利用Python写一个代码，要求随机生成障碍物的概率为0.3的20*20的地图，先生成地图，再利用Astar算法进行寻路

以下是一个示例代码，其中包含地图生成和A*算法的实现：

import random

# 定义地图大小
MAP_SIZE = 20

# 定义障碍物概率
OBSTACLE_PROBABILITY = 0.3

# 定义地图中的符号
SYMBOL_EMPTY = '-'
SYMBOL_OBSTACLE = 'X'
SYMBOL_START = 'S'
SYMBOL_END = 'E'
SYMBOL_PATH = '*'

# 定义节点类
class Node:
    def __init__(self, x, y):
        self.x = x
        self.y = y
        self.parent = None
        self.g = 0
        self.h = 0
        self.f = 0

    def __eq__(self, other):
        return self.x == other.x and self.y == other.y

# 定义A*算法函数
def astar(start, end, map):
    open_list = [start]
    closed_list = []

    while len(open_list) > 0:
        current_node = open_list[0]
        current_index = 0

        # 找到f值最小的节点
        for index, node in enumerate(open_list):
            if node.f < current_node.f:
                current_node = node
                current_index = index

        # 将当前节点从开放列表中移除，并加入封闭列表
        open_list.pop(current_index)
        closed_list.append(current_node)

        # 找到目标节点
        if current_node == end:
            path = []
            current = current_node
            while current is not None:
                path.append(current)
                current = current.parent
            return path[::-1]

        # 获取当前节点的相邻节点
        neighbors = []
        for new_x, new_y in [(0, -1), (0, 1), (-1, 0), (1, 0)]:
            node_x = current_node.x + new_x
            node_y = current_node.y + new_y

            if node_x < 0 or node_x >= MAP_SIZE or node_y < 0 or node_y >= MAP_SIZE:
                continue

            if map[node_x][node_y] == SYMBOL_OBSTACLE:
                continue

            new_node = Node(node_x, node_y)
            new_node.g = current_node.g + 1
            new_node.h = ((new_node.x - end.x) ** 2) + ((new_node.y - end.y) ** 2)
            new_node.f = new_node.g + new_node.h
            new_node.parent = current_node

            neighbors.append(new_node)

        # 处理相邻节点
        for neighbor in neighbors:
            if neighbor in closed_list:
                continue

            if neighbor.f > 1000000:
                continue

            if neighbor in open_list:
                index = open_list.index(neighbor)
                if open_list[index].g > neighbor.g:
                    open_list[index].g = neighbor.g
                    open_list[index].parent = current_node
            else:
                open_list.append(neighbor)

    return None

# 生成地图
map = [[SYMBOL_EMPTY for x in range(MAP_SIZE)] for y in range(MAP_SIZE)]

for x in range(MAP_SIZE):
    for y in range(MAP_SIZE):
        if random.uniform(0, 1) < OBSTACLE_PROBABILITY:
            map[x][y] = SYMBOL_OBSTACLE

# 随机选择起点和终点
start_x, start_y = random.randint(0, MAP_SIZE-1), random.randint(0, MAP_SIZE-1)
end_x, end_y = random.randint(0, MAP_SIZE-1), random.randint(0, MAP_SIZE-1)

while map[start_x][start_y] == SYMBOL_OBSTACLE or map[end_x][end_y] == SYMBOL_OBSTACLE:
    start_x, start_y = random.randint(0, MAP_SIZE-1), random.randint(0, MAP_SIZE-1)
    end_x, end_y = random.randint(0, MAP_SIZE-1), random.randint(0, MAP_SIZE-1)

# 标记起点和终点
map[start_x][start_y] = SYMBOL_START
map[end_x][end_y] = SYMBOL_END

# 输出地图
for row in map:
    print(' '.join(row))

# 寻找最短路径
start_node = Node(start_x, start_y)
end_node = Node(end_x, end_y)
path = astar(start_node, end_node, map)

# 标记路径
if path is not None:
    for node in path:
        map[node.x][node.y] = SYMBOL_PATH

# 输出地图和路径
print('---')
for row in map:
    print(' '.join(row))

该代码将生成一个20x20的地图，并随机在地图上放置障碍物。然后，代码会随机选择起点和终点，并使用A*算法寻找它们之间的最短路径。最后，代码会在地图上标记路径，并输出地图和路径。