[Numpy-discussion] shape, size
Todd Miller
jmiller at stsci.edu
Fri Jan 30 13:50:02 EST 2004
On Thu, 2004-01-29 at 23:12, Daniel Holth wrote:
> In python, if na is a numarray:
>
> >>> na
> array([[0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0],
> [1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1]])
>
> I can type
>
> >>> nb = na[:,:4]
> >>> nb
> array([[0, 1, 0, 1],
> [1, 0, 1, 0]])
>
> >>> nb[0][0]=17
>
> >>> na
> array([[17, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0],
> [ 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1]])
>
> nb and na share data.
>
> How do you write nb = na[:,:4] in a C extension module?
Here's the quick and dirty way:
nb = (PyArrayObject *) PyObject_CallMethod(na, "view", NULL);
if (na->dimensions[1] >= 4)
nb->dimensions[1] = 4;
Todd
>
> Thanks,
>
> Daniel Holth
>
>
>
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--
Todd Miller
Space Telescope Science Institute
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