large arrays in python (scientific)

[Mark Grant]

I'm new to python programming.  I was hoping I could get some feedback
about some difficulty I'm having
creating a large array in python. 

I have a data set that contains values for positions in 3D space. 
There are about 2 million data points
(128x128x128).

I'm trying to fit a function to the data. I want to use the
LeastSquaresFit procedure in ScientificPython,
which takes an array of elements of the format:

[[(xposition1, yposition1, zposition1), value1],
[[(xposition2, yposition2, zposition2), value2],
...,
...,
]

When I try to create this array, I create about a million of the
elements, and then the script slows down and
eventually stops.  I'm not sure why this is happening. 

Thanks for any help.

Mark Grant
markrgrant at yahoo.com