[Numpy-discussion] array, asarray as contiguous and friends

Colin J. Williams cjw at sympatico.ca
Fri Mar 24 06:50:04 CST 2006


Tim Hochberg wrote:

> Colin J. Williams wrote:
>
>> Tim Hochberg wrote:
>>
>>>
>>>
>>> I was just looking at the interface for array and asarray to see 
>>> what other stuff should go in the interface of the hypothetical 
>>> ascontiguous.  There's 'dtype', which I knew about, and 'fortran', 
>>> which I didn't, but which makes sense. However, there's also 
>>> 'ndmin'. First off, it's not described in docstring for asarray, but 
>>> I was able to find it in the docstring for array without a problem. 
>>> Second, is it really necessary? It seems to be useful in an awfully 
>>> narrow set of circumstances, particularly since when you are padding 
>>> axes not everyone wants to pad to the left.
>>>
>>> It would seem to be more useful to ditch the ndmin and have some 
>>> sort of paddims function that was more full featured (padding to 
>>> either the left or the right at a minimum). I'm not entirely sure 
>>> what the best interface to such a beast would look like, but a 
>>> simple tactic would be to just provide leftpaddims and rightpaddims.
>>>
>>> If it's not allready clear by now (;), I prefer several narrow 
>>> interfaces to one broad one.
>>>
>>> -tim
>>>   
>>
>>
>>
>> What does ascontiguous do that copy doesn't?  
>
>
> What it doesn't do is always copy the argument. Just like asarray, it 
> returns it unchanged if it's contiguous.

Fair enough.  I guess that, for some array a, "b= ascontiguous(a)"  
saves a few keystrokes as compared
with "b= a if a.flags.contiguous else a.copy()".  The intent of the 
latter is clearer and probably burns fewer cycles.

numarray has an iscontiguous method, which is a bit simpler than 
concerning the Python user with flags.

>
>> In numarray, transpose created a discontiguous array.  copy() made 
>> the array contiguous.  Is there sufficient benefit to justify another 
>> method?
>
>
> I was proposing a function, not a method. The array object has plenty 
> of methods already.

Since the function would only operate on ArrayType instances, would it 
not be better as a method?

Colin W.

>
> -tim
>
>>
>> Colin W.
>>
>>
>
>





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