numpy-discussion

[Numpy-discussion] flat indexing of object arrays

[Martin W. <mar...@gm...>]

Hi list,

when I try to assign a sequence as an element of an object array via flat 
indexing only the first element of the sequence is assigned:

>>> import numpy
>>> numpy.version.version
'1.0rc1.dev3171'
>>> from numpy import *
>>> a = ndarray ((2,2), object)
>>> a.flat [2] = (1, 2, 3)
>>> a.flat [2]
1
>>> a
array([[None, None],
       [1, None]], dtype=object)

Is this a feature? Wouldn't a naive user like me expect
a.flat [2] == (1, 2, 3)?

Thanks in advance,
Martin Wiechert

Re: [Numpy-discussion] flat indexing of object arrays

[Matthew B. <mat...@gm...>]

Hi,

On 10/5/06, Martin Wiechert <mar...@gm...> wrote:
> Hi list,
>
> when I try to assign a sequence as an element of an object array via flat
> indexing only the first element of the sequence is assigned:

I've also been having trouble with flat on object arrays.

Is this intended?

In [1]: from numpy import *

In [2]: a = arange(2)

In [3]: a[1]
Out[3]: 1

In [4]: a.flat[1]
Out[4]: 1

In [5]: b = array([a], dtype=object)

In [6]: b[1]
---------------------------------------------------------------------------
exceptions.IndexError                                Traceback (most
recent call last)

/home/mb312/devel_trees/scipy/Lib/io/<ipython console>

IndexError: index out of bounds

In [7]: b.flat[1]
Out[7]: 1

Best,

Matthew

Re: [Numpy-discussion] flat indexing of object arrays

[Travis O. <oli...@ee...>]

Matthew Brett wrote:

>Hi,
>
>On 10/5/06, Martin Wiechert <mar...@gm...> wrote:
>  
>
>>Hi list,
>>
>>when I try to assign a sequence as an element of an object array via flat
>>indexing only the first element of the sequence is assigned:
>>    
>>
>
>I've also been having trouble with flat on object arrays.
>
>Is this intended?
>
>In [1]: from numpy import *
>
>In [2]: a = arange(2)
>
>In [3]: a[1]
>Out[3]: 1
>
>In [4]: a.flat[1]
>Out[4]: 1
>
>In [5]: b = array([a], dtype=object)
>
>In [6]: b[1]
>---------------------------------------------------------------------------
>exceptions.IndexError                                Traceback (most
>recent call last)
>
>/home/mb312/devel_trees/scipy/Lib/io/<ipython console>
>
>IndexError: index out of bounds
>
>In [7]: b.flat[1]
>Out[7]: 1
>
>  
>

This is correct behavior.  Look at the shape of b.  It is being indexed 
correctly.

The problem is that it is ambiguous as to what is wanted when you write

b = array([a], dtype=object).

We have gone through the rounds on this one and the current behavior is 
our best compromise.

-Travis

Re: [Numpy-discussion] flat indexing of object arrays

[Travis O. <oli...@ee...>]

Martin Wiechert wrote:

>Hi list,
>
>when I try to assign a sequence as an element of an object array via flat 
>indexing only the first element of the sequence is assigned:
>
>  
>
>>>>import numpy
>>>>numpy.version.version
>>>>        
>>>>
>'1.0rc1.dev3171'
>  
>
>>>>from numpy import *
>>>>a = ndarray ((2,2), object)
>>>>a.flat [2] = (1, 2, 3)
>>>>a.flat [2]
>>>>        
>>>>
>1
>  
>
>>>>a
>>>>        
>>>>
>array([[None, None],
>       [1, None]], dtype=object)
>
>Is this a feature? Wouldn't a naive user like me expect
>a.flat [2] == (1, 2, 3)?
>
>  
>
You are probably right.    This should be changed.

-Travis