Hello, your idea sounds good and handles the exception on teardown as well. (I did not think about the if XXX!=None check in teardown()) I will now provide each of the instruments with an explicit shutdown() method which frees the interface card as well.
These methods will be called in a finally clause after run. I think this is much better than to wait for or rely on garbage collection. Of course there is a hardware protection of the setup as well. I am amazed how well Python handles lab instrumentation, it is really fun to develop with Py. Many thanks for your help -- http://mail.python.org/mailman/listinfo/python-list
