Dot graph language - how to make bidirectional edges automatically?

Question

Here is a very simplified example of my Dot graph:

strict digraph graphName {
A->B
B->A
}

This creates

Instead I want a single edge shown between A and B but with a double arrow head. I know how to get the double arrowhead as a global option:

strict digraph graphName {
  edge [dir="both"]
A->B
B->A
}

But that looks very ugly, and not all of my edges should be dual headed.

If I do more processing of the graph and detect the double reference myself and replace the two edges with a single edge, it looks OK. But I'd rather not have to do this extra step

strict digraph graphName {
A->B [dir="both"]
}

Any better solutions?

Posthaste

Answer 1

How about 'concentrate=true'?:

strict digraph graphName {
concentrate=true
A->B
B->A
}

From the documentation:

If true, use edge concentrators. This merges multiedges into a single edge and causes partially parallel edges to share part of their paths. The latter feature is not yet available outside of dot.

Optimal

Works with a label for me, and I'm running an older version. – Hydrodynamics

If it helps... this didn't work for me, in so much as it coalesced the edges, but only put a single arrow on the end. Then I tried to "strict digraph"... and it works perfectly then. – Ague

This is silly but it's what the OP wanted, so big up! – Gottschalk

@Ague It does not work for me either, I get edges with a single arrowhead only. I am using pygraphviz, and I tried pgv.AGraph(directed=True, strict=True), but it does not work either, i get two edges again... Any suggestions? – Garygarza

Answer 2

You should just use:

A -> B [dir=both]

Jolie

This saved me some redundant lines, and I'm using it as well as the top answer where appropriate. – Hydrodynamics

You don't need quotes around "both" – Dyslogistic

@NoahSussman It can't be the accepted answer because it doesn't actually answer the question ;) – Gottschalk