Tuple Semantics - Rationale'?

[Chris Barker]

Tim Daneliuk wrote:

> From what I've read, to force the data structure to be maintained correctly,
> I have to add a trailing comma to the single arg pair like this:
> 
>       )
>        (name-n, descrip-n),
>        ( (argA-1, argB-1), )
>       ),

That's right

> And that works fine.  But *why* is the trailing comma designed into the
> language semantics this way.  I've been scratching my head and cannot come
> up with a rationale'.  It seems to me that the explicit use of the parens
> should be telling python that I want the second entry in each data
> structure to be a *tuple* of 0 or more tuples.

because parens are used for other kinds of groupings as well. Would
(a*b) be a single value or a one-tuple? It's unfortunate, but there are
only so many kinds of brackets on a keyboard.

> Supposed I did want 0 argument pairs in that tuple, but I wanted to prepare
> the way for adding some later.  Would I use:
> 
>         (()), (), ((,)) ???

tuples are immutable, so you can't add anything later anyway. Perhaps
you'd be better off with lists here.

-Chris

-- 
Christopher Barker,
Ph.D.                                                           
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