当我不按按钮时，为什么我的图像消失了？

Question

The code funs fine and my images flip as they should, but when I am not pressing a key, my image disappears...I know this has to do with when the screen.blit method is called during each 'if' statement in the update function, but I don't know how to get around this...

 import pygame, sys, glob
from pygame import *

h=400
w=800

screen = pygame.display.set_mode((w,h))

clock = pygame.time.Clock()

class player:
    def __init__(self):
        self.x = 200
        self.y = 300

        self.ani_speed_init = 8
        self.ani_speed=self.ani_speed_init

        self.Lani_speed_init = 8
        self.Lani_speed=self.Lani_speed_init

        self.ani = glob.glob("D:\Projects\pygame\TestGame\sprite*.png")
        self.Lani = glob.glob("D:\Projects\pygame\TestGame\Lsprite*.png")

        self.ani.sort()
        self.ani_pos=0

        self.Lani.sort()
        self.Lani_pos=0
        #takes length of the amount of images and subtracts 1 since count starts at 0
        self.ani_max=len(self.ani) -1
        self.Lani_max=len(self.Lani) -1

        self.img = pygame.image.load(self.ani[0])
        self.Limg = pygame.image.load(self.Lani[0])

        self.update(0, 0)

    def update(self, pos, posL):

        if pos != 0:
            #subtracts 1 from 10
            self.ani_speed-=1
            #adds self.x to itself
            self.x+=pos
            if self.ani_speed==0:
                self.img = pygame.image.load(self.ani[self.ani_pos])
                self.ani_speed = self.ani_speed_init
                if self.ani_pos == self.ani_max:
                    self.ani_pos = 0
                else:
                    self.ani_pos+=1

            screen.blit(self.img,(self.x,self.y))

        if posL != 0:
            #subtracts 1 from 10
            self.Lani_speed-=1
            #adds self.x to itself
            self.x+=posL
            if self.Lani_speed==0:
                self.Limg = pygame.image.load(self.Lani[self.Lani_pos])
                self.Lani_speed = self.Lani_speed_init
                if self.Lani_pos == self.Lani_max:
                    self.Lani_pos = 0
                else:
                    self.Lani_pos+=1    

            screen.blit(self.Limg,(self.x,self.y))      

player1 = player()
pos = 0
posL = 0

while 1:
    screen.fill((255,255,255))
    clock.tick(60)

    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            sys.exit()
            pygame.quit()
        elif event.type == KEYDOWN and event.key == K_RIGHT:
            pos = 1

        elif event.type == KEYUP and event.key == K_RIGHT:
            pos = 0
        elif event.type == KEYDOWN and event.key == K_LEFT:
            posL = -1

        elif event.type == KEYUP and event.key == K_LEFT:
            posL = 0

    player1.update(pos, posL)
    pygame.display.update()

Answer 1

This is a suggestion rather than an answer as it's difficult to tell what you're trying to do but I need to format code so a comment isn't really useful. Would it work to extend the update function to have a default behaviour as follows:

def update(self, pos, posL):
    updated = False

    if pos != 0:
        (logic removed)
        screen.blit(self.img,(self.x,self.y))
        updated = True

    if posL != 0:
        (logic removed)
        screen.blit(self.Limg,(self.x,self.y))      
        updated = True

    if not updated:
        screen.blit(something sensible for arguments of 0,0)

You could avoid the 'updated' variable if you just tested for pos == 0 and posL == 0 but the updated test allows the logic above to possibly not do a screen.blit and the final test will ensure that something always gets written to the screen.

Answer 2

Rather than allowing the update function to blit player to the screen I would add player to the default pygame sprite group and draw it via the while loop! I would also avoid loading the image each update (due to overhead) and rather load all images at once and then blit them when needed!