[PyGame] object's movement to left leave shadow on the screen

[nilamo]

Look closely at that, and try to rethink how you can do it.
That inner-while loop is drawing the player over and over in multiple places, without ever clearing the screen. That's why you have the shadow... you never clear the screen.

In general, if you have the line pygame.display.update() in more than one place, there's probably a better way to organize your code.

For example, if you use a direction/velocity variable to keep track of which direction it should be moving (instead of a hardcoded +0.2 at the start of your event loop), you can just change the direction. Something like this (I don't have your images, so I changed the player to a white box):

import pygame 
pygame.init()
screen=pygame.display.set_mode((800,600)) 
 
pygame.display.set_caption('visual rhythm')
#icon=pygame.image.load("song.png")
#pygame.display.set_icon(icon)
 
#playerImg=pygame.image.load('spaceship.png')
playerImg = pygame.Surface((10, 10))
playerImg.fill((255, 255, 255))

playerX=370
playerY=400
def player(x,y):
    screen.blit(playerImg,(x,y))
 
directionX = 0.2
running=True
while running:
    screen.fill((0,255,0))
     
    for event in pygame.event.get():
        if event.type==pygame.QUIT:
            running=False
    playerX += directionX
    player(playerX,playerY)
    if playerX<=0:
        directionX = 0.2
        player(playerX,playerY)
    elif playerX>=746:
        directionX = -0.2
    pygame.display.update()