En Fri, 13 Mar 2009 17:33:51 -0200, Hrvoje Niksic <[email protected]>
escribió:
"andrew cooke" <[email protected]> writes:
Hrvoje Niksic wrote:
Kottiyath <[email protected]> writes:
I have 2 lists
a = [(4, 1), (7, 3), (3, 2), (2, 4)]
b = [2, 4, 1, 3]
Now, I want to order _a_ (a[1]) based on _b_.
i.e. the second element in tuple should be the same as b.
i.e. Output would be [(3, 2), (2, 4), (4, 1), (7, 3)]
a.sort(key=lambda (x, y): b[y - 1], reverse=True)
that's hilarious! i have no idea how it works
Glad to have made someone laugh, but it in fact wasn't meant to. :-)
It was a combination of misunderstanding the question *and* trying out
the answer.
I understood that the second element of each tuple should be sorted
according to the corresponding element in b. This part is partly
correct, but I took corresponding to mean that it should be sorted by
the value of b[x], x being the second element of each tuple. Since
those elements appear to be 1-based, I added -1. This produced a list
in exactly the reverse order, so I added reverse=True.
This shows how important is to provide a good, unambiguous example in any
specification. Not just a "correct" example, but one that also shows how
things are not to be done. In case of doubt, people always look at the
examples for clarification.
--
Gabriel Genellina
--
http://mail.python.org/mailman/listinfo/python-list
