Vertex class

The Graph Abstract Data Type describes a strategy for using Vertex objects to describe a Graph.

The Vertex class describes the nodes in the graph. Its ADT includes:

• Vertex(key) - creates a new vertex with a given key
• addNeighbor(neighborVertex, weight) - creates a connection of the specified weight to another vertex
• getConnections() - identifies all of the vertices this one is connected to
• getID() - returns the key for this vertex
• getWeight(neighborVertex) = identifies the weight of the edge between this vertex and the specified neighbor

Use the following code as a template for writing the Vertex class.

class Vertex(object):
    """Describes a vertex object in terms of a "key" and a
    dictionary that indicates edges to neighboring vertices with
    a specified weight.
    """
    def __init__(self, key):
        """Constructs a vertex with a key value and an empty dictionary
        "connected_to" where we'll store other vertices to which this vertex is connected.
        """

    def add_neighbor(self, neighbor_vertex, weight=0):
        """Adds a reference to a neighboring Vertex object to the dictionary, 
        to which this vertex is connected by an edge. If a weight is not indicated, 
        default weight is 0.
        """


    def __repr__(self):
        """Returns a representation of the vertex and its neighbors,
        suitable for printing. Check out the example of 
        'list comprehension' here!
        """
        return str(self.id) + ' connected_to: ' + str([x.id for x in self.connected_to])

    def get_connections(self):
        """Returns the keys of the vertices we're connected to
        """

    def get_id(self):
        """Returns the id ("key") for this vertex
        """

    def get_weight(self, neighbor_vertex):
        """Returns the weight of an edge connecting this vertex with another.
        """

You can test your class by running the following commands:

v1 = Vertex(1)
v2 = Vertex(2)
v3 = Vertex(3)
v1.add_neighbor(v2)
v1.add_neighbor(v3,7)
print("Vertex v1 is ", v1)
print("Vertex v1 is connected to ", v1.get_connections())
print("The weight between v1 and v3 is ", v1.get_weight(v3))
print("Vertex v2 is connected to ", v2.get_connections())

Expected output similar to:

Vertex v1 is 1 connected to: [2, 3]
Vertex v1 is connected to  dict_keys([<__main__.Vertex object at 0x7f85981cca90>, <__main__.Vertex object at 0x7f85981a2370>])
The weight between v1 and v3 is  7
Vertex v2 is connected to  dict_keys([])