Can anyone tell me why this png keeps creating a clone every time it hits a boundary?

user_18403979 0
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So Im really new to pygame and trying to recreate space invaders. This is just the code for the enemy, can anyone tell me why it keep messing up whenever it hits a boundary? Im using pycharm to code this btw.

import pygame
screen = pygame.display.set_mode((800, 600))
pygame.init()
enemyIMG = pygame.image.load("ufo (2).png")
enemyX = 360
enemyY = 50
enemyY_change = 40
enemyX_change = 0.3


def enemy(x, y):
    screen.blit(enemyIMG, (x, y))


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

    enemyX += enemyX_change
    if enemyX <= 0:
        enemyY += enemyY_change
        enemyX_change = 0.3
    elif enemyX >= 736:
        enemyY += enemyY_change
        enemyX_change = -0.3
    enemy(enemyX, enemyY)
    pygame.display.update()

I was trying to make the alien hit a boundary then go down 40 pixels, then go the other way. But instead, it created a clone of its self and stayed there while the other clone continued as normal.

pygame python
1 Answers

The entire scene is redrawn in every frame. Therefor you have to clear the display in every frame:

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

    enemyX += enemyX_change
    if enemyX <= 0:
        enemyY += enemyY_change
        enemyX_change = 0.3
    elif enemyX >= 736:
        enemyY += enemyY_change
        enemyX_change = -0.3

    # clear display
    screen.fill((0, 0, 0))       # <-- this is missing

    # draw scene
    enemy(enemyX, enemyY)

    # update display
    pygame.display.update()

The typical PyGame application loop has to:

user_55777650
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