[Numpy-discussion] Array interface

Travis Oliphant oliphant at ee.byu.edu
Sun Apr 3 21:29:12 EDT 2005

> Probably.   Since, I guess you can only have one of < or > .  Thanks..
>>  - What are the semantics when __array_typestr__ isn't V[0-9]+ and
>>    __array_descr__ is set? Is __array_typestr__ ignored? Or... What
>>    would it be used for?
> I would say that the __array_descr__ always gives more information but 
> not every array implementation will support looking at it.  For 
> example, current Numeric (24.0 in CVS) ignores __array_descr__ and 
> just looks at the typestr (and doesn't support 'V').  So,  I suspect 
> that another array package that knows this may choose something else 
> besides 'V' if it really wants Numeric to still understand it.
> Suppose you have a complex short int array with
> __array_descr__ = 'V8

Let me finish this example:

Suppose you have a complex short int array with

__array_descr__ = [('real','i2'),('imag','i2')]

you could describe this as

__array_typestr__ = 'V4'  

or think of it as a 4 byte integer if you want to make sure that another 
array package that may not support void pointers can still manipulate 
the data, and so the creator of the complex short int array may decide that

__array_typestr__ = 'i4'

is the right thing to do for packages that ignore the __array_descr__  


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