[Numpy-discussion] use slicing as argument values?

Jonathan Helmus jjhelmus@gmail....
Thu Jul 12 15:55:00 CDT 2012


On 07/12/2012 04:46 PM, Chao YUE wrote:
> Hi Ben,
>
> it helps a lot. I am nearly finishing a function in a way I think 
> pythonic.
> Just one more question, I have:
>
> In [24]: b=np.arange(1,11)
>
> In [25]: b
> Out[25]: array([ 1,  2,  3,  4,  5,  6,  7,  8,  9, 10])
>
> In [26]: b[slice(1)]
> Out[26]: array([1])
>
> In [27]: b[slice(4)]
> Out[27]: array([1, 2, 3, 4])
>
> In [28]: b[slice(None,4)]
> Out[28]: array([1, 2, 3, 4])
>
> so slice(4) is actually slice(None,4), how can I exactly want retrieve 
> a[4] using slice object?
>
> thanks again!
>
> Chao

slice is a build in python function and the online docs explain its use 
(http://docs.python.org/library/functions.html#slice).  b[slice(4,5)] 
will give you something close to b[4], but not quite the same.

In [8]: b[4]
Out[8]: 5

In [9]: b[slice(4,5)]
Out[9]: array([5])

     - Jonathan Helmus



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