"Russ P." <russ.paie...@gmail.com> writes: > On Jan 25, 10:04 am, Mark Wooding <m...@distorted.org.uk> wrote: > > But what if you type "mumble._seekrit" in several places, then the > library implementer decides to give in to your nagging and makes it > "public" by changing it to "mumble.seekrit".
There's a possibly better fix: introduce a property `seekrit' (or perhaps a better name!) which diddles the _seekrit attribute under the covers. > Now suppose you forget to make the corresponding change somewhere in > your code, such as > > mumble._seekrit = zzz > > You will get no warning at all. You will just be inadvertently > creating a new "private" attribute -- and the assignment that you > really want will not get done. True. That's a shame. It'd be nice if there were a way to fix that. There's this __slots__ thing I keep hearing about... > For that matter, the library implementer himself could make the same > mistake and get no warning. He could do. Why he didn't do a search and replace like any sensible person is a mystery. Testing is good, too. > When you think about it, you soon realize that the leading underscore > convention violates the spirit if not the letter of one of the first > principles of programming 101: if you have a constant parameter that > appears in several places, assign the literal value in one place > rather than repeating it everywhere. You mean `once and only once'. Yeah, I like that one too. > Then if you need to change the value, you only need to change it in > one place. That reduces effort, but more importantly it reduces the > potential for error. The same principle applies to "declaring" an > attribute private. Introducing a property hides the problem, but doesn't actually solve it, because you're right on this. Fortunately the problem doesn't actually come up that often. But yes, basically, I agree with you on this particular point: it's easier to add an alias than to rename, which avoids the problem but is error prone. -- [mdw] -- http://mail.python.org/mailman/listinfo/python-list
