用pygame写一个A*算法，并有详细注释

好的，以下是一个使用pygame实现的A*算法示例，带有详细注释：

import pygame
from queue import PriorityQueue

# 设置窗口大小和标题
WIDTH = 800
WIN = pygame.display.set_mode((WIDTH, WIDTH))
pygame.display.set_caption("A* Path Finding Algorithm")

# 定义颜色常量
RED = (255, 0, 0)
GREEN = (0, 255, 0)
BLUE = (0, 0, 255)
YELLOW = (255, 255, 0)
WHITE = (255, 255, 255)
BLACK = (0, 0, 0)
PURPLE = (128, 0, 128)
ORANGE = (255, 165, 0)
GREY = (128, 128, 128)
TURQUOISE = (64, 224, 208)

# 定义一个格子类
class Node:
    def __init__(self, row, col, width, total_rows):
        self.row = row
        self.col = col
        self.x = row * width
        self.y = col * width
        self.color = WHITE
        self.neighbors = []
        self.width = width
        self.total_rows = total_rows

    def get_pos(self):
        return self.row, self.col

    def is_closed(self):
        return self.color == RED

    def is_open(self):
        return self.color == GREEN

    def is_barrier(self):
        return self.color == BLACK

    def is_start(self):
        return self.color == ORANGE

    def is_end(self):
        return self.color == TURQUOISE

    def reset(self):
        self.color = WHITE

    def make_closed(self):
        self.color = RED

    def make_open(self):
        self.color = GREEN

    def make_barrier(self):
        self.color = BLACK

    def make_start(self):
        self.color = ORANGE

    def make_end(self):
        self.color = TURQUOISE

    def make_path(self):
        self.color = PURPLE

    def draw(self, win):
        pygame.draw.rect(win, self.color, (self.x, self.y, self.width, self.width))

    def update_neighbors(self, grid):
        self.neighbors = []
        if self.row < self.total_rows - 1 and not grid[self.row + 1][self.col].is_barrier(): # 下方节点
            self.neighbors.append(grid[self.row + 1][self.col])
        if self.row > 0 and not grid[self.row - 1][self.col].is_barrier(): # 上方节点
            self.neighbors.append(grid[self.row - 1][self.col])
        if self.col < self.total_rows - 1 and not grid[self.row][self.col + 1].is_barrier(): # 右方节点
            self.neighbors.append(grid[self.row][self.col + 1])
        if self.col > 0 and not grid[self.row][self.col - 1].is_barrier(): # 左方节点
            self.neighbors.append(grid[self.row][self.col - 1])

    def __lt__(self, other):
        return False

# 计算估价函数
def h(p1, p2):
    x1, y1 = p1
    x2, y2 = p2
    return abs(x1 - x2) + abs(y1 - y2)

# 绘制路径
def reconstruct_path(came_from, current, draw):
    while current in came_from:
        current = came_from[current]
        current.make_path()
        draw()

# A*算法的主函数
def algorithm(draw, grid, start, end):
    count = 0 # 用于在优先队列中排序
    open_set = PriorityQueue()
    open_set.put((0, count, start))
    came_from = {}
    g_score = {node: float("inf") for row in grid for node in row}
    g_score[start] = 0
    f_score = {node: float("inf") for row in grid for node in row}
    f_score[start] = h(start.get_pos(), end.get_pos())

    open_set_hash = {start}

    while not open_set.empty():
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                pygame.quit()

        current = open_set.get()[2]
        open_set_hash.remove(current)

        if current == end:
            reconstruct_path(came_from, end, draw)
            start.make_start()
            end.make_end()
            return True

        for neighbor in current.neighbors:
            temp_g_score = g_score[current] + 1

            if temp_g_score < g_score[neighbor]:
                came_from[neighbor] = current
                g_score[neighbor] = temp_g_score
                f_score[neighbor] = temp_g_score + h(neighbor.get_pos(), end.get_pos())
                if neighbor not in open_set_hash:
                    count += 1
                    open_set.put((f_score[neighbor], count, neighbor))
                    open_set_hash.add(neighbor)
                    neighbor.make_open()

        draw()

        if current != start:
            current.make_closed()

    return False

# 绘制网格线
def draw_grid(win, rows, width):
    gap = width // rows
    for i in range(rows):
        pygame.draw.line(win, GREY, (0, i * gap), (width, i * gap))
        for j in range(rows):
            pygame.draw.line(win, GREY, (j * gap, 0), (j * gap, width))

# 初始化网格
def make_grid(rows, width):
    grid = []
    gap = width // rows
    for i in range(rows):
        grid.append([])
        for j in range(rows):
            node = Node(i, j, gap, rows)
            grid[i].append(node)

    return grid

# 绘制所有节点
def draw(win, grid, rows, width):
    win.fill(WHITE)

    for row in grid:
        for node in row:
            node.draw(win)

    draw_grid(win, rows, width)
    pygame.display.update()

# 鼠标点击事件
def get_clicked_pos(pos, rows, width):
    gap = width // rows
    y, x = pos

    row = y // gap
    col = x // gap

    return row, col

# 主函数
def main(win, width):
    ROWS = 50
    grid = make_grid(ROWS, width)

    start = None
    end = None

    run = True
    started = False

    while run:
        draw(win, grid, ROWS, width)
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                run = False

            if started:
                continue

            if pygame.mouse.get_pressed()[0]: # 左键点击
                pos = pygame.mouse.get_pos()
                row, col = get_clicked_pos(pos, ROWS, width)
                node = grid[row][col]
                if not start and node != end:
                    start = node
                    start.make_start()
                elif not end and node != start:
                    end = node
                    end.make_end()
                elif node != end and node != start:
                    node.make_barrier()

            elif pygame.mouse.get_pressed()[2]: # 右键点击
                pos = pygame.mouse.get_pos()
                row, col = get_clicked_pos(pos, ROWS, width)
                node = grid[row][col]
                node.reset()
                if node == start:
                    start = None
                elif node == end:
                    end = None

            if event.type == pygame.KEYDOWN:
                if event.key == pygame.K_SPACE and not started:
                    for row in grid:
                        for node in row:
                            node.update_neighbors(grid)

                    algorithm(lambda: draw(win, grid, ROWS, width), grid, start, end)

                if event.key == pygame.K_c:
                    start = None
                    end = None
                    grid = make_grid(ROWS, width)

    pygame.quit()

main(WIN, WIDTH)

在这个示例中，我们定义了一个`Node`类，用于表示地图上的每一个节点。每个节点都有一些属性和方法，比如：颜色、位置、是否是起点/终点/障碍物、更新邻居节点等。

在`algorithm`函数中，我们使用了A*算法来寻找起点到终点的最短路径。我们使用一个优先队列来存储待处理的节点，并通过计算估价函数`h`来排序，从而保证每次处理的都是距离终点最近的节点。在A*算法的过程中，我们使用了一个`came_from`字典来记录每个节点的最佳前驱节点，最终通过这个字典来还原路径。

在主函数中，我们通过监听鼠标事件和键盘事件来实现交互操作。我们可以通过左键点击创建起点、终点或障碍物，通过右键点击删除这些节点。我们还可以通过按空格键来启动A*算法的执行，按C键来清除地图上的所有节点。

希望这个示例对你有所帮助！