Augmented Assignment (was: Re: PEP scepticism)

[Thomas Wouters]

On Mon, Jul 02, 2001 at 02:00:51AM +0000, Rainer Deyke wrote:
> "Delaney, Timothy" <tdelaney at avaya.com> wrote in message
> news:mailman.994035602.29848.python-list at python.org...

> An interesting (and AFAIK legal) optimization would be to make tuples act as
> mutable objects with respect to augmented assignment if their reference is
> 1.

But they are never 1 unless you're in a C extention that just created it.
When you call 'x += y', the refcount for both x and y is always 2 when the
arguments arrive at the __iadd__ (or C equivalent.)

So you mean '2'. But then you could run into trouble on, say,

  () += y

because the empty tuple is shared, just like interned strings and integers.
The refcount *could* be 2, and you end up modifying someone else's empty
tuple.

-- 
Thomas Wouters <thomas at xs4all.net>

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