The code would be less redundant if you did this and line 101.. in a loop, i.e.,

    for ii, data in enumerate([lh_data, rh_data]):
        if len(vertno[ii]) != 0:
            idx = np.argsort(vertno[ii])
            vertno[ii] = vertno[ii][idx]
            data.append(np.concatenate(data)[idx])