| Jeff Abrahamson on 25 Dec 2005 02:18:43 -0000 |
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On Sat, Dec 24, 2005 at 06:56:29PM -0500, Dan Crosta wrote: > [43 lines, 228 words, 1446 characters] Top characters: teio_nar > > Jeff Abrahamson wrote: > > I just wrote the following loop in python, which sums those values of > > the matrix W that have the property that their distinct coordinates > > are both in a set called H: > > > > for i in range(len(k)): > > for j in range(len(k)): > > if(i != j and i in H and j in H): > > w += W[i,j] > > > > I feel I ought to be able to do this with a list comprehension, but > > it's not clear how to get the double loop. Any thoughts? > > > > w = sum([W[i,j] for ?? ]) > > > > I don't think so -- or at least, I can't figure out a syntax to make it > work. However, especially if your matrix is large, it probably makes > more sense to iterate over the set H rather than over the matrix: > > for i in H: > for j in H: > if i is not j: > sum += W[i, j] Good idea. I was thinking of it backwards. H is *much* smaller than len(k)^2 in my application. Thanks. -- Jeff Jeff Abrahamson <http://www.purple.com/jeff/> +1 215/837-2287 GPG fingerprint: 1A1A BA95 D082 A558 A276 63C6 16BF 8C4C 0D1D AE4B Attachment:
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