Storing empties (was Re: Automatic binding of **kwargs to variables)

In article <1h58k4p.12xd7rj1t5peh0N%aleaxit@yahoo.com>,
Alex Martelli <aleaxit@yahoo.com> wrote:
>
>the canonical idiom when you need such distinction is:
>
>_not_there = object()
>def foo(bar=_not_there, baz=_not_there, bap=_not_there):
> if bar is _not_there: ...
>
>Other unique objects can be substituted for the 'sentinel', but I prefer
>an empty "object()" because it has no other possible meaning except that
>of a distinguishable, identifiable sentinel. IOW, you could set the
>_not_there name to [] or {} or many other things, but that could be
>slightly confusing for the reader (since the other things might have
>other meanings and purposes) while 'object()' shouldn't be.

What's your preferred idiom when you're dealing with storable objects?

-- 
Aahz (aahz@pythoncraft.com)           <*>         http://www.pythoncraft.com/
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