[Numpy-discussion] Re: Trying out Numeric3
konrad.hinsen at laposte.net
konrad.hinsen at laposte.net
Mon Mar 28 02:25:04 EST 2005
On 25.03.2005, at 23:52, Stephen Walton wrote:
> where str is a string is not allowed because strings are immutable.
> But if I type "b=7" followed by "b=3", do I really care whether the 3
> gets stuck in the same memory location previously occupied by the 7
> (mutable) or the symbol b points to a new location containing a 3
> (immutable)? What are some circumstances where this might matter?
>
The most important one in practice is
a = some_array[0]
b = a
a += 3
If the indexing operation returns a scalar (immutable), then "a" and
"b" will have different values. If it returns a rank-0 (mutable), then
"a" and "b" will be the same. This matters for code that is written
with scalars in mind and which then gets fed rank-0 arrays as
arguments.
Konrad.
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Konrad Hinsen
Laboratoire Leon Brillouin, CEA Saclay,
91191 Gif-sur-Yvette Cedex, France
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Fax: +33-1 69 08 82 61
E-Mail: khinsen at cea.fr
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