[Numpy-discussion] floats for indexing, reshape - too strict ?

[Sebastian Berg]

On Mi, 2015-07-01 at 10:05 -0400, josef.pktd at gmail.com wrote:
> About the deprecation warning for using another type than integers, in
> ones, reshape, indexing and so on:
> 
> 
> Wouldn't it be nicer to accept floats that are equal to an integer?
> 

Hmmm, the biggest point was that the old solution was to basically
(besides strings) use `int(...)`, which means it does not raise any
errors as you also mention.
I am open to think about allowing exact floats for most of this
(frankly, not advanced indexing at least for the moment, but we never
did there), I think scipy may be doing that for some functions?

The disadvantage I see is, that some weirder calculations would possible
work most of the times, but not always, what I mean is such a case.
A -- possibly silly -- example:

In [8]: for i in range(10):
   ...:     print i, i == i * 0.1 * 10
   ...:     
0 True
1 True
2 True
3 False
4 True
5 True
6 False
7 False
8 True
9 True

I am somewhat opposed to rounding a lot (i.e. not noticing if you got
3.3333 somewhere), so not sure if you can define a "tolerance"
reasonable here unless it is exact. Though I guess you are right that
`//` will also just round silently already.

- Sebastian

> 
> for example
> 
> 
> >>> 5.0 == 5
> True
> 
> 
> >>> np.ones(10 / 2)
> array([ 1.,  1.,  1.,  1.,  1.])
> >>> 10 / 2 == 5
> True
> 
> 
> or the python 2 version
> 
> 
> >>> np.ones(10. / 2)
> array([ 1.,  1.,  1.,  1.,  1.])
> >>> 10. / 2 == 5
> True
> 
> 
> I'm using now 10 // 2, or int(10./2 + 1)   but this is unconditional
> and doesn't raise if the numbers are not close or equal to an integer
> (which would be a bug)
> 
> 
> 
> 
> Josef
> 
> 
> 
> 
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