> With your CD example, you need an external resource (the CD itself) in > order to calculate the hash - in that case, you can't safely defer > the hash calculation until the first time you know you need it, > since you don't know whether or not you'll have access to the > physical CD at that point.
OK. Then instead of a CD, use a (read-only) disk file. The example is still valid in that case, and avoids the extraneous matter of operator intervention. It's still the case that evaluating a hash might be expensive the first time you do it, so you may want to be able to test whether it can be done and actually do it only later. _______________________________________________ Python-3000 mailing list Python-3000@python.org http://mail.python.org/mailman/listinfo/python-3000 Unsubscribe: http://mail.python.org/mailman/options/python-3000/archive%40mail-archive.com
