[Numpy-discussion] NumPy C-API equivalent of np.float64()

Keith Goodman kwgoodman@gmail....
Wed Dec 29 11:55:49 CST 2010


On Wed, Dec 29, 2010 at 9:48 AM, Matthew Brett <matthew.brett@gmail.com> wrote:
> Hi,
>
> On Wed, Dec 29, 2010 at 5:37 PM, Robert Bradshaw
> <robertwb@math.washington.edu> wrote:
>> On Wed, Dec 29, 2010 at 9:05 AM, Keith Goodman <kwgoodman@gmail.com> wrote:
>>> On Tue, Dec 28, 2010 at 11:22 PM, Robert Bradshaw
>>> <robertwb@math.washington.edu> wrote:
>>>> On Tue, Dec 28, 2010 at 8:10 PM, John Salvatier
>>>> <jsalvati@u.washington.edu> wrote:
>>>>> Wouldn't that be a cast? You do casts in Cython with <double>(expression)
>>>>> and that should be the equivalent of float64 I think.
>>>>
>>>> Or even <numpy.float64_t >(expression) if you've cimported numpy
>>>> (though as mentioned this is the same as double on every platform I
>>>> know of). Even easier is just to use the expression in a the right
>>>> context and it will convert it for you.
>>>
>>> That will give me a float object but it will not have dtype, shape,
>>> ndim, etc methods.
>>>
>>>>> m = np.mean([1,2,3])
>>>>> m
>>>   2.0
>>>>> m.dtype
>>>   dtype('float64')
>>>>> m.ndim
>>>   0
>>>
>>> using <np.float64_t> gives:
>>>
>>> AttributeError: 'float' object has no attribute 'dtype'
>
> Forgive me if I haven't understood your question, but can you use
> PyArray_DescrFromType with e.g  NPY_FLOAT64 ?

I'm pretty hopeless here. I don't know how to put all that together in
a function.


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