Python - Passing Function Arguments
I am struggling on how to work out how I pass arguments from a function so that I can populate a list in another function - my code is:
infinity = 100开发者_运维技巧0000
invalid_node = -1
startNode = 0
#Values to assign to each node
class Node:
distFromSource = infinity
previous = invalid_node
visited = False
#read in all network nodes
def network():
f = open ('network.txt', 'r')
theNetwork = [[int(node) for node in line.split(',')] for line in f.readlines()]
print theNetwork
return theNetwork
#for each node assign default values
def populateNodeTable():
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
#find the nearest neighbour to a particular node
def nearestNeighbour(currentNode, theNetwork):
nearestNeighbour = []
nodeIndex = 0
for node in nodeTable:
if node != 0 and currentNode.visited == false:
nearestNeighbour.append(nodeIndex)
nodeIndex +=1
return nearestNeighbour
currentNode = startNode
if __name__ == "__main__":
nodeTable = populateNodeTable()
theNetwork = network()
nearestNeighbour(currentNode, theNetwork)
So, I am trying to fill the nearestNeighbour list in my nearestNeighbour function with a list of nodes nearest to the other nodes. Now, the all the other functions work correctly, with all argument passing functioning as it should. However, my nearestNeighbour function throws up this error message:
if node != 0 and theNetwork[currentNode].visited == false: AttributeError: 'list' object has no attribute 'visited'
(Apologies for the layout, haven't quite fathomed the use of the code quotes yet)
class Node(object):
def __init__(self, me, dists):
super(Node,self).__init__()
self.me = me
self.dists = dists
_inf = Network.INF
self.neighbors = sorted((i for i,dist in enumerate(self.dists) if i!=me and dist!=_inf), key=dists.__getitem__)
self.clear()
def clear(self):
self.dist = None
self.prev = None
def nearestNeighbor(self):
try:
return self.neighbors[0]
except IndexError:
return None
def __str__(self):
return "{0}: {1}".format(self.me, self.dists)
class Network(object):
INF = 10**6
@classmethod
def fromFile(cls, fname, delim=None):
with open(fname) as inf:
return cls([[int(dist) for dist in line.split(delim)] for line in inf])
def __init__(self, distArray):
super(Network,self).__init__()
self.nodes = [Node(me,dists) for me,dists in enumerate(distArray)]
def __str__(self):
return '\n'.join(self.nodes)
def floodFill(self, fromNode):
_nodes = self.nodes
for n in _nodes:
n.clear()
_nodes[fromNode].dist = 0
# left as an exercise ;-)
def distances(self):
return [n.dist for n in self.nodes]
def main():
nw = Network.fromFile('network.txt', delim=',')
print(nw)
nw.floodFill(fromNode=0)
print(nw.distances())
if __name__=="__main__":
main()
That's because theNetwork[currentNode]
returns a list. In other words: theNetwork
is a list of lists.
This is the line where it is done:
theNetwork = [[int(node) for node in line.split(',')] for line in f.readlines()]
theNetwork = [[int(node) for node in line.split(',')] for line in f.readlines()]
theNetwork
is a list of lists. A list (theNetwork[currentNode]
) doesn't have a visited
attribute.
Perhaps you intended something like:
for line in f.readlines():
theNetwork.extend((int(node) for node in line.split(',')))
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