Moving a Sprite in PyGame

Question

I'm currently working on a school project, but I'm stuck trying to get my sprite to move. My error message is saying that I'm missing 1 required positional argument: 'self' in Mario.handle_keys().

Here's my main code:

import pygame
import sys
from pygame.locals import*
from Mario import Mario
from Ladder import Ladder

pygame.init()
b = Mario([0, 800])
c = Ladder([600, 800])
game_over = False
dispwidth = 600
dispheight = 800
cellsize = 10
white = (255, 255, 255)
black = (0, 0, 0)
bg = white


def main():
    FPS = 30
    while not game_over:
        for event in pygame.event.get():
            if event.type == QUIT:
                pygame.quit()
                sys.exit()

        Mario.handle_keys()

        Mario.draw(screen)
        screen.fill(bg)
        screen.blit(b.image, b.rect)
        screen.blit(c.image, c.rect)
        pygame.display.update()
        fpstime.tick(FPS)

while True:
    global fpstime
    global screen

    fpstime = pygame.time.Clock()
    screen = pygame.display.set_mode((dispwidth, dispheight))
    pygame.display.set_caption('Donkey Kong')
    main()

And my sprite:

import pygame
from pygame.locals import*


class Mario(pygame.sprite.Sprite):
    image = None

    def __init__(self, location):
        pygame.sprite.Sprite.__init__(self)

        if Mario.image is None:

            Mario.image = pygame.image.load('mario3.png')
        self.image = Mario.image

        self.rect = self.image.get_rect()
        self.rect.bottomleft = location

        self.x = 0
        self.y = 0

    def handle_keys(self):

        keys_pressed = pygame.key.get_pressed()

        if keys_pressed[K_LEFT]:
            self.x -= 5

        if keys_pressed[K_RIGHT]:
            self.y += 5

    def draw(self, surface):

        surface.blit(self.image, (self.x, self.y))

Thanks in advance.

I appreciate any advice!

Answer 1

Mario is a class. The method handle_keys(self) is an instance method -- meaning it can only be called against an Mario instance. (It is possible to have a classmethod , but that's not what you want here since you need to modify self .)

At the top you made a b = Mario([0, 800]) -- I'd change b to mario everywhere and c to ladder .

 mario = Mario([0, 800])

Then instead of Mario.handle_keys() you would use mario.handle_keys() .

More background:

When you call mario.handle_keys() what is actually happening underneath is more or less handle_keys(mario) . The object mario ends up being the argument self . Since you are attempting to call handle_keys on the class Mario instead, Python is complaining that nothing is being passed to handle_keys for the self parameter.

More off into the weeds:

If you define a class method, you would do it like this:

class Foo():
    @classmethod
    def my_class_method(cls):
        ...

You would call it Foo.my_class_method() , which would pass Foo to my_class_method as the cls parameter.