Thanks a lot Oscar, The lexsort you suggested was the way to go.
import h5py import numpy as np f=np.loadtxt(inputFile,delimiter=None) xcoord=np.sort(np.unique(f[:,0])) ycoord=np.sort(np.unique(f[:,1])) zcoord=np.sort(np.unique(f[:,2])) x=f[:,0] y=f[:,1] z=f[:,2] val=f[:,3] ind = np.lexsort((val,z,y,x)) # Sort by x, then by y, then by z, then by val sortedVal=np.array([(val[i]) for i in ind]).reshape((xcoord.size,ycoord.size,zcoord.size)) -- https://mail.python.org/mailman/listinfo/python-list
