[Zope-dev] Re: hasattr implementation for Zope?

[Paul Winkler]

On Fri, May 27, 2005 at 12:08:55PM -0400, Paul Winkler wrote:
> On Fri, May 27, 2005 at 11:49:03AM -0400, Jim Fulton wrote:
> > BTW, I prefer to code things like this in the following way:
> > 
> >   def safe_hasattr():
> >       marker = object()
> > 
> >       def safe_hasattr(obj, attr):
> >           return getattr(obj, attr, marker) is not marker
> > 
> >       return safe_hasattr
> > 
> >   safe_hasattr = safe_hasattr()
> >
> > This way, there aren't any extra arguments or funny
> > globals to confuse matters.  (I've seen code that broke
> > because people tried to reuse marker definitions accross
> > modules.

One more thought... as for "funny globals", it seems to me that a 
"private" global like __marker = [] results in cleaner code than either
your approach or the keyword arg hack.  Anybody who imports a __foo name
deserves whatever problems they get :-)

But of course we don't do it because accessing globals in a method that
might be looped over is slow.  Which, hopefully, will become a non-issue
some day (PEP 267, 268, 280).

-- 

Paul Winkler
http://www.slinkp.com