Python graph-tool - remove unconnected vertices

Question

I am writing a program that uses the Python graph-tool library, and I have had luck using a radial tree layout with graph_tool.draw.radial_tree_layout(g,vertexes[0]). However, there are several segments of my graph that are cut off from the rest and have no edges leading to any parts of the graph that I want. When I draw the graph, the disconnected nets get put into the middle, on top of he vertex that I want to be central. Therefore, I need an algorithm that will either remove these vertexes that have no route to vertexes[0], or a function to put them somewhere else on the graph, out of the way.

Answer 1

And I figured it out:

(I was pulling from an SQLite database)

c.execute('SELECT * FROM connections')
ucon = c.fetchall()

lastlevel = ['Philosophy']
nextlevel = []

pcon = []

while lastlevel != []: 
    for i in ucon:
        if i[1] in lastlevel:
            nextlevel.append(i[0])
            pcon.append(i)
    lastlevel = nextlevel
    nextlevel = []

Each line in the SQLite db was a tuple of start point and end point for a spanning edge. This isn't very efficient, but it does work well!