[Python-Dev] PEP 332 revival in coordination with pep 349? [ Was:Re: release plan for 2.5 ?]

[Jim Jewett]

On 2/14/06, Neil Schemenauer wrote:
> People could spell it bytes(s.encode('latin-1'))

Guido wrote:
> At the cost of an extra copying step.

I asked:
> ... why not just add some smarts to the bytes constructor?

Guido wrote:

> ... the VM usually keeps an extra reference
> on the stack so the refcount is never 1. But
> you can't rely on that

I did miss this, but _PyString_Resize seems to
work around it, and I'm not sure that the bytes
object can't be just as intimate.

Even if that is insurmountable, bytes objects
could recognize two states -- one normal, and
one for "I'm delegating to a string, and have to
copy to my own buffer before I actually mutate
anything."

Then a new bytes object would still need its
own header, but the data copying could often
be avoided.

But back to the possibility of not creating
even a new object header...
> the str's underlying array is allocated inline
> with the str header, this require str and
> bytes to have the same object layout. But
> since bytes are mutable, they can't.

Looking at the arraymodule, the only extra
fields in an array are weakrefs, description
(which will no longer be needed) and tracking
for the indirection.  There are even a few extra
bytes leftover that could be used to indicate
that ob_item was redirected later, the way
tables do with small_table.

-jJ