property collections

[Ben Wolfson]

In article <g44pZKATy8B7Ewa2 at jessikat.fsnet.co.uk>, "Robin Becker"
<robin at jessikat.fsnet.co.uk> wrote:

> I'm looking for ways to spell property collection ie
> 
> PC.attr1 = value1
> PC.attr2 = value2
> 
> PC[i].attr1 = value
> 
> ...
> 
> if PC[i].attr hasn't been explicitly set then the default is found on
> the un-indexed thing.
> 
> My solutions seem to involve elements which need to refer to the parent
> and thus create a loop.

I don't think this creates a loop:

class PropertyCollection:
	class Properties:
		def __init__(self, dict):
			self.__dict__.update(dict)
	def __init__(self):
		self.__dict__['attrs'] = {}
		self.__dict__['i_attrs'] = {}
	def __getitem__(self, i):
		if not self.i_attrs.has_key(i):
			self.i_attrs[i] = self.Properties(self.attrs)
		return self.i_attrs[i]
	def __getattr__(self, k):
		return self.attrs[k]
	def __setattr__(self, k, v):
		self.attrs[k] = v
	def __delattr__(self, k):
		del self.attrs[k]
-- 
Barnabas T. Rumjuggler
I had a son once, I ain't got no son today
My son is gone now, my son is gone, oy weh
 -- Joe Frank, "Woman and Bull in a Paint Factory"