NameError: global name 'self' is not defined i cant fix this

Question

import pygame, random
pygame.init()

screen = pygame.display.set_mode((640, 480))

class Ship(pygame.sprite.Sprite):
    def __init__(self):
        pygame.sprite.Sprite.__init__(self)
        self.screen = screen
        self.image = pygame.image.load("ship.jpg")
        self.image = self.image.convert()
        self.rect = self.image.get_rect()
        self.rect.center = (320, 400)
        self.dx = 0 
        self.dy = 0
        self.x = self.rect.centerx
        self.y = self.rect.centery      

    def update(self):
        self.checkBounds()

    def checkBounds(self):
        screen = self.screen
        if self.x > screen.get_width():
            self.x = screen.get_width()
        if self.x < 0:
            self.x = 0


class Missile(pygame.sprite.Sprite):
    def __init__(self):
        pygame.sprite.Sprite.__init__(self)
        self.image = pygame.image.load("missile.jpg")
        self.image = self.image.convert()
        self.rect = self.image.get_rect()
        self.reset()

    def update(self):
        self.rect.centery += self.dy
        if self.rect.top > screen.get_height():
            self.reset()

    def reset(self):
        self.rect.bottom = 0
        self.rect.centerx = random.randrange(0, screen.get_width())
        self.dy = random.randrange(5, 10)


def main():
    background = pygame.Surface(screen.get_size())

    background.fill((0, 0, 0))
    screen.blit(background, (0, 0))
    ship = Ship()
    missile = Missile()

    allSprites = pygame.sprite.Group(missile, ship)
    clock = pygame.time.Clock()
    keepGoing = True
    while keepGoing:
        clock.tick(30)
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                keepGoing = False
            elif event.type == pygame.KEYDOWN:
                if event.key == pygame.K_LEFT:
                    ship.rect.centerx = ship.rect.centerx-10
                elif event.key == pygame.K_RIGHT:
                    ship.rect.centerx = ship.rect.centerx + 10
                elif event.type == pygame.KEYUP:
                    ship.rect.centerx = ship.rect.centerx + 0
                elif event.key == pygame.K_DOWN:
                    ship.rect.centerx = ship.rect.centerx - 0
        if pygame.sprite.collide_rect(ship,missile) == True:
            self.image = pygame.image.load("explosion.jpg")

        allSprites.clear(screen, background)
        allSprites.update()
        allSprites.draw(screen)

        pygame.display.flip()
    pygame.quit()


if __name__ == "__main__":
    main()

Answer 1

self.image = pygame.image.load("explosion.jpg")

This line is not part of any class. There is no self here. I guess you mean

ship.image = pygame.image.load("explosion.jpg")

or something similar. Might as well be

missile.image = pygame.image.load("explosion.jpg")