[PLUG] python, list comprehensions

[Jeff Abrahamson <jeff@purple.com>]

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 ?? ])

-- 
 Jeff

 Jeff Abrahamson  <http://www.purple.com/jeff/>    +1 215/837-2287
 GPG fingerprint: 1A1A BA95 D082 A558 A276  63C6 16BF 8C4C 0D1D AE4B

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