13518219792
这篇文章主要介绍了Python3 A*寻路算法的示例分析，具有一定借鉴价值，感兴趣的朋友可以参考下，希望大家阅读完这篇文章之后大有收获，下面让小编带着大家一起了解一下。
直接上代码吧！
# -*- coding: utf-8 -*-
import math
import random
import copy
import time
import sys
import tkinter
import threading
# 地图
tm = [
'############################################################',
'#S............................#............#.....#.........#',
'#..........#..................#......#.....#.....#.........#',
'#..........#..................#......#.....#.....#.........#',
'#..........#..................#......#.....#.....#.........#',
'#..........#.........................#.....#.....#.........#',
'#..........#..................#......#.....#...............#',
'#..#########..................#......#.....#.....#.........#',
'#..#..........................#......#.....#.....#.........#',
'#..#..........................#......#.....#.....#.........#',
'#..############################......#.....#.....#.........#',
'#.............................#......#.....#.....#.........#',
'#.............................#......#...........#.........#',
'#######.##################################################.#',
'#....#........#.................#.............#............#',
'#....#........#........#........#.............#............#',
'#....####.#####........#........#.............#............#',
'#.........#............#........#.............#............#',
'#.........#............#........#.............#............#',
'#.........#............#........#.............#............#',
'#.........#............#........#.............#............#',
'#.........#............#........#.............#............#',
'#.........#............#........####.#######.##............#',
'#.........#............#........#....#.......#.............#',
'#.........#............#........#....#.......#.............#',
'#......................#........#....#.......#.............#',
'#.........#............#........##.########..#.............#',
'#.........#............#..................#..########.######',
'#.........#............#..................#...............E#',
'############################################################']
# 存储搜索时的地图
test_map = []
#----------- 开放列表和关闭列表的元素类型，parent用来在成功的时候回溯路径 -----------
class Node_Elem:
def __init__(self, parent, x, y, dist):
self.parent = parent # 回溯父节点
self.x = x # x坐标
self.y = y # y坐标
self.dist = dist # 从起点到此位置的实际距离
#----------- A*算法 -----------
class A_Star:
def __init__(self, root, s_x, s_y, e_x, e_y, w=60, h=30):
self.s_x = s_x # 起点x
self.s_y = s_y # 起点y
self.e_x = e_x # 终点x
self.e_y = e_y # 终点y
self.open = [] # open表
self.close = [] # close表
self.path = [] # path表
# 创建画布
self.root = root # 画布根节点
self.width = w # 地图w，默认60
self.height = h # 地图h，默认30
self.__r = 3 # 半径
# Tkinter.Canvas
self.canvas = tkinter.Canvas(
root,
width=self.width * 10 + 100,
height=self.height * 10 + 100,
bg="#EBEBEB", # 背景白色
xscrollincrement=1,
yscrollincrement=1
)
self.canvas.pack(expand=tkinter.YES, fill=tkinter.BOTH)
self.title("A*迷宫算法(e:开始搜索或退出)")
self.__bindEvents()
self.new()
# 按键响应程序
def __bindEvents(self):
self.root.bind("e", self.quite) # 退出程序
# 退出程序
def quite(self, evt):
self.root.destroy()
# 更改标题
def title(self, s):
self.root.title(s)
# 初始化
def new(self):
node = self.canvas.create_oval(100 - self.__r,
20 - self.__r, 100 + self.__r, 20 + self.__r,
fill="#ff0000",
outline="#ffffff",
tags="node",
)
self.canvas.create_text(130, 20,
text=u'Wall',
fill='black'
)
node = self.canvas.create_oval(200 - self.__r,
20 - self.__r, 200 + self.__r, 20 + self.__r,
fill="#00ff00",
outline="#ffffff",
tags="node",
)
self.canvas.create_text(230, 20,
text=u'Path',
fill='black'
)
node = self.canvas.create_oval(300 - self.__r,
20 - self.__r, 300 + self.__r, 20 + self.__r,
fill="#AAAAAA",
outline="#ffffff",
tags="node",
)
self.canvas.create_text(330, 20,
text=u'Searched',
fill='black'
)
for i in range(self.width):
for j in range(self.height):
# 生成障碍节点，半径为self.__r
if test_map[j][i] == '#':
node = self.canvas.create_oval(i * 10 + 50 - self.__r,
j * 10 + 50 - self.__r, i * 10 + 50 + self.__r, j * 10 + 50 + self.__r,
fill="#ff0000", # 填充红色
outline="#ffffff", # 轮廓白色
tags="node",
)
# 显示起点
if test_map[j][i] == 'S':
node = self.canvas.create_oval(i * 10 + 50 - self.__r,
j * 10 + 50 - self.__r, i * 10 + 50 + self.__r, j * 10 + 50 + self.__r,
fill="#00ff00", # 填充绿色
outline="#ffffff", # 轮廓白色
tags="node",
)
self.canvas.create_text(i * 10 + 50, j * 10 + 50 - 20, # 使用create_text方法在坐标处绘制文字
text=u'Start', # 所绘制文字的内容
fill='black' # 所绘制文字的颜色为灰色
)
# 显示终点
if test_map[j][i] == 'E':
node = self.canvas.create_oval(i * 10 + 50 - self.__r,
j * 10 + 50 - self.__r, i * 10 + 50 + self.__r, j * 10 + 50 + self.__r,
fill="#00ff00", # 填充绿色
outline="#ffffff", # 轮廓白色
tags="node",
)
self.canvas.create_text(i * 10 + 50, j * 10 + 50 + 20, # 使用create_text方法在坐标处绘制文字
text=u'End', # 所绘制文字的内容
fill='black' # 所绘制文字的颜色为灰色
)
# 生成路径节点，半径为self.__r
if test_map[j][i] == '*':
node = self.canvas.create_oval(i * 10 + 50 - self.__r,
j * 10 + 50 - self.__r, i * 10 + 50 + self.__r, j * 10 + 50 + self.__r,
fill="#0000ff", # 填充蓝色
outline="#ffffff", # 轮廓白色
tags="node",
)
# 生成搜索区域，半径为self.__r
if test_map[j][i] == ' ':
node = self.canvas.create_oval(i * 10 + 50 - self.__r,
j * 10 + 50 - self.__r, i * 10 + 50 + self.__r, j * 10 + 50 + self.__r,
fill="#AAAAAA", # 填充白色
outline="#ffffff", # 轮廓白色
tags="node",
)
# 查找路径的入口函数
def find_path(self):
# 构建开始节点
p = Node_Elem(None, self.s_x, self.s_y, 0.0)
while True:
# 扩展节点
self.extend_round(p)
# 如果open表为空，则不存在路径，返回
if not self.open:
return
# 取F值最小的节点
idx, p = self.get_best()
# 到达终点，生成路径，返回
if self.is_target(p):
self.make_path(p)
return
# 把此节点加入close表，并从open表里删除
self.close.append(p)
del self.open[idx]
# 生成路径
def make_path(self, p):
# 从结束点回溯到开始点，开始点的parent == None
while p:
self.path.append((p.x, p.y))
p = p.parent
# 判断是否为终点
def is_target(self, i):
return i.x == self.e_x and i.y == self.e_y
# 取F值最小的节点
def get_best(self):
best = None
bv = 10000000 # MAX值
bi = -1
for idx, i in enumerate(self.open):
value = self.get_dist(i)
if value < bv:
best = i
bv = value
bi = idx
return bi, best
# 求距离
def get_dist(self, i):
# F = G + H
# G 为当前路径长度，H为估计长度
return i.dist + math.sqrt((self.e_x - i.x) * (self.e_x - i.x)) + math.sqrt((self.e_y - i.y) * (self.e_y - i.y))
# 扩展节点
def extend_round(self, p):
# 八个方向移动
xs = (-1, 0, 1, -1, 1, -1, 0, 1)
ys = (-1, -1, -1, 0, 0, 1, 1, 1)
# 上下左右四个方向移动
xs = (0, -1, 1, 0)
ys = (-1, 0, 0, 1)
for x, y in zip(xs, ys):
new_x, new_y = x + p.x, y + p.y
# 检查位置是否合法
if not self.is_valid_coord(new_x, new_y):
continue
# 构造新的节点，计算距离
node = Node_Elem(p, new_x, new_y, p.dist + self.get_cost(
p.x, p.y, new_x, new_y))
# 新节点在关闭列表，则忽略
if self.node_in_close(node):
continue
i = self.node_in_open(node)
# 新节点在open表
if i != -1:
# 当前路径距离更短
if self.open[i].dist > node.dist:
# 更新距离
self.open[i].parent = p
self.open[i].dist = node.dist
continue
# 否则加入open表
self.open.append(node)
# 移动距离，直走1.0，斜走1.4
def get_cost(self, x1, y1, x2, y2):
if x1 == x2 or y1 == y2:
return 1.0
return 1.4
# 检查节点是否在close表
def node_in_close(self, node):
for i in self.close:
if node.x == i.x and node.y == i.y:
return True
return False
# 检查节点是否在open表，返回序号
def node_in_open(self, node):
for i, n in enumerate(self.open):
if node.x == n.x and node.y == n.y:
return i
return -1
# 判断位置是否合法，超出边界或者为阻碍
def is_valid_coord(self, x, y):
if x < 0 or x >= self.width or y < 0 or y >= self.height:
return False
return test_map[y][x] != '#'
# 搜寻过的位置
def get_searched(self):
l = []
for i in self.open:
l.append((i.x, i.y))
for i in self.close:
l.append((i.x, i.y))
return l
# 获取起点坐标
def get_start_XY():
return get_symbol_XY('S')
# 获取终点坐标
def get_end_XY():
return get_symbol_XY('E')
# 查找特定元素
def get_symbol_XY(s):
for y, line in enumerate(test_map):
try:
x = line.index(s)
except:
continue
else:
break
return x, y
# 标记路径位置
def mark_path(l):
mark_symbol(l, '*')
# 标记已搜索过的位置
def mark_searched(l):
mark_symbol(l, ' ')
# 标记函数
def mark_symbol(l, s):
for x, y in l:
test_map[y][x] = s
# 标记起点和终点
def mark_start_end(s_x, s_y, e_x, e_y):
test_map[s_y][s_x] = 'S'
test_map[e_y][e_x] = 'E'
# 将地图字符串转化为表
def tm_to_test_map():
for line in tm:
test_map.append(list(line))
# 寻找路径
def find_path():
s_x, s_y = get_start_XY()
e_x, e_y = get_end_XY()
# A*算法
a_star = A_Star(tkinter.Tk(), s_x, s_y, e_x, e_y)
a_star.root.mainloop()
a_star.find_path()
searched = a_star.get_searched()
path = a_star.path
# 标记已搜索过的位置
mark_searched(searched)
# 标记路径位置
mark_path(path)
# 标记起点和终点
mark_start_end(s_x, s_y, e_x, e_y)
print(u"路径长度:%d" % (len(path)))
print(u"搜索过的区域:%d" % (len(searched)))
a_star = A_Star(tkinter.Tk(), s_x, s_y, e_x, e_y)
a_star.root.mainloop()
#----------- 程序的入口处 -----------
if __name__ == '__main__':
print (u"""
--------------------------------------------------------
程序：A*迷宫问题程序
作者：Gm
日期：2019-7-08
语言：Python 3.7
--------------------------------------------------------
""")
# 载入地图
tm_to_test_map()
# 寻找路径
find_path()
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