[Python-3000] Immutable bytes type and dbm modules

[Chris Monson]

On 8/6/07, Guido van Rossum <guido at python.org> wrote:
>
> On 8/6/07, "Martin v. Löwis" <martin at v.loewis.de> wrote:
> > >> If that is not acceptable, please tell me how else
> > >> to fix the dbm modules.
> > >
> > > By fixing the code that uses them?
> >
> > I don't know how to do that. All implementation strategies I
> > can think of have significant drawbacks.
>
> Can you elaborate about the issues?
>
> > > By using str8 (perhaps renamed to
> > > frozenbytes and certainly stripped of its locale-dependent APIs)?
> >
> > Ok. So you could agree to a frozenbytes type, then? I'll add one,
> > reusing the implementation of the bytes object.
>
> Not quite. It's the least evil. I'm hoping to put off the decision.
>
> Could you start using str8 instead for now? Or is that not usable for
> a fix? (If so, why not?)
>
> > If that is done:
> >
> > a) should one of these be the base type of the other?
>
> No. List and tuple don't inherit from each other, nor do set and
> frozenset. A common base class is okay. (We didn't quite do this for
> sets but it makes sense for Py3k to change this.)
>
> > b) should bytes literals be regular or frozen bytes?
>
> Regular -- set literals produce mutable sets, too.


But all other string literals produce immutable types:

""
r""
u"" (going away, but still)
and hopefully b""

Wouldn't it be confusing to have b"" be the only mutable quote-delimited
literal?  For everything else, there's bytes().

:-)

- C

> c) is it still ok to provide a .freeze() method on
> >    bytes returning frozenbytes?
>
> I'd rather use the same kind of API used between set and frozenset:
> each constructor takes the other as argument.
>
> > d) should unicode.defenc be frozen?
>
> Yes. It's currently a str8 isn't it? So that's already the case.
>
> > e) should (or may) codecs return frozenbytes?
>
> I think it would be more convenient and consistent if all APIs
> returned mutable bytes and the only API that creates frozen bytes was
> the frozen bytes constructor. (defenc excepted as it's a C-level API
> and having it be mutable would be bad.)
>
> --
> --Guido van Rossum (home page: http://www.python.org/~guido/)
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