road_graph.py

class Node(object):
    """A node in the road graph. Node functionality doesn't matter, we just
    need something to refer to by name."""

    def __lt__(self, other):
        """Use the object ID Just so we have a canonical way to sort Nodes."""
        id(self) < id(other)


class Edge(object):
    """Connection between two Nodes."""

    def __init__(self, node_pair):
        """Calculate the edge's length."""
        pass  # TODO

    def weight(self):
        """How long does it take to traverse this edge? Used for pathing."""
        return 1000  # TODO


class Graph(object):
    """Collection of Nodes and the Edges that connect them."""

    def __init__(self):
        self.nodes = set()
        # type: set[Node]
        """For easy reference to the Nodes themselves."""

        self.edges = {}
        # type: Dict[ Tuple[Node, Node], Edge ]
        """Each connection between nodes. Because an edge works both ways
        (this is a normal graph, not a directional graph), sort the two Nodes
        before using them as a key. That way, we only have to store edges once.
        Ergo, (a, b) and (b, a) should mean the same thing."""

    def add_node(self, n):
        """Add a new node to the graph."""
        for other in nodes:
            node_pair = tuple(sorted([n, other]))
            edges[node_pair] = Edge(node_pair)
        nodes.add(n)

    def path(self, a, b):
        """Find a path from a to b.

        Returns a list of Nodes beginning with `a` and ending with `b`."""
        pass  # TODO do A* pathing