Why is my player animation still happening when I am not moving?

Question

I have it so that my character will play a walking animation when they move left or right, and when they stop moving they are idle. The animation part works fine, but when I let go of left/right, it still plays and the player never goes idle. The code for my player animation and player controls are below.

def animation_state():
    global player_surface, player_index, player_rect
    

    player_index += 0.15
    if player_index >= len(player_right_walk):
        player_index = 0
    
    if LEFT == True:
        player_surface = player_left_walk[int(player_index)]
    elif RIGHT == True:
        player_surface = player_right_walk[int(player_index)]


    if LEFT == False and RIGHT == False:
        player_surface = pygame.image.load('graphics/dino_idle_right.png').convert_alpha()
    
    if event.type == pygame.KEYUP:
        if event.key == pygame.K_LEFT:
            player_surface = pygame.image.load('graphics/dino_idle_left.png').convert_alpha()
        elif event.key == pygame.K_RIGHT:
            player_surface = pygame.image.load('graphics/dino_idle_right.png').convert_alpha()

    
    screen.blit(player_surface,player_rect)

player control
def player_control():
    global LEFT, RIGHT
    player_velocity = 0
    player_gravity = 0
    

    player_gravity += 3
    player_rect.y += player_gravity
    if player_rect.bottom >= 500:
        player_rect.bottom = 500
    
    keys = pygame.key.get_pressed()

    if keys[pygame.K_LEFT]:
        player_velocity -= 11
        LEFT = True
        RIGHT = False
        if player_rect.x < -50:
            player_rect.x = 800
    elif keys[pygame.K_RIGHT]:
        player_velocity += 11
        LEFT = False
        RIGHT = True
        if player_rect.x > 800:
            player_rect.x = -50

        
    if event.type == pygame.KEYUP:
        if event.key == pygame.K_LEFT or pygame.K_RIGHT:
                player_velocity = 0

    player_rect.x += player_velocity

Answer 1

Because you do not reset LEFT and RIGHT if no key is pressed. Set LEFT and RIGHT to False before checking the keys. Set LEFT or RIGHT depending on the key that is pressed:

def player_control():
    # [...]

    keys = pygame.key.get_pressed()

    LEFT = False
    RIGHT = False
    if keys[pygame.K_LEFT]:
        player_velocity -= 11
        LEFT = True
        if player_rect.x < -50:
            player_rect.x = 800
    elif keys[pygame.K_RIGHT]:
        player_velocity += 11
        RIGHT = True
        if player_rect.x > 800:
            player_rect.x = -50