How to make combo descriptors (like circularity..)

[hughesadam87]

Maybe not worth it because it's super easy to just define these functions:

def circ(p):
return 4pi * p.area/p.perimeter**2

But still might be worth doing.

[hughesadam87]

FOR NOW, ADDED AS A HACK TO GETATTR OF PARTICLE MANAGER

    # Bypasses a bug (or pyparty design flaw?) in ipython notebook 2.0 beta
    # when ending a cell w/ c.particles
    if attr == '_ipython_display_':
        return         

    # HACK HACK HACK
    if attr == 'circularity':
        area = np.array([getattr(p, 'area') for p in self.plist])
        perim = np.array([getattr(p, 'perimeter') for p in self.plist])
        return 4 *  np.pi * (  area / (perim**2) )

    return np.array([getattr(p, attr) for p in self.plist])