[Python-Dev] Misc re.match() complaint

[Antoine Pitrou]

Le Mon, 15 Jul 2013 21:53:42 -0700,
Guido van Rossum <guido at python.org> a écrit :
> Hm. I'd still like to change this, but I understand it's debatable...
> Is the group() method written in C or Python?

Is there a strong enough use case to change it? I can't say the current
behaviour seems very useful either, but some people may depend on it.
I already find it a bit weird that you're passing a bytearray or
memoryview to re.match(), to be honest :-)

Regards

Antoine.


> If it's in C it should
> be simple enough to let it just do a little bit of pointer math and
> construct a bytes object from the given area of memory -- after all,
> it must have a pointer to that memory area in order to do the matching
> in the first place (although I realize the code may be separated by a
> gulf of abstraction :-).
> 
> --Guido
> 
> On Mon, Jul 15, 2013 at 8:03 PM, Nick Coghlan <ncoghlan at gmail.com>
> wrote:
> > On 16 July 2013 12:20, Guido van Rossum <guido at python.org> wrote:
> >> On Mon, Jul 15, 2013 at 7:03 PM, Stephen J. Turnbull
> >> <stephen at xemacs.org> wrote:
> >>> Or is this something deeper, that a group *is* a new object in
> >>> principle?
> >>
> >> No, I just think of it as returning "a string" and I think it's
> >> most useful if that is always an immutable object, even if the
> >> target string is some other bytes buffer.
> >>
> >> FWIW, it feels as if the change in behavior is probably just due to
> >> how slices work.
> >
> > I took a look at the way the 2.7 re code works, and the change does
> > indeed appear to be due to the difference in the way slices work for
> > buffer and memoryview objects:
> >
> > Slicing a buffer creates an 8-bit string:
> >
> >>>> buffer(b"abc")[0:1]
> > 'a'
> >
> > Slicing a memoryview creates another memoryview:
> >
> >>>> memoryview(b"abc")[0:1]
> > <memory at 0x7f3320541b98>
> >
> > Unfortunately, memoryview doesn't currently allow subclasses, so it
> > isn't easy to create a derivative that coerces to bytes on
> > slicing :(
> >
> > Cheers,
> > Nick.
> >
> > --
> > Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia
> 
> 
>