numpy-discussion

[Numpy-discussion] asmatrix and asarray exception

[Keith G. <kwg...@gm...>]

This works:

>> M.asmatrix(['a', 'b', None])
matrix([[a, b, None]], dtype=object)

But this doesn't:

>> M.asmatrix(['a', 'b', None, 'c'])
TypeError: expected a readable buffer object

>> M.__version__
'1.0rc1'

It also doesn't work for asarray and for tuples.

Re: [Numpy-discussion] asmatrix and asarray exception

[Keith G. <kwg...@gm...>]

On 10/11/06, Keith Goodman <kwg...@gm...> wrote:
> This works:
>
> >> M.asmatrix(['a', 'b', None])
> matrix([[a, b, None]], dtype=object)
>
> But this doesn't:
>
> >> M.asmatrix(['a', 'b', None, 'c'])
> TypeError: expected a readable buffer object
>
> >> M.__version__
> '1.0rc1'
>
> It also doesn't work for asarray and for tuples.
>

Here's a workaround:

>> M.asmatrix(['a', 'b', None, 'c'], dtype=object)
matrix([[a, b, None, c]], dtype=object)

Re: [Numpy-discussion] asmatrix and asarray exception

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

Keith Goodman wrote:

>On 10/11/06, Keith Goodman <kwg...@gm...> wrote:
>  
>
>>This works:
>>
>>    
>>
>>>>M.asmatrix(['a', 'b', None])
>>>>        
>>>>
>>matrix([[a, b, None]], dtype=object)
>>
>>But this doesn't:
>>
>>    
>>
>>>>M.asmatrix(['a', 'b', None, 'c'])
>>>>        
>>>>
>>TypeError: expected a readable buffer object
>>
>>    
>>
>>>>M.__version__
>>>>        
>>>>
>>'1.0rc1'
>>
>>It also doesn't work for asarray and for tuples.
>>
>>    
>>
>
>  
>
It is pretty fragile to rely on NumPy's "detection" of object arrays.  
The problem is that with the introduction of string, unicode, and record 
array styles, what is supposed to be an object array is harder to detect. 

The type-error propagates up from trying to create a record-array 
(apparently that's what was detected).  You can only create record-array 
items from tuples or objects exposing the buffer interface. 

It's interesting that the detection algorithm gets thrown off by the 
addition of an other element.  There may be an easy fix there.

-Travis

Re: [Numpy-discussion] asmatrix and asarray exception

[Charles R H. <cha...@gm...>]

On 10/11/06, Keith Goodman <kwg...@gm...> wrote:
>
> On 10/11/06, Keith Goodman <kwg...@gm...> wrote:
> > This works:
> >
> > >> M.asmatrix(['a', 'b', None])
> > matrix([[a, b, None]], dtype=object)
> >
> > But this doesn't:
> >
> > >> M.asmatrix(['a', 'b', None, 'c'])
> > TypeError: expected a readable buffer object
> >


As a side observation, I note that the 'None' is also non-printing:

>>> a = asarray(['a', 'b', None, 'c'], dtype=object)
>>> a[2]
>>> str(a[2])
'None'

I wonder if this should be changed?

Chuck

Re: [Numpy-discussion] asmatrix and asarray exception

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

Charles R Harris wrote:

>
>
> On 10/11/06, *Keith Goodman* <kwg...@gm... 
> <mailto:kwg...@gm...>> wrote:
>
>     On 10/11/06, Keith Goodman <kwg...@gm...
>     <mailto:kwg...@gm...>> wrote:
>     > This works:
>     >
>     > >> M.asmatrix(['a', 'b', None])
>     > matrix([[a, b, None]], dtype=object)
>     >
>     > But this doesn't:
>     >
>     > >> M.asmatrix(['a', 'b', None, 'c'])
>     > TypeError: expected a readable buffer object
>     >
>
>
> As a side observation, I note that the 'None' is also non-printing:
>
> >>> a = asarray(['a', 'b', None, 'c'], dtype=object)
> >>> a[2]
> >>> str(a[2])
> 'None'
>
> I wonder if this should be changed?

That's Python's decision.  You are getting back the None object when you 
access element a[2].  Thus, there is no way to change it.

-Travis