Pierre Thibault, some people here surely know enough Python (and C++) to solve your problem, but often the problem is understanding the problem. I have understood your problem just partially, so the following are just ideas.
First of all I suggest you to use a normal Python list to keep the data, and later modify the code to use an array if it is too much slow or if you need arrays to do some special things, like plotting, etc. Developing using normal Python lists is a bit simpler. With python you can redefine the __getitem__ and __setitem__ of an object according to its crystal symmetries. Then you can define some method like iterkeys that yields (with yield) the only indexes that the symmetry allows to be set. Then you can iterate on those indexes and update the values in the list attribute. Bye, bearophile -- http://mail.python.org/mailman/listinfo/python-list
