[Numpy-discussion] in the NA discussion, what can we agree on?
Lluís
xscript@gmx....
Fri Nov 4 09:22:49 CDT 2011
Gary Strangman writes:
> For the non-destructive+propagating case, do I understand correctly that
> this would mean I (as a user) could temporarily decide to IGNORE certain
> portions of my data, perform a series of computation on that data, and the
> IGNORED flag (or however it is implemented) would be propagated from
> computation to computation? If that's the case, I suspect I'd use it all
> the time ... to effectively perform data subsetting without generating
> (partial) copies of large datasets. But maybe I misunderstand the
> intended notion of propagation ...
I *think* you're right. I say "think" because to *me* IGNORE is the opposite of
propagate.
For example, you could temporarily (non-destructively) decide to assign a
propagating special value to array "a". Then do "a+=2; a*=5" and get something
like (which I think is the kind of use case you were talking about):
# original values
>>> a
[1, 1, 1]
# with special value
>>> a
[1, SPECIAL, 1]
# computations
>>> a += 2
>>> a *= 5
# result
>>> a
[15, SPECIAL, 15]
# without special value
>>> a
[15, 1, 15]
So yes, separating both properties is not only a matter of elegance and
simplicity, but also has the practical impact of (as Ben said in another mail)
making the non-destructive property into a fancy form of indexing.
Lluis
--
"And it's much the same thing with knowledge, for whenever you learn
something new, the whole world becomes that much richer."
-- The Princess of Pure Reason, as told by Norton Juster in The Phantom
Tollbooth
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