dtype always copies

Charles R Harris charlesr.harris at gmail.com
Tue Oct 17 14:10:55 CDT 2006


On 10/13/06, Stefan van der Walt <stefan at sun.ac.za> wrote:
>
> Hi all,
>
> I've noticed that 'astype' always forces a copy.  Is this
> behaviour intended?  It seems to conflict with 'asarray', that
> tries to avoid a copy.
>
> For example, when wrapping code in ctypes, the following snippet
> would have been useful:
>
> def foo(x):
>     # ensure x is an array of the right type
>     x = N.ascontiguousarray(x).astype(N.intc)
>
> but that will cause a copy, so you'll have to do
>
> def foo(x):
>     try:
>         x = N.ascontiguousarray(x,N.intc)
>     except:
>         x = N.ascontiguousarray(x).astype(N.intc)


This seems to work now:

In [21]: a
Out[21]:
array([[ 1.,  2.],
       [ 3.,  4.]])

In [22]: ascontiguousarray(a, dtype=int)
Out[22]:
array([[1, 2],
       [3, 4]])

Chuck
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