It's in the code. See longobject.c:
Py_SIZE(v) = ndigits*sign;
You can also see Py_SIZE(v) used on PyLongs all over the place in
longobject.c, for example:
v = (PyLongObject *)vv;
i = Py_SIZE(v);
Just do a ctrl-f for Py_SIZE(v) in longobject.c. Like I said, by looking in
the implementation I was able to figure out that Py_SIZE is interpreted as
the sign times the number of digits (unless I'm missing something), but
this should be in the docs IMO.
On Wed, Oct 19, 2016 at 7:24 PM Thomas Nyberg <tomuxi...@gmx.com> wrote:
> On 10/19/2016 09:04 PM, Elliot Gorokhovsky wrote:
> > A quick note:
> >
> > I'm working on a special-case compare function for bounded integers for
> > the sort stuff. By looking at the implementation, I figured out that
> > Py_SIZE of a long is the sign times the number of digits (...right?).
> > Before looking at the implementation, though, I had looked for this info
> > in the docs, and I couldn't find it anywhere. Since Py_SIZE is public, I
> > think the documentation should make clear what it returns for PyLongs,
> > for example somewhere on the "Integer Objects" page. Apologies if this
> > is specified somewhere else in the docs and I just couldn't find it.
> >
> > Elliot
>
> I don't think this is right.
>
>
> https://github.com/python/cpython/blob/master/Include/object.h#L119
> https://docs.python.org/3/c-api/structures.html#c.Py_SIZE
> https://docs.python.org/3/c-api/structures.html#c.PyVarObject
>
> It returns the `ob_size` fields of a PyVarObject. I think this has to do
> with objects with variable sizes like lists. PyLongs are not
> PyVarObjects because they have no notion of length.
>
> Why would a long be stored as a sequence of digits instead of a (say) 64
> bit integer as 8 bytes?
>
> Cheers,
> Thomas
>
> _______________________________________________
> Python-ideas mailing list
> Python-ideas@python.org
> https://mail.python.org/mailman/listinfo/python-ideas
> Code of Conduct: http://python.org/psf/codeofconduct/
>
_______________________________________________
Python-ideas mailing list
Python-ideas@python.org
https://mail.python.org/mailman/listinfo/python-ideas
Code of Conduct: http://python.org/psf/codeofconduct/
