in my game, up and down movements are working properly but left and right are not for the same piece of code . what to do?

Question

in my game, up and down movements are working properly but left and right are not for the same piece of code . what to do? in python pygame program and this problem occurs in 2nd level of game like maze runner. also after deletion any key like up ,down it's work abnormally.

while not done:

for event in pygame.event.get():
    if event.type == pygame.QUIT:
        done = True

    elif event.type == pygame.KEYDOWN:
        if event.key == pygame.K_LEFT:
            player.changespeed(-3, 0)
        elif event.key == pygame.K_RIGHT:
            player.changespeed(3, 0)
        elif event.key == pygame.K_UP:
            player.changespeed(0, -3)
        elif event.key == pygame.K_DOWN:
            player.changespeed(0, 3)

    elif event.type == pygame.KEYUP:
        if event.key == pygame.K_LEFT:
            player.changespeed(3, 0)
        elif event.key == pygame.K_RIGHT:
            player.changespeed(-3, 0)
        elif event.key == pygame.K_UP:
            player.changespeed(0, 3)
        elif event.key == pygame.K_DOWN:
            player.changespeed(0, -3)

all_sprite_list.update()

screen.fill(BLACK)

all_sprite_list.draw(screen)