How can i make continous movement in pygame

Question

for event in pygame.event.get():
    if event.type == pygame.QUIT:
        pygame.quit()
        exit()
    if event.type == pygame.KEYDOWN:
        if event.key == pygame.K_a:
            x -= 10
        if event.key == pygame.K_d:
            x += 10
        if event.key == pygame.K_w:
            y -= 10
        if event.key == pygame.K_s:
            y += 10

if i hold down a key it only moves once how can i make it continous?