Why does my game made with Pygame suddenly lag for a few seconds? [duplicate]

问题

I made a little space invaders game with pygame, I noticed that the game lags for a few seconds periodically. I do not know what the problem is. I am a beginner. Can you tell me why this happens? Is there any fix to this?

Also, why does everything slow down once you add the background image in the main game loop?

import pygame
from pygame import mixer
import random
import math

# Starting pygame
pygame.init()

# window
screen = pygame.display.set_mode((800, 600))
background = pygame.image.load('background.png')

# title and icon
pygame.display.set_caption("Space Invaders")
icon = pygame.image.load('icon.png')
pygame.display.set_icon(icon)

# background
mixer.music.load('galaxy.ogg')
mixer.music.play(-1)

# player
playerimg = pygame.image.load('rocket.png')
playerX = 370
playerY = 480
playerX_change = 0

# Enemy
enemy_img = []
enemyX = []
enemyY = []
enemyX_change = []
enemyY_change = []
num_of_enemies = 1

for i in range(num_of_enemies):
    enemy_img.append(pygame.image.load('Enemy.png'))
    enemyX.append(random.randint(0, 735))
    enemyY.append(random.randint(50, 300))
    enemyX_change.append(4)
    enemyY_change.append(40)

# Bullet
bulletimg = pygame.image.load('bullet.png')
bulletX = 0
bulletY = 480
bulletX_change = 0
bulletY_change = 10
bullet_state = "ready"

# ready = you can't see the bullet on the screen
# fire = the bullet is currently moving

# score
score_value = 0
font = pygame.font.Font('freesansbold.ttf', 32)

textX = 10
textY = 10

# gameover text
over_font = pygame.font.Font('freesansbold.ttf', 70)


def show_score(x, y):
    score = font.render("Score: " + str(score_value), True, (255, 255, 255))
    screen.blit(score, (x, y))


def game_over_text():
    over_text = over_font.render("GAME OVER!", True, (255, 0, 0))
    screen.blit(over_text, (200, 250))


def player(x, y):
    screen.blit(playerimg, (x, y))


def enemy(x, y, i):
    screen.blit(enemy_img[i], (x, y))


def fire_bullet(x, y):
    global bullet_state
    bullet_state = "fire"
    screen.blit(bulletimg, (x + 25, y + 10))


def iscollision(enemyX, enemyY, bulletX, bulletY):
    distance = math.sqrt(math.pow(enemyX - bulletX, 2) + math.pow(enemyY - bulletY, 2))
    if distance < 30:
        return True
    else:
        return False


# gameloop
running = True
while running:
    # RGB screen
    screen.fill((0, 0, 0))
    screen.blit(background, (0, 0))

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

        # Check keystroke left or right
        if event.type == pygame.KEYDOWN:
            if event.key == pygame.K_LEFT:
                playerX_change = -10
            if event.key == pygame.K_RIGHT:
                playerX_change = 10
            if event.key == pygame.K_SPACE:
                if bullet_state is "ready":
                    bullet_sound = mixer.Sound('shoot.wav')
                    bullet_sound.play()
                    # gets the current x cor of the player
                    bulletX = playerX
                    fire_bullet(bulletX, bulletY)

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

    playerX += playerX_change

    if playerX <= 0:
        playerX = 0
    elif playerX >= 736:
        playerX = 736

    for i in range(num_of_enemies):

        # game over
        if enemyY[i] > 440:
            for j in range(num_of_enemies):
                enemyY[j] = 2000
            game_over_text()
            break

        enemyX[i] += enemyX_change[i]
        if enemyX[i] <= 0:
            enemyX_change[i] *= -1
            enemyY[i] += enemyY_change[i]
        elif enemyX[i] >= 736:
            enemyX_change[i] *= -1
            enemyY[i] += enemyY_change[i]

        # collision
        collision = iscollision(enemyX[i], enemyY[i], bulletX, bulletY)
        if collision:
            explosion_sound = mixer.Sound('explosion.wav')
            explosion_sound.play()
            bulletY = 480
            bullet_state = "ready"
            score_value += 1
            # print(score)
            enemyX[i] = random.randint(0, 735)
            enemyY[i] = random.randint(50, 300)

        enemy(enemyX[i], enemyY[i], i)

    # if enemyY <= 50:
    # enemyY_change *= -1
    # elif enemyY >= 300:
    # enemyY_change *= -1

    if bulletY <= 0:
        bulletY = 480
        bullet_state = "ready"

    if bullet_state is "fire":
        fire_bullet(bulletX, bulletY)
        bulletY -= bulletY_change

    player(playerX, playerY)
    show_score(textX, textY)
    pygame.display.update()

回答1:

Call convert() on the background image. That ensures that the image has the same pixel format as the display Surface and will help blit to operate with optimal performance:

screen = pygame.display.set_mode((800, 600))
background = pygame.image.load('background.png').convert()

Note, if the surface has a different format than the display, then blit has to convert the format on the fly in every frame.

来源：https://stackoverflow.com/questions/60222282/why-does-my-game-made-with-pygame-suddenly-lag-for-a-few-seconds

标签

python

pygame

pygame-surface