[SciPy-User] determining types in dtype
Ernest Adrogué
eadrogue@gmx....
Sun Mar 21 12:41:11 CDT 2010
21/03/10 @ 13:14 (-0400), thus spake Skipper Seabold:
> Is there an easy way to determine if the dtype of a (non-nested)
> structured-array is homogenous/similar? Basically, I want to know if
> all elements are int and/or float so it can be safely cast to an
> ndarray or if it contains strings (or, more generally, other objects)
> so it needs some more processing.
>
> I thought issctype might provide what I'm looking for but
>
> import numpy as np
> X = np.array([('1', 1.0), ('1', 1.0), ('1', 1.0)],
> dtype=[('foo', 'a1'), ('bar', '<f8')])
> np.issctype(X.dtype)
> # True
>
> Similar result for nested structs of string type
>
> Y = np.array([(('1','2'), 1.0), (('1','2'), 1.0), (('1','2'), 1.0)],
> dtype=[('foo', 'a1', (1,2)), ('bar', '<f8')])
> np.issctype(Y.dtype)
> # True
>
> In particular, I find this odd
>
> np.issctype(str)
> # True
>
> I would expect this to be like
>
> np.issctype(object)
> # False
>
> Unless there is something I don't understand about types, which is
> probably the case.
>
> The only other way I can think of is to use X.dtype.descr and actually
> parse the list to determine the types. Any thoughts?
Yes, this is what I do. From X.dtype.fields you get the dtype
of each field:
dtypes = set(i[0] for i in X.dtype.fields.values())
if len(dtypes) == 1:
print 'homogenous'
view = X.view(dtypes.pop())
else:
print 'heterogenous'
Bye.
> Skipper
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