On Saturday, February 24, 2018 at 9:56:04 AM UTC+1, Alasdair wrote:
>
> Hello,
>
> I have defined a polyhedron by a collection of linear inequalities over
> three variables, and it's all lovely: I can access the vertices, draw all
> sorts of nice pictures, get all sorts of information. The one problem is
> the vertex graph. If my polyhedron is P, say, then P.vertex_graph() gives
> me a graph where each vertex is labelled something like "A vertex at
> (0,1,0)". This seems somewhat redundant labelling, and ideally I'd like to
> relabel the vertices to simply "(0,1,0)".
>
> I attempted to relabel the vertex graph with:
>
> dict ={i:j, for (i,j) in zip(P.vertices(),P.vertex_list())
> G = P.vertex_graph()
> G.relabel(dict)
>
>
> However, that attempt produced the error:
>
> TypeError: unhashable type: 'list'
>
>
> I'm not sure how to go about this relabelling... any idea? Thanks!
>
a 'list' cant be a vertex of a graph. It needs to be something hashable,
like a 'tupe'. Try the code below.
Cheers
Moritz
sage: P = polytopes.cube()
sage: G = P.graph()
sage: G.vertices()
[A vertex at (-1, -1, -1),
A vertex at (-1, -1, 1),
A vertex at (-1, 1, -1),
A vertex at (-1, 1, 1),
A vertex at (1, -1, -1),
A vertex at (1, -1, 1),
A vertex at (1, 1, -1),
A vertex at (1, 1, 1)]
sage: dict ={i:tuple(j) for (i,j) in zip(P.vertices(),P.vertices_list())}
sage: G.relabel(dict)
sage: G.vertices()
[(-1, -1, -1),
(-1, -1, 1),
(-1, 1, -1),
(-1, 1, 1),
(1, -1, -1),
(1, -1, 1),
(1, 1, -1),
(1, 1, 1)]
sage: dict
{A vertex at (-1, -1, -1): (-1, -1, -1),
A vertex at (-1, -1, 1): (-1, -1, 1),
A vertex at (-1, 1, -1): (-1, 1, -1),
A vertex at (-1, 1, 1): (-1, 1, 1),
A vertex at (1, -1, -1): (1, -1, -1),
A vertex at (1, -1, 1): (1, -1, 1),
A vertex at (1, 1, -1): (1, 1, -1),
A vertex at (1, 1, 1): (1, 1, 1)}
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