[Numpy-discussion] immutable arrays

Martin Wiechert martin.wiechert at gmx.de
Thu Sep 21 03:04:57 CDT 2006


Thanks Travis.

Do I understand correctly that the only way to be really safe is to make a 
copy and not to export a reference to it?
Because anybody having a reference to the owner of the data can override the 
flag?

Cheers,
Martin

On Wednesday 20 September 2006 20:18, Travis Oliphant wrote:
> Martin Wiechert wrote:
> > Hi list,
> >
> > I just stumbled accross NPY_WRITEABLE flag.
> > Now I'd like to know if there are ways either from Python or C to make an
> > array temporarily immutable.
>
> Just setting the flag
>
> Python:
>
>   make immutable:
>   a.flags.writeable = False
>
>   make mutable again:
>   a.flags.writeable = True
>
>
> C:
>
>   make immutable:
>   a->flags &= ~NPY_WRITEABLE
>
>   make mutable again:
>   a->flags |= NPY_WRITEABLE
>
>
> In C you can play with immutability all you want.  In Python you can
> only make something writeable if you either 1) own the data or 2) the
> object that owns the data is itself "writeable"
>
>
> -Travis
>
>
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