Problems with PropertyValue when Graph's vertices are Lists

Question

I create a Graph which vertices are lists (points in n-dimensional space)

v1 = {{1, 2} -> {3, 4}, {5, 6} -> {7, 8}};
g1 = Graph[v1];
PropertyValue[{g1, VertexList[g1][[1]]}, VertexWeight] = 10

and I get a message error:

Set::write: Tag PropertyValue in PropertyValue[...] is protected

Now, if I do

v2 = {1 -> 2, 3 -> 4};
g2 = Graph[v2];
PropertyValue[{g2, VertexList[g2][[1]]}, VertexWeight] = 10

everything is fine.

g1 and g2 are structurally indentical, the difference is only in vertices type: list(g1) and scalar(g2).

What's the problem here?

Answer 1

It works if you specify weights in the following way:

g = Graph[{{1, 2} -> {3, 4}, {5, 6} -> {7, 8}}];
g = SetProperty[g, VertexWeight -> {{1, 2} -> 10}];
PropertyValue[g, VertexWeight]

{10, 1, 1, 1}