Python - 迪杰斯特拉算法中的距离计算

Question

我在计算每个节点离起始节点的距离时遇到了一些问题，或者说根本没有得到任何信息。
我运行的函数没有任何输出，具体代码在下面的链接里。

#Values to assign to each node
class Node:
     distFromSource = infinity
     previous = invalid_node
     visited = False

#for each node assign default values    
def populateNodeTable(network): 
    nodeTable = []
    index = 0
    f = open('network.txt', 'r')
    for line in f: 
      node = map(int, line.split(',')) 
      nodeTable.append(Node())

      print "The previous node is " ,nodeTable[index].previous 
      print "The distance from source is " ,nodeTable[index].distFromSource 
      index +=1
    nodeTable[startNode].distFromSource = 0 

    return nodeTable

#calculate the distance of each node from the start node
def tentativeDistance(currentNode, nodeTable):
    nearestNeighbour = []
    for currentNode in nearestNeighbour:
      currentDistance == currentNode.distFromSource + [currentNode][nearestNeighbour] #gets current distance from source
      print "The current distance"
      if currentDistance != 0 & currentNode.distFromSource < Node[currentNode].distFromSource:
         nodeTable[currentNode].previous = currentNode
         nodeTable[currentNode].length = currentDistance
         nodeTable[currentNode].visited = True
         nodeTable[currentNode] +=1
         nearestNeighbour.append(currentNode)
         for currentNode in nearestNeighbour:
           print nearestNeighbour

    return nearestNeighbour

我心里觉得我的逻辑是对的，但当代码运行时，我连错误信息都没有看到。

Answer 1

你应该重新考虑一下你的算法设计。可以查一下Dijkstra算法的伪代码定义，然后试着用Python来实现它。特别是，你需要想想你程序中的控制流程。

你可能还想看看这个食谱，里面有Dijkstra算法的Python实现，看看你能不能理解它。

Answer 2

你把 nearestNeighbour 设置成了一个空列表，然后你用 for currentNode in nearestNeighbour 这个循环去遍历它——但是这个循环什么都不做，因为列表是空的——最后你就直接从函数里返回了。

（我猜 tentativeDistance 是你调用的那个函数，但你什么也没看到结果。）