namespaces module (a.k.a. bunch, struct, generic object, etc.) PEP

[Nick Coghlan]

Nick Coghlan wrote:
>     class Namespace(object):
>         # etc
>         def _update_dict(self, other):
>             for k in other:
>                 setattr(self, k, other[k])

This doesn't work, as it doesn't allow the sequence of 2-tuples. So I copied the 
relevant check for a keys() attribute from dict.update:

     def _update_dict(self, other):
         """Allow subclasses to easily override handling of dict updates
         Also allows dotted names in the source to be handled correctly

         Uses the "keys" attribute to identify mappings
         """
         try:
             items = other.keys()
         except AttributeError:
             for k, v in other:
                 setattr(self, k, v)
         else:
             for k in items:
                 setattr(self, k, other[k])

Another change I made was to the Record class. It now uses __new__ to initialise 
the instance dictionary with the defaults from the subclass definition, leaving 
__init__ free to be used to invoke update() like it is for a standard namespace:

     Py> from namespaces import Record
     Py> class Example(Record):
     ...   a = 1
     ...   b = ""
     ...   class _sub_sf(Record):
     ...     c = 3
     ...   def _sub_calc(): return "Calculated value!"
     ...
     Py> x = Example()
     Py> x
     Example(a=1, b='', calc='Calculated value!', sf=_sub_sf(c=3))
     Py> x = Example(a=3)
     Py> x
     Example(a=3, b='', calc='Calculated value!', sf=_sub_sf(c=3))
     Py> x = Example([("sf.c", 5)], a=3, b="altered")
     Py> x
     Example(a=3, b='altered', calc='Calculated value!', sf=_sub_sf(c=5))
     Py> x = Example({"sf.c": 5}, a=3, b="altered")
     Py> x
     Example(a=3, b='altered', calc='Calculated value!', sf=_sub_sf(c=5))

I also moved the module to my normal site:
http://boredomandlaziness.skystorm.net/misc/namespaces.py

Steven: Feel free to pick through this for anything you want to add to the PEP. 
That's why I'm posting it, after all :)

Cheers,
Nick.

-- 
Nick Coghlan   |   ncoghlan at email.com   |   Brisbane, Australia
---------------------------------------------------------------
             http://boredomandlaziness.skystorm.net