直到被击中才在pygame中出现敌人精灵

我正在像游戏一样入侵太空，一切都很好，但是自从我使用列表添加了多个敌人以来，他们的图像/精灵消失了，只在被击中一秒钟后才再次出现，然后又消失了一次。
我检查了图像文件是否正常，并且据我所知，此后也未发生任何异常情况，每当有敌人被击中时，分数总和就很好。
可能是什么问题？

import pygame
import random
import math
# Initializing pygame
pygame.init()
# Screen creation and config
screen = pygame.display.set_mode((1024,600))
# Background
background = pygame.image.load('court_level_bg.jpg')
# Title and Icon
pygame.display.set_caption("Space Invaders")
# Player config
player_img = pygame.image.load('Mini_Bibi.png')
playerX = 430
playerY = 480
playerX_change = 0
# Enemy config
enemy_img = []
enemyX = []
enemyY = []
enemyX_change = []
enemyY_change = []
num_enemies = 5
for i in range(num_enemies):
enemy_img.append(pygame.image.load('Enemy1.png'))
enemyX.append(random.randint(0,1024))
enemyY.append(random.randint(5,150))
enemyX_change.append(1.5)
enemyY_change.append(40)
# Bullet config
bullet_img = pygame.image.load('Weapon.png')
bulletX = 0
bulletY = 480
bulletX_change = 0
bulletY_change = 6
bullet_state = "ready"
score = 0
# Create player
def player(x,y):
screen.blit(player_img,(x,y))
# Create enemy
def enemy(x,y,i):
screen.blit(enemy_img[i],y))
def fire_bullet(x,y):
global bullet_state
bullet_state = "fire"
screen.blit(bullet_img,(x + 16,y + 10))
def isCollision(enemyX,enemyY,bulletX,bulletY):
distance = math.sqrt((math.pow(enemyX - bulletX,2)) + (math.pow(enemyY - bulletY,2)))
if distance <27:
return True
else:
return False
# Game Loop
scrn_stat = True
while scrn_stat:
# Screen RGB color config
screen.fill((0,0))
# Background image
screen.blit(background,(0,0))
for event in pygame.event.get():
if event.type == pygame.QUIT:
scrn_stat = False
# X axis Keystroke listening
if event.type == pygame.KEYDOWN:
if event.key == pygame.K_LEFT:
playerX_change = -4
if event.key == pygame.K_RIGHT:
playerX_change = 4
if event.key == pygame.K_SPACE:
if bullet_state is "ready":
bulletX = playerX
fire_bullet(bulletX,bulletY)
if event.type == pygame.KEYUP:
if event.key == pygame.K_LEFT or event.key == pygame.K_RIGHT:
playerX_change = 0
playerX += playerX_change
# Player boundaries
if playerX <= 0:
playerX_change = 0;
elif playerX >= 945:
playerX_change = 0;
# Enemy movement
for i in range(num_enemies):
enemyX[i] += enemyX_change[i]
if enemyX[i] <= 0:
enemyX_change[i] = 3
enemyY[i] += enemyY_change[i]
elif enemyX[i] >= 945:
enemyX_change[i] = -3
enemyY[i] += enemyY_change[i]
# Collision
collision = isCollision(enemyX[i],enemyY[i],bulletY)
if collision:
bulletY = 480
bullet_state = "ready"
score += 1
print(score)
enemyX[i] = random.randint(0,945)
enemyY[i] = random.randint(50,150)
enemy(enemyX[i],i)
# Bullet Movement
if bulletY <= 0:
bulletY = 480
bullet_state = "ready"
if bullet_state is "fire":
fire_bullet(bulletX,bulletY)
bulletY -= bulletY_change
player(playerX,playerY)
pygame.display.update()


enemy()，而不是仅在发生冲突的情况下。这是一个Indentation问题：

for i in range(num_enemies):
enemyX[i] += enemyX_change[i]
if enemyX[i] <= 0:
enemyX_change[i] = 3
enemyY[i] += enemyY_change[i]
elif enemyX[i] >= 945:
enemyX_change[i] = -3
enemyY[i] += enemyY_change[i]
# Collision
collision = isCollision(enemyX[i],enemyY[i],bulletX,bulletY)
if collision:
bulletY = 480
bullet_state = "ready"
score += 1
print(score)
enemyX[i] = random.randint(0,945)
enemyY[i] = random.randint(50,150)
#<--|
enemy(enemyX[i],i)