[Numpy-discussion] dtype repr change?

[Nathaniel Smith]

I have a different question about this than the rest of the thread. I'm
confused at why there isn't a programmatic way to create a datetime dtype,
other than by going through this special string-based mini-language. I guess
I generally think of string-based dtype descriptors as being a legacy thing
necessary for compatibility, but probably better to avoid in new code, now
that we have nice python ways to describe dtypes with scalar types and such.
Probably that's a minority opinion, but even putting it aside: it certainly
isn't the case that we can describe arbitrary dtypes using strings right now
- think of record types and so on. And even restricting ourselves to atomic
styles, I'm skeptical about this claim that we'll be able to use strings for
everything in the future, too. My pet possible future dtype is one for
categorical data, which would be parametrized by the set of possible
categories; I don't relish the idea of making up some ad hoc syntax for
specifying such lists within the dtype mini-language.

So is the plan actually to promote strings as the canonical way of
describing dtypes? Aside from the question of what repr does, shouldn't
there actually be some sort of syntax like dtype=np.datetime64("D")
available as a working option?

- Nathaniel
On Jul 27, 2011 10:55 AM, "Mark Wiebe" <mwwiebe at gmail.com> wrote:
> This was the most consistent way to deal with the parameterized dtype in
the
> repr, making it more future-proof at the same time. It was producing reprs
> like "array(['2011-01-01'], dtype=datetime64[D])", which is clearly wrong,
> and putting quotes around it makes it work in general for all possible
> dtypes, present and future.
>
> -Mark
>
> On Wed, Jul 27, 2011 at 12:50 PM, Matthew Brett <matthew.brett at gmail.com
>wrote:
>
>> Hi,
>>
>> I see that (current trunk):
>>
>> In [9]: np.ones((1,), dtype=bool)
>> Out[9]: array([ True], dtype='bool')
>>
>> - whereas (1.5.1):
>>
>> In [2]: np.ones((1,), dtype=bool)
>> Out[2]: array([ True], dtype=bool)
>>
>> That is breaking quite a few doctests. What is the reason for the
>> change? Something to do with more planned dtypes?
>>
>> Thanks a lot,
>>
>> Matthew
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