2d array slicing problem

jeg j.e.geach at durham.ac.uk
Fri Oct 7 19:04:13 CEST 2005

dear all,

i'm an astronomer working with 2d images -- 2d numarrays. i have a
script which basically does some operations on some images, and one of
the first steps is to find a galaxy on an image (at, say, a known x,y
coord), and create a sub-image by slicing out part of the larger array
to create a more managable smaller one (e.g. 50x50 pixels from a
1000x1000 array).

i was running this fine under python 2.3.4, but due to the slowness of
my machine, moved to a speedy 64-bit linux box running version 2.4.2.
arrays were no longer being sliced in the correct way, for example:

B = A[3:7,6:10]

generates different Bs if i run an identical script on the same image
on the different machines.

note: we deal with FITS format images, which are read into numarrays
using the pyfits.py module. does anyone know any obvious reason this
should be happening? 

many thanks if you can help, 


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