Creating a City Graph with Nodes & Edges

  • Comp Sci
  • Thread starter fishturtle1
  • Start date
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    Graph Nodes
In summary: 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'):
  • #1
fishturtle1
394
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...

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?
 
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  • #2
I fixed the getNode method but now it when i run, the code returns None.

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.")
        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
        raise NameError(name)

    def __str__(self):
        result = ''
        print(self.edges)
        for src in self.edges:
            print('hi')
            for dest in self.edges[src]:
                print('here')
                result += src.get_name() + "->" + dest.get_name() + "\n"
        return result #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)))
 
  • #3
Now it works, I forgot to return g in the buildCityGraph.

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.")
        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
        raise NameError(name)

    def __str__(self):
        result = ''
        print(self.edges)
        for src in self.edges:
            for dest in self.edges[src]:
                result += src.get_name() + "->" + dest.get_name() + "\n"
        return result #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')))

    return g

print(str(buildCityGraph(Digraph)))
 
  • Like
Likes Mark44 and pbuk
  • #4
That is a great example of self help! Glad you fixed it :smile:
 
  • Like
Likes fishturtle1
  • #5
pbuk said:
That is a great example of self help! Glad you fixed it :smile:
Thanks!
 

FAQ: Creating a City Graph with Nodes & Edges

What is a city graph?

A city graph is a visual representation of a city's infrastructure, including roads, buildings, landmarks, and other features. It is created using nodes (points or vertices) and edges (lines or arcs) to connect the different elements of the city.

Why is it important to create a city graph?

Creating a city graph allows us to better understand the layout and structure of a city. It can help with urban planning, transportation management, and disaster response. It also allows for data analysis and visualization, which can aid in decision-making and problem-solving.

What are nodes and edges in a city graph?

Nodes are points or vertices that represent specific locations or objects in a city, such as intersections, buildings, or landmarks. Edges are lines or arcs that connect the nodes and represent the relationships or connections between them, such as roads, paths, or rivers.

How is a city graph created?

A city graph can be created using various methods, such as manual mapping, aerial photography, or satellite imagery. It can also be generated using Geographic Information Systems (GIS) software, which allows for the input and manipulation of data to create a digital representation of the city.

What are some applications of city graphs?

City graphs have many practical applications, including urban planning, transportation management, disaster response, and navigation. They are also used in data analysis and visualization for various purposes, such as identifying patterns, predicting trends, and monitoring changes in a city's infrastructure.

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