Martin Raspaud wrote:

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Hello,

I work on a 64bit machine with 64bits enable fedora on it.

I just discovered that numpy.int on the python part are 64bits ints, while npy_int in the C api are 32bits ints.

np.intc Dag Sverre

I can live with it, but it seems to be different on 32bit machines, hence I wonder what is the right way to do when retrieving an array from python to C.

Here is what I use now: data_pyarray = (PyArrayObject *)PyArray_ContiguousFromObject(data_list, PyArray_INT, 1, 2);

but that implies that I send np.int32 arrays to the C part.

Should I use longs instead ?

Regards, Martin -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (GNU/Linux) Comment: Using GnuPG with Fedora - http://enigmail.mozdev.org/

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On Thu, Mar 18, 2010 at 08:33, Martin Raspaud <martin.raspaud@smhi.se> wrote:

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Hello,

I work on a 64bit machine with 64bits enable fedora on it.

I just discovered that numpy.int on the python part are 64bits ints, while npy_int in the C api are 32bits ints.

Note that np.int is just Python's builtin int type (there only for historical reasons). It corresponds to a C long. npy_int corresponds to a C int.

I can live with it, but it seems to be different on 32bit machines, hence I wonder what is the right way to do when retrieving an array from python to C.

Here is what I use now: data_pyarray = (PyArrayObject *)PyArray_ContiguousFromObject(data_list, PyArray_INT, 1, 2);

but that implies that I send np.int32 arrays to the C part.

Should I use longs instead ?

Not necessarily; C longs are the cause of your problem. On some platforms they are 64-bit, some they are 32-bit. Technically speaking, C ints can vary from platform to platform, but they are typically 32-bits on all modern platforms running numpy. Of course, numpy defaults to using a C long for its integer arrays, just as Python does for its int type, so perhaps using a C long would work best for you. It's platform dependent, but it matches the platform dependent changes in numpy. It depends on what your needs are. If you need a consistent size (perhaps you are writing bytes out to a file), then always use the int32 or int64 specific types. -- Robert Kern "I have come to believe that the whole world is an enigma, a harmless enigma that is made terrible by our own mad attempt to interpret it as though it had an underlying truth." -- Umberto Eco