local variable 'x' referenced before assignment, but x = 0

Question

I am making game in pygame, but when I call update() function for zombie class it says UnboundLocalError: local variable 'x' referenced before assignment but x is = 0, and if I call update from Zombie init function it says NameError: name 'update' is not defined

class Zombie:
    x = 0
    y = 0
    movX = 0

    def movStop(self):
        movX = 0

    def update(self):
        x += movX

    def movX(self):
        movX = -2

    def __init__(self, _x, _y):
        x, y = _x, _y
        image = pygame.image.load('zombie.png')
        win.blit(image, (x, y))

def main():
    # init window
    pygame.display.set_caption(title)
    pygame.init()
    clock = pygame.time.Clock()

    # game loop and user input
    isClosed = False
    while not isClosed:
        for event in pygame.event.get():
            if event.type == pygame.QUIT: # check if exit button is pressed
                isClosed = True
            # user input
            # render
            win.fill(green)
            zomb = Zombie(50,50)
            if event.type == pygame.KEYDOWN:
                if event.key == pygame.K_a:
                    zomb.movX()
            if event.type == pygame.KEYUP:
                if event.key == pygame.K_a:
                    movStop()
            zomb.update()
            geWrite('health', 40, 20, 20)
            # redisplay
            pygame.display.update()
            clock.tick(120)
    pygame.quit()
    quit()

Answer 1

x is local variable. You have to use self.x , self.y , self.movX in class method.

Your class could look like this

class Zombie:

    def __init__(self, x=0, y=0):

        self.mov_x = 0

        self.image = pygame.image.load('zombie.png')
        self.rect = self.image.get_rect()

        self.rect.x = x
        self.rect.y = y

        # or in one line
        # self.rect = self.image.get_rect(x=x, y=y)

    def draw(self, surface)
        surface.blit(self.image, self.rect)

    def movStop(self):
        self.mov_x = 0

    def update(self):
        self.x += self.mov_x

    def movX(self):
        self.mov_x = -2

I use rect ( pygame.Rect() ) because it useful - you can get rect.center , rect.right and some pygame classes need it to draw elements - see pygame.sprite.Group.draw .

You can't have variable movX and method movX at the same time.