Simple game - Help with beginner problem

I'm trying to move the "ball" using the arrow keys but i can't figure out what i am doing wrong.

When i launch the game from terminal and the window pops up the "ball" is still, arrows does not work.

Can you help me solve this problem?

import pygame
import os

pygame.init()

size = width, height = 750, 422
screen = pygame.display.set_mode(size)

img_path = os.path.join('--folder--', 'ball.png')
background_image = pygame.image.load('--folder/background.png').convert()

pygame.display.set_caption("BallGame")

class Ball(object):
    def __init__(self):
        self.image = pygame.image.load(img_path)
        self.x = 0
        self.y = 0

    def handle_keys(self):
        key = pygame.key.get_pressed()
        dist = 5
        if key[pygame.K_DOWN]:
            self.y += dist # move down
        elif key[pygame.K_UP]:
            self.y -= dist # move up
        if key[pygame.K_RIGHT]:
            self.x += dist # move right
        elif key[pygame.K_LEFT]:
            self.x -= dist # move left

    def draw(self, surface):
        surface.blit(self.image, (self.x, self.y))

pygame.init()
screen = pygame.display.set_mode((750, 422))

ball = Ball()
clock = pygame.time.Clock()

running = True
while running:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            pygame.quit()
            running = False

    ball.handle_keys()

    screen.blit(background_image, [0, 0])
    ball.draw(screen)
    pygame.display.update()

    clock.tick(40)