Re: [Boost-users] dijkstra_shortest_paths and Python

30 Nov 2006

      Hi,

I couldn't find the add_vertex_property method. But, I found my way
nonetheless... Here's the code for future reference:

import boost

class PathFind:
    def __init__(self):
        self.graph = boost.Graph()
        self.weights = self.graph.edge_property_map('float')
        self.vertexesid = self.graph.vertex_property_map('integer')
        self.vertexes = {}

    def __addvertex__(self, id):
        if not self.vertexes.has_key(id):
            v = self.graph.add_vertex()
            self.vertexes[id] = v
            self.vertexesid[v] = id
            return v

        return self.vertexes[id]

    def addEdge(self, srcVertex, dstVertex, cost):
        src = self.__addvertex__(srcVertex)
        dst = self.__addvertex__(dstVertex)

        edge = self.graph.add_edge(src, dst)
        self.weights[edge] = cost

    def findPath(self, src, dst):
        p = self.graph.vertex_property_map('vertex')
        boost.dijkstra_shortest_paths(self.graph, self.vertexes[src],
                                      predecessor_map = p,
                                      weight_map = self.weights)

        path = [dst]
        while src != dst:
            dst = self.vertexesid[p[self.vertexes[dst]]]
            path.append(dst)
        path.reverse()

        return path

a = PathFind()
a.addEdge(1, 2, 5)
a.addEdge(2, 3, 3)
a.addEdge(2, 4, 4)
a.addEdge(3, 4, 0.5)

print a.findPath(1, 4)

Cheers!

Hugo Ferreira

On 11/30/06, John Reid <j.reid@mail.cryst.bbk.ac.uk> wrote:
...
Hi,
This works for me:
import boost.graph as bgl
graph = bgl.Graph()
a = graph.add_vertex()
b = graph.add_vertex()
e = graph.add_edge(a, b)
weights = graph.add_edge_property('integer')
weights[e] = 5
predecessors = graph.add_vertex_property('vertex')
bgl.dijkstra_shortest_paths(
        graph,
        a,
        predecessor_map = predecessors,
        weight_map = weights
)
Hope that helps,
John.
Hugo Ferreira wrote:
...
HI there,
I'm trying to use the BGL bindings for python found here:
http://www.osl.iu.edu/~dgregor/bgl-python/
The problem is that I can't seem to understand how the
dijkstra_shortest_paths() and the corresponding graph works. My code,
so far, is like this:
---8<---8<---
import boost as bgl
graph = bgl.Graph()
a = graph.add_vertex()
b = graph.add_vertex()
e = graph.add_edge(a, b)
weights = graph.edge_property_map('integer')
weights[e] = 5
graph.edge_properties['weight'] = weights
boost.dijkstra_shortest_paths(graph, a)
---8<---8<---
Which, of course, complains about the dijkstra_shortest_paths function
signature. Can anyone please provide me an working example of setting
up a graph and calling this function? I basically need the shortest
path from vertex A to vertex B.
Thanks in advance,
Hugo Ferreira
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