The keyword is "multiedges" not "multi_edges". Weird artifact of using
NetworkX as the default implementation historically...
On 7 December 2010 20:57, mhs <schraud...@math.uni-heidelberg.de> wrote:
> Hi,
>
> I encountered a strange behaviour of the add_edges method for DiGraphs
> (using SAGE 4.5.1). Perhaps this is intended behaviour, but as it
> seems quiet odd to me I would like to hear the opinion of more
> experienced (di)graph-users. Maybe this is a real bug...
>
> If I define a looped, multi-edge empty digraph with
>
> G=DiGraph({},multi_edges=True,loops=True)
>
> I can add a couple of edges at once using
>
> G.add_edges([[0,1],[0,1],[1,1],[0,0],[1,0],[0,1]])
>
> this gives the correct graph (having 2 vertices and 6 edges).
>
> Nevertheless, if I define my digraph with
>
> G=DiGraph(multi_edges=True,loops=True)
>
> or
>
> G=DiGraph([],multi_edges=True,loops=True)
>
> the same command to add edges
>
> G.add_edges([[0,1],[0,1],[1,1],[0,0],[1,0],[0,1]])
>
> gives a digraph on 2 vertices but with only 4 edges (the double edge
> is not created).
> Even stranger: If I put edge labels I can see that whenever I add more
> edges afterwards an old edge gets deleted and is replaced by a new
> one, but never does the graph have multi-edges.
>
> Looking forward to an explanation of this funny behaviour.
>
> Best
> M.
>
> --
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--
Robert L. Miller
http://www.rlmiller.org/
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