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用 Python 为 Astar 程序编写代码，以找到城市之间的最短路径。得到上述错误，我完全不知所措。在几个 .py 文件之间拉取，以下是相关部分：

来自 asdriver.py -添加了完整的 asdriver

import adata   # Map data
import astar   # A* class
import sys

# Default start, goal cities
defaultcities = ('Yakima, WA', 'Tampa, FL')

def printnode(n):
    print n.toString()

adata.input()

startcity = raw_input("Start city [{0}]: ".format(defaultcities[0])).strip()
if startcity == '':  startcity = defaultcities[0]
if startcity not in adata.cities:
     print "City not recognized"
     sys.exit(0)

goalcity = raw_input("Goal city [{0}]: ".format(defaultcities[1])).strip()
if goalcity == '':  goalcity = defaultcities[1] 
if goalcity not in adata.cities:
    print "City not recognized"
    sys.exit(0)

dbg = raw_input("Debug Options: [none]").strip()

findpath = astar.AS(startcity, goalcity, printnode)
ans = findpath.astar_run(printnode, dbg)
    if not ans:
        print "No answer"
    else:
        print "Final Path:"
        print ans.toString()

来自 astar.py

 import adata

 class AS:
     def __init__(self, startcity, goalcity, tracefunc):
        self.startcity = startcity
        self.goalcity = goalcity
        self.tracefunc = tracefunc
        self.openlist = [Node([startcity])]
        self.closedlist = []

     def heuristic(self, printnode, start, end):
        raise NotImplementedError

     def astar_run(self, startcity, endcity, dbg = ""):
        while self.openlist:
            citystep = min(self.openlist, key = lambda o:o.g + o.h)
            if citystep == self.goalcity:
                 path = []
                 while citystep.parent:
                path.append(citystep)
                citystep = citystep.parent
            path.append(citystep)
            return path[::-1]
        self.openlist.remove(citystep)
        self.closedlist.append(citystep)
        for printnode in self.openlist:   #was self.tracefunc
            if printnode in self.closedset:
                continue
            elif printnode in self.openset:
                newG = citystep.g + citystep.cost(printnode)
                if printnode.g > newG:
                    printnode.g = newG
                    printnode.parent = citystep
                else:
                    printnode.g = citystep.g + citystep.cost(printnode)
                    printnode.h = self.heuristic(printnode, start, end)
                    printnode.parent = citystep
                    self.openset.add(printnode)
        return self    



class Node:
def __init__(self, path=[], f=0, g=0, h=0):
    self.path = path[:]
    self.f = f
    self.g = g
    self.h = h
    self.parent = None

def toString(self):
    s = 'f=%d g=%d h=%d ' % (self.f, self.g, self.h)
    for city in self.path:
        s = s + ' ' + city
    return s

def cost(self):
    raise NotImplementedError

'

完整的初学者，所以任何帮助将不胜感激。

提前致谢！！！

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1 回答 1

0

您的def astar_run()方法返回self（请参见方法的最后一行），或者它通过切片返回一个列表path[::-1]，两者都没有toString()方法，因此您会收到此异常。如果你想打印你的类的表示，那么声明这个方法是很正常的__repr__()，然后你就可以了print ans。如果您希望能够转换为字符串，则通常调用该方法__str__()。

您期望从什么返回astar_run()？从同一个函数返回两种不同的类型通常是不好的做法。

于 2013-09-16T02:08:01.730 回答