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A* pathfinding algorithm. Please see comments below for a fork of this gist that includes bug fixes!
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class Node(): | |
"""A node class for A* Pathfinding""" | |
def __init__(self, parent=None, position=None): | |
self.parent = parent | |
self.position = position | |
self.g = 0 | |
self.h = 0 | |
self.f = 0 | |
def __eq__(self, other): | |
return self.position == other.position | |
def astar(maze, start, end): | |
"""Returns a list of tuples as a path from the given start to the given end in the given maze""" | |
# Create start and end node | |
start_node = Node(None, start) | |
start_node.g = start_node.h = start_node.f = 0 | |
end_node = Node(None, end) | |
end_node.g = end_node.h = end_node.f = 0 | |
# Initialize both open and closed list | |
open_list = [] | |
closed_list = [] | |
# Add the start node | |
open_list.append(start_node) | |
# Loop until you find the end | |
while len(open_list) > 0: | |
# Get the current node | |
current_node = open_list[0] | |
current_index = 0 | |
for index, item in enumerate(open_list): | |
if item.f < current_node.f: | |
current_node = item | |
current_index = index | |
# Pop current off open list, add to closed list | |
open_list.pop(current_index) | |
closed_list.append(current_node) | |
# Found the goal | |
if current_node == end_node: | |
path = [] | |
current = current_node | |
while current is not None: | |
path.append(current.position) | |
current = current.parent | |
return path[::-1] # Return reversed path | |
# Generate children | |
children = [] | |
for new_position in [(0, -1), (0, 1), (-1, 0), (1, 0), (-1, -1), (-1, 1), (1, -1), (1, 1)]: # Adjacent squares | |
# Get node position | |
node_position = (current_node.position[0] + new_position[0], current_node.position[1] + new_position[1]) | |
# Make sure within range | |
if node_position[0] > (len(maze) - 1) or node_position[0] < 0 or node_position[1] > (len(maze[len(maze)-1]) -1) or node_position[1] < 0: | |
continue | |
# Make sure walkable terrain | |
if maze[node_position[0]][node_position[1]] != 0: | |
continue | |
# Create new node | |
new_node = Node(current_node, node_position) | |
# Append | |
children.append(new_node) | |
# Loop through children | |
for child in children: | |
# Child is on the closed list | |
for closed_child in closed_list: | |
if child == closed_child: | |
continue | |
# Create the f, g, and h values | |
child.g = current_node.g + 1 | |
child.h = ((child.position[0] - end_node.position[0]) ** 2) + ((child.position[1] - end_node.position[1]) ** 2) | |
child.f = child.g + child.h | |
# Child is already in the open list | |
for open_node in open_list: | |
if child == open_node and child.g > open_node.g: | |
continue | |
# Add the child to the open list | |
open_list.append(child) | |
def main(): | |
maze = [[0, 0, 0, 0, 1, 0, 0, 0, 0, 0], | |
[0, 0, 0, 0, 1, 0, 0, 0, 0, 0], | |
[0, 0, 0, 0, 1, 0, 0, 0, 0, 0], | |
[0, 0, 0, 0, 1, 0, 0, 0, 0, 0], | |
[0, 0, 0, 0, 1, 0, 0, 0, 0, 0], | |
[0, 0, 0, 0, 0, 0, 0, 0, 0, 0], | |
[0, 0, 0, 0, 1, 0, 0, 0, 0, 0], | |
[0, 0, 0, 0, 1, 0, 0, 0, 0, 0], | |
[0, 0, 0, 0, 1, 0, 0, 0, 0, 0], | |
[0, 0, 0, 0, 0, 0, 0, 0, 0, 0]] | |
start = (0, 0) | |
end = (7, 6) | |
path = astar(maze, start, end) | |
print(path) | |
if __name__ == '__main__': | |
main() |
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