帮我写个贪吃蛇小游戏代码

好的，以下是贪吃蛇小游戏的 Python 代码：

import pygame
import random

# 定义常量
WIDTH = 640
HEIGHT = 480
SIZE = 20
BG_COLOR = (50, 50, 50)
SNAKE_COLOR = (255, 255, 255)
FOOD_COLOR = (0, 255, 0)

# 初始化 Pygame
pygame.init()
screen = pygame.display.set_mode((WIDTH, HEIGHT))
pygame.display.set_caption("贪吃蛇小游戏")

# 定义 Snake 类
class Snake:
    def __init__(self):
        self.body = []
        self.direction = "right"
        for i in range(4):
            self.body.append((SIZE * (i + 1), SIZE))

    # 获取蛇头坐标
    def head(self):
        return self.body[-1]

    # 移动方法
    def move(self):
        x, y = self.head()
        if self.direction == "up":
            y -= SIZE
        elif self.direction == "down":
            y += SIZE
        elif self.direction == "left":
            x -= SIZE
        elif self.direction == "right":
            x += SIZE
        self.body.append((x, y))
        self.body.pop(0)

    # 改变方向方法
    def change_direction(self, direction):
        if direction == "up" and self.direction != "down":
            self.direction = "up"
        elif direction == "down" and self.direction != "up":
            self.direction = "down"
        elif direction == "left" and self.direction != "right":
            self.direction = "left"
        elif direction == "right" and self.direction != "left":
            self.direction = "right"

    # 绘制蛇方法
    def draw(self):
        for x, y in self.body:
            rect = pygame.Rect(x, y, SIZE, SIZE)
            pygame.draw.rect(screen, SNAKE_COLOR, rect)

# 定义 Food 类
class Food:
    def __init__(self):
        self.pos = self.new_pos()

    # 生成新的食物位置
    def new_pos(self):
        x = random.randint(0, WIDTH // SIZE - 1) * SIZE
        y = random.randint(0, HEIGHT // SIZE - 1) * SIZE
        return (x, y)

    # 绘制食物方法
    def draw(self):
        x, y = self.pos
        rect = pygame.Rect(x, y, SIZE, SIZE)
        pygame.draw.rect(screen, FOOD_COLOR, rect)

# 创建 Snake 和 Food 对象
snake = Snake()
food = Food()

# 创建时钟对象
clock = pygame.time.Clock()

# 游戏循环
while True:
    # 处理事件
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            pygame.quit()
            exit()
        elif event.type == pygame.KEYDOWN:
            if event.key == pygame.K_UP:
                snake.change_direction("up")
            elif event.key == pygame.K_DOWN:
                snake.change_direction("down")
            elif event.key == pygame.K_LEFT:
                snake.change_direction("left")
            elif event.key == pygame.K_RIGHT:
                snake.change_direction("right")

    # 判断是否吃到食物
    if snake.head() == food.pos:
        food.pos = food.new_pos()
    else:
        snake.body.pop(0)

    # 判断是否死亡
    if snake.head()[0] < 0 or snake.head()[0] >= WIDTH:
        pygame.quit()
        exit()
    if snake.head()[1] < 0 or snake.head()[1] >= HEIGHT:
        pygame.quit()
        exit()
    for x, y in snake.body[:-1]:
        if snake.head() == (x, y):
            pygame.quit()
            exit()

    # 绘制背景
    screen.fill(BG_COLOR)

    # 绘制蛇和食物
    snake.move()
    snake.draw()
    food.draw()

    # 刷新屏幕
    pygame.display.update()

    # 控制帧率
    clock.tick(10)

希望你喜欢这个贪吃蛇小游戏！