[Numpy-discussion] Access dtype kind from cython

[Eric Moore]

On Monday, December 29, 2014, Valentin Haenel <valentin at haenel.co> wrote:

> Hi,
>
> how do I access the kind of the data from cython, i.e. the single
> character string:
>
> 'b' boolean
> 'i' (signed) integer
> 'u' unsigned integer
> 'f' floating-point
> 'c' complex-floating point
> 'O' (Python) objects
> 'S', 'a' (byte-)string
> 'U' Unicode
> 'V' raw data (void)
>
> In regular Python I can do:
>
> In [7]: d = np.dtype('S')
>
> In [8]: d.kind
> Out[8]: 'S'
>
> Looking at the definition of dtype that comes with cython, I see:
>
>   ctypedef class numpy.dtype [object PyArray_Descr]:
>       # Use PyDataType_* macros when possible, however there are no macros
>       # for accessing some of the fields, so some are defined. Please
>       # ask on cython-dev if you need more.
>       cdef int type_num
>       cdef int itemsize "elsize"
>       cdef char byteorder
>       cdef object fields
>       cdef tuple names
>
> I.e. no kind.
>
> Also, i looked for an appropriate PyDataType_* macro but couldn't find one.
>
> Perhaps there is something simple I could use?
>
> best,
>
> V-
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>
>From C or cython I'd just use the typenum. Compare against the appropriate
macros, NPY_DOUBLE e.g.

Eric
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