Subclassing numarray's arrays

Mizrandir mizrandir at hotmail.com
Sun Aug 15 11:11:57 CEST 2004


First of all, thanks for helping.

> Numarray wasn't designed with subclassing in mind, but there are
> workarounds for most problems.

On numarray's website there is a paper by the Numarray authors saying:
"... The new approach allows arrays to be subclassed as well as ...",
so I thought it should be something easy to do.

Anyway, I hadn't read anything about numarraycore, is it explained
anywhere. For example, I don't understand what the statement
"self.__setstate__(arr.__getstate__())" does.


> You might try something like:
> import numarray.numarraycore as _num
> class NewClass(_num.NumArray):
>    def __init__(self, n, a):
>      ''' n provides the length of each dimension,
>          a is the constant value to be plugged.
>        '''
>      arr= _num.array(sequence= n * n * [a], shape= (n, n))
>      self.__setstate__(arr.__getstate__())
> 
>    def __repr__(self):
>      " Return printable representation of instance."
>      className= self.__class__.__name__
>      className= className.zfill(5).replace('0', ' ')
>      arr= self.copy()
>      arr.__class__= _num.NumArray
>      rep= className + _num.NumArray.__repr__(arr)[5:]
>      return rep
> 
>    def __str__(self):
>      " Return a pretty printed string of the instance."
>      stri= self.copy()
>      stri.__class__= _num.NumArray
>      return _num.NumArray.__str__(stri)
> 
> 
> if __name__ == '__main__':
>    a= NewClass(2, 2)
>    print a
>    b= NewClass(3, 4)
>    print `b`

miz.



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