[Numpy-discussion] subtract.reduce behavior
Pauli Virtanen
pav@iki...
Fri Jul 23 09:37:54 CDT 2010
Fri, 23 Jul 2010 10:29:47 -0400, Alan G Isaac wrote:
[clip]
> >>> np.subtract.reduce([])
> 0.0
>
> Getting a right identity for an empty array is surprising. Matching
> Python's behavior (raising a TypeError) seems desirable. (?)
I don't think matching Python's behavior is a sufficient argument for a
change. As far as I see, it'd mostly cause unnecessary breakage, with no
significant gain.
Besides, it's rather common to define
sum_{z in Z} z = 0
prod_{z in Z} z = 1
if Z is an empty set -- this can then be extended to other reduction
operations. Note that changing reduce behavior would require us to
special-case the above two operations.
--
Pauli Virtanen
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