[Python-ideas] Allow using ** twice

[Oleg Broytman]

On Thu, Jun 06, 2013 at 05:30:41PM -0400, Devin Jeanpierre <jeanpierreda at gmail.com> wrote:
> On Thu, Jun 6, 2013 at 3:33 PM, Peter Jung <ilmiacs at gmail.com> wrote:
> > I'd take "+= is not allowed" as synonymous to "is immutable".
> 
>     >>> a = (1,2)
>     >>> a += (3, 4)
>     >>> a
>     (1, 2, 3, 4)
> 
> By this definition, tuples are not immutable. That would be
> nonstandard terminology.
> 
> I think you've confused "mutability" of variables (more clearly:
> rebindability) with mutability of objects.

   It's quite easy to explain the difference:

>>> l = [1, 2]
>>> id(l)
3071923884L
>>> l += [3, 4]
>>> id(l)
3071923884L
>>> 
>>> t = (1, 2)
>>> id(t) 
3074977068L
>>> t += (3, 4)
>>> id(t)
3075097020L

   Lists are updated in-place. Tuples are recreated.

Oleg.
-- 
     Oleg Broytman            http://phdru.name/            phd at phdru.name
           Programmers don't die, they just GOSUB without RETURN.