On Fri, Aug 23, 2013 at 6:02 AM, Chris Barker - NOAA Federal < chris.barker@noaa.gov> wrote:
Hi folks,
I had thought that maybe a numpy.long dtype was a system (compiler)-native C long.
But on both 32 and 64 bit python on OS-X, it seems to be 64 bit. I'm pretty sure that on OS-X 32 bit, a C long is 32 bits. (gdd, of course)
I don't have other machines to test on , but as the MS compilers and gcc do different things with a C long on 64 bit platforms, I"m curious how numpy defines it.
In general, I prefer the "explicit is better than implicit" approach and use, e.g. int32 and int64. However, in this case, we are using Cython, and calling C code that used "long" -- so what I want is "whatever the compiler thinks is a long" -- is there a way to do that without my own kludgy platform-dependent code?
I note that the Cython numpy.pxd assigns:
ctypedef signed long npy_long
Is that a bug? (or maybe npy_long is not supposed to match np.long....
npy_long is indeed just an alias to C long, np.long is an alias to python's long: arch -32 python -c "import numpy as np; print np.dtype(np.int); print np.dtype(np.long)" int32 int64 arch -64 python -c "import numpy as np; print np.dtype(np.int); print np.dtype(np.long)" int64 int64 and python -c "import numpy as np; print np.long is long" will print True All this is on python 2.7, I am not sure how/if that changes on python 3 (that consolidated python int/long). David
-Chris
--
Christopher Barker, Ph.D. Oceanographer
Emergency Response Division NOAA/NOS/OR&R (206) 526-6959 voice 7600 Sand Point Way NE (206) 526-6329 fax Seattle, WA 98115 (206) 526-6317 main reception
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