2010/8/23 Steven D'Aprano <st...@pearwood.info>: > On Tue, 24 Aug 2010 06:50:19 am Guido van Rossum wrote: > >> > * Is there anything that hasattr(obj, key) can or should do that >> > can't already be done with getattr(obj, key, None)? >> > If not, do we really need to change anything? >> >> getattr(obj, 'key', None) returns None when obj.key exists and has >> the value None. The workaround is ugly. > > Why do you say it's ugly? It's a short, sweet, simple two-liner: > > mark = object() > getattr(obj, 'key', mark) is not mark > > Nothing ugly about it at all. But if somebody really objected to using a > two lines, they could put it in a utility function.
That's not all, though. You still have to test it with an "if" and that gets cumbersome after a while. > > I have always thought that hasattr() does what it says on the box: it > tests for the *existence* of an attribute, that is, one that statically > exists rather than being dynamically generated. In other words, it is a > key in the instance __dict__ or is inherited from the class __dict__ or > that of a superclass, or a __slot__. > > Now that I know that hasattr doesn't do what I thought it does or what > the name implies it does, it has little or no utility for me. In the > future, I'll just write a try...except block and catch errors if the > attribute doesn't exist. Well, that's exactly what hasattr does... -- Regards, Benjamin _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
