Denis -
What you are seeing is standard procedure for any built-in type - no dynamic
assignment of attributes allowed. Here is an analogous case to your
example, but based on str instead of object:
greeting = "bon jour"
greeting.language = "French" # raises AttributeError: 'str' object has no
attribute 'language'
class I18NString(str):
pass
greeting = I18NString("bon jour")
greeting.language = "French" # OK
The example you cited of creating a thin derived class from object, for the
simple purpose of supporting dynamically assigned attributes, sometimes goes
by the name Bag, from the Smalltalk object framework. The Traits framework
uses a "root" class HasTraits so that you can easily attach attributes, and
then use the traits.ui package to bring up a GUI editor.
Here is a recipe from the Python Cookbook:
http://code.activestate.com/recipes/259174/
There is also the new namedtuple type in the Python 2.6 collections module,
which started out as this recipe:
http://code.activestate.com/recipes/500261/.
Happy New Year!
-- Paul
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