python 键盘上下左右控制

bif="1.jpg"mif="2.jpg"import pygame,sysfrom pygame.locals import *pygame.init()screen=pygame.display.set_mode((640,360),0,32)background=pygame.image.load(bif).convert()mouse_c=pygame.image.load(mif).convert_alpha()x,y=0,0movex,movey=0,0while True:    for event in pygame.event.get():        if event.type ==QUIT:            pygame.quit()            sys.exit()        if event.type==KEYDOWN:            if event.key==K_LEFT:                movex=-1            if event.key==K_RIGHT:                movex=+1            elif event.key==K_UP:                movey=-1            elif event.key==K_DOWN:                movey=+1        if event.type==KEYUP:            if event.key==K_LEFT:                movex=0            if event.key==K_RIGHT:                movex=0            elif event.key==K_UP:                movey=0            elif event.key==K_DOWN:                movey=0    x+=movex    y+=movey        screen.blit(background,(0,0))    screen.blit(mouse_c,(x,y))        pygame.display.update()