[Numpy-discussion] ndarray __getattr__ to perform __getitem__

Ian Stokes-Rees ijstokes@hkl.hms.harvard....
Fri Oct 29 08:58:33 CDT 2010


> Note that there are various extant projects that I think attempt to  
> provide similar functionality to what you're wanting (unless I badly  
> misread your original email, in which case apologies):
> http://projects.scipy.org/numpy/wiki/NdarrayWithNamedAxes

Having looked into it more, I think recarray is probably what I want.  I
need to play with this and see how easy it is to convert ndarrays into
recarrays.

The main thing is that I'm looking for something *really* simple that
would, truly, just allow the conversion of:

myarray['myaxis']

to

myarray.myaxis

My suggestion is to define __getattr__ directly on the ndarray class. 
This is, TTBOMK, only called if an attribute is *not* found on the
object.  In this event, prior to throwing an AttributeError exception,
the object could check to see if the specified attribute exists as a
named axis/dimension of the multi-dimensional array, and if so, return
this.  Otherwise, carry on with the AttributeError exception.

I've spent an hour looking at the numpy code (my first time), and I
don't see any obvious way to do this, since ndarray is (AFAICT) a pure-C
object with auto-generated wrappers, which seems to preclude (easily)
adding a "__getattr__(self,attr)" method to the class.  If someone can
point me in the right direction, I'll keep looking into this, otherwise
I'm giving up and will just try and use recarray.

Ian


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