[Numpy-discussion] Adding keyword to asarray and asanyarray.

Charles R Harris charlesr.harris at gmail.com
Thu Mar 5 12:33:52 EST 2015

On Thu, Mar 5, 2015 at 10:04 AM, Chris Barker <chris.barker at noaa.gov> wrote:

> On Thu, Mar 5, 2015 at 8:42 AM, Benjamin Root <ben.root at ou.edu> wrote:
>> dare I say... datetime64/timedelta64 support?
> well, the precision of those is 64 bits, yes? so if you asked for less
> than that, you'd still get a dt64. If you asked for 64 bits, you'd get it,
> if you asked for datetime128  -- what would you get???
> a 128 bit integer? or an Exception, because there is no 128bit datetime
> dtype.
> But I think this is the same problem with any dtype -- if you ask for a
> precision that doesn't exist, you're going to get an error.
> Is there a more detailed description of the proposed feature anywhere? Do
> you specify a dtype as a precision? or jsut the precision, and let the
> dtype figure it out for itself, i.e.:
> precision=64
> would give you a float64 if the passed in array was a float type, but a
> int64 if the passed in array was an int type, or a uint64 if the passed in
> array was a unsigned int type, etc.....
> But in the end,  I wonder about the use case. I generaly use asarray one
> of two ways:
> Without a dtype -- to simple make sure I've got an ndarray of SOME dtype.
> or
> With a dtype - because I really care about the dtype -- usually because I
> need to pass it on to C code or something.
> I don't think I'd ever need at least some precision, but not care if I got
> more than that...

The main use that I want to cover is that float64 and complex128 have the
same precision and it would be good if either is acceptable.  Also, one
might just want either float32 or float64, not just one of the two. Another
intent is to make the fewest possible copies. The determination of the
resulting type is made using the result_type function.

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