[Python-3000] Immutable bytes type and dbm modules

[Chris Monson]

Wow.  +1 for pure lucid reasoning.

(Sorry for top-posting; blame the crackberry)


On 8/7/07, Talin <talin at acm.org> wrote:
> Guido van Rossum wrote:
>
> > Assuming you weren't being sarcastic, array('B') and bytes() are very
> > close except bytes have a literal notation and many string-ish
> > methods. The buffer objects returned by the buffer() builtin provide a
> > read-only view on other objects that happen to have an internal
> > buffer, like strings, bytes, arrays, PIL images, and numpy arrays.
> > Lists of integers don't have the property that the other three share
> > which is that their C representation is a contiguous array of bytes
> > (char* in C). This representation is important because to do efficient
> > I/O in C you need char*.
>
> I've been following the discussion in a cursory way, and I can see that
> there is a lot of disagreement and confusion around the whole issue of
> mutable vs. immutable bytes.
>
> If it were up to me, and I was starting over from scratch, here's the
> design I would create:
>
> 1) I'd reserve the term 'bytes' to refer to an immutable byte string.
>
> 2) I would re-purpose the existing term 'buffer' to refer to a mutable,
> resizable byte buffer.
>
> Rationale: "buffer" has been used historically in many computer
> languages to refer to a mutable area of memory. The word 'bytes', on the
> other hand, seems to imply a *value* rather than a *location*, and
> values (like numbers) are generally considered immutable.
>
> 3) Both 'bytes' and 'buffer' would be derived from an abstract base
> class called ByteSequence. ByteSequence defines all of the read-only
> accessor methods common to both classes.
>
> 4) Literals of both types are available - using a prefix of small 'b'
> for bytes, and capitol B for 'buffer'.
>
> 5) Both 'bytes' and 'buffer' would support the 'buffer protocol',
> although in the former case it would be read-only. Other things which
> are not buffers could also support this protocol.
>
> 6) Library APIs that required a byte sequence would be written to test
> vs. the abstract ByteSequence type.
>
> 7) Both bytes and buffer objects would be inter-convertible using the
> appropriate constructors.
>
> -- Talin
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