fishturtle1
- 393
- 82
- Homework Statement
- This is code from a lecture but it won't work for me. My question is about the buildCityGraph function. It seems like the for loop doesn't work and I don't know why. Also i'm confused why we are adding edges the way we do. Why?
- Relevant Equations
- .
Edit: Trying to fix the formatting...
When i run this i get the error: NameError: 'Boston'. Why do we use g.addEdge(Edge(g.getNode('Boston'), g.getNode('Providence')))? It seems like g.addEdge(Edge(Node('Boston'), Node('Providence'))) is what we want? When I try this
I get the error: ValueError: At least one node not in graph. Why is the for loop in buildCityGraph function not working?
Python:
class Node(object):
def __init__(self, name):
self.name = str(name)
def get_name(self):
return self.name
def __str__(self):
return self.name
class Edge(object):
def __init__(self, src, dest):
self.src = src
self.dest = dest
def getSource(self):
return self.src
def getDestination(self):
return self.dest
def __str__(self):
return self.src.get_name() + "->" + self.dest.get_name()class Digraph(object):
def __init__(self):
self.edges = {}
def addNode(self, node):
if node in self.edges:
raise ValueError("Duplicate node found.")
else:
self.edges[node] = []
def addEdge(self, edge):
src = edge.getSource()
dest = edge.getDestination()
if not (src in self.edges and dest in self.edges):
raise ValueError("At least one node not in graph.")
else:
self.edges[src].append(dest)
def childrenOf(self, node):
return self.edges[node]
def hasNode(self, node):
return node in self.edges
def getNode(self, name):
for n in self.edges:
if n.get_name == name:
return n
else:
raise NameError(name)
def __str__(self):
result = ''
for src in self.edges:
for dest in self.edges[src]:
result += src.get_name() + "->" + dest.get_name() + "\n"
return result[:-1] #omit final new lineclass Graph(Digraph):
def addEdge(self, edge):
Digraph.addEdge(self, edge)
rev = Edge(edge.getDestination(), edge.getSource())
Digraph.addEdge(self, rev)
def buildCityGraph(graphType):
g = graphType()
for name in ('Boston', 'Providence', 'New York', 'Chicago',
'Denver', 'Phoenix', 'Los Angeles'): #Create 7 nodes
g.addNode(Node(name))
g.addEdge(Edge(g.getNode('Boston'), g.getNode('Providence')))
g.addEdge(Edge(g.getNode('Boston'), g.getNode('New York')))
g.addEdge(Edge(g.getNode('Providence'), g.getNode('Boston')))
g.addEdge(Edge(g.getNode('Providence'), g.getNode('New York')))
g.addEdge(Edge(g.getNode('New York'), g.getNode('Chicago')))
g.addEdge(Edge(g.getNode('Chicago'), g.getNode('Denver')))
g.addEdge(Edge(g.getNode('Chicago'), g.getNode('Phoenix')))
g.addEdge(Edge(g.getNode('Denver'), g.getNode('Phoenix')))
g.addEdge(Edge(g.getNode('Denver'), g.getNode('New York')))
g.addEdge(Edge(g.getNode('Los Angeles'), g.getNode('Boston')))
print(str(buildCityGraph(Digraph)))When i run this i get the error: NameError: 'Boston'. Why do we use g.addEdge(Edge(g.getNode('Boston'), g.getNode('Providence')))? It seems like g.addEdge(Edge(Node('Boston'), Node('Providence'))) is what we want? When I try this
Python:
class Node(object):
def __init__(self, name):
self.name = str(name)
def get_name(self):
return self.name
def __str__(self):
return self.name
class Edge(object):
def __init__(self, src, dest):
self.src = src
self.dest = dest
def getSource(self):
return self.src
def getDestination(self):
return self.dest
def __str__(self):
return self.src.get_name() + "->" + self.dest.get_name()class Digraph(object):
def __init__(self):
self.edges = {}
def addNode(self, node):
if node in self.edges:
raise ValueError("Duplicate node found.")
else:
self.edges[node] = []
def addEdge(self, edge):
src = edge.getSource()
dest = edge.getDestination()
if not (src in self.edges and dest in self.edges):
raise ValueError("At least one node not in graph.")
else:
self.edges[src].append(dest)
def childrenOf(self, node):
return self.edges[node]
def hasNode(self, node):
return node in self.edges
def getNode(self, name):
for n in self.edges:
if n.get_name == name:
return n
else:
raise NameError(name)
def __str__(self):
result = ''
for src in self.edges:
for dest in self.edges[src]:
result += src.get_name() + "->" + dest.get_name() + "\n"
return result[:-1] #omit final new lineclass Graph(Digraph):
def addEdge(self, edge):
Digraph.addEdge(self, edge)
rev = Edge(edge.getDestination(), edge.getSource())
Digraph.addEdge(self, rev)
def buildCityGraph(graphType):
g = graphType()
for name in ('Boston', 'Providence', 'New York', 'Chicago',
'Denver', 'Phoenix', 'Los Angeles'): #Create 7 nodes
g.addNode(Node(name))
g.addEdge(Edge(Node('Boston'), Node('Providence')))
# g.addEdge(Edge(g.getNode('Boston'), g.getNode('New York')))
# g.addEdge(Edge(g.getNode('Providence'), g.getNode('Boston')))
# g.addEdge(Edge(g.getNode('Providence'), g.getNode('New York')))
# g.addEdge(Edge(g.getNode('New York'), g.getNode('Chicago')))
# g.addEdge(Edge(g.getNode('Chicago'), g.getNode('Denver')))
# g.addEdge(Edge(g.getNode('Chicago'), g.getNode('Phoenix')))
# g.addEdge(Edge(g.getNode('Denver'), g.getNode('Phoenix')))
# g.addEdge(Edge(g.getNode('Denver'), g.getNode('New York')))
# g.addEdge(Edge(g.getNode('Los Angeles'), g.getNode('Boston')))
print(str(buildCityGraph(Digraph)))I get the error: ValueError: At least one node not in graph. Why is the for loop in buildCityGraph function not working?
