Why doesn't array(a, dtype=single, copy=0) downcast a double array.

Travis Oliphant oliphant.travis at ieee.org
Mon Oct 16 13:33:43 CDT 2006

Charles R Harris wrote:
> It seems to me that since the behaviour when copy=0 is to make a copy 
> only if necessary, it should find it necessary and make the downcast. 
> After all, array(a, dtype=single, copy=1) does just that without 
> complaint. Some common code in linalg could be replaced if array and 
> asarray would do that operation.
Well, the fact that it makes the copy without raising an error is 
different behavior from Numeric and should be considered an unintended 

We definitely should make this consistent for copy=0 or copy=1.  The 
only question, is do we raise the error in both cases or allow the 
conversion in both cases.

The long-standing behavior is to raise the error on possible-loss 
conversion and so my opinion is that we should continue with that behavior.


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