[albatross-users] impedance mismatch 1

[Gregory Bond]

> Dawn breaks over Marblehead.  In other words, folks use attributes on objects
> every single day thinking that they are class variables and treating them as
> such.  this single concept I think was the biggest block in my mind.  It
> deserves a prominent position in the documentation.

This isn't an Albatross thing, it's a Python thing(*).  Getting you head 
around this one is a big step forward as a python hacker.

For the sort of work I do, it's one of the best things about Python (compared
to a strongly-typed language such as C++) - the ability to take existing
objects and "decorate" them with new attributes without having to do silly
things like keep parallel arrays or hash lookups or "(caddr_t)user_data" or
whatever.  Yes, you can be burned when the underlying object adds a "real"
attribute with the same name, but the alternatives also break in ugly ways,
too.

I'm forever doing things like

	list = get_lots_of_orders()
	for o in list:
		o.is_local = o.deliver_country == 'aus'
		o.gst_payable = o.is_local and o.client_type != 'exempt'
	# Display the list, including an indicator of which are local, etc
			

(*) or a smalltalk thing, or a perl thing -- basically, any dynamically-typed 
language.