[Numpy-discussion] datetime dtype possible regression

[Mark Wiebe]

I've done some comparisons of 1.6.1 and 1.7 (master), and written up some
key differences in a pull request here:

https://github.com/numpy/numpy/pull/264/files#diff-0

What you've discovered here looks like an interaction between the automatic
unit detection and struct dtypes, it's a bug to do with how flexible types
work. To match how the struct dtypes work with flexible string dtypes, it
should raise an error when trying to create a dtype with just 'M8' and no
unit specified, at In [4].

-Mark

On Fri, Apr 27, 2012 at 3:52 PM, Travis Vaught <travis at vaught.net> wrote:

> With NumPy 1.6.1 (from EPD 7.2-2) I get this behavior:
>
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> In [1]: import numpy as np
>
> In [2]: schema = np.dtype({'names':['symbol', 'date', 'open', 'high',
> 'low',
>    ...:                        'close', 'volume', 'adjclose'],
>    ...:                    'formats':['S8', 'M8', float, float, float,
> float,
>    ...:                        float, float]})
>
> In [3]: data = [("AAPL", "2012-04-12", 600.0, 605.0, 598.0, 602.0,
> 50000000, 602.0),]
>
> In [4]: recdata = np.array(data, dtype=schema)
>
> In [5]: recdata
> Out[5]:
> array([ ('AAPL', datetime.datetime(2012, 4, 12, 0, 0), 600.0, 605.0,
> 598.0, 602.0, 50000000.0, 602.0)],
>       dtype=[('symbol', '|S8'), ('date', ('<M8[us]', {})), ('open',
> '<f8'), ('high', '<f8'), ('low', '<f8'), ('close', '<f8'), ('volume',
> '<f8'), ('adjclose', '<f8')])
>
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
>
> With numpy-1.7.0.dev_3cb783e I get this:
>
> >>> import numpy as np
>
> >>> schema =
> np.dtype({'names':['symbol','data','open','high','low','close','volume','adjclose'],
> 'formats':['S8','M8',float,float,float,float,float,float]})
>
> >>> data =  [("AAPL", "2012-04-12", 600.0, 605.0, 598.0, 602.0, 50000000,
> 602.0),]
>
> >>> recdata = np.array(data, dtype=schema)
> Traceback (most recent call last):
>   File "<stdin>", line 1, in <module>
> ValueError: Cannot create a NumPy datetime other than NaT with generic
> units
>
> >>> np.version.version
> '1.7.0.dev-3cb783e'
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> Any hints about a regression I can check for? Or perhaps I missed an api
> change for specifying datetime dtypes?
>
> Best,
>
> Travis
>
>
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