[Numpy-discussion] types as functions convert 1 elm arrays to scalars

Charles R Harris charlesr.harris@gmail....
Tue Apr 29 01:51:14 CDT 2008


On Tue, Apr 29, 2008 at 12:28 AM, Hoyt Koepke <hoytak@gmail.com> wrote:

> Hello,
>
> I have a quick question that I'm hoping will improve my numpy
> understanding.  I noticed some behavior when using float64 to convert
> a matrix type that I didn't expect:
>
>
> In [35]: b1 = array([1.0])
>
> In [36]: float64(b1)
> Out[36]: 1.0
>
> In [37]: b2 = array([1.0, 2.0])
>
> In [38]: float64(b2)
> Out[38]: array([ 1.,  2.])
>
>
> I didn't expect calling float64 would convert b1 to a scalar. Seems
> like an inconsistency.  I assume this is intentional, as someone would
> have noticed it a long time ago if not, so could someone explain the
> reasoning behind it?  (or point me to a source that will help?)
>

It's inconsistent and looks like a bug:

In [4]: float32(array([[[1]]]))
Out[4]: array([[[ 1.]]], dtype=float32)

In [5]: float64(array([[[1]]]))
Out[5]: 1.0

Float64 is a bit special because it starts as the python float. Maybe Travis
can say what the differences are.

Chuck
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