[SciPy-user] New bmat constructor in SciPy

[Perry Greenfield]

> On Tue, 23 Sep 2003, Nils Wagner wrote:
> 
> > In this context it would be nice to have a tool to remove 
> > rows and columns of a matrix 
> > In Matlab: 
> >  
> > > > a=rand(4,4) 
> >  
> > a = 
> >  
> >     0.9501    0.8913    0.8214    0.9218 
> >     0.2311    0.7621    0.4447    0.7382 
> >     0.6068    0.4565    0.6154    0.1763 
> >     0.4860    0.0185    0.7919    0.4057 
> >  
> > use 
> >  
> > > > a(:,2)=[] 
> 
> I wonder if in Python
> 
> >>> del a[:,2]
> 
> would be possible. Currently Numeric raises ValueError, numarray raises 
> TypeError and 
>   m=mat(a); del a[:,2]
> gives AttributeError: __delitem__ not found.
> 
> Pearu

I've given this a tiny bit of thought. In principle there isn't 
any reason why numeric arrays couldn't be resizable (or a subclass),
where they would have behavior similar to Python lists in this regard;
space is overallocated for arrays and so rows and columns may be added or
deleted. If there isn't enough space a new larger buffer is created and
the data copied, and if it shrinks a lot, a smaller buffer is created
and the larger released. But I don't think it is something we have the
resources (or need) to tackle in the near term.

Perry