), meaning that here: my_sprite = Sprite((x, y)) x and y are copied to the function. That means that when you change the value of x or y it doesnt get reflected in my_sprite. Is there a method for modifying the sprite object directly? — lvrf
Looks like you can define an update method for the sprite. I would recommend looking into that and modifying your x and y coords by calling said method: pygame.org/docs/ref/sprite.html#pygame.sprite.Sprite — lvrf
I've added an update method, still isn't working, will update question — user13668033

Rabbid76 Rabbid76 · Accepted Answer · 2021-01-25T05:40:19

See pygame.sprite.Group.draw:

Draws the contained Sprites to the Surface argument. This uses the Sprite.image attribute for the source surface, and Sprite.rect for the position.

Therefore you need to update the rect attribute after changing the position (pos) of the Sprite:

class Sprite(pygame.sprite.Sprite):
    def __init__(self, pos):
        super(Sprite, self).__init__()
        self.image = demon
        self.pos = [pos[0], pos[1]]
        self.rect = self.image.get_rect(center = pos)
    
    def update(self, moveX, moveY):
        Sprite.pos[x] += moveX
        Sprite.pos[y] += moveY 
        self.rect = self.image.get_rect(center = pos)

You don't actually need the pos attribute at all. You can move the Sprite by changing the position stored in rect:

class Sprite(pygame.sprite.Sprite):
    def __init__(self, pos):
        super(Sprite, self).__init__()
        self.image = demon
        self.rect = self.image.get_rect(center = pos)
    
    def update(self, moveX, moveY):
        self.rect.x += moveX
        self.rect.y += moveY

Additionally update is an instance method. You need to call it with the object instead of the class:

if keys[pygame.K_w]:
    my_sprite.update(0, 50)
if keys[pygame.K_s]:
    my_sprite.update(0, -50)
if keys[pygame.K_d]:
    my_sprite.update(50, 0)
if keys[pygame.K_a]:
    my_sprite.update(-50, 0)

Why is param moveY not apearing? Pygame update method

1 Answers