iteration: select a random element from random list

I have a tree (or "matrix") containing a bunch of line position points:

tree = [[[x,y][x,y],[x,y]],
    [[x,y],[x,y],[x,y]],
    [[x,y],[x,y],[x,y]]]

My goal is to connect even more lines from random points on each "branch" to other random points on separate branches. Once a line is created, the position points on both branches will be unusable for future line creation.

I've managed to randomize the point iteration with random.shuffle(), but I'm currently taking one branch at a time and comparing it's points with only one neighboring branch at a time. This gives me a bunch of lines connecting from one branch to the first branch it checks, but I want them all over the place, connecting to many branches.

Here's what I have so far. The functions are native to Cinema 4D. The searchable API can be found here: http://ift.tt/1VzxBij Function GetSplinePoint() simply returns the position of a spline (3D line) object.

rand_pts = [_ for _ in xrange(spline_resolution)]        
for p_spline in xrange(len(splines)):
    random.shuffle(rand_pts)
    for p in rand_pts:
        if p == 0 or p == spline_resolution-1 or occupied[p_spline][p] == True: continue
        mindist = 99999
        new_connection = False
        p_amt = c4d.utils.RangeMap(p, 0, spline_resolution-1, 0, 1, False)
        p_pt = spline_objs[p_spline].GetSplinePoint(p_amt)
        for n_spline in xrange(len(splines)):
            if n_spline != p_spline:
                random.shuffle(rand_pts)
                for n in rand_pts:
                    if n == 0 or n == spline_resolution-1 or occupied[n_spline][n] == True: continue
                    n_amt = c4d.utils.RangeMap(n, 0, spline_resolution-1, 0, 1, False)
                    n_pt = spline_objs[n_spline].GetSplinePoint(n_amt)
                    dist = (p_pt - n_pt).GetLength()
                    if dist < op[c4d.ID_USERDATA,5] and dist < mindist:
                        mindist = dist
                        new_connection = True
                        break