[Numpy-discussion] Bug in numpy std, etc. with other data structures?

[Wes McKinney]

On Sat, Sep 17, 2011 at 4:48 PM, Skipper Seabold <jsseabold at gmail.com> wrote:
> Just ran into this. Any objections for having numpy.std and other
> functions in core/fromnumeric.py call asanyarray before trying to use
> the array's method? Other data structures like pandas and larry define
> their own std method, for instance, and this doesn't allow them to
> pass through. I'm inclined to say that the issue is with numpy, though
> maybe the data structures shouldn't shadow numpy array methods while
> altering the signature. I dunno.
>
> df = pandas.DataFrame(np.random.random((10,5)))
>
> np.std(df,axis=0)
> <snip>
> TypeError: std() got an unexpected keyword argument 'dtype'
>
> np.std(np.asanyarray(df),axis=0)
> array([ 0.30883352,  0.3133324 ,  0.26517361,  0.26389029,  0.20022444])
>
> Though I don't think this would work with larry yet.
>
> Pull request: https://github.com/numpy/numpy/pull/160
>
> Skipper
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Note I've no real intention of making DataFrame fully ndarray-like--
but it's nice to be able to type:

df.std(axis=0)
df.std(axis=1)
np.sqrt(df)

etc. which works the same as ndarray. I suppose the
__array__/__array_wrap__ interface is there largely as a convenience.