How to make sprites from sheet transparent?

Question

Python

Help make sprites transparent when moving
I have sprites in a list, I can't make sprites transparent

import pygame

pygame.init()
x = 50
y = 530
speed = 5
screen_width = 1200
screen_height = 600
clock = pygame.time.Clock()
screen = pygame.display.set_mode((screen_width, screen_height))
playerstop = pygame.image.load('images/playerstop.png')
playerleft = [(pygame.image.load('images/playerleft1.png')), (pygame.image.load('images/playerleft2.png')), (pygame.image.load('images/playerleft3.png'))]
playerright = [(pygame.image.load('images/playerright1.png')), (pygame.image.load('images/playerright2.png')), (pygame.image.load('images/playerright3.png'))]
bg = pygame.transform.smoothscale(pygame.image.load('images/background3.jpg'), (screen_width, screen_height))

class Player():
    def __init__(self, x, y, width, height):
        self.screen = screen
        self.back = bg
        self.cord = self.back.get_rect()
        self.cord.x = 0
        self.cord.y = 0
        self.x = x
        self.y = y
        self.screen = screen
        self.width = width
        self.height = height
        self.val = 4
        self.left = False
        self.right = False
        self.playerstop = playerstop
        self.playerstop.set_colorkey((255, 255, 255))
        self.playerstop = True
        self.animCount = 0

    def draw(self, screen):
        self.screen.blit(self.back, self.cord)
        if self.animCount + 1 >= 15:
            self.animCount = 0

        if not self.playerstop:
            if self.left:
                screen.blit(playerleft[self.animCount // 5], (self.x, self.y))
                self.animCount += 1
            elif self.right:
                screen.blit(playerright[self.animCount // 5], (self.x, self.y))
                self.animCount += 1
        else:
            screen.blit(playerstop, (self.x, self.y))

    def move(self):
        key = pygame.key.get_pressed()
        if key[pygame.K_d]:
            self.x += self.val
            self.left = False
            self.right = True
            self.playerstop = False
        elif key[pygame.K_a]:
            self.x -= self.val
            self.left = True
            self.right = False
            self.playerstop = False
        else:
            self.playerstop = True

man = Player(0, 530, 1200, 600)

run = True
while run:
    clock.tick(40)
    screen.fill((0, 0 ,0))
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            run = False

    man.draw(screen)
    man.move()
    pygame.display.update()

Who is not difficult to write please
Thank you