利用python，写一个贪吃蛇的程序

以下是一个简单的贪吃蛇程序，基于Python的pygame库实现。程序中使用了一些常用的pygame函数，如`pygame.init()`初始化、`pygame.display.set_mode()`创建窗口、`pygame.draw.rect()`绘制矩形等。

import pygame
import random

# 初始化Pygame
pygame.init()

# 设置窗口尺寸
WINDOW_SIZE = (400, 400)
screen = pygame.display.set_mode(WINDOW_SIZE)

# 设置游戏参数
BLOCK_SIZE = 10
SCORE_FONT = pygame.font.SysFont("arial", 20)
SNAKE_COLOR = (0, 255, 0)
FOOD_COLOR = (255, 0, 0)

# 定义Snake类
class Snake:
    def __init__(self):
        self.body = [(WINDOW_SIZE[0] // 2, WINDOW_SIZE[1] // 2)]
        self.direction = (0, -1)
        self.score = 0

    # 更新蛇的状态
    def update(self, food_pos):
        # 更新蛇头位置
        head = (self.body[0][0] + self.direction[0] * BLOCK_SIZE, self.body[0][1] + self.direction[1] * BLOCK_SIZE)
        self.body.insert(0, head)

        # 如果吃到了食物
        if head == food_pos:
            self.score += 1
        else:
            self.body.pop()

        # 如果撞到了墙壁
        if head[0] < 0 or head[0] >= WINDOW_SIZE[0] or head[1] < 0 or head[1] >= WINDOW_SIZE[1]:
            return False

        # 如果撞到了自己的身体
        if head in self.body[1:]:
            return False

        return True

    # 绘制蛇的身体
    def draw(self, screen):
        for pos in self.body:
            pygame.draw.rect(screen, SNAKE_COLOR, (pos[0], pos[1], BLOCK_SIZE, BLOCK_SIZE))

    # 改变蛇的方向
    def change_direction(self, direction):
        if direction == "up":
            self.direction = (0, -1)
        elif direction == "down":
            self.direction = (0, 1)
        elif direction == "left":
            self.direction = (-1, 0)
        elif direction == "right":
            self.direction = (1, 0)

# 定义Food类
class Food:
    def __init__(self):
        self.pos = (random.randint(0, WINDOW_SIZE[0] // BLOCK_SIZE - 1) * BLOCK_SIZE,
                    random.randint(0, WINDOW_SIZE[1] // BLOCK_SIZE - 1) * BLOCK_SIZE)

    # 绘制食物
    def draw(self, screen):
        pygame.draw.rect(screen, FOOD_COLOR, (self.pos[0], self.pos[1], BLOCK_SIZE, BLOCK_SIZE))

    # 重新生成食物
    def respawn(self):
        self.pos = (random.randint(0, WINDOW_SIZE[0] // BLOCK_SIZE - 1) * BLOCK_SIZE,
                    random.randint(0, WINDOW_SIZE[1] // BLOCK_SIZE - 1) * BLOCK_SIZE)

# 初始化游戏
snake = Snake()
food = Food()

# 游戏循环
while True:
    # 处理事件
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            pygame.quit()
            quit()
        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")

    # 更新蛇的状态
    if not snake.update(food.pos):
        pygame.quit()
        print("Game Over!")
        quit()

    # 判断是否吃到了食物
    if snake.body[0] == food.pos:
        food.respawn()

    # 绘制游戏界面
    screen.fill((255, 255, 255))
    food.draw(screen)
    snake.draw(screen)

    # 显示分数
    score_text = SCORE_FONT.render("Score:{}".format(snake.score), True, (0, 0, 0))
    screen.blit(score_text, (10, 10))

    # 更新屏幕
    pygame.display.update()

运行程序后，可以使用方向键来控制蛇的移动，蛇会不断地移动并尝试吃到食物。当蛇撞到墙壁或自己的身体时，游戏结束。程序还显示了当前的得分。