[Python-3000] Weird error message from bytes type

[Guido van Rossum]

No, I don't want length-1-bytes to get special treatment here. That
would just perpetuate confusion, since b[0] *returns* an int no matter
what you might have set it to.

--Guido

On 2/25/07, Georg Brandl <g.brandl at gmx.net> wrote:
> Thomas Wouters schrieb:
> >
> > This is because a bytes object is not a sequence of bytes objects, like
> > strings. It's a sequence of small integer values, so you need to assign
> > a small integer value to it. You can assign b'a'[0] to it, or assign
> > b'a' to x[:1]. I guess we could specialcase length-1 bytes to make this
> > work 'naturally', but I'm not sure that's the right approach. Guido?
>
> If it is deemed right, see attached patch.
>
> BTW, is it intentional that the setitem/setslice code is duplicated in
> bytesobject.c?
>
> Georg
>
> Index: Objects/bytesobject.c
> ===================================================================
> --- Objects/bytesobject.c       (Revision 53912)
> +++ Objects/bytesobject.c       (Arbeitskopie)
> @@ -451,7 +451,18 @@
>              slicelen = 1;
>          }
>          else {
> -            Py_ssize_t ival = PyNumber_AsSsize_t(values, PyExc_ValueError);
> +            Py_ssize_t ival;
> +            /* if the value is a length-one bytes object, assign it */
> +            if (PyBytes_Check(values)) {
> +                if (PyBytes_GET_SIZE(values) != 1) {
> +                    PyErr_SetString(PyExc_ValueError, "cannot assign bytes "
> +                                    "object of length != 1");
> +                    return -1;
> +                }
> +                self->ob_bytes[i] = ((PyBytesObject *)values)->ob_bytes[0];
> +                return 0;
> +            }
> +            ival = PyNumber_AsSsize_t(values, PyExc_ValueError);
>              if (ival == -1 && PyErr_Occurred())
>                  return -1;
>              if (ival < 0 || ival >= 256) {
>
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-- 
--Guido van Rossum (home page: http://www.python.org/~guido/)