Guido van Rossum wrote: > On 9/28/05, Jim Fulton <[EMAIL PROTECTED]> wrote: > ... > I think we need to be real careful with chosing a name -- in Jim's > example, *anyone* could assign to Spam().eggs to override the value. > The name "readproperty" is too close to "readonlyproperty",
In fact, property creates read-only properties for new-style classes. (I hadn't realized, until reading this thread, that for classic classes, you could still set the attribute.) > but > read-only it ain't! "Lazy" also doesn't really describe what's going > on. I agree. > I believe some folks use a concept of "memo functions" which resemble > this proposal except the notation is different: IIRC a memo function > is always invoked as a function, but stores its result in a private > instance variable, which it returns upon subsequent calls. This is a > common pattern. Jim's proposal differs because the access looks like > an attribute, not a method call. Still, perhaps memoproperty would be > a possible name. > > Another way to look at the naming problem is to recognize that the > provided function really computes a default value if the attribute > isn't already set. So perhaps defaultproperty? Works for me. Oleg Broytmann wrote: > On Wed, Sep 28, 2005 at 10:16:12AM -0400, Jim Fulton wrote: > >> class readproperty(object): > > [skip] > >>I do this often enough > > > I use it since about 2000 often enough under the name CachedAttribute: > > http://cvs.sourceforge.net/viewcvs.py/ppa/qps/qUtils.py Steven Bethard wrote: > Jim Fulton wrote: > ... > I've also needed behavior like this a few times, but I use a variant > of Scott David Daniel's recipe[1]: > > class _LazyAttribute(object): Yup, the Zope 3 sources have something very similar: http://svn.zope.org/Zope3/trunk/src/zope/cachedescriptors/property.py?view=markup I actually think this does too much. All it saves me, compared to what I proposed is one assignment. I'd rather make that assignment explicit. Anyway, all I wanted with readproperty was a property that implemented only __get__, as opposed to property, which implements __get__, __set__, and __delete__. I'd be happy to call it readproprty or getproperty or defaulproperty or whatever. :) I'd prefer that it's semantics stay fairly simple though. Jim -- Jim Fulton mailto:[EMAIL PROTECTED] Python Powered! CTO (540) 361-1714 http://www.python.org Zope Corporation http://www.zope.com http://www.zope.org _______________________________________________ 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
