[Numpy-discussion] copy on demand

Konrad Hinsen hinsen at cnrs-orleans.fr
Sat Jun 15 01:56:03 CDT 2002


> I'd be strongly against this. This has the same problem that other
> customized array objects have (whether regarding slicing behavior,
> operators, coercion...). In particular, it is clear which kind it
> is when you create it, but you may pass it to a module that
> presumes different array behavior. Having different kind of arrays

We already have that situation with lists and arrays (and in much of
my code netCDF arrays, which have copy semantics) , but in my
experience this has never caused confusion. Most general code working
on sequences doesn't modify elements at all. When it does, it either
clearly requires view semantics (a function you call in order to
modify (parts of) an array) or clearly requires copy semantics (a
function that uses an array argument as an initial value that it then
modifies).

> floating around just seems like an invitation for confusion. I'm
> very much in favor of picking one or the other behaviors and then
> making some means of explicitly getting the other behavior.

Then the only solution I see is the current one: default behaviour is
view, and when you want a copy yoy copy explicitly. The inverse is not
possible, once you made a copy you can't make it behave like a view
anymore.

Konrad.
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