[Numpy-discussion] Question about indexing

Alan G Isaac aisaac@american....
Thu May 29 22:50:38 CDT 2008


>> On Thu, 29 May 2008, Keith Goodman apparently wrote:
>>>>>> a[[0,1]] 
>>> That one looks odd. But it is just shorthand for:
>>>>>> a[[0,1],:] 


> On Thu, May 29, 2008 at 6:32 PM, Alan G Isaac 
> <aisaac@american.edu> wrote:
>> Do you mean that ``a[[0,1],:]`` is a more primitive 
>> expression than ``a[[0,1]]``?  In what sense, and does it 
>> ever matter? 

>> Is ``a[[0,1]]`` completely equivalent to ``a[[0,1],...]`` 
>> and ``a[[0,1],:]``? 


On Thu, 29 May 2008, Keith Goodman apparently wrote:
> I can see how the difference between 

> a[0,1] 
> a[[0,1]] 

> is not obvious at first, especially if you come from octave/matlab. 
> The first example has an obvious i and j. But the second 
> example doesn't. So I tried to point out that i=[0,1] and 
> j=:. 



My questions were real questions, not rhetorical.
Anyway...

I think the initial mind-bender is the difference between 
a[(0,1)] and a[[0,1]].  The latter might also be
written a[[0,1],], which I think links to your point.

Cheers,
Alan





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