Python - Calculating Distance in Dijkstra

I am having some trouble in determining the distance of each node from the start node, or rather getting any information back at all. I get no output from my function, attached in the following link.

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

#for each node assign default values    
def populateNodeTa开发者_开发问答ble(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

My logic is, at least in my mind, correct; however, I don't get as much as an error message when the code is run.

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You're setting nearestNeighbour to be an empty list, and then you're looping over it with for currentNode in nearestNeighbour -- which does nothing, because the list is empty -- and then you're returning from the function.

(I assume tentativeDistance is the function you're calling and seeing nothing from.)

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You should rethink your algorithm design. Try looking up a pseudocode definition of Dijkstra's algorithm and implementing that in Python. In particular, you should think about the control flow in your program.

You might want to have a look at this cookbook recipe for a Python implementation of Dijkstra and see if you can understand it.