On Wed, 09 Feb 2005 21:56:54 +1000, Nick Coghlan <[EMAIL PROTECTED]> wrote: > Alex Martelli wrote: > > One thing I'd like to see in namespaces is _chaining_ -- keeping each > > namespace separate but having lookups proceed along the chain. (The > > best semantics for _bindings_ as opposed to lookups isn't clear though). > > Hmm, so if it doesn't find it in the current namespace, it looks in the > parent? > > For bindings, you could just go with standard Python semantics - normal name > binding always happens in the innermost scope, so binding a name in a > namespace > should happen in the directly referenced namespace. Then you can shadow names > from outer scopes, and later regain access to them using 'del'.
What does PyPy do in this case? It seems that a 'namespace' class, or at least part of its behavior, is needed there anyway... It seems to be worth checking. > Rough concept: > Have a '__fallback__'** attribute that is initialised to None > Have a custom __getattr__ that falls back to the containing namespace if > the > result is not found in the current namespace. > Have a class method which allows a namespace to be 'put inside' another > namespace. > > ** Blech. Trying to add *any* state to namespace instances is going to suck. > Maybe it would be better to just have a single __impl__ attribute and have any > implementation related variables hang off it. This could make life easier when > subclassing. I'm tempted to say update() should just ignore any field with a > leading underscore by default (then we can just use normal private attributes, > which are altered at the user's risk), but that may be too draconian. > > On a complete tangent, I thought it might be worthwhile summarising the ideas > that have come up in this thread > > - using type(self).method(self,...) as a polymorphism friendly way to > access a > class method. > > - a 'view' alternate constructor to allow manipulation of an existing > dictionary such as globals() > > - a 'record' data type that allows the use of class definition syntax for > simple data structures > > - lookup chaining, allowing fallback to an 'outer scope'. > > Even though we'll probably end up dropping the last couple as overengineering > things for the first pass, they're still interesting ideas to kick around. Another idea, maybe even more distantly related but still worthy keeping in mind: the 'named tuples' that we talked about a few months ago. It is in some sense a variation on some of the ideas presented here; it is an alternative way to build simple records or bunch-like structures. -- Carlos Ribeiro Consultoria em Projetos blog: http://rascunhosrotos.blogspot.com blog: http://pythonnotes.blogspot.com mail: [EMAIL PROTECTED] mail: [EMAIL PROTECTED] -- http://mail.python.org/mailman/listinfo/python-list
