[Numpy-discussion] how to use masked arrays

Pierre GM pgmdevlist@gmail....
Wed May 14 12:33:34 CDT 2008

On Wednesday 14 May 2008 13:19:55 Eric Firing wrote:
> Pierre GM wrote:
> > (almost) equivalent [1]:
> >>>> mydata._data
> >>>> mydata.view(np.ndarray)
> Shouldn't the former be discouraged, on the grounds that a leading
> underscore, by Python convention, indicates an attribute that is not
> part of the public API, but is instead part of the potentially
> changeable implementation?

* Please keep the note [1] in mind: the two commands are NOT equivalent: the 
former outputs a subclass of ndarray (when appropriate), the latter a regular 
* You can use mydata.data to achieve the same result as mydata._data. In 
practice, both _data and data are properties, without a fset method and a 
with fget= lambda x:x.view(x._baseclass). I'm not very comfortable with 
using .data myself, it looks a bit awkward (personal taste), and it may let a 
user think that the readbuffer object is accessed (when in fact, it's 
* The syntax ._data is required for backwards compatibility (that was the data 
portion of the old MaskedArray object). So is ._mask
* You can also use the getdata(mydata) function: it returns the ._data part of 
a masked array or the argument as a ndarray, depending which is available.

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