在开始时加载

本课属于 Coddy Pygame 学习旅程的“游戏规则”单元。第 21 课，共 30 课。

记录已经保存；现在，在游戏开始时把它读回来。int(file.read()) 会把文件中的文本转换成数字。第一次运行时，文件还不存在，open 会通过 FileNotFoundError 停止程序。

try 和 except 会捕获这个错误，并改为执行其他操作：

def load_best():
    try:
        with open("highscore.txt") as file:
            return int(file.read())
    except FileNotFoundError:
        return 0


best = load_best()

Python 会运行 try 代码块。如果 open 引发 FileNotFoundError，程序就会跳到 except 代码块并返回 0。其他错误仍会停止程序，这正是你想要的，因为那是真正的 bug。

不指定模式的 open("highscore.txt") 会以读取模式打开文件。

在桌面设备上，关闭游戏后再运行一次，上一局的最高分就会显示在第一次出现的游戏结束画面上。在浏览器中，每次你按下“开始”时也会发生同样的情况，直到页面重新加载。

挑战

中等

游戏开始时，读取已保存的最高分。

编写 load_best()：它会返回 highscore.txt 中的数字；如果文件不存在，则返回 0。
将 best = 0 替换为 best = load_best()。

按下开始并输掉游戏：“游戏结束”界面会显示最高分，该分数从文件中读取后又会保存回文件。然后点击检查。

亲手试试

import random
import pygame

pygame.init()
screen = pygame.display.set_mode((480, 360))
pygame.display.set_caption("Meteor Dodge")
clock = pygame.time.Clock()
heart = pygame.image.load("assets/images/heart.png").convert_alpha()
heart_empty = pygame.image.load("assets/images/heart_empty.png").convert_alpha()
font = pygame.font.Font("assets/fonts/pixel.ttf", 24)
big_font = pygame.font.Font("assets/fonts/pixel.ttf", 48)
WHITE = (240, 240, 240)
PLATE = (60, 60, 90)
POINT = pygame.USEREVENT + 1
SPAWN = pygame.USEREVENT + 2


def reset():
    global player, rocks, score, lives
    player = pygame.Rect(220, 300, 40, 40)
    rocks = []
    score = 0
    lives = 3
    pygame.time.set_timer(POINT, 1000)
    pygame.time.set_timer(SPAWN, 800)


def draw_menu():
    screen.fill((30, 30, 46))
    title = big_font.render("Meteor Dodge", True, WHITE)
    title_rect = title.get_rect(center=(240, 140))
    pygame.draw.rect(screen, PLATE, title_rect.inflate(24, 12))
    screen.blit(title, title_rect)
    hint = font.render("Press Enter to play", True, WHITE)
    screen.blit(hint, hint.get_rect(center=(240, 200)))


def draw_game():
    screen.fill((30, 30, 46))
    pygame.draw.rect(screen, (255, 196, 0), player)
    for rock in rocks:
        pygame.draw.rect(screen, (235, 80, 80), rock)
    score_text = font.render(f"{score:05}", True, WHITE)
    score_rect = score_text.get_rect(topright=(470, 10))
    pygame.draw.rect(screen, PLATE, score_rect.inflate(12, 8))
    screen.blit(score_text, score_rect)
    for i in range(3):
        if i < lives:
            screen.blit(heart, (10 + i * 40, 10))
        else:
            screen.blit(heart_empty, (10 + i * 40, 10))


def play_frame():
    global rocks, lives, state, best
    keys = pygame.key.get_pressed()
    if keys[pygame.K_LEFT]:
        player.x -= 6
    if keys[pygame.K_RIGHT]:
        player.x += 6
    player.clamp_ip(screen.get_rect())

    kept = []
    for rock in rocks:
        rock.y += 3
        if rock.colliderect(player):
            lives -= 1
        elif rock.top <= 360:
            kept.append(rock)
    rocks = kept
    if lives <= 0:
        state = "over"
        best = max(best, score)
        with open("highscore.txt", "w") as file:
            file.write(str(best))
    draw_game()


def draw_over():
    draw_game()
    message = big_font.render("Game over", True, WHITE)
    screen.blit(message, message.get_rect(center=(240, 160)))
    hint = font.render("Press R to play again", True, WHITE)
    screen.blit(hint, hint.get_rect(center=(240, 200)))
    best_text = font.render(f"Best: {best}", True, WHITE)
    screen.blit(best_text, best_text.get_rect(center=(240, 240)))


reset()
state = "menu"
best = 0

running = True
while running:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False
        if event.type == POINT and state == "play":
            score += 1
        if event.type == SPAWN and state == "play":
            rocks.append(pygame.Rect(random.randint(0, 456), -24, 24, 24))
        if event.type == pygame.KEYDOWN:
            if event.key == pygame.K_RETURN and state == "menu":
                reset()
                state = "play"
            elif event.key == pygame.K_r and state == "over":
                reset()
                state = "play"

    if state == "menu":
        draw_menu()
    elif state == "play":
        play_frame()
    else:
        draw_over()
    pygame.display.flip()
    clock.tick(60)

pygame.quit()

游戏规则中的所有课

自己练习： Pygame 在线编辑器