[Numpy-discussion] Fixing PyArray_Descr flags member size, ABI vs pickling issue

Travis Oliphant travis@continuum...
Tue Mar 6 12:25:40 CST 2012

Why do we want to return a single string char instead of an int?

There is a need for more flags on the dtype object.   Using an actual attribute call seems like the way to go.  This could even merge the contents of two struct members so that we can add more flags but preserve ABI compatibility.


Travis Oliphant
(on a mobile)

On Mar 6, 2012, at 8:07 AM, David Cournapeau <cournape@gmail.com> wrote:

> On Tue, Mar 6, 2012 at 6:20 AM, Robert Kern <robert.kern@gmail.com> wrote:
>> On Tue, Mar 6, 2012 at 03:53, David Cournapeau <cournape@gmail.com> wrote:
>>> Hi,
>>> This is following the discussion on bug
>>> http://projects.scipy.org/numpy/ticket/2017
>>> Essentially, there is a discrepency between the actual type of the
>>> flags member in the dtype C structure (char) and how it is declared in
>>> the descriptor table (T_INT). The problem is that we are damned if we
>>> fix it, damned if we are not:
>>>  - fixing T_INT to T_BYTE. flag in python is now fixed, but it breaks
>>> pickled numpy arrays
>> Is the problem that T_BYTE returns a single-item string?
> Yes (although it is actually what we want, instead of an int).
>> My handwrapping skills are rusty (Cython has blissfully eradicated this
>> from my memory), but aren't these T_INT/T_BYTE things just convenient
>> shortcuts for exposing C struct members as Python attributes? Couldn't
>> we just write a full getter function for returning the correct value,
>> just returned as a Python int instead of a str.
> You're right, I did not think about this solution. That's certainly
> better than the two I suggested.
> Thanks,
> David
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