gogurt - 9 months ago 43

Python Question

This is a ridiculously basic question about graph-tool which should be trivial to figure out how to solve using the documentation, but I'm spinning in circles. I don't doubt that documentation comprehensive, but it certainly isn't making this easy.

**GOAL: Given a graph G, extract the induced subgraph based on a list of vertices of G.**

I know I should be doing this with a

`GraphView`

`PropertyMap`

The documentation is very lacking here. For example, the page on PropertyMaps says that each

`PropertyMap`

`PropertyMaps`

For this problem, I get the vague sense that I need to use the Boolean type, because maybe I want to set the vertices I want in the subgraph to "true" while the vertices I don't want in the subgraph to "false." But does that mean the

`PropertyMap`

Answer

You are right. You have to use `GraphView`

. In the following example a induced subgraph with vertices 0, 1, 3 are created from a complete graph with 5 vertices

```
from graph_tool import GraphView, generation
g = generation.complete_graph(5)
# select some vertices
vfilt = g.new_vertex_property('bool');
vfilt[0] = True
vfilt[1] = True
vfilt[3] = True
sub = GraphView(g, vfilt)
print [(g.vertex_index[e.source()], g.vertex_index[e.target()])
for e in sub.edges()]
```

Output

```
[(0, 1), (0, 3), (1, 3)]
```