Re: [Numpy-discussion] Determining if two arrays share data

[Stefan v. d. W. <st...@su...>]

On Thu, Jul 06, 2006 at 11:39:19AM +0900, Bill Baxter wrote:
> Often when I'm doing interactive prototyping I find myself wanting to c=
heck
> whether two arrays are sharing a copy of the same data.
>=20
> It seems like there ought to be a concise way to do that, but right now=
 seems
> like the only way is with a little function like this:
>=20
> def same_base(a,b):
>     ab =3D a.base
>     if ab is None: ab =3D a
>     bb =3D b.base
>     if bb is None: bb =3D b
>     return ab is bb  =20
>=20
> is there some easier built-in way?  Does the above function even cover =
all the
> bases? (so to speak...)

Say you have

x =3D N.array([1,2,3,4])

and

y =3D x.reshape((2,2))

then x and y share the same data.  You can see this when you do

x.__array_interface__['data'][0] =3D=3D y.__array_interface__['data'][0]

Still, this only holds for full data views.  If you had

z =3D y[1:,1:]

then the data memory position would differ.

Cheers
St=E9fan