Re: Named tuples
From: Carlos Ribeiro (carribeiro_at_gmail.com)
Date: 11/18/04
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Date: Thu, 18 Nov 2004 11:58:09 -0200 To: duncan.booth@suttoncourtenay.org.uk
On 18 Nov 2004 12:58:49 GMT, Duncan Booth <duncan.booth@invalid.invalid> wrote:
> Carlos Ribeiro wrote:
>
>
>
> > There are a few requirements that can be imposed to avoid problems.
> > First, __names__ is clearly a property, acessed via get & set (which
> > allows to trap some errors). It should accept only tuples as an
> > argument (not lists) to avoid potential problems with external
> > references and mutability of the names. As for the validation, I'm not
> > sure if it's a good idea to check for strings. maybe just check if the
> > 'names' stored in the tuple are immutable (or perhaps 'hashable') is
> > enough.
> >
>
> Your idea of a __names__ attribute suffers from a problem that the common
> use case would be to return a tuple with appropriate names. Right now you
> can do that easily in one statement but if you have to assign to an
> attribute it becomes messy.
>
> An alternative would be so add a named argument to the tuple constructor so
> we can do:
>
> return tuple(('1', '2'), names=('ONE', 'TWO'))
>
> and that would set the __names__ property. If you allow this then you can
> make the __names__ property readonly and the problem of introducing a cycle
> in the __names__ attributes goes away.
I think that a better way to solve the problem is to create a names
method on the tuple itself:
return ('1', '2').names('ONE', 'TWO')
It's shorter and clean, and avoids a potential argument against named
parameters for the tuple constructor -- none of the standard
contructors take named parameters to set extended behavior as far as I
know.
-- Carlos Ribeiro Consultoria em Projetos blog: http://rascunhosrotos.blogspot.com blog: http://pythonnotes.blogspot.com mail: carribeiro@gmail.com mail: carribeiro@yahoo.com
- Next message: Steve Holden: "Re: SQL Server stored prcedures with output parameters"
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- In reply to: Duncan Booth: "Re: Named tuples"
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