Multiple refactoring of an original version of boids [Boids](http://dl.acm.org/citation.cfm?doid=37401.37406)  as an exercise.  update_boids_bad) ground version bad_boids : origina boids downloaded from git hub. No refactoring has been done  update_boids_array)  np_boids : boids implemented with no object oriented programming and but refactored with numpy arrays  update_boids_oo)  oo_boids : boids implemented using object oriented programming and mvc programming pattern  update_boids_oo_array)  oo_numpy_boids :  boids implemented using object oriented programming, mvc programming pattern and  numpy arrays  Each version has been tested. See test folder. Performances of each refactoring has been compared with each others. See performance_comparison.