[Numpy-discussion] numpy.int32, type inheritance and tp_flags
Charles R Harris
Tue Jun 2 01:32:43 CDT 2009
On Mon, Jun 1, 2009 at 11:58 PM, David Cournapeau <
> Charles R Harris wrote:
> > On Mon, Jun 1, 2009 at 11:08 PM, David Cournapeau
> > <email@example.com <mailto:firstname.lastname@example.org>>
> > wrote:
> > Hi,
> > I have a question related to #1121
> > (http://projects.scipy.org/numpy/ticket/1121). With python 2.6,
> > PyInt_Check(a) if a is an instance of numpy.int32 does not work
> > anymore.
> > It think this is related to the python issue 2263
> > (http://bugs.python.org/issue2263), where the tp_flags has been
> > changed
> > for the python int object, change which influences PyInt_Check
> > behavior.
> > It would be nice if the python folks would document
> > Py_TPFLAGS_INT_SUBCLASS so we knew what it did. I also wonder if the
> > problem with struct and the related bug with timeseries aren't python
> > bugs. Shouldn't python be checking for conversion calls rather than an
> > integer subclass?
> I found this while walking through the python hg log:
Hmm, makes me think even more that the python code is the buggy one here.
Why should it depend on inheritance from the int type? I mean, isn't that
kind of limiting? All they need to know is that it can be *converted* to a
python integer. It's like duck typing is being replaced by strict typing.
Because it's faster to interpret (duh).
Of course, I may have no idea what I'm talking about.
> As I understand it, that's basically an optimization for fast subclass
> testing, and is indeed not documented. But instead of hard-coding the
> additional flag for types which support this in numpy, I think it would
> be better to have something which will not break again when another flag
> is added to some types.
There speaks the build guy ;)
> Specially since related bugs are quite hard to
> track. I don't know how to do it, though, as the python doc says that
> inheriting tp_flags is tricky...
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