[Python-Dev] "buffer interface" messages

[Antoine Pitrou]

On Fri, 03 Dec 2010 18:09:39 +0100
Georg Brandl <g.brandl at gmx.net> wrote:
> Am 03.12.2010 17:57, schrieb Antoine Pitrou:
> > On Sat, 4 Dec 2010 02:45:42 +1000
> > Nick Coghlan <ncoghlan at gmail.com> wrote:
> >> On Sat, Dec 4, 2010 at 2:28 AM, Antoine Pitrou <solipsis at pitrou.net> wrote:
> >> > On Fri, 03 Dec 2010 10:11:29 -0500
> >> > "R. David Murray" <rdmurray at bitdance.com> wrote:
> >> >> >
> >> >> > >>> 'abc'.transform('hex')
> >> >> > TypeError: 'str' does not support the buffer interface
> >> >> > >>> b'abc'.transform('rot13')
> >> >> > TypeError: expected an object with the buffer interface
> >> >>
> >> >> I find these 'buffer interface' error messages to be the most confusing
> >> >> error message I get out of Python3 no matter what context they show up
> >> >> in.  I have no idea what they are telling me.  That issue is more
> >> >> general than transform/untransform, but perhaps it could be fixed
> >> >> for transform/untransform in particular.
> >> >
> >> > I agree. "buffer interface" is a technicality that the Python user
> >> > doesn't do about (unless (s)he also writes C extensions). How about
> >> > "expected a bytes-compatible object"?
> >> 
> >> Why not "binary data interface"? That's what they're actually looking for.
> > 
> > I don't think it's more understandable, since it's not a well-known
> > Python concept.
> > (and in this specific case, the transform() method is on str and bytes,
> > not on arbitrary bytes-like objects)
> 
> "object that can be handled as bytes"?
> "object that provides bytes"?
> 
> >> It seems odd for 'rot13' to be throwing that error though.
> > 
> > Agreed.
> 
> rot13 is a str<->str codec.

Then why does it claim to expect an object with the buffer interface?
bytes has the buffer interface, while str doesn't ;)

I'll also mention that getting a TypeError when you call a method with
the correct type of argument is a bit surprising.

cheers

Antoine.