Re: [graph-tool] Vertex variable name from a string

4 Jun 2012


      On 06/04/2012 08:48 AM, jarino wrote:
...
Hi,
I am wondering: is it possible to generate a vertex variable name from a
string.
Let me explain: I need to read a set of vertices from a csv file, and a set
of arcs from another file. My vertices have names of the form XYZ, and my
arcs then indicate whether there is a connection between XYZ and, say, ABC.
Of course, I could define a property "name", assign it to the vertex, then
find the indices of the origin and end vertices when I browsing my
connection file.
But I am wondering.. From the examples, I would like to do something like
v1 = g.add_vertex()
v2 = g.add_vertex()
e = g.add_edge(v1, v2)
but where v1, v2, etc., would be replaced by vertexName[i] (in a loop).
Probably it is my incompetence with python, but I don't seem to be able to
do that. A call to
for i in range(1, len(vertexName)):
    vertexName[i] = g.add_vertex()
does not give an error. But when I try to assign an edge using the "same"
method,
for i in range(1, len(listVertices)):
    e = g.add_edge(origVertex[i], destVertex[i])
I get
Traceback (innermost last):
  File "<stdin>", line 1, in <module>
  File "import_graph.py", line 59, in <module>
    e = g.add_edge(origVertex[i], destVertex[i])
  File "/usr/local/lib/python2.7/dist-packages/graph_tool/__init__.py", line
1109, in add_edge
    e = libcore.add_edge(weakref.ref(self), source, target)
TypeError: No registered converter was able to extract a C++ reference to
type graph_tool::PythonVertex from this Python object of type str
I'm slightly confused by what you are attempting to achieve, but I think
you simply want a mapping from a string to a vertex object, correct? All
you have to do is keep a dictionary:

    vmap = {}
    ...
    name = "foo" # you get this from your files
    vmap[name] = g.add_vertex()
    ...

    for i in xrange(0, len(listVertices)):  # you should start from 0, and use xrange!
        e = g.add_edge(vmap[origVertex[i]],
                       vmap[destVertex[i]])


Cheers,
Tiago


-- 
Tiago de Paula Peixoto <tiago@skewed.de>